Technology

Mar 3 2013

From Ybry charts to work-combination charts

Ybry chart used on French railroads in 2013
Ybry chart used on French railroads in 2013

This is a screen shot from yesterday’s evening news on the France 2 channel, part of a story about TGV high-speed trains used on regular tracks to bring vacationers to ski areas. The TGVs, of course run at regular speeds on these single line tracks and must stop at sidings to let regular trains through in the opposite direction. In an earlier post, I discussed the charts invented by Charles Ybry in 1846 for railroad scheduling, and this newscast shows that they are still used in railroads today. Besides railroad scheduling, they are also used in the management of multiple, concurrent projects, and  I believe they were the basis for Toyota’s work combination charts.

The x-axis is time; the y-axis, position along the line. On the chart, the downward lines represent trains going down the line; the upward lines, trains coming up the line. When and where the lines cross, trains cross, and there must be a siding available. The news story had the TGV pilot call in his position on a siding to a control center in Chambéry where the chart was displayed. On the high-speed TGV lines, the signalling is all electronic, and the system automatically knows where the trains are; when you run a TGV train at reduced speed on a regular line, however, it seems that the driver has to report what happens the old-fashioned way.

I learned about these charts in Edward Tufte’s Envisioning Information, where he describes them as a special case of a “narrative of space and time.” Among the examples he gave were a similar railroad scheduling application from Switzerland 80 years ago and the development of Wagner’s operas over almost 50 years in the 19th century:

Trains running up and down between Neuchatel and Chaux de Fonds in Switerland in 1932
Trains running up and down between Neuchatel and Chaux de Fonds in Switerland in 1932
Development timeline of Wagners operas from 1835 to 1892
Development timeline of Wagner’s operas from 1835 to 1892

Work combination charts are a tool to design and communicate about production jobs that require operators to perform a sequence of operations on multiple machines that operate automatically between visits. This is a Japanese example of such a chart:

A Japanese work-combination chart example
A Japanese work-combination chart example

The concept looks similar, doesn’t it? I found this chart particularly useful when you need to plan the activities of more than one operator, as in the following example:

Work combination chart for machining operations
Work combination chart for machining operations

In the Legend, “Manual In” refers to time spent by the operator on the machine with it stopped; “Manual Out,” time spent on the machine while it runs.

To this date, in the US, this powerful technique is far from enjoying the popularity it deserves. It is generally perceived as “too complicated” and I still don’t know of any software tools that fully support it. In designing jobs that involve interactions between human and machines, however, the consequence of not using it is leaving about 50% of the potential productivity improvement on the table. It may take a project team an extra day to do it, but the result is achieving a 40% productivity increase instead of 20%. Details are discussed in Chapter 7 of  Working with Machines.

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Toyota plant in Ohira Miyagi

Feb 26 2013

New assembly methods at Toyota

Toyota’s latest plants in Ohira, in Japan’s Miyagi prefecture and in Tupelo, Mississippi, feature new approaches to assembly. According to press reports, the Miyagi plant is small, with 900 employees making 250 cars/day for export to the US, with a plan to double output and employment. It was designed to require a minimal investment and be easy to change. The plant started operations shortly before the Fukushima earthquake and, even though it is the Northern part of Japan that was most affected, it resisted well and was able to resume operations about six weeks later.

This is how Barry Render described it:

“The Miyagi factory is designed for advanced low-volume, hyperefficient production, with 1/2 the workers and 1/2 the square footage of Toyota’s 16 other plants. Inside, half-built Corollas and Yaris sit side-by-side, rather than bumper-to-bumper, shrinking the assembly line by 35% and requiring fewer steps by workers. Instead of car chassis dangling from overhead conveyor belts, they are perched on raised platforms. This is 50% cheaper, and also reduces cooling costs by 40% because of lower ceilings. Finally, the assembly line uses quiet friction rollers to move the cars along. The rollers use fewer moving parts than typical chain-pulled conveyor belts.”

Toyota is not providing details, but I have been able to glean some information about it from the press and Barry Render’s blog, on the following features:

This is followed by a few conclusions.

Side-by-side assembly

Side-by-side assembly at Toyota Miyagi
Side-by-side assembly at Toyota Miyagi

I have seen side-by-side assembly at the Volvo Bus factory in Turku, Finland. In the picture of the building below, bus bodies are assembled in the hall on the left, side-by-side under they are mounted on a chassis and move forward on their wheels, laid out front to back in the hall you see in the background.

