Column Archive: September 2011

Dear Gemba Coach,

My management wants to build our own version of the TPS (Toyota Production System) house in order to standardize our lean approach. Do you have any advice on how to do this?

Actually, on this specific question, I do: don’t do it. I’ve seen many lean “houses” over the years and just by googling “TPS house” you’ll probably find more. In my experience, such efforts are about implementing lean in the company, not helping the company to become lean – and rarely pay off. There are two main issues to consider when adopting the TPS house: firstly, how and why it actually came up within Toyota and secondly how these concepts translate out of Toyota and in your own organization.

As John Shook has pointed out, one should not confuse the Toyota Production System and Toyota’s system of production: TPS is fairly different from what Toyota actually does on its production lines. It sounds fairly close, you’ll say, and I have to agree.  TPS shows the way to perfection, the True North. Toyota’s system of production is the set of actual practices that Toyota has in place right now – which evolves according to events and local competence. Any Toyota plant is only as good as its plant manager.

The ambiguous term “system” has also caused a lot of lean heartache over the years. Bear in mind that we all tend to interpret what we see from our own pre-existing perspective. Understanding any artifact from the point of view of its creator is often difficult, as can be experienced when we look at any new piece of art or technology. Our traditional industrial perspective is clearly Taylorist. We’ve been brought up to believe that if we design the right process and we apply it across the board, we’ll get the right results. Logically, it’s easy to interpret the concept of “production system” as a set of processes that need to be standardized across all operations. In this mindset, lean means replacing our existing processes by “leaner” processes – and it makes sense to systematize these lean processes in a roadmap, house, manual, etc.

Never-Ending Homework

When Toyota pioneers dreamed up their system, they were working from a very different premise. Their obsession was kaizen, not systematization of processes. From this perspective, a system meant “a set of interrelated activities to improve quality, cost, lead-time, and productivity.” It was NOT a set of actual production processes, but a box of homework exercises that, if practiced assiduously, would lead to improved processes. There is no such thing as a lean process: opportunities for further kaizen can always be found. The activities summarized in the “system” give a clear direction for the next step of kaizen:

1. Customer satisfaction -- Oddly, but quite revealingly, this aspect often disappears from adapted houses. The first exercise to work on in order to become lean is to improve customer satisfaction. To start with this means striving to deliver good parts on time: no quality complaints, no late deliveries. Sure, this can be achieved by holding a inventory and lots of quality inspection, which is exactly what Toyota engineers do when they’ve got a doubt about a process: they put finished goods inventory and add inspection operators, with the explicit aim to kaizen it away. For any company, asking oneself what would customers complete satisfaction look like is the key to getting everything else right.
2. Jidoka -- The jidoka pillar is probably the most original part of TPS and the hardest to understand, because it blends a certain understanding of quality with a vision of the relationship between human work and machine work. To take one aspect of it, the homework exercises are about built-in-quality. No step in the process should accept bad parts, make bad parts or pass on bad parts to the next step. The basic exercise is to stop whenever any defect has been identified (by either the operator or the machine) and investigate until the cause of the defect is found and eradicated. This will lead you first to eliminate human errors, due to not following standardized work, then to work with manufacturing engineering to eliminate causes of defects in the way machines are designed and finally to improve product design so that less defects can occur, at which level one can accurately speak of “build in quality.” There are a number of technical tricks to do so, from andon to poka- yoke, but the main idea is to practice the activity of “stop and investigate at every defect” in order to learn about what causes defects.
3. Just-in-time -- The favorite pillar to most industrial companies, JIT is about learning to deliver exactly what has been ordered exactly when it has been ordered and in exactly the right quantity. The emphasis is on “exactly”; no less, no more.  Now, this turns out to be quite a challenge, because production systems are usually conceived to be kept running (for labor cost and equipment payback considerations) regardless of technical issues or part shortages. Forcing oneself NOT to produce more than immediate demand BUT not to accept to produce late is very demanding and mechanically involves reducing batch sizes and stabilizing processes. THERE IS NO JUST-IN-TIME PROCESS in the abstract. Or, more to the point, every process has its level of just-in-time: month? week? day? hour? You start with what you’ve got, level the plan, reduce the batch size and fight each production loss until you increase your level of just-in-time.
4. Standardized work and kaizen -- Involving operators in designing or redesigning their own work stations has been a Toyota obsession from very early on. Indeed, in the first published paper about TPS, the authors highlighted two major distinctive features of the production system: just-in-time production and respect for humans, meaning that workers are allowed to display in full their capabilities through active participation in running and improving their own workshops. The underlying mechanism to do this is to practice standardized work and kaizen relentlessly.

