Goals for creating a flow of single items. Advantages of one-piece flow. When a problem is not a problem

The Tao of Toyota Liker Jeffrey

Heijunka – alignment of production and work schedule

Heijunka– alignment of production and work schedule

Heijunka represents the leveling of production both in terms of volume and product range. To prevent sudden ups and downs, products are not released in the order in which customer orders are received. First, orders are collected over a period of time, after which their execution is planned in such a way as to produce the same range of products in the same quantity every day.

From the very beginning, TPS assumed the production of small batches of products taking into account the needs of the consumer (both external and internal). When there is a flow single products you can produce items A and B according to the order in which orders are received (for example, A, B, A, B, A, B, B, B, A, B...). But this means that the production of parts will be disorderly. So if you receive twice as many orders on Monday as on Tuesday, you will have to pay the workers on Monday for overtime work, and on Tuesday send them home before the end of the working day. To align your work schedule, you should find out the consumer’s needs, decide on the product range and volume, and create a balanced schedule for each day. For example, you know that for every five A's you make five B's. You can level production and produce them in the sequence ABABAB. This is called leveled production with a mixed product mix, because you produce heterogeneous products, but at the same time, predicting consumer demand, you build a certain sequence of production of different products with a balanced level of volume and product range.

In Fig. Figure 10.2 shows an example of an unbalanced schedule in a plant that produces small engines for lawn mowing equipment (a case study of one plant).

Rice. 10.2. Traditional production (no leveling)

In this case, the production line produces three types of motors: small, medium and large. Medium engines enjoy most in demand, so they are made at the beginning of the week: on Monday, Tuesday and part of Wednesday. The line is then retooled, which takes a few hours, and production of small engines begins, which are built the rest of Wednesday, Thursday and Friday morning. The least demand is for large engines, which are manufactured on Friday. This uneven schedule creates four problems:

1, It is usually impossible to predict the order in which consumers will purchase engines.. Consumers are stocking up on medium and large engines all week. So if a customer unexpectedly decides to purchase a large quantity of large engines at the beginning of the week, the plant will be in trouble. They can be solved if you keep them in reserve a large number of ready-made engines of all types, but these stocks, due to the associated costs, will be very expensive for the enterprise.

2, It is not always possible to sell all engines. If the plant doesn't sell all the mid-engines it makes from Monday to Wednesday, it will have to keep them in stock.

3, Unbalanced use of resources. It's likely that different sized motors require different amounts of labor to make, and the most labor intensive is to make larger motors. Therefore, at the beginning of the week the level of labor costs is average, then it decreases, and at the end of the week it increases sharply. Therefore, there are clearly expressed hm? yes And m?ra.

4, Uneven demands are placed on previous stages of the process. This is perhaps the most serious problem. Because the plant buys different parts for three types of engines, it asks suppliers to send one type of part from Monday to Wednesday, and different types of other parts the rest of the week. Experience shows that consumer demand is constantly changing and the plant somehow fails to adhere to this schedule. Often there are sudden changes in the product mix, for example, a rush order for large engines comes in, and the plant spends the entire week working on only that type of product. Suppliers have to be prepared for the worst case scenario and keep at least a week's supply of components for each of the three types of engines. The so-called shepherd's whip effect causes the manufacturer's behavior to be transmitted down the supply chain to the beginning of the supply chain, meaning that a small wave of the hand creates a huge force at the tip of the whip. Thus, a slight change in schedule at an engine assembly plant leads to the creation of ever-increasing inventories at all stages of the supply chain, as we move from the end consumer to the beginning of it.

The goal of mass production is to achieve economies of scale for each piece of equipment. Changing tools to move from product A to product B leads to equipment downtime during the changeover, and consequently to losses. You have to pay the operator for the time during which his machine is readjusted. It would seem that the conclusion suggests itself - before switching to product B, make a large batch of product A. But for heijunka This approach is unacceptable.

In the engine example, the plant carefully analyzed the situation and found that line changeovers took so long because of the need to ship, return, install and dismantle parts and tools for different types engines. Pallets of different sizes were used for different engines. It was decided to supply the line operator with a small amount of all types of parts on mobile racks. The tools needed for all three engines were installed above the production line. In addition, it was necessary to create a pallet on which motors of any size could be mounted. This made it possible to avoid complete readjustment of equipment, allowing the plant to produce engines in any sequence. As a result, it became possible to determine the repeating sequence of manufacturing engines of all three types, taking into account consumer orders (see Fig. 10.3). Flattening the graph provided four benefits:

Rice. 10.3. Balanced production with mixed items

1. Flexibility - now the plant can give the consumer what he needs in right time . This leads to a reduction in inventory and the elimination of other related problems.

2. Reducing the risk that finished products will not be sold. If a factory makes only what the customer orders, they don't have to worry about inventory holding costs.

3. Balanced use labor resources and machines. The plant can now standardize work and level out production to account for the fact that some engines require less labor than others. And if one large engine, which requires more intensive work, is not followed by another, the workers successfully cope with the load. If a company adjusts its schedule to account for labor costs, it can ensure a balanced and even work load throughout the day.

4. Balance of orders issued to previous processes and suppliers. If a plant uses a just-in-time system and suppliers deliver components several times a day, suppliers will have a steady supply of orders. This will allow them to reduce the volume of inventories, and therefore costs, which will be reflected in the cost of production, which means that everyone will benefit from equalization.

But all this will be impossible if the plant fails to reduce changeover time.

It's hard to believe, but this can be done in almost any situation. Several decades ago, Shigeo Shingo proved that this is where we should start. Shingo did not work for Toyota, but worked closely with it. He was a production engineer and meticulously took into account every microscopic movement of the worker. In true Toyota fashion, he took a close look at the process of setting up large stamping presses and discovered that most of the work done fell into one of two categories: this or hm? yes, or something that can be done while the press is running. He called the second category “external adjustment,” as opposed to “internal adjustment,” which can only be done when the press is turned off.

In traditional mass production, the team that is retooling the production line for a product changeover starts by shutting down the press. Shingo wondered how much of the changeover work could be done while the press was still running. Trying to expand the range of such operations, he organized the operator’s workplace differently and introduced a number of technical improvements. With the press running, you could take the next die and tooling, warm up the die, and put it next to the press—all of these were “external” operations and could be done while the press was still producing parts. When the press is turned off, all that remains is to replace the die and continue working. Unexpectedly, it turned out that multi-ton presses, which previously took hours to reconfigure, can be reconfigured in a few minutes. It was as difficult to imagine as a car repair crew at a car race, which takes no more than a minute to get the car in order.

Over the years, retooling has become something of a national sport in Japan, similar to American rodeo. During a trip to Japan in the 1980s, I visited one of the suppliers of stamped Mazda door panels. The team from this plant won a prize at national competitions for retooling a press with a force of several hundred tons in 52 seconds.

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Combining people and equipment based on the principle of specialization creates another problem: the product the consumer needs is not tied to one department. To turn into what the consumer requires, it wanders through different departments. Design, procurement and financing are handled by different departments. There are many value streams flowing through these departments, so there is a delay every time a product is passed on to another department. The flow of single products assumes that you sequentially build all technological operations into a single line, which allows you to fulfill the consumer’s order in the shortest possible time.

In Fig. Figure 8.1 schematically shows a computer company consisting of three departments. One department manufactures system units, the second produces monitors and connects them to the system unit, and the third tests finished computers (in fact, when manufacturing a computer, many companies and departments are involved in the technological chain). With this structure, the transportation department finds it practical to move a batch of 10 units at a time. Each department spends one minute per unit, therefore, a batch of computers goes through each department in 10 minutes. Without taking into account the travel time between departments, the production and testing of the first batch of 10 units will take 30 minutes. It takes 21 minutes to get the first computer ready to ship and ship to the consumer, even though it only takes three minutes to add value during the manufacturing process.

In Ohno's system, the efficiency of a particular process or transportation department does not determine the ideal lot size. The ideal batch size for a lean approach remains the same – it is one product. It did not try to optimize the use of people and equipment in isolated departments. The first Toyota plant worked exactly according to the method of Ford plants. But this did not produce the desired results, because Toyota could not compete with Ford in terms of production volumes and economies of scale. So Ono decided to optimize the flow of material so that it moves through the plant faster. This meant a smaller batch. And to do this, the easiest way was to break down the barriers between departments and, instead of islands that specialized in individual operations, create work cells united by products rather than by processes.

In Fig. Figure 8.2 shows the same computer manufacturing process, organized according to the principle of a work cell through which a flow of single products passes. If Ohno had taken over this process, he would have taken from one department the equipment necessary to manufacture the system unit, from another department the equipment for making the monitor and the test bench from the testing department, and built a sequential chain of these operations. In other words, it would create a unit flow cell. Then he would make sure that operators do not create inventories between these three operations. For example, someone who makes system units should not start making the next unit until the monitor for the previous unit has been made and until the finished product has been created from these two subassemblies. In other words, no one should produce more than what is immediately needed. As a result, in 12 minutes the operators of such a cell produce 10 computers. In addition, this lean process allows the first working computer to be ready for shipment in just three minutes instead of 21. These three minutes represent pure value-added time. The flow allowed us to get rid of overproduction and inventory.