Volvo Bus assembly building in Turku, Finland
Volvo Bus assembly building in Turku, Finland
Volvo bus main assembly flows
Volvo bus main assembly flows

The ratio of width to length  is more favorable to this arrangement for buses than for cars. A straight assembly line with a front-to-back arrangement throughout would require a long and narrow building and a snaking line would have problematic turnarounds. With cars, the side-by-side arrangement seems suitable for work done at the front or the back of the car, such as installing headlights or bumpers. but less for work that requires access from the middle, such as installing instrument panels or upholstery. The following press picture (AP), however, shows an assembly operation done inside the car body in what appears to be a side-by-side layout. It implies that space for the part cart must be provided between cars, which forces them apart.

Assembly operation at Miyagi
Assembly operation at Miyagi

None of the available pictures from the Miyagi plant shows the raku-raku seat that was a prominent feature of the early 1990s designs and made it easier for operators to work inside the car bodies. Not only is a raku-raku seat an added investment, but it is also easier to use in a front-to-back than in a side-by-side layout.

Raku-Raku seat
Raku-raku seat in a 1990s plant

Modular paint booths

I could not find pictures or sketches of the Miyagi painting system. Following is how CNN Money described it on 2/18/2011:

“…Toyota developed a modular paint spray line. The modules can be built somewhere else and are assembled at the plant in a much shorter time. Advantage: Cost savings. However, you don’t build a modular paint spray line factory somewhere unless you intend to build a lot of paint spray lines. Usually, cars get three coats of paint, usually water-based, and usually each coat is dried with heat. Not in Ohira. Here, the third coat is applied onto the still wet second coat and both are dried together. Advantage: Huge energy savings, faster paint time. Lower expenses…”

Friction roller conveyors

Toyota assembly line new concepts 2011 Miyagi plant Conveyance

Following is how CNN Money described the Miyagi conveyor systems on 2/18/2011:

“Where the car moves along the floor, factories usually have below ground pits that house the motors, chains and gears that keep the line moving. Not in Ohira. Here, the cars move on maybe a foot high conveyor system that is simply bolted into the concrete flooring. Advantage: Cheaper to build, cheaper to tear down and rebuild somewhere else. The line can be lengthened or shortened at will. The assembly line doesn’t ‘grow roots’ as they say in Toyota-speak.”

Note that the sketch shows car bodies without wheels. In this system, the bar supporting the cars forms

A photographs of final assembly at Ohira shows operations done further downstream, with the wheels on:

toyota--ohira-plant-in-japan-front-to-back assembly line 2011
Assembly operations after wheels are put on

In this picture, the floor the operators stand on is flush with the assembly line,  meaning that it is either a classical line with the drive mechanism in a pit under the floor, or the operators are in a raised platform spanning the length of this assembly line segment.

Elevated platform versus suspension conveyor

Toyota assembly line new concepts 2011 Miyagi plant Suspension
From suspension conveyor to elevated platform

The following photographs contrast the suspension conveyor approach as previously used at Toyota with the elevated platform at Tupelo, Mississippi:

From these pictures, it is clear that the elevated platform is a cheaper system to build, but I can see two issues with it:

  1. Flexibility in vehicle widths. The Yaris and the Corolla differ in width by less than half an inch, and therefore the same elevated platform can accommodate both. A Land Cruiser, on the other hand, is 11 inches wider, which makes you wonder whether it could share an elevated platform with the Yaris. The jaws of the suspension conveyor, on the other hand, look adjustable to a broad range of widths.
  2. Ergonomics. Working standing with your head cocked back and your arms overhead is just as ergonomically inadequate in both cases. By contrast, the VW plant in Dresden, Germany, uses suspended conveyors that can tilt the body, which is both ergonomically better and much more expensive:
VW Dresden suspended adjustable conveyor
VW Dresden suspended tilting conveyor

Conclusions

The journalists take on the Ohira plant is that it is intended to prove a design for low-volume, low-cost, high-labor content plants that can be deployed easily in emerging economies with small markets. The designs of the early 1990s instead used more automation to make the work easier for an aging work force, with tools like the raku-raku seat. This is a different direction, addressing different needs. But why build it in Northern Japan rather than, say, the Philippines? It shows Toyota’s commitment to domestic manufacturing in Japan, and it is easier to test and refine the concept locally than overseas.