Housing Bubble

There is not ONE version of the Toyota house, but several according to when and by whom it is drawn. Some place heijunka along with standardized work and kaizen on the base. Others insist that there should be a further basic step of “stability.” The French plant came up with 5S, TPM, and problem solving as a base below standardization and kaizen. Since Fujio Cho formulated the Toyota Way 2001, 10 years ago, some houses now have kaizen and respect as their basic pillars, and so on. I’ve just seen one with “finding waste and problems” at the top and “visual control and flexibility” as the base. All equally correct.

The point is that the Toyota Production System house is Toyota’s – not your company’s, and appropriating is through making your own is likely to 1) not make much sense culturally and 2) induce misunderstandings you’ll later rue. Use the TPS house as a way to explain what lean is about and how Toyota does it, by all means – we certainly all refer to it frequently, but don’t try to design your own – that’s missing the point.

The point of the house is that certain activities can be performed independently of industry or job, whether in engineering, production, purchasing (maybe even sales?), etc. For instance, getting to the next level of just-in-time is pretty much like saying: lose weight by walking faster and exercising more often. Fair enough. The details of how Toyota actually practices this are very industry specific (there’s nothing quite like automotive) and Toyota specific. They can inspire, but copying the results of years of practicing just-in-time or jidoka improvement will NOT deliver anything for your own business. At best, you’ll invest in implementing stuff on the shop floor no one will ever know how to use properly.

On the other hand, it’s hard to fight city hall, so if management wants it, you’re going to have to comply sooner or later. In this case, I’d suggest:

First, try to get the management group to formulate clearly what they want out of their lean efforts – the test method so to speak. For instance, if we take Art Byrne’s list from Wiremold (in Lean Thinking) this would be something like:

• 100 percent on time delivery
• 50 percent defects reduction every year
• 20 percent productivity gain every year
• 20x inventory turns
• a visual workplace utilizing 5S

Getting agreement on something like this and getting this on paper is key to your success and can rekindle the deeper argument of how to become lean.

Second, stay as close as you can to the basic TPS house seen as improvement practices:

• Customer satisfaction must be improved on quality, cos,t and lead-time
• Start with safety and morale
• Just-in-time levels must be improved from month, week, day, hour, minute etc.
• Jidoka must be improved by better visualizing problems and responding right away rather than working around them
• Workstations must be improved by getting operators to standardize and improve constantly how they work.

DO NOT try to fit all tools and practices to help people make sense of the “toolbox.” This is a common mistake and its incomplete, confusing and encourages precisely the wrong kind of thinking.

• Third, as your company is taking its lead from Toyota by creating its own production system, make sure to insist that the “system” formulation is never permanent in Toyota, but subject to rethinking and evolution. The “Toyota Way” was termed the Toyota Way 2001 to explicitly make the point that this was what Toyota thought in 2001 but that it should be seen as a signpost on the journey, not the ending.

The one consistent feedback on translating TPS into other companies is that first, companies pick and choose which aspects they think will work for them, and ignore the others. You can see this easily by comparing how often just-in-time is attempted or written about to how rarely jidoka gets mentioned.

Secondly, firms will “adapt” the tools and principles to make them more palatable to the local culture. Most plant managers will actually argue this point vehemently.