Why does "faster" mean "better" when there is a flow?

It often seems to us that speeding up the process leads to a decrease in quality; faster means more careless. But flow leads to the exact opposite result - as a rule, quality increases. In Fig. 8.1 and 8.2 show a defective computer whose monitor is crossed out. During the testing phase it was not possible to enable it. When releasing a large batch according to the scheme shown in Fig. 8.1, by the time the problem is identified, there will be at least 21 products in operation, and it is possible that they will all have the same defect. If this is a defect that was caused by the department that produces system units, then the testing department will find out about it only after 21 minutes. In Fig. 8.2, when a defect is discovered, there are only two computers with the same defect in operation, and it will take only two minutes to find out which operation made the mistake. Thus, when producing large batches, work in progress may lie between individual operations for weeks, and weeks or even months may pass from the moment a defect is introduced to the moment it is discovered. But the trace has already “cooled down”, and it will be almost impossible to identify the cause of the defect.

The same logical chain applies to any technological or business process. If you allow isolated departments to do their work in batches and pass those batches on to other departments, you are guaranteed to experience delays in completing the work. There will also be bureaucratic delays, officials will begin to set standards for each department and many positions will be created to track the flow that are not related to adding value. Projects will spend most of their time waiting for action or decisions. This will lead to confusion and poor quality. Pick up the right people that create added value, define the sequence of activities and run the project through the created chain, taking care of how to connect their actions, and you will get the pace, productivity and quality you need.

Takt time: pulse of single piece flow

In rowing competitions, an important role is played by the helmsman, who sits at the stern and shouts “and one, and one, and one.” He coordinates the activities of all rowers, making sure that they act harmoniously and row at the same speed. What happens if one of the rowers is faster than the others? That's right, the order is disrupted and the boat moves slower. Excess force and speed slows down movement.

Something similar happens in any work, whether we are talking about production or the provision of services. If a single department is operating at excessive capacity, it will overwhelm other departments with mountains of inventory and paperwork, causing confusion and slowing down the process. The activities of the departments must be coordinated. How do you determine at what speed the single-piece flow cell you've created should operate? What should the power of the equipment be? How many people will be needed? To do this, you need to determine the takt time.

The German word takt means rhythm or tempo. Takt time is determined by consumer demand - the rate at which products are purchased. If the working day is 7 hours 20 minutes (440 minutes), 20 days per month, and the consumer purchases 17,600 units of product per month, then 880 units need to be produced per day, that is, one product per 30 seconds. With a properly organized flow of single products, each stage of the process should take 30 seconds. If the work goes faster, it will lead to overproduction, if it goes slower, a bottleneck will appear in the process. The concept of "tact" is used when it is necessary to determine the pace of production and prevent workers from falling behind or in too much of a hurry.

Continuous flow and takt time are most easily applied to mass production of goods or services. However, with creativity, these concepts can be applied to any repetitive process by listing its steps and identifying and eliminating waste (see Chapter 21). An example of such a checklist at a US Navy ship repair facility is provided at the end of this chapter. My colleagues and I have encountered many other examples in the course of our work: filling out invoices when designing ships, checking people by the security service of a Navy shipyard, accepting new members into a professional association, reimbursing employees, working with applicants for jobs... You can find many others yourself examples. Of course, the concept of takt time and unit flow is most easily applied to highly repetitive maintenance operations that require some consistency in cycle time per unit, but the Toyota Way is not about looking for shortcuts.

Benefits of One Piece Flow

Creating a flow of single products involves a wide program of measures to eliminate all kinds of muda (losses). Let's take a closer look at some of the benefits of flow.

1. Built-in quality. The flow of one-pieces greatly simplifies the integration of quality. Each operator is also a controller and tries to solve the problem on the spot without passing it on to the next stage. Even if he missed the defects and they moved on, they will be detected very quickly and the problem will be immediately identified and corrected.

2. True flexibility. If equipment becomes part of a production line, our ability to use it for other purposes will be reduced. But the order fulfillment time is reduced to the limit, which means that we respond more flexibly to consumer requests, producing what he really needs. Instead of waiting weeks for the ordering system to deliver the product, we can fulfill the order within a few hours. The transition to a new range of products, which is required by changing consumer demand, is carried out almost instantly.

3. Increased productivity. When work was divided into departments, you thought that this was how you achieved maximum productivity, since work efficiency was measured by the workload of people and equipment. In fact, it is difficult to determine how many people are required to produce a given number of units in high-volume production because productivity is not measured in terms of value-adding work. Who knows what the productivity loss is when people are busy producing excess parts that then have to be sent to a warehouse? How much time is lost when searching for defective parts and repairing finished products? If there is a cell for one-piece flow, non-value-added work such as moving materials is minimized. You can immediately see who is overloaded and who is left idle. It is very easy to cost the value-adding work and calculate how many people are required to achieve a given output. When it comes to converting a mass production supplier to a TPS line, the Toyota Supplier Support Center is able to achieve at least a 100% increase in productivity in every case.

4. Freeing up space in the workshop. When equipment is distributed among areas, significant areas between them are wasted, although most of them are occupied by reserve deposits. In a single-piece flow cell, all blocks fit together and inventory takes up almost no space. If production space is used more efficiently, the construction of new facilities can be avoided.

5. Increased security. An early adopter of TPS in America, Wiremold Corporation has an exemplary safety record and has received numerous government safety awards. However, when the company decided to take on the challenge of converting high-volume production to single-piece flow, it was decided that a special safety program was not needed. The reorganization was led by Art Byrne, a former company president who had studied TPS and realized that one-piece flow would automatically lead to improved safety by reducing the amount of material that had to be moved around the plant. Reducing cargo volume eliminates the need for forklifts, which are a common cause of accidents. The volume of containers that need to be lifted and moved will also be reduced, which means fewer container lifting accidents. If you deal with flow, security improves itself, even if you don’t pay special attention to it.

6. Increased morale. Wiremold, when implementing lean manufacturing, found that employee morale improved every year. Before the changes, only 60% of employees said in surveys that they worked for a good company. This figure grew every year and in the fourth year of transformation exceeded 70% (Emilani, 2002). The flow of one-piece products means that most of the time people are busy creating added value and can quickly see the fruits of their labor, and when they see their successes, they feel satisfied.

7. Reducing inventory. By not investing capital in inventory that is sitting dead, you can use it for something else. At the same time, you will also save on bank interest, which must be paid for funds frozen in reserves. You will also avoid stock obsolescence.

In Fig. Figure 8.3 shows a traditional workshop where equipment is grouped by type. One tool that can be used to diagram the flow of materials is a spaghetti diagram. If we diagram the flow of materials in a workshop, we will get something reminiscent of spaghetti, which is randomly mixed on a plate. The product is moved haphazardly in different directions. The work of individual sections when moving the product is not coordinated. No amount of schedules or plans can eliminate the variability inherent in a system in which material moves randomly.

In Fig. In Figure 8.4, where the lean manufacturing cell is presented, we see a different picture. Equipment is grouped according to the flow of material as it is converted into a finished product. In this case, the equipment is placed in a U shape, since this arrangement facilitates the efficient movement of materials and people and facilitates the exchange of information. You can organize a cell in the form of a straight line or the letter L. In this case, we showed the trajectory of two people who serve the cell. What if demand halves? Leave one operator on the cell. What if demand doubles? Assign four people to service the cell. Of course, in order to serve various technological operations, people must be prepared to combine professions; these are the requirements of Toyota factories.

Why is it difficult to create a thread?

Do you think that as soon as you create cells for the flow of single products, life will immediately improve and all problems and misfortunes will disappear? Don't even hope! If you start thinking in lean terms, life will become much more difficult for a while, at least until you learn to continually improve the process. Taiichi Ohno says:

In 1947, we lined up the machines in parallel lines, and in some places we arranged them in the letter L and tried to place one worker on three or four machines in accordance with the technological route. Although there was no talk of overtime, the workers desperately resisted. The machine operators did not like that the new layout required them to combine professions. They did not like the transition from a system of “one operator - one machine” to a system of “one operator - many machines for different operations.” They were understandable. In addition, other problems emerged. Once it became clear what kind of problems these were, I was able to decide in which direction to move. Although I was young and energetic, I decided not to insist on immediate radical changes, but be patient (Ohno, 1988).

In traditional mass production, if there is a failure at one stage of the process, for example, it will take a long time to retool a machine, someone will not come to work due to illness, or equipment will fail, other “independent” stages of the process will be carried out as before, because you have plenty of supplies. When you link individual operations to create a one-piece flow, if a failure occurs in one area, the entire cell stops. Either you swim together, or you all go down together. So why not make your life easier and create a reserve stock? However, any kind of inventory - accumulations of material or virtual accumulations of information that are waiting for a long time in the wings - prevents the identification of problems and inefficiencies. Inventory develops a bad habit of working around problems. If you avoid solving problems, you are not improving processes. One-piece flow and continuous improvement (kaizen) go hand in hand! If your competitor decides to take the difficult and thorny path of a lean approach, no amount of inventory will help you, you will face bankruptcy. Minora, former president of Toyota Motor Manufacturing and student of Taiichi Ohno, says:

Someone who has started production using a one-piece flow system is unable to maintain the desired number of pieces, so at first everyone is discouraged and does not know what to do. But it makes people think: how can we get the right amount? This is the essence of TPS; we can say that we deliberately confuse people so that they are forced to change their approach to a problem.