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Feb 9 2013

RICKS versus 5S

In the TPS Principles and Practices discussion group on LinkedIn, Frederick Stimson Harriman started a thread about why it is silly to translate 5S into English.

I think the main problem with the commonly used translation of 5S is that it is wrong and misleading. I don’t think it is silly to translate if you can get the meaning right. What is truly silly and hopeless is trying to find 5 English words with the right meaning and starting with “S.”

Back when 5S was only 4S, I heard the following in the UK: “Remove, Identify, Clean, and Keep clean” or R.I.C.K., and I thought it was both reasonably accurate and mnemonic.

For the fifth “S,” Shitsuke, I see it as the state you achieve when you have done the first four S’s long enough for the activities to become second-nature. If telling your kid every day to brush his teeth is Seiketsu, what you have accomplished when he does it on his own without prompting is Shitsuke. So I would translate Shitsuke by “Second-nature,” which happens to start with S.

With that, we could have R.I.C.K.S. as an improved translation. What do you think?

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Scale-space filtering

Nov 21 2012

Mitigating “Mura,” or unevenness

The Japanese word Mura (ムラor斑） is the third member of the Muri, Muda, Mura axis of manufacturing evils. It means unevenness. In terms of volume of activity, if Muri refers to overburdening resources, Mura then really is the conjunction of overburdening some resources while others wait, or of alternating over time between overburdening and underutilizing the same resources.

Unevenness, however, is not only about volumes, but about quality as well. Unevenness in products is even synonymous with bad quality. From production managers facing “unpredictable” environments to academics promoting genetic algorithms or other cures, everyone bemoans how variable, or uneven, manufacturing is. The litany of causes is endless. Following are a few points that I think may clarify the issues:

  1. Mura in space, Mura in time, and Mura in space and time
  2. Degrees of severity: Deterministic, random, and uncertain environments
  3. What is special about Manufacturing?
  4. Internal versus external causes of unevenness
  5. Most useful skills in dealing with Mura

Mura in space, Mura in time, and Mura in space and time

Mura in space is imbalance in the work loads or utilization among resources at the same time; Mura in time, variability in the work load of a resource over time. The two can be present in the same factory. You may notice a kitting team working feverishly while the next one is waiting but, two hours later, you find the roles reversed.
Mura is often symbolized by two trucks arriving in sequence with different loads. I tend to think of working with Mura as moving around a city built on hills. A city built on a plain is even and easy to cross, and is often planned with a grid of numbered streets, like Manhattan in New York, or Kyoto. A city built on hills is uneven and offers many obstacles. San Francisco is built on hills, but its planners have chosen to ignore the terrain and slap on it a grid of straight streets. It makes for great views and dramatic car chases, but its steep slopes challenge your engine, your suspension, and your parking skills. Most hilly cities, like Nagasaki, Japan, for example, instead have streets that follow contour lines and therefore meander. The path by car from point A to point B may be longer than a straight line, but it is a smooth ride.

Navigating the peaks and valleys of product demand is like driving in a hilly city. If you just go straight, you keep alternating between pressing the accelerator and the brake, but by hugging contour lines, you can reach to your destination while going at a steady pace. This is what fighting Mura is about.

Degrees of severity: Deterministic, random, and uncertain environments

Some businesses are deterministic. They are “boring” and predictable. They have no variability. A manager once explained to me the electricity meter business in the market his plant was serving, as follows: “There are 20 million households with electricity meters in the country. Each meter lasts 20 years. Every year, I have to make 1 million.” The same products are made for many years, in stable quantities, and with mature processes that have no problem meeting tolerances. Of course, it only lasts until the advent of a disruptive technology, like smart meters.

This kind of environment is not common but it does exist. If your are in one, you should focus your improvement efforts on the opportunities it offers, and avoid tools that are overkill for it. For example, large, diversified companies that make a corporate decision to deploy the same planning and scheduling system in all their plants burden their simplest and most stable business units with unnecessary complexity.

Other business have variations that can be best be described as fluctuations around a smooth trend. If you make consumer goods, the demand every day is the result of decisions from a large number independent agents and will vary in both aggregate volume and mix, but within ranges that can be predicted. In terms of quality characteristics, if you fire ceramics, they shrink, by factors that still vary, even though we have been using this process for thousands of years. This level of variability is very common. The best term to describe it is randomness, and there is a rich body of knowledge on ways to work with it, including the Kanban system to regulate fluctuating flows and techniques to adjust processes in order to obtain consistent results from materials that are not. In ceramics, for example, you make your parts from a slurry that is a moving average of batches of powders received from the supplier, in order to even out their characteristics.