Twenty years experience show that both tendencies are a sure recipe for disappointing, indifferent results. TPS works first because it’s a system, and you can’t ignore a part of it any more than you can choose tables with only the left legs, and secondly it delivers when you adapt yourself to it, not the other way around. This is exactly what Toyota has done, as it continues to struggle to be better at customer satisfaction, just-in-time, jidoka and standardized work and kaizen, and THAT is the example to copy and take heart from.

Dear Gemba Coach,

I’m a manufacturing engineer and since I have started participating in kaizen workshops, I have noticed that production supervisors tend to disconnect some of the poka-yokes we’ve put in place in the machines. When I challenge them about this they argue that operators can’t run production and cope with the complexity of our machines. I am perplexed by this and wondered whether you’d have a comment.

This is not unusual. In several cases, I’ve seen production teams abandon their automated equipment altogether and return to manual assembly processes and end up increasing productivity. There is no right or wrong in the matter, and it’s a question of spending more time at the gemba observing how people actually connect to the machines in order to make good parts.

The three most common situations I’m familiar with are supervisors disconnecting in-built poka-yoke because:

1. The poka-yoke (error-proofing device) is built in such a way that it adds to the operators’ burden in making the part.
2. It’s so strict the machine is stopped all the time.
3. It gives too many false positives that hinder production, or it’s so unreliable it’s down all the time.

People Proof

Just the other day, I was looking at an automotive supplier’s efforts to build a pick-to-light system. In order to make sure the operator assembled various parts in the right sequence (which, they knew, had an impact on quality), they’d rigged the component bins with lights which would indicate to the operator which part to grab next. The engineers had also built in a poka-yoke: an electric cell spotting the person’s hand going into the bin. If the person skipped a part in the sequence, the process would stop, and if the person went into the same bin twice, ditto.

Regardless of how elaborate the engineering system was, the ergonomics of the workstation were unfortunately not so great. Operators had to reach over a conveyor (with the assembled product on it) and to dip into largish containers – which were particularly awkward when they had to grab the last remaining components in the bin. As a result, they had frequent mishaps, such as letting go of the part and having to fish for it again or, in a case of a complex-shaped  component, having to shake the parts to extract one. As a result, the poka-yoke would be triggered and stop the process several times an hour, which got on everyone’s nerves (they had to call the supervisor and document the stop and so on.) There are easier methods of checking that the operator has grabbed the right part, such as asking them to push the light as they go. And these methods assume that people work hard at making good products rather than, as many engineers assume, that the equipment has to be people proof.

In a case of the second instance, an electronics company I know decided it had to tackle seriously its quality problems. So corporate issued an instruction to reprogram the machines with poka-yokes so that they’d stop at the first defect as opposed to all the varied rules they used locally (three consecutive defects, five defect in an hour, etc.). Asian plants reacted immediately, and chaos erupted in many areas where the process was really not under control. As a result they stepped back and planned a more layered approach, distinguishing machines with stop-at-defect (green sticker) and not-stop-at-defect (red sticker). In Europe, as can be expected, people went at it more cautiously, as the contradiction between stop-at-defect and hit capacity appeared starkly: don’t try it on an unstable process with capacity constraints. On the whole it has to be said that in this case the stop-at defect campaign had spectacular results, decreasing complaints by 30% globally.

Killing Quality

Stop-at-defect is the test to see that you’re serious about quality. Without stop-at-defect, you can’t see the context of the problem when it occurs, and investigation happens too late – it is said that in murder investigation the probability to catch the killer decreases exponentially with the time it takes for the investigators to get on the scene. But stop-at-defect is first and foremost a social challenge. For it to succeed, you need a social structure ready and able to cope with it. If the frontline management is not primed and keen to investigate when the process stops, chances are they will disconnect the poka-yokes in order to run production smoothly, and trust to final inspection.

Finally, some of the poka-yokes manufacturing engineers dream up can be over-engineered or just too complex for the job. Cameras, for instance, are notoriously fickle and require lots of imagery software and computer crunch power to spot defects, particularly when there are variations on how the part is presented. In one such case, the supplier received numerous complaints from the OEM because of misplaced labels on the part. Since the label doesn’t do much functionally, no one at the supplier worried about it overmuch until it became a serious management issue. After many misunderstandings it was finally discovered the OEM has a poka-yoke reading the label on the part for traceability. Without the correct label, the assembly process would stop. In fact, if the label was slightly misaligned or misplaced, the assembly equipment would stop.