Many companies I've been to when implementing flow have made one of two mistakes. The first was that the flow was not real. The second mistake was to immediately abandon the flow as soon as problems arose.

An example of pseudo-flow was the rearrangement of equipment. By moving blocks of equipment together, the company created the appearance of a cell for the flow of single products, but at each stage they continued to engage in mass production, without thinking about the takt time, which is determined by the consumer. It looked like a cell for product flow, but the work was done the old fashioned way, according to the principle of mass production.

Will-Burt Company in Orville, Ohio, manufactures a variety of products from billet steel. One product that is produced in high volume is a family of telescopic steel masts that are used in vans for radar or film crews. Each mast has its own characteristics depending on the scope of application, so all products are different. This company called the mast manufacturing process a cell and believed that it had created Lean. When I was helping organize a process review as a lean manufacturing consultant, the production manager warned us that the variety of parts was so diverse that we were unlikely to be able to improve the existing flow.

During a week-long kaizen workshop, the current situation was analyzed and it turned out that we were dealing with a classic pseudo-flow. The time required to create one mast (value-added processing time) was 431 minutes. However, the pieces of equipment used to produce each mast were located so far apart that large pallets of masts had to be moved using forklifts from one work site to another. Every workplace had stocks of work in progress. The total lead time from raw materials to the finished product, taking into account the length of time in the incomplete state, was 37.8 days. Most of this time was spent storing tubular blanks and finished products. In terms of processing time at the factory, a job that took 431 minutes, from sawing to the final stage of welding, took four days. Moving within the plant, each mast covered a distance of 1,792 feet (546 meters - Editor's note). To solve these problems, it was proposed to place equipment blocks closer friend to each other, process products one by one, one after another, refuse to use a forklift between operations (to move products between operations that could not be carried out side by side, a special trolley was designed, the height of which corresponded to the level of the workplace). In addition, it was proposed to issue a separate work order for each mast instead of a set of work orders for a set of masts. These changes resulted in significant reductions in lead times (see Figure 8.5), reductions in inventory, and savings in production space.

Among other things, it was checked how long it takes to place a work order, and this made it possible to obtain an additional positive effect by eliminating the old method. The accumulation of batches of work orders generated a lot of losses; and when such a system was put an end to, the time was reduced from 207 minutes to 13 minutes. In Fig. Figure 8.6 shows the flow before and after a week-long kaizen workshop. It can be seen that the “before” situation is actually a pseudo-flow. The pieces of equipment seem to be located nearby, but in reality there is nothing like a flow of single items. The employees working at the plant did not fully understand what flow was and did not realize that they were dealing with pseudo-flow. The “after” situation improved qualitatively, which surprised and delighted everyone in the company. They were shocked that this was done in just a week.

The second mistake that those who implement flow make is abandoning the chosen course. As soon as it becomes clear that creating a flow may lead to certain costs, the company refuses decision taken. This can happen in any of the following situations:

Stopping one of the equipment blocks leads to the fact that the entire cell stops working.

Retooling one piece of equipment takes longer than expected and slows down the cell as a whole as production stops.

When creating a stream, you have to invest in a process step that was previously carried out in another plant (for example, heat treatment) to produce it on site.

I've seen companies choose not to use flow in similar cases. They thought flow was a great thing as long as the benefits of batch size reduction and a flow system were shown to you in a theoretical model. But it is not nearly as good when we try it out and see that it immediately causes all sorts of troubles and costs. Once a single-piece flow cell is established, maintaining it requires discipline, something that many manufacturing companies find impossible because they do not fully understand the complexities and challenges associated with continuous improvement. However, in the long term, these troubles and short-term costs will certainly pay off, leading to amazing results.

In any process, Toyota strives to create a true flow of one-piece products without waste, as demonstrated by Principle 2: A continuous flow process helps identify problems. Creating a flow means linking together operations that were previously separate. When this connection is created, the team works more cohesively, the system quickly responds to quality problems, the process becomes manageable, and immediate problem solving becomes an urgent need, forcing people to think and develop. Ultimately, for Toyota's approach The main benefit of one-piece flow is that it forces people to think and improve.

Emphasizing the need to think, Toyota deciphers the name of its production system, TPS, as “Thinking Production System.” production system"). To identify problems, Toyota is willing to stop production, knowing that this will force team members to find a solution. Inventory hides problems and allows you to put off their solution. With the Toyota approach, the problem is solved as soon as it is discovered. Chapter 11 (on jidoka) covers this in more detail.

Case study: description of processes at a Navy ship repair plant

An excellent example of how one-piece flow can be applied to a repair facility is the Naval Shipyard Puget Sound. Single piece flow began to be used here in the fall of 2001. The plant is engaged not in construction, but in repair of Navy ships - from submarines to aircraft carriers. The repair of each ship is unique, so the work is carried out in close contact with engineers who diagnose the problem and draw up assignments for the upcoming repair work. Technical documentation, including instructions for performing the work, are put into a folder and sent to the factory so that qualified workers can carry out the appropriate repairs. As a result, mechanics had to deal with permitting, financing, and other paperwork to get their jobs done. The instruction folder often became a bottleneck in the planning process and led to additional costs.

To improve the process, a week-long hands-on kaizen workshop was held. It was preceded by thorough preparation. Preparations were being made for the reorganization; a room was allocated in the office for a cross-functional cell that was supposed to deal with production tasks. The workshop focused on mapping the existing process and developing a new process. A step-by-step analysis of the process identified waste, including rework, redundant systems, various storage media (e.g. summary statements), waiting for forms, verification, unnecessary checks and approvals, an ill-conceived document registration system, lack of necessary reference materials, unnecessary walking, waiting and incomplete information.

The solution was to develop a cross-functional cell to bring all work instructions together. As a result, the number of document hand-overs has been reduced and non-value-added activities have been eliminated. Taking into account the need for work instructions (these needs are very easy to predict) and the time required to develop them, the takt time was determined. The most important thing was to select the employees who do the bulk of the work and remove the barriers that separated them. The cell was created in the office, and a folder with work instructions was transferred from one position to another in record time. Previously, in the office, employees were grouped according to their functions, and the rooms were separated by high partitions so that everyone had their own office. Now, if there was a cell, the tables of the leading specialists were located around a round table. Production tasks were passed along the table from one specialist to another, forming a flow of individual objects. Timing the time it took to create added value before and after the transformation showed amazing results. Note that some wasted time on non-value-added processes is inevitable, such as completing a number of paperwork in accordance with Navy regulations, although this paperwork is not always needed for mechanics' work. We presented such time costs in a special column, separately from the “waiting time”, which represents losses in their pure form. The results of the reorganization are shown in Fig. 8.7.

Principle 3: Use a pull system to avoid overproduction

The more inventory a company has... the less hope it has of having what it needs.

Taiichi Ohno

Imagine finding out about a great online ordering service. Now all dairy products will be delivered to your home, and at a good discount. There is only one difficulty - you need to determine the amount of food for the week in advance. The company can only guarantee one thing - delivery within a week. The company asks you to decide on your order in advance because it needs to know how many and what products need to be shipped from the warehouse. This will allow her to sell all the products she receives. The products will be left on your porch in a special refrigerator container. You calculate how many eggs, milk and butter you typically consume during the week. But you don’t know what day they will be picked up. Perhaps it will be Monday, or perhaps Friday. Therefore, you have to keep a reserve stock of food in the refrigerator. If your groceries arrive on Monday and you already have a week's supply of dairy products in your refrigerator, you'll struggle to find room for more. You buy another refrigerator and put it in the garage. If you go on vacation and forget to cancel your order for the week, you return to find a container on your porch with a week's supply of spoiled food.

This is an example of an inventory push system. Wholesalers are often pushed into retail trade goods and services, regardless of whether the retailer can sell them or not. The retailer, in turn, pushes goods and services to you without asking whether you need them now or not. As a result, you end up with excess inventory that you don't need at the moment, and the retailer itself is forced to hold huge amounts of inventory as well.

Now imagine that the mentioned Internet service, having received many complaints, decided to improve its service system. They sent you a special transmitter that has a button for each of the products you need. When you open a new bottle of milk or carton of eggs, you press the appropriate button. The next day you will receive exactly the same amount of groceries as you unpacked. As a result, you will have one printed package plus one more. There will be reserves, but very small. If you know you'll need a lot of milk, you can simply go online or call and have what you need delivered to you immediately. The company itself has revised agreements with suppliers of dairy products. If consumers order a lot of products, the company informs suppliers and they deliver the products in quantities that do not exceed the required quantity. This is an example of a "pull" system. You get what you need only when you need it, and the retailer orders products based on customer demand. To avoid being pushed out, I'm guessing you'd be willing to pay a little more for on-demand service.