Contrast this with a toy manufacturer who cannot tell ahead of time which one or two products will be hits at Christmas, when most of the year’s sales occur. In process technology, there are similar differences in variability between mature, stable industries and high technology suffering from events like “yield crashes” during which a manufacturing organization “loses the recipe” for a product. Various terms are used to describe such situations, which, following Matheron, I call uncertainty. In such circumstances, the best you can expect from the techniques used to deal with randomness is to let you know that they no longer work. For example, dealerships can shield your plants from fluctuations in consumer purchases, where direct selling would let you find out sooner when demand drops for good or when consumer tastes change.

Calling our environment deterministic, random, or uncertain is always a judgment call. The deterministic electricity meter business turns uncertain with the advent of smart meters. If you view your environment as random, you expect fluctuations with a predictable range, and the signal of a shift into uncertainty manifests itself in changes beyond this range. You can use a variety of tests to detect that such as shift has occurred. Furthermore, with the possible exception of quantum physics, randomness is always in the eye of the beholder, and not intrinsic to a phenomenon.

What is special about Manufacturing?

Manufacturing is not the only kind of business to have high overhead; others include aviation or hospitals. In all such cases, companies must invest upfront in resources that pay off over time, and this is easiest to achieve with activities that place a balanced load on all resources and don’t vary over time — that is, without Mura.

Internal versus external causes of unevenness

Some unevenness comes from outside the organization, in many forms:

  • Fickle customers.
  • Seasonal variations in demand as in the toy industry.
  • Seasonal variations in supply, such as crop seasons in the food industry.
  • Changes in the macro-economy, such as a financial crisis.
  • Natural disasters, like earthquakes, tsunamis, and floods.
  • Raw materials with uneven characteristics, like ores or electronic waste for recycling.
  • Epidemics, as when 10% of your work force has the flu.
  • Unreliable suppliers.
  • …

You do not have the power to eliminate this kind of unevenness, but you can use countermeasures to mitigate its effects. On the other hand, you can and should eliminate unevenness that is self-inflicted. If you have not paid attention to balancing the work load of the various stations on your production lines, you are likely to have both overburdened and underutilized operators. Because of the different roles machines play, the workload can rarely be balanced across machines in a line, but the workloads of operators can be.

If you order materials from suppliers, for example by relying on an ERP system to issue orders by an algorithm for timing and quantities that you don’t undertand, you may well cause alternations of feast and famine in your suppliers’ order books for materials that you, in fact, consume at a steady pace. This creates unevenness not only in your suppliers’ operations, but also in your internal logistics. In The Lean Turnaround, Art Byrne explains that, at Wiremold, he eliminated volume discounts and incentives for Sales to book the largest possible orders. Instead, he preferred a steady flow of small orders, that smoothed the aggregate demand.

Not all resources need to be treated the same way. You want resources that can be described as producers to be generating useful output all the time. Other resources, which we may call responders, must be available when needed, and this is a radically different objective. Unevenness is an enemy for producers, but, unless responders’ work loads provide enough slack, they are unable to respond. Firefighters fighting fires 100% of the time would be unavailable when a new fire breaks out, and the same logic applies to maintenance technicians and operators who work as floaters on a production line. And it applies to machines as well as people. In a machine shop, for example, machines that carry out the primary processes, like hobbing a gear or milling pockets in a slab, are producers, while devices used for secondary processes, like deburring or cleaning, are responders. This is often, but not always, related to the cost of the machines, with expensive machines as producers and cheap ones as responders. However, some of the most expensive equipment, like machining centers, may be bought for its flexibility more than for its capacity, in which case its primary role is to respond to orders for short runs or prototypes.

Most useful skills in dealing with Mura

Permanently uneven workloads among operators can be addressed by balancing, using Yamazumi charts for manual operations and work-combination charts for operations involving people and machines. If the unevenness pattern shifts or oscillates over time, then the workload itself needs to be smoothed, with is done by the various techniques known as heijunka.

Many organizations are not aware of Mura as a problem, and, when aware, are oblivious to patterns in the unevenness that can be used to mitigate or eliminate it. Management, for example, may be struggling to cope with occasional large orders and fail to notice that they arrive like clockwork every other Wednesday from the same customer. A modicum of data mining skills is needed to recognize such patterns in the records of plant activity.