Lines with overly complex poka-yoke devices tend to lose much productivity by having operators simply run the part through the detection device again until a part would be consistently stopped. Not surprisingly, production management can be tempted to simply disconnect the poka- yoke in order to run the line.

Make Machines Talk

Poka-yokes are one of the tools in a lean system’s jidoka pillar. Jidoka is one of the least studied (and as a result the least known) aspects of the Toyota Production System and many experts argue that it is also the hidden part of the iceberg: stocks reflect variations and leaning a process to carry less inventory requires a robust methodology to solve technical problems.

Jidoka’s translation in plain English is complex as the Japanese kanji meanings are complex and very nuanced, open to a wide scope of interpretations. In the early days it was translated as “autonomation: automation with a human touch,” which, I don’t know about you, but I don’t find very enlightening. Two key aspects of jidoka are:

1. Built-in-quality: stop rather than pass a defect forward.
2. Separate human work from machine work (http://www.toyota-global.com/company/vision_philosophy/toyota_production_system/jidoka.html).

Poka-yokes are an essential part of jidoka inasmuch as they allow both detecting defects and separating human work from machine work (no need for a person to keep watch on that part of the process) – but if, and only if, they actually help to visualize or highlight problems. The essential idea is to “make the machine talk to the operator” rather than make the machine operator proof. Toyota’s current definition of jidoka is to drive daily improvements by:

1. A machine detects a problem and communicates it.
2. A situation deviates from the normal workflow.
3. The line is stopped.
4. Manager/supervisor removes the cause of the problem.
5. Improvements are incorporated into the standard workflow so that good products can be produced. The emphasis is on machines detecting problems by themselves, and then humans reacting to it and solving the problem.

In response to your question, this means that the best poka-yokes are part of a kaizen process rather than imagined ex nihilo by manufacturing engineers. Good poka-yokes should:

• Not hinder the operator in any way. Separating machine work from human work means that the machine can produce the part on its own while the person is dealing with the next step of the process. If the poka-yoke imposes on the operator to slow down or backtrack on the process, it’s the wrong solution.
• Identify and stop bad parts. There are prevention devices and detection devices. The ideal is to have prevention devices which stop the operator from making a mistake or stop a nonconforming part from progressing in the process. In many cases, this is hard to do so people build all sorts of detection devices – which is dangerous when the detection technology becomes too complex and not reliable enough.
• Give quick and specific feedback. The whole point of a poka- yoke is to be able to kaizen the process by eliminating the cause of the mistake. The purpose of the poka-yoke is to give the operator immediate feedback on what is wrong where, and stopping the equipment so that the person can safely inspect the various operating conditions and find out what’s wrong and fix it rather than run in degraded mode. For instance, make sure the defective part has to be taken out manually in order to inspect the process and analyze what went wrong.
• Be cheap and simple. Any device adds cost to the process both in terms of investment and operator labor. Cheap and simple devices can help the operator to do a better job, but unfortunately many poka-yokes I see are too elaborate and both costly and demanding for the people who have to build parts every day.

In fact, I believe you’re asking exactly the right question and are already on the path to solving it yourself. The ideal poka-yoke is a device invented by an operator in the course of doing kaizen. For instance, in one assembly process where they had to switch from one bin to the other according to variants, the operators simply covered the redundant part bin to avoid dipping in the wrong one. Or a simple modification of a fixture so that the part can’t be wrongly placed, and so on.

If you’re involving yourself in kaizen, you’ll probably discover that people are right to disconnect the poka-yokes that hinder them, but also that when they’re asked the right questions, operators can come up with very clever ideas to mistake-proof the process. The operational answer to your question would be to have manufacturing engineers to kaizen similar processes before designing the new machines so they understand the true purpose of poka-yokes from the operators’ perspective rather than as feats of engineering