Principle 4: Equalize the scope of work (heijunka)

When you implement TPS, you must start by leveling production. This is the primary responsibility of those involved in production management. It is possible that alignment of the production schedule may require you to speed up or delay the shipment of some products, and you will have to ask some of your customers to wait a little. If the production level remains more or less constant throughout the month, you can apply a pull system and keep the assembly line running in a balanced manner. But if the level of production - output - varies from day to day, there is no point in trying to apply all the other systems, because in these circumstances you simply will not be able to standardize the work.
Fujio Te, President of Toyota Motor Corporation

Following Dell Computer and other successful companies, many American businesses are striving to create a build-to-order manufacturing model. They focus only on what the customer needs and when, that is, they strive to create flawless lean production. Unfortunately, consumers are often unpredictable and their orders change monthly, even weekly. If you manufacture products on a first-come, first-served basis, you will have to periodically push your employees and equipment to their limits to produce great amount products, and pay for overtime work. After this, periods of calm will come, people will have nothing to do, and equipment will be idle. In this type of work, you don’t know how many components to order from suppliers, and you will be forced to keep a huge stock of what the consumer may need. It is impossible to conduct lean production with this approach. Rigidly following the build-to-order model leads to the creation of huge inventories, which hides problems and ultimately leads to poor quality. Chaos in the enterprise is growing, and order fulfillment time is increasing. Toyota discovered that in order to create the best possible lean production and improve the customer experience, it was necessary to align the production schedule without always strictly following the order in which orders were received.

A number of companies I've worked with that have tried to do a make-to-order approach often have the customer wait six to eight weeks for the product they order. At the same time, “particularly valuable” customers could get in the queue, and their orders were urgently fulfilled to the detriment of others. But is it worth disrupting the rhythm of work to fulfill an order today, if the consumer will still receive the ordered product only in six weeks? Wouldn't it be better to collect orders and smooth out the production schedule instead? This will allow you to speed up order fulfillment, reduce parts inventory, and all customers will be pleased to know that standard lead times have been significantly reduced. Isn’t this better than the alternation of rush jobs and downtime that the “make-to-order” principle required?

Toyota managers and workers use the term "m'uda" when talking about waste, and eliminating m'uda is the essence of lean manufacturing. But for the organization of such production, two other M are also important, and these three M represent unified system. Dealing with only the eight types of waste (m'uda) will only harm the efficient functioning of people and the production system. The Toyota Way document talks about "eliminating the m'uda, m'ouri, m'ura." What do the three M's represent?

Muda are actions that do not add value. The most famous M includes the eight types of losses mentioned above. These are actions that increase order lead time, force unnecessary travel to deliver a part or tool, lead to excess inventory, or force waits.

Muri - overload of people or equipment. In a certain sense, it is the opposite of m'uda. M'uri forces a machine or a person to work at its limit. Overloading people threatens their safety and causes quality problems. Overloading equipment leads to accidents and defects.

Mura - unevenness. This "M" is in some way a result of the first two. At times, in normally functioning production systems there is more work than the people and equipment can handle, and at times there is not enough work. The cause of unevenness is poor scheduling or fluctuations in production volumes caused by internal problems such as downtime, missing parts, or defects. M'uda is the result of mura. The unevenness of the level of production makes it necessary to match the available resources (equipment, materials, people) to the maximum volume of production, even if in fact its average level is much lower.

Imagine that your production schedule is highly variable, uneven, and unreliable. You have decided to move to a lean production system and are only thinking about how to eliminate m'uda from your production system. You begin to reduce inventory levels. Then you try to ensure a steady pace of work and reduce the number of people in the system*. After that, you work on organizing your workspaces to eliminate unnecessary movement. Finally, you start the system. And sadly you discover that the system is running out of steam due to peaks in consumer demand that force people and equipment to work too hard, and therefore inefficiently! Production is now organized as a flow of single products, there are no stocks, but the pace of production and the range of products are constantly and dramatically changing. All you've achieved is an extremely unstable flow of one-off items. Your workers are overworked. Equipment breaks down even more often than before. You are missing details. And you conclude: “Lean doesn’t work here.”

* Toyota never fires or demotes workers who have to be displaced due to increased productivity. Such a short-sighted move, which at first glance appears to reduce costs, is sure to create hostility towards the company, and the rest of the workers will be reluctant to participate in kaizen work in the future. For those displaced by manufacturing improvements, Toyota is always looking for alternative value-adding jobs.

Interestingly, increased attention to m'uda is a very common approach when implementing "lean tools", since identifying and eliminating costs is not that difficult. But most companies forget the more complex process of stabilizing the system and achieving uniformity—creating a balanced lean flow. This is a concept called heijunka, which requires balancing your work schedule. This is perhaps the most consciously applied principle within the Toyota approach. Realization of heijunka is a prerequisite for the elimination of mura, and this, in turn, is necessary for the elimination of muri and muda.

Overload followed by underload leads to constant starts and stops and is incompatible with high quality, standardization of work, productivity and continuous improvement. As Taiichi Ohno said:

A slow but persistent tortoise does not create as many losses and is much better than a hasty hare who rushes forward headlong and stops from time to time to take a nap. The Toyota Production System can only be understood when all workers become turtles (Ohno, 1998).

I have heard more than once from other Toyota executives: “We prefer to be slow and persistent like a tortoise than to jump like a hare.” US production systems make workers rabbits. They work until exhaustion, and then take a break. In many American factories, workers are united in pairs - while one works for two, the other is free. If it does not affect the daily production rate, managers turn a blind eye to it.

Heijunka - alignment of production and work schedule

Heijunka is the leveling of production both in terms of volume and product range. To prevent sudden ups and downs, products are not released in the order in which customer orders are received. First, orders are collected over a period of time, after which their execution is planned in such a way as to produce the same range of products in the same quantity every day. From the very beginning, TPS assumed the production of small batches of products taking into account the needs of the consumer (both external and internal). If you have a one-piece flow, you can produce items A and B according to the order in which orders are received (for example, A, B, A, B, A, B, B, B, A, B...). But this means that the production of parts will be disorderly. So if you receive twice as many orders on Monday as you did on Tuesday, you will have to pay workers overtime on Monday and send them home before the end of the day on Tuesday. To align your work schedule, you should find out the consumer’s needs, decide on the product range and volume, and create a balanced schedule for each day. For example, you know that for every five A's you make five B's. You can level production and produce them in the sequence ABABAB. This is called leveled production with a mixed product mix, because you produce heterogeneous products, but at the same time, predicting consumer demand, you build a certain sequence of production of different products with a balanced level of volume and product range.

In Fig. Figure 10.2 shows an example of an unbalanced schedule in a plant that produces small engines for lawn mowing equipment (a case study of one plant).

In this case, the production line produces three types of motors: small, medium and large. Medium engines are in greatest demand, so they are made at the beginning of the week: Monday, Tuesday and part of Wednesday. The line is then retooled, which takes a few hours, and production of small engines begins, which are built the rest of Wednesday, Thursday and Friday morning. The least demand is for large engines, which are manufactured on Friday. This uneven schedule creates four problems:

Typically, it is impossible to predict how consumers will purchase engines. Consumers are stocking up on medium and large engines all week. So if a customer unexpectedly decides to purchase a large quantity of large engines at the beginning of the week, the plant will be in trouble. They can be solved by keeping a large number of ready-made engines of all types in stock, but these stocks, due to the associated costs, will be very expensive for the enterprise.
It is not always possible to sell all engines. If the plant doesn't sell all the mid-engines it makes from Monday to Wednesday, it will have to keep them in stock.
Unbalanced use of resources. It's likely that different sized motors require different amounts of labor to make, and the most labor intensive is to make larger motors. Therefore, at the beginning of the week the level of labor costs is average, then it decreases, and at the end of the week it increases sharply. Consequently, m'uda and m'ura are clearly expressed here. 4. Uneven demands are placed on previous stages of the process. This is perhaps the most serious problem. Because the plant buys different parts for three types of engines, it asks suppliers to send one type of part from Monday to Wednesday, and different types of other parts the rest of the week. Experience shows that consumer demand is constantly changing and the plant somehow fails to adhere to this schedule. Often there are sudden changes in the product mix, for example, a rush order for large engines comes in, and the plant spends the entire week working on only that type of product. Suppliers have to be prepared for the worst case scenario and keep at least a week's supply of components for each of the three types of engines. The so-called shepherd's whip effect causes the manufacturer's behavior to be transmitted down the supply chain to the beginning of the supply chain, meaning that a small wave of the hand creates a huge force at the tip of the whip. Thus, a slight change in schedule at an engine assembly plant leads to the creation of ever-increasing inventories at all stages of the supply chain, as we move from the end consumer to the beginning of it.