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Nov 14 2012

Applying Lean to retail

In the Lean Logistics group on LinkedIn, Shouvik Chattopadhyay asked the following question:

Is it possible to implement LEAN in the retail industry?

Retail is a broad sector. The issues and opportunities will not be the same depending on whether you are selling shoes, books, or food.

Assume you are running a supermarket chain. Then there are opportunities in the customer interaction within your stores, in the shelf replenishment operations, in the receiving and preparation of the goods, and in all aspects of supply chain management.

On the floor, for example, you might work on the following:

  1. Reduce customer waiting times at check-stands.
  2. Lay out the shelves on the floor to make the most frequently bought items easily available.
  3. Collocate items that are frequently bought together.
  4. If you have deli counters, you can work on the kitchen where the items are prepared to increase productivity, reduce spoilage and assure the availability of all items on the floor.

Behind the scenes, there may be opportunities in the flow of goods from trucks to the shelves customers pick from. Trucks deliver in pallets or cases that need to be received, put away, and broken into the totes or display cases for customers. Observation of these operations usually uncovers improvement opportunities.

You may have a distribution center receiving some or all your items from suppliers, in which you may be able to do the following:

  1. Improve the breakdown between items that are delivered straight to stores or go through the distribution center.
  2. Organize delivery milk runs from the distribution center to stores.
  3. Organize collection milk runs to suppliers.
  4. Improve flow and visibility in warehousing or cross-docking operations within the distribution center.

Then you may pursue further opportunities in the information systems used to run the chain. It sells thousands of items to tens of thousands of individual consumers every day. There may be opportunities to improve the way this flow of transaction data translates into orders to suppliers, with their attendant consequences. These transaction data also need to be mined for differences in customer behavior in different locations, trends, or correlations between items.

Identifying opportunities is the easy part; changing the organization to take advantage of these opportunities, the hard part. The top management of the chain has to want it for strategic reasons, and to have the determination and perseverance to make it happen. Unlike manufacturing, retail is an area where the most successful innovations in recent decades have come from companies in the US, like WalMart or Amazon, or in Europe, like Auchan or Ikea. To the management of a supermarket chain, these may be more compelling sources of ideas than Toyota.

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Oct 31 2012

Takt time: can it be universally applied to all types of production?

This is the question Casey Ng asked in the TPS Only discussion group on LinkedIn. He elaborated as follow:

What are the essential conditions to implement takt time successfully? What are the cases when it fails and if you refer to the fundamental principle of takt and yet couldn’t find the solution? Then what are the exception areas and what alternate solution can be used?

To date, it has generated 43 comments, many with the high level of depth and the implementation examples that are characteristic to this group. It is a new LinkedIn group, with only 118 members — compared with 151,503 for Lean Six Sigma — but passionate and providing meaty technical content. I recommend it in general, and this discussion in particular. Here, I will be including only my own contributions on takt time, and its relevance to the following:

Monuments

With monuments — the very large machines used for heat treatment, electroplating, painting, cutting of sheet metal, etc. — you usually have to load multiple parts simultaneously in order to meet demand, but these parts often do not have to be identical. I don’t recall anyone mentioning this in the earlier comments, but the parts that you load together can be a matching set rather than a batch. If your takt times are long enough, as, for example, in aircraft production, you can actually process one plane-set at a time, to takt time.

Gigantic products with long takt times

Gigantic products, like oil tankers, with takt times of six months or more, are built out of vertical hull slices made at much shorter takt times in a shop, and then welded together in the dry dock. Pioneered in the US with Liberty Ships during World War II, this is now standard shipyard practice, and enhances of the repetitiveness of the process, applying the concepts of takt time and one-piece flow.

Refueling outages in nuclear power plants

I am puzzled by Todd McCann‘s use of the takt time concept in the context of nuclear plant refueling outages, a problem I had the opportunity to work on 20 years ago in France, not in the US. I don’t know who the top performers are in this area today. At the time, it was a tie between the French and the Japanese, at about three weeks from shutdown to restart for one reactor, which is substantially longer than the 193 hours you were quoting for 2006, assuming that the work continues 24 hours/day, 7 days/week.

The French performance was accomplished by standardization. They had 55 reactors with only two designs, producing respectively 900MW and 1300MW, run by a single company. The procedures were the same everywhere, with any improvement quickly shared. The Japanese performance was based on using techniques from TPM. They had nine different reactor designs, run by different utility companies.