In the engine example, the plant carefully analyzed the situation and found that line changeovers took so long because of the need to ship, return, install and dismantle parts and tools for different types of engines. Pallets of different sizes were used for different engines. It was decided to supply the line operator with a small amount of all types of parts on mobile racks. The tools needed for all three engines were installed above the production line. In addition, it was necessary to create a pallet on which motors of any size could be mounted. This made it possible to avoid complete readjustment of equipment, allowing the plant to produce engines in any sequence. As a result, it became possible to determine the repeating sequence of manufacturing engines of all three types, taking into account consumer orders. Flattening the graph provided four benefits:

Flexibility - the plant can now give the consumer what he needs at the right time. This leads to a reduction in inventory and the elimination of other related problems.
Reducing the risk that finished products will not be sold. If a factory makes only what the customer orders, they don't have to worry about inventory holding costs.
Balanced use of labor resources and machines. Now the plant can standardize work and level out production to account for the fact that some engines require less labor than others, AND if one large engine that requires more intensive work is not followed by another, the workers can handle the load successfully. If a company adjusts its schedule to account for labor costs, it can ensure a balanced and even work load throughout the day.
Balance of orders issued to previous processes and suppliers. If a plant uses a just-in-time system and suppliers deliver components several times a day, suppliers will have a steady supply of orders. This will allow them to reduce the volume of inventories, and therefore costs, which will be reflected in the cost of production, which means that everyone will benefit from equalization.

The Tao of Toyota Liker Jeffrey

Benefits of One Piece Flow

Creating a flow of single products involves a wide program of measures to eliminate all kinds of hm? yes(losses). Let's take a closer look at some of the benefits of flow.

1. Embedded quality. The flow of one-pieces greatly simplifies the integration of quality. Each operator is also a controller and tries to solve the problem on the spot without passing it on to the next stage. Even if he missed the defects and they moved on, they will be detected very quickly and the problem will be immediately identified and corrected.

2. True flexibility. If equipment becomes part of a production line, our ability to use it for other purposes will be reduced. But the order fulfillment time is reduced to the limit, which means that we respond more flexibly to consumer requests, producing what he really needs. Instead of waiting weeks for the ordering system to deliver the product, we can fulfill the order within a few hours. The transition to a new range of products, which is required by changing consumer demand, is carried out almost instantly.

3. Productivity increase. When work was divided into departments, you thought that this was how you achieved maximum productivity, since work efficiency was measured by the workload of people and equipment. In fact, it is difficult to determine how many people are required to produce a given number of units in high-volume production because productivity is not measured in terms of value-adding work. Who knows what the productivity loss is when people are busy producing excess parts that then have to be sent to a warehouse? How much time is lost when searching for defective parts and repairing finished products? If there is a cell for one-piece flow, non-value-added work such as moving materials is minimized. You can immediately see who is overloaded and who is left idle. It is very easy to cost the value-adding work and calculate how many people are required to achieve a given output. When it comes to converting a mass production supplier to a TPS line, the Toyota Supplier Support Center is able to achieve at least a 100% increase in productivity in every case.

4. Freeing up space in the workshop. When equipment is distributed among areas, significant areas between them are wasted, although most of them are occupied by reserve deposits. In a single-piece flow cell, all blocks fit together and inventory takes up almost no space. If production space is used more efficiently, the construction of new facilities can be avoided.

5. Increased security. An early adopter of TPS in America, Wiremold Corporation has an exemplary safety record and has received numerous government safety awards. However, when the company decided to take on the challenge of converting high-volume production to single-piece flow, it was decided that a special safety program was not needed. The reorganization was led by Art Byrne, a former company president who had studied TPS and realized that one-piece flow would automatically lead to improved safety by reducing the amount of material that had to be moved around the plant. Reducing cargo volume eliminates the need for forklifts, which are a common cause of accidents. The volume of containers that need to be lifted and moved will also be reduced, which means fewer container lifting accidents. If you deal with flow, security improves itself, even if you don’t pay special attention to it.

6. Boosting morale. Wiremold, when implementing lean manufacturing, found that employee morale improved every year. Before the changes, only 60% of employees said in surveys that they worked for a good company. This figure grew every year and in the fourth year of transformation exceeded 70% (Emilani, 2002). The flow of one-piece products means that most of the time people are busy creating added value and can quickly see the fruits of their labor, and when they see their successes, they feel satisfied.

7. Inventory reduction. By not investing capital in inventory that is sitting dead, you can use it for something else. At the same time, you will also save on bank interest, which must be paid for funds frozen in reserves. You will also avoid stock obsolescence.

Rice. 8.3. Disordered flow when combining similar equipment

Rice. 8.4. U-shaped cell for single piece flow

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CREATE ASSOCIATED PROCESS THREAD

IDEAL - SINGLE PRODUCT FLOW

Taiichi Ohno taught that the ideal is a flow of single products. A correct answer on a school exam gets an A. The correct answer is one-piece flow. It turns out that to master lean manufacturing you just need to create a flow of single products. What could be simpler? In fact, Ohno taught that creating a one-piece flow is extremely difficult and its use is not always practical. He said:

In 1947, we lined up the machines in parallel lines, and in some places arranged them in the shape of an L, and tried to put one worker on three or four machines according to the processing sequence. Although there was no talk of increasing the pace of work or overtime, the workers desperately resisted. The machine operators did not like that the new layout required them to combine professions... In addition, other problems were discovered. Once it became clear what kind of problems these were, I was able to decide in which direction to move. Although I was young and energetic, I decided not to push for immediate, radical changes, but I was patient.

It learned to be patient and careful in reducing waste while always moving toward one-piece flow, also called “continuous flow.” Products go through sequential processing steps, waiting times between operations and product movement paths are minimized - all this ensures maximum efficiency. Flow reduces overall production cycle time, speeds up cash flow and leads to improved quality. However, Ohno understood that the flow of single products was very vulnerable.

Attempts to create continuous flow lead to the identification of problems that impede flow. Essentially, to create a thread, have to solve problems, and this leads to reduction of losses. We often compare production to a ship sailing through a sea full of underwater rocks. High water levels, like high reserves, hide rocks, i.e. problems. But if the level of water and reserves drops, the ship can crash in no time, hitting the rocks. Most operations have many pitfalls, and it is natural that we try to keep enough inventory, which hides problems.

Ohno discovered that if inventory levels were reduced, problems came to the surface. People have to solve them, because otherwise the production system will stop. This is not bad as long as the problems are not too severe and people are able to optimize the process, preventing the same problems from occurring again. Ohno also realized that this required a minimum level of system stability, otherwise reducing inventory would only lead to a loss of productivity, as we saw in Chapter 4.

Linking two or more processes into a continuous flow makes any problem more acute and requires immediate resolution. A connected flow across an entire enterprise means that unless the problem is effectively resolved, it will stop. All enterprise, and maybe several enterprises. Think about how important equipment readiness, availability work force and material supplies, if in the event of any malfunction thousands of people will be forced to stop working! This happens on Toyotas from time to time. Since all processes are connected together, a problem with one of the main components leads to the shutdown of the entire plant within a few hours. I

Many organizations believe that such production stoppages are unacceptable. Those who stopped production have a direct route to the labor exchange. However, Toyota views this situation as an opportunity to identify weak spots system, overcome identified deficiencies and strengthen the system as a whole. Such a paradoxical way of thinking baffles those who are accustomed to thinking only about financial results. The Toyota Way suggests that by viewing failures as opportunities for improvement, you can significantly improve your performance. long term. The traditional way of thinking, on the contrary, is based on the assumption that success is possible only when failures do not occur at all.

So the goal is not to compromise performance. A smart approach requires preparing to create flow by addressing the underlying problems, and then moving forward in a meaningful and purposeful manner, starting with planning and developing a problem-solving discipline. As the process improves and is reproducible, further leveling is carried out, within which the control parameters are made even more stringent, which allows the next layer of problems to be identified during the next cycle of continuous improvement.

WHY FLOW?

Most often, implementation failures stem from the mistaken belief that success is rooted in the application of lean tools (for example, creating a cell). We often arrange visits for our clients to lean factories, sometimes to Toyota plants, and it can be very interesting to hear what they take away from such excursions. They are usually impressed by cleanliness, order, discipline, thoroughness and people focused on their work. But when they see something that they can immediately apply in their own enterprise, their eyes literally light up.

One day during a tour of a lean facility, someone noticed that next to each cell there was a small cabinet with supplies and the cell leader wrote out the materials as needed. To replenish the stock of, say, plastic gloves, a kanban system was used. Our “industrial tourist” was burning with impatience to return to his factory and create a similar ordering system Supplies. Unfortunately, he noticed only one tool and lost sight of the interconnectedness and interdependence of the entire set of elements. For successful creation The lean process requires a good understanding of how a particular tool works to achieve a goal. It is unlikely that an experienced mechanic, when repairing a car, will first take the first wrench he comes across and then start looking for a suitable nut for it. First of all, he will determine the essence of the problem and the measures that will eliminate it, and only then will he select the tools necessary for the job.