Even though they had the best performance in the world, I saw many opportunities for improvement, based on borrowing techniques from SMED, improved planning and scheduling for materials, tooling, and the 1000+ contractors involved, and operational details. Such a detail, for example, was security. Their procedures were effective at controlling access, but inefficient, with utility employees at all levels spending too much time getting contractors into and out of the facility.

The concept of takt, on the other hand, did not strike me as particularly relevant, given that a refueling outage is a yearly burst of intense activity for any given reactor, as opposed to a repetitive process.

Rate work versus response work

More generally about takt time, most businesses have both what my colleague Crispin Vincenti-Brown called Rate Work and Response Work. In manufacturing, if you do a Runner-Repeater-Stranger analysis of your products, Your Runners and Repeaters are rate work; your Strangers, response work.

Runners are products with enough volume to warrant a dedicated line. Repeaters are products that you group into families that, in aggregate, have enough volume for a line. Strangers are all the other products, including R&D prototypes, sample quantities of new products, spare parts for obsolete products, and any other special request. Even in aggregate, they account neither for a high volume nor for high revenue, but you still must produce them promptly. They require a small job-shop set up with your most flexible equipment, staffed with your most versatile operators, and its own operating policies.

While takt time is fundamental to line design for Runners and Repeaters, it isn’t much use for Strangers.

Non-repetitive operations

I have a hard time seeing the relevance of takt time in the absence of repetitiveness. In an assembly process, the takt time gives you an upper bound for the process time at each operation. As you broaden the mix of products you assemble on the same line, it becomes more difficult to balance the work among stations. Past a certain point, you are better off using approaches like bucket brigades, a.k.a. bump-back system, or even a yatai, which are not based on takt time.

Takt time and its calculation

Outside of mathematics, concepts are not reducible to formulas. Time/Demand is the way you calculate takt time, but it tells you neither the rules by which you are supposed to use that number nor how it maps to shop floor activity.

In mass production plants, managers use the inverse of this ratio: Demand/Time, which gives you the same information. Mathematically, working at a takt time of 1 minute and making 60 units/hour (uph) is equivalent. Yet, you and I know that, depending on whether the manager thinks the plant is producing at a takt time of 1 minute or making 60 uph, the shop floor will be radically different.

If you think in terms of uph, it doesn’t matter if nothing comes out for the first 59 minutes of each hour as long as all 60 come out in the end. If you think in terms of takt, 1 unit will come out like clockwork every minute.

What this says is that there is more to takt time than the formula. This is discussed extensively in Lean Assembly, with the following definition of takt time:

“Assuming we complete the product one unit at a time at a constant rate during the net available work time, the takt time is the amount of time that must elapse between two consecutive unit completions in order to meet the demand.”

As I recall, this is,more formally, the way Ohno described the concept in Toyota Production System.

Takt-driven production as the ideal state

The takt time allows you to define an ideal state, that John Shook and Pascal Dennis call True North, but that I prefer to call takt-driven production. In this state, you perform all operations one-piece at a time with process times that exactly match the takt time, and with instant transfer to the next operation at every beat. Of course, it is never perfectly realized, even on an assembly line. Real lines can only be approximations of it. The point is that it gives us a direction.

All deviations from takt-driven production translate to Ohno’s waste categories, overproduction, waiting, excess inventory, etc. Since any local project that move production in this direction eliminates waste, it can be undertaken with the confidence that it contributes to global improvement and is not sub-optimization.

Chronos, kairos, and takt time

Joachim Knuf : “… The ancient Greeks differentiated between two types of time: chronos (chronological, sequence of intervals, typically of equal extension) and kairos, best thought of as ‘the opportune moment.’ In this case, intervals begin and end under sets of conditions. This concept applies, for example, to healthcare, when next process steps are initiated by a preset configuration of values (patient’s blood pressure, glycemic index, bowel movement), not by elapsed time…”

I had never heard of Kairos, but, if the ancient Greeks made the distinction between Kronos and Kairos, why shouldn’t we? There is a rich toolbox associated with the pursuit of takt-driven production. Where the concept of takt does not apply, we can’t use these tools. As you said, extending usage of the word to Kairos-driven activities just adds confusion. These activities need different tools, and Casey pointed out some of them in his comments on Strangers. Let us keep different words to hang them on.

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