And yet, we often see organizations reaching for tools before understanding what is happening. “We're going to implement visual controls,” managers say, as if it were a puzzle piece that needs to be slotted into place. The key to long-term success is a shared effort that includes reflection. basic principles or concepts, effective strategy, which presupposes the mandatory implementation of this concept, the methodology for applying this concept, lean manufacturing tools for implementing the chosen method and an effective approach to measuring the overall result.

We believe it is useful to think about the relationship between unit flow and cost reduction in the context of a broader model, as shown in Figure 1. 5-1. Instead of jumping headlong into creating flow and a pull system, stop and think about what goal you want to achieve. This model emphasizes the connection between the core principle of lean manufacturing - identifying and eliminating costs - and the method of achieving this goal - reducing batch size, which moves closer to creating a continuous flow. Creating continuous flow is often considered the primary goal of building a lean process, but in fact, creating continuous flow is aimed at eliminating waste in all operations. The primary task is to eliminate losses.

When material and information flow in a continuous flow, the amount of waste in the process is reduced. This is true by definition. Significant volume losses will not allow the creation of a flow of material or information. However, what is happening also has a deeper meaning. Maintaining a continuous flow between processes ties them together and one process becomes dependent on the other. This interdependence and the limited volume of buffer stocks make any flow disruption more serious.

Anyone who has tried to create a one-piece flow (and it really is not an easy task!) understands that exacerbating problems can be a big advantage... or a huge detriment. In the absence of effective system support, exposing problems is tantamount to a death sentence. This is why lean manufacturing tools are so important: they can create a structure that will help you achieve success and avoid failure. Lean manufacturing tools promote the creation of both support systems and control methods that allow you to adequately respond to identified problems.

LESS IS MORE: REDUCING LOSSES BY CONTROLING OVERPRODUCTION

True one-piece flow means that each operation produces only what the next one currently needs. If the next operation is stopped for some reason, all operations preceding it are stopped. It would seem that what could be more unpleasant than stopping. However, the alternative to stopping work is overproduction, where we produce more or faster than the next operation needs. Toyota considers overproduction to be the most dangerous of the seven types of waste, since it gives rise to the other six (excess inventory, unnecessary movements, unnecessary processing, hidden defects, etc.). This allows you to understand how less can become more (less means fewer parts produced in individual process steps, more means increasing the proportion of value-adding work in the overall process). Below is an example typical situation overproduction, which negatively affects the satisfaction of consumer requirements.

Case Study: Overproduction Control Improves Operational Availability

Standing in a circle and observing the production line revealed that overproduction is extremely common. Product stocks accumulated along the line - products lay in stacks. All workers were constantly busy, but we noticed that operators spent a significant amount of time storing excess product. When there was no work, most operators tinkered with inventory (the result of overproduction). Comparing cycle time with takt time showed - and this was not surprising - that the duration of all operations was less than takt time, which meant that operators had extra time. Since they were not performing other value-adding tasks, they spent that time overproducing and handling inventory.

In addition, observation showed that as a result of overproduction in the next operation (consumer process), additional time is spent moving and unpacking products arriving in large quantities, and this creates additional inconvenience. The cycle time of this operation fit within the takt time, however, due to extra work The total time required to move and unpack products exceeded the takt time, and as a result, the operation could not meet customer requirements within the planned working hours. In this case, the excess losses were created by the supplying process, and Negative consequences detected by the consumer process.

We asked operators who were performing previous operations to stop and stand without causes, rather than continuing to work despite the fact that the next process is swamped with excess material. Of course, the operators felt very uncomfortable, because their superiors instilled in them that it was unacceptable to stand and do nothing. The importance of this approach is well understood at Toyota, as it allows everyone to see and understand the scale of the opportunity. When the picture is not foggy hectic activity (overproduction), everyone sees how much time is wasted.

When did the operators start working? less(manufacture fewer parts), the loss of time for consumer processes was reduced and they could spend it on promotion productivity. Controlling overproduction has significantly increased the overall yield of the process as a whole.

Of course, we were not happy with the operators standing around doing nothing - waiting is also a type of loss. Next, it was necessary to decide how to eliminate additional losses in performing these operations and, by combining operations, to achieve “full utilization”. Analysis of standardized work helped solve this problem (an example of such analysis is described in Chapter 4).

Case Study: Creating Flow in Aircraft Repair at Naval Air Station Jacksonville

Repair work have even greater variability than production. It is possible to understand what the problem is and how long it will take to fix it only after a thorough examination. Therefore, repair is often viewed as a craft job that requires the collective participation of a whole team of specialists. It feels like a throwback to the days of yore, when a team of craftsmen gathered around a booth to assemble a Model T Ford.

The US Department of Defense carries out a huge amount of work to repair and modernize ships, submarines, tanks, weapons systems and aircraft. These are all very large objects. Aircraft repairs almost always need to be done urgently. If a fighter is in a repair hangar, that means there is one less aircraft ready for battle.

The largest facility in Jacksonville, Florida, is an air base that repairs U.S. Navy aircraft. Aircraft periodically come in for major repairs, and some of them also have serious defects that require special treatment. Since the aircraft needs to be adjusted and returned to service as quickly as possible, as soon as it arrives at the base, it is rolled into a hangar and qualified personnel get to work, dismantling the aircraft into parts. The skin is removed from the aircraft, individual components are repaired or replaced, one part after another is checked, and finally it is reassembled, after which the aircraft is again ready to take off. There is another incentive to complete the work immediately - payment. The base bills hourly for aircraft repairs.

Although aircraft repairs at the air base have been carried out for decades, the need to reduce the time an aircraft spends on the ground remains very pressing. It happens that aircraft are taken out of production, which leads to a reduction in the fleet. If aircraft sit in a repair hangar for too long, the time to complete planned combat missions is reduced. The Naval Air Systems Command has launched the Air Speed program to speed up the repair process for aircraft across the Navy's fleet.

Two aircraft were received in Jacksonville for repairs - RZ and F18 fighters. Repair work was carried out in different hangars. Hired consultants worked at the base as lean manufacturing experts. They supervised the work of teams mastering lean manufacturing and helped them acquire the relevant knowledge and skills. Independently of each other, experts analyzed the current situation for RZ and F18 and came to the same conclusions:

Each aircraft was considered as unique project, and the technicians who repaired it did not use any standardized process.

The work area around the aircraft was cluttered with tools and parts that were lying around haphazardly.

Maintenance workers spent an inordinate amount of time walking around searching for the right tools, parts, and supplies.

After disassembling the aircraft, the parts were placed in boxes and sent to storage facilities (for this, for example, automated system storage and transportation), and when the parts are returned from the warehouse so that the aircraft can be reassembled, a lot of time is spent disassembling the boxes and finding the necessary parts. Parts often went missing because they were used to repair another aircraft. Repair of several aircraft is carried out simultaneously, and when for some reason (for example, a shortage of basic parts) work on one of them was suspended, the mechanics were transferred to work on another aircraft.

There was a belief that the arrival of aircraft for repairs was unpredictable and it was impossible to draw up a plan that would ensure a stable, leveled volume of work.

Value stream mapping revealed a huge amount of waste in existing processes. Maps of the future state were developed, where solutions of a uniform nature were proposed for all aircraft:

The process of disassembly, fault analysis, repair and assembly should be divided into clear steps.

It is necessary to create a production line for each repair area, each of which must perform a certain type of work.

It is necessary to bring the line operation into line with the takt time. Analysis of actual data showed that the supply of aircraft is much more stable than is commonly believed.

A standardized work procedure should be developed for each site. I

To stabilize the process and reduce the amount of non-value-added walking around searching for tools and parts, the 5S method should be applied.

It is necessary to create a “stationary” so that if work on one of the aircraft is suspended (for example, due to waiting for parts that take a long time to manufacture), the aircraft can be placed in it and the overall flow will not be stopped. Management must know the process thoroughly and stop the practice of accepting aircraft at any time. It is necessary to keep the volume of work in progress under control, not allowing the number of aircraft to exceed the number of repair areas on the production lines (this will be discussed below).

The work area was divided into work stations. This presented a technically challenging task of moving the aircraft from one place to another. At some point, the plane was completely disassembled: the wings and landing gear were removed. The F18 fighter was a new aircraft for the base, and it was possible to purchase a rig for it, which was a huge contraption on wheels that allowed the disassembled aircraft to be moved from one repair area to another. However, it was impossible to do this with the RZ fighter, and in this case it was decided to create a “virtual production line.” Maintenance crews approached the aircraft at set intervals to perform a specific type of work. This meant that they had to take with them the tools and materials needed for the operation in question.

To debug individual components of the system, several practical kaizen workshops were held. Among them were seminars on 5S, during which the work area at the base was redesigned, everything had its place and standard places were marked. Practical material flow workshops helped develop a more streamlined approach to aircraft dismantling. Now the aircraft parts were placed in special boxes, and when they were returned from storage, they were all as they should be. Hazardous materials were placed on carts in containers. All containers, parts and materials were replenished using pull systems By to the extent that cash reserves are used. Started off slow and difficult process detailed analysis of each operation to develop standardized work procedures and bring the pace of work of each section in accordance with takt time.

The RZ fighter is a fairly old model that will soon be withdrawn from service. The Navy decided to reduce the fleet of these aircraft by 50 units, from 200 to 150, with the condition that about 120 of these aircraft were constantly in combat readiness. To ensure the combat readiness of such a number of aircraft, it is necessary to reduce the time Maintenance. Since these aircraft have experienced fuel system problems and fatigue due to aging, the need for additional mechanical strength testing makes the repair requirements more stringent and therefore further complicates the work, which must be completed under very tight deadlines. It could be said that from a Navy perspective the situation was a crisis, but from a Lean perspective it was an ideal opportunity to demonstrate the value of eliminating waste.

Before additional requirements for testing and work were imposed, the repair of such a fighter took 247 calendar days. To constantly maintain 120 aircraft in combat readiness, it was necessary to reduce the cycle time to 173 days, i.e. by 30%.

The official development of lean manufacturing under the guidance of an experienced consultant 5 began in April 2004. Less than a year later, by February 2005, after value stream mapping and numerous hands-on kaizen workshops, the results shown in the table became visible.

It is one thing to establish a process, another to manage it. This skill required a completely different approach to management than the one to which current managers were accustomed. It was necessary not only to deal with a variety of tools - 5S, standardized work, problem solving, etc., but also to stop attempts to accept an excessive number of aircraft. The last task was one of the most difficult. The basis of the flow concept is a fixed amount of work in progress. The line has a certain amount of work areas and a “stationary”; there are no other places for aircraft in the hangar. When the repair of one aircraft is completed and it leaves the hangar, the next one can be accepted.

This contradicted all the guidelines of the managers and the accepted system of indicators. First, management was convinced that if the aircraft remained outside the hangar, it would take longer to repair it. The adoption of lean manufacturing has proven just the opposite - lead times are significantly reduced when working on a fixed number of aircraft. Accept

another plane is possible only after space at the beginning is freed production line, and until then it is better to leave the plane outside the hangar. Secondly, it used to happen that workers were left idle because all the work on repairing the aircraft in the hangar had been completed. Managers were wary of this situation because they were judged by the hours the production workers worked, and it was for these reasons that support labor was provided in the hangars. At times, when a new aircraft arrived for repairs, one of the higher management ordered it to be accepted for repairs. The lean consultants had to use all their influence to get the plane out of the hangar. It was a real culture clash.

The Navy was amazed at the results. The Jacksonville base soon became a favorite excursion destination. staffing The Navy, Air Force, Navy Aircraft Depot, and other organizations that wanted to see true lean manufacturing in action. The airbase has become a role model. The most surprising thing, perhaps, was that the aircraft were repaired on a line resembling an assembly line. Creating a production line with a given takt time allowed for continuous improvement, eliminating waste and ensuring balanced operation of the line as a whole. Chaos and disorganization began to replace control and stability.

STRATEGIES FOR CREATING A CONNECTED PROCESS FLOW

Table 5-1 presents strategies for creating a cohesive process flow, as well as commonly used basic and supporting tools.

Table 5-1. Strategies and Tools Used in Creating a Coupled Process Flow

Strategies	Basic Lean Manufacturing Tools	Supporting Lean Manufacturing Tools
* Continuously eliminate waste* Identify problemsMake problem solving a necessity Create related processes, ensuring their interdependence* Identify weak links in the flow and strengthen them	Workplace/ Cell layoutPull MethodsClearly defined customer/supplier relationshipVisual control	KanbanKanban boardsSupermarketsFIFO queuesProblem solving

lean manufacturing. Depending on the circumstances, you can use both those tools that were already used at the stabilization stage and additional ones. As for the above-mentioned goals and strategies, they are all required.

SINGLE ITEM FLOW

The quest to create one-piece flow—the ideal of flow—has become something of a fad, with many companies failing to achieve this level. Creating a one-piece flow is an extremely complex task that requires a well-established process and special conditions. Often it is simply impossible to create such a flow; in other cases, before you can reach this level, you need to go through many turns of the spiral of continuous improvement.

As an analogy, imagine a line of people passing buckets of water at a fire. At one time, only one bucket is passed from hand to hand. This is how a flow of single products is formed when an item is transferred from one participant in the chain to the hands of another. This requires perfect coordination among all participants in the chain. Having passed a bucket to his friend further down the chain, the chain participant immediately accepts the next bucket from his neighbor on the other side. If the rhythm of the movements of two participants in the chain is not coordinated, one of them will have to wait for the other, and this is one of the types of losses. Achieving flawless coordination is extremely difficult and is only possible with clearly agreed-upon cycle times. If anyone in the line hesitates a little or makes a mistake, it will unsettle everyone else and the house will burn down.

On most manufacturing enterprises In single-piece flow systems, one piece is placed between work stations, and thus the slight variation in individual worker cycle times does not create waits. However, even at this level, the balance of cycle times of individual operations must be extremely high. The presence of additional products between operations allows you to work with a higher variation in cycle time in different operations, but this approach leads to an increase in overproduction, which represents losses. This is a real puzzle. Reducing buffer stocks between operations reduces overproduction, but increases losses due to unbalanced work cycles.

Moving along the path of creation lean processes, you should stick to the golden mean. Along with resolving a certain number of pressing problems that cannot be ignored, care must be taken to ensure that insurance is in place until the reproducibility of the process allows the process steps to be more closely aligned. The spiral model of continuous improvement discussed in this section, ensures the reproduction of this cycle. Incremental equalization requires reducing the amount of buffer stock throughout the flow, which leads to the identification of increasingly smaller problems. This again causes instability, and the spiral makes a new turn, taking it to a new level efficient work in more severe conditions.

CLUE

When is a problem not a problem?

At Toyota, managers are required not only to stop work and fix problems, but also to constantly and vigilantly identify potential problems before how they arose. In a well-functioning lean manufacturing environment with continuous, connected flow, there are certain signs that the system may be failing that serve as “warning indicators” for everyone to see. The ability to identify problems before they occur allows managers to take proactive corrective action and thus prevent failure. Note: Toyota does not believe that failure is always a bad thing.

In essence, the absence of failures in the system is considered an indicator of excess losses. The inability to predict when and where failure will occur is an indicator of an ill-designed system.

IMPORTANT CRITERIA FOR THE PRESENCE OF FLOW

As we said in the previous chapter, a number of conditions are necessary to create an uninterrupted flow. Typically, these criteria are met during the stabilization phase, but we will repeat them again.

The primary task of stabilization is to ensure stable reproducibility, at least during the day. The process must meet customer requirements on a daily basis.

Sustainable reproducibility requires stability in resources—people, materials, and equipment—and their availability. Failures in resource availability are the main obstacle to thread creation. It is necessary to use methods that ensure the availability of resources (this is not just about increasing the volume of resources, which increases costs).

An indispensable condition is the reliability of the process and equipment. In the early stages, it's about larger issues such as downtime and changeovers, but as the process matures, attention should also be paid to smaller ones, such as ease of use.

The work cycle time must correspond to (be equal to) the takt time. If operations have different cycle times, waiting and overproduction occur.

TRAP

Trying to prematurely create one-piece flow is risky.

We've seen company representatives come back from lean classes excited about the flow of one-offs and immediately get to work creating cells. However, they soon discovered that the cell was idle most of the time, and came to the conclusion that lean manufacturing did not work in the real world. The phenomenon that gave rise to their problems is called “piece-through output.” Let's take a situation where five machines are lined up in a flow of single products and each of the machines is faulty 10% of the time, in other words, operational 90% of the time. The time that the cell remains in working condition will be:

0.9 5 =0.9 X 0.9 X 0.9 X 0.9 X 0.9=59%!

Solution: Store a few units of work-in-process between operations, carefully considering where exactly such buffer stock should be provided. This will increase the productive operation time of the cell by up to 90%.

Specific situation: danger of creating one-piece flow for processes with short cycle times

The transition from traditional batch and queue processing methods to material flow has become a fad. With most fashion hobbies there are extremes that cause negative consequences. In many cases, being carried away by the flow of single items leads to a decrease in performance indicators. Single piece flow may not be the most efficient method for short cycle times (30 seconds or less).

The objective of one of the practical kaizen workshops was to create a flow of single items during an assembly operation. The product was a fitting, the assembly of which took 13 seconds. The takt time based on customer demand was 5 seconds. The work was distributed between three operators and created

cell (another fad) to transfer product from operator to operator, which is necessary to create flow.

Several months later, the site was struggling to meet customer demand, and operators were again stockpiling product runs between operations. As the cycle ratio graph in Fig. 1 shows. 5-2, the cycle times of the operators were not balanced properly.

This imbalance is the main reason why operators deviate from the “no batch” rule. If operators deviate from the original plan, this clearly indicates a failure of the plan. Unfortunately, usually in such cases, management tries to force subordinates to follow the rules and maintain flow, rather than stopping and reflecting on the shortcomings of the process. Learn to perceive deviations made by the operator as a positive phenomenon! Stop, observe and identify the real cause of the problem. Eliminating it will benefit the process.

Even if the cycle times are properly balanced and a smooth flow is created, there is another less visible problem. Trying to create a flow of one-piece items with very short cycle times generates a high waste ratio, which is calculated as the ratio of waste to value-added work. Here's why this happens: in any workflow, there is a certain amount of unavoidable waste, such as taking a part and putting it in the next operation. These losses can be minimized, but in the best scenario, one movement will take from half a second to a second (pick up and put down). Suppose the conditions are optimal, and this operation takes

second during the work cycle - half a second to pick up a part, half a second to put it down. We get a second of extra movements during the cycle. If the cycle time is five seconds, one second spent moving material is 20% of the total cycle time! If the operation is carried out in 3 seconds, this figure will exceed 30%. This is a huge percentage of losses. However, such waste is often overlooked because it is assumed that because material flows and operators are constantly moving, we have lean manufacturing. As you can see, this is not at all true.

This operation can be improved by not breaking the job into many different operations in an attempt to create flow, but by having two operators take the part and process it from start to finish. This will reduce the time by two seconds, resulting in the job being completed in 11 seconds (Figure 5-3). The net time spent processing one product is 5.5 seconds (two people working simultaneously produce two products every 11 seconds, 11 divided by 2 = 5.5 seconds per unit), which exceeds the takt time by 0.5 seconds. The next step is to reduce other waste and simplify the operation so that it can be completed in 10 seconds or less and a unit processed in 5 seconds or less.

In this example, creating a thread resulted in a 33% performance hit (three operations instead of two). Moreover, on the scale of the entire value stream, this operation was a small fraction of the total material flow. There were far greater opportunities to create flow and reduce overall cycle time by linking activities in other areas using the pull methods described below.

PULLING

The terms "pull" or "pull system" are often confused with "flow". It should be understood that pull, like flow, is a concept. These two concepts are related, but do not mean the same thing. Flow is the state of a material as it moves from one operation to another. Pull determines when material movement occurs and who (the consumer) dictates the need for this movement.

Many people do not understand the difference between push and pull methods. Some people mistakenly believe that they are engaged by pulling as the material continues to flow. However, flow can exist without pulling. Pulling differs from pushing in three main ways:

1. Certainty. The presence of a clear agreement between the supplier and the consumer, which sets the limit values for the volume of production, assortment and sequence of production.

2. Consolidation. Objects shared between two named parties must be assigned to them. This applies to resources, location, storage, containers, etc., as well as the overall timestamp (takt time).

3. Control. Simple control methods using visual warnings and physical restrictions as agreed.

In a push system, there is no agreement between supplier and customer regarding the quantity of work to be delivered and the timing of delivery. The supplier works at his own pace, guided by his own work schedule. The material is then delivered to the consumer, whether the consumer requested it or not. The location of the material is not defined, and it is placed wherever there is free space. Since there is no certainty of mutual obligations and location, it is impossible to develop a clear method of control, since it is not clear what and how to control.

Of course, the situation is partly controlled by expediting dispatch, changing the schedule and rearranging people, but this only creates additional losses and variation. Of course, one could argue that the terms of the parties' contract are determined by the schedule. All processes operate according to a single schedule. The schedule may indeed be uniform, but this still does not ensure coordinated actions.

A pulling system is a collection of several elements that support the pulling process. The Kanban signal is one of the tools used as part of a pull system. Kanban is just a method of communication, it can be a card, an empty box, a cart or other signal with which the consumer says: “I am ready to take the next portion.” In addition, there are other elements, including visual inspection and standardized work. If the three named elements of the pull system function properly, there is a “linking” between the supplier processes and the customer processes. The three listed elements determine the parameters of “linking” and how close and stable this connection is.

The specific situation described below illustrates by example the three requirements that a pull system must meet. These are most easily illustrated and conceptualized in a single-piece flow, but the same principles apply to any variation and in any situation, whether producing a wide variety of products in small batches or working in batches where the volume of output between processes is much larger. We took the most easy-to-understand example, but the principles mentioned are applicable in any conditions.

Case Study: Creating a One Piece Flow

Operation A supplies parts to Operation B, which supplies parts to Operation C.

Is there a clear contract with specific terms and conditions?

Yes. We said that this is a flow of single products, and this very definition implies specified quantity. (As we will see later, implied definitions are not enough.)

What are the terms of the agreement?

Supply of products one at a time.

At what point does the submission take place?

When is the previous product accepted at the next operation (remember the line of people with buckets at the fire)?

By observing what is happening, we can determine whether the contract is being fulfilled. In Fig. 5-4 we see that operation B does not fulfill the contract and exceeds the specified limit (one product).

How to determine whether a contract has been violated?

The term "unit item flow" implies that there should be no more than one item between operations. THIS IS NOT ENOUGH! The terms of the agreement must be extremely clear and presented in a visual way accessible to everyone form.

What happens if they are not clear and presented clearly?

The contract will not be respected, this will cause deviations (create variation) from the agreed standard (we see that by creating a pull system, we begin to create a structure that supports the next stage - standardization).

How to provide visibility, which will allow Is it easy to control the situation?

Define space for a single product and secure him behind him. Outline this area with tape or paint so that it is clear that only one product is allowed here, and provide the designation with an explanatory inscription so that it is as clear as possible (if the outline of a square is applied to the table, you should add an inscription or symbol explaining what this means). square), as shown in Fig. 5-5.

In addition to visual markings, you can limit the physical space so that only one product fits in a given space. This technique is especially effective when the parts are oriented vertically and can be inserted into a special recess, thereby controlling the quantity.

One of the main benefits of flow and clear agreement is that the consequences of problems are now made explicit. If in the example above, the means visual control indicate a constant deviation from the terms of the contract, which means another problem has arisen.

Deviation clearly indicates that there is a hidden problem that needs to be solved. In such a situation, managers often complain: “They know perfectly well what to do, but we can’t get them to work as expected.” Many managers make the mistake of blaming the operator for not following the rules when in fact the operator's actions are compensating for a problem that needs solving. Stop and stand in a circle to determine what deficiency the operator is compensating for.

There are usually two reasons for this situation. First, you need to make sure that the terms of the contract are presented visually in a form that everyone can understand; secondly, check whether there are additional problems that the operator is forced to work around.

The main reasons for deviations in the operator’s work are:

1. An imbalance in the cycle time of individual operations, which may be caused by normal variations in the volume of work, the skill of the operator, or the cycle time of the machine. Usually the one who deviates from the rules is the one who has extra time.

2. Periodic downtime due to lack of parts (or fear that parts will run out). Operators leave the work area to take over execution additional functions- for example, bring parts or check their quality. Suspension of work due to equipment failures or correction of defects.

3. Intermittent suspensions due to difficulties in operating equipment or fixtures, or when performing overly complex operations.

4. Various reasons, for example, the desire to create a reserve in order to gain time for changeover, sometimes the operator leaves the line for some reason, goes for lunch or a break sliding schedule, as well as other reasons of this kind.

In some situations, it makes sense to adjust the amount of work in progress depending on the operation. Single piece flow requires flawless balancing the duration of operations, which is an extremely difficult task. Imagine an operation, such as deburring an injection molded part, where worker time variation is common.

Cycle times will vary slightly each time because most of the work we do is done manually and no one can cycle through it multiple times in the same amount of time (even Olympic athletes can't run the same distance twice). with the same result). This slight variation can cause intermittent flow glitches. Operators do not like to sit idle, and to compensate for the problem, they begin to increase buffer stocks. Increasing buffer stocks is a logical choice to compensate insignificant time variations; however, the volume of build-up should be limited to the standard. In this case, the agreed buffer sizes, compensating for minor time variations, should be no more than two or three units of production.

CLUE

The benefits of an outside perspective

Often communication difficulties are caused by the fact that it is difficult for us

- “j/ realize why others do not understand seemingly obvious things. The point of a standard terms agreement is to ensure that those terms are understood by everyone on the same page. To check how successful you are, find a person unfamiliar with the work area, show him the standard and ask him to explain the essence of the contract. You'll be surprised at how difficult it is to communicate the terms of a contract using visual media!

WORKING WITH COMPLEX FLOW

Looking at a more complex example, we will see that the same concepts are used here as a basis. In our case, three different product models are being produced - 1, 2 and 3 - and we need to provide flexibility that will allow us to produce one of these models at any time. Organization diagram

Suppose Operation C requires the production of Model 2. The operator takes one product from a given place between Operation B and Operation C. According to the terms of the contract, this serves as a signal for Operation B: the empty space is a signal, and when the consumer pulls out the product, this should be signaled the next place is to make a part for model 2. Now the situation corresponds to Fig. 5-7.

Operation B then picks up part 2, which is between operations A and B, which prompts operation A to start making part for model 2. When the job is completed, operation B replenishes the stock between operation B and operation C. The picture now matches Fig. 5-8.

Of course, this is a simplified model, but it does all three necessary conditions and their compliance is supported by visual means. This basic model is applicable to high-volume or low-volume production, or to handling inventory. Its main advantage is flexibility, which allows you to produce any model at any time and quickly switch from one model to another.

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