toyota production system

Lean Learnings # 6 – Why Takt time must be considered ‘Pure’

Over time I have seen may organisations try and put their interpretation on takt time. Most try to put some form of ‘fudge factor’ into the calculation. This is normally so they can accommodate and ‘efficiency ratio’ or some form of equipment efficiency measure. But why do they do this?

Well most of the time it is because the organisation has completely missed the point of using takt time as a tool. Most understand that takt time is the ‘beat of the customer’, but few really understand that is is also a measure of waste within the process.

It’s also an Abnormality management tool………..

Used properly it is very easy to understand the cost of stoppages, for example, if our production line is planned to run for 40 hours and produce 2400 units (takt time = 60 seconds) but we only produced 2000 units, then we have a loss of 400 units. it is very easy to see we would have to run 400 minutes overtime to catch back. This in turn we can attribute a true cost to.  But the reality is that it makes little sense to add cost to the process in this way. So we have to consider another alternative.


Within the Takt time calculation the key phrase is ‘Available time’. It is quite acceptable  to include ‘Planned down-time’ into the calculation so long as it is planned ahead of time.

So we could choose to build into the calculation and amount of time for maintenance and TPM activities to that when we run the process during the planned up-time we can measure the success of our TPM and maintenance.

This is why companies like Toyota do not generally run 3 shift operations. They choose to spend time each day working on preventative maintenance so that when the bulk of the manpower is on site, the lines run to pure takt time. That way they can look for not only at the quality of the equipment maintenance, but also look for small incremental losses. The trick is to have a very good capture system and have the infrastructure to put into place good countermeasures.

The moment you add ‘fudge factors’ into the calculation you are sending the message that some inefficiencies are OK and you loose the ability to put pressure on the organisation to find and fix its inherent abnormalities.

So before you try to make up your own takt time rules, think about the message you are sending and is there a way you can organise the operation in a different way to drive people to improve and look for small losses.

Lean Learning’s #1 Yokoten

Having spent years working in a Toyota plant, I know how it ticks. But one  of the skill’s that the team had there that I have yet to experience with
such commitment anywhere else is to perform a technique called  Yokoten

The direct translation of Yokoten is “Across everywhere” or “Best practice sharing”

When a problem, be it safety, quality, breakdown or supply chain, occurs, firstly the problem is addressed, and the countermeasure is confirmed as good.

Then a very simple question is asked “Could the problem exits of occur somewhere else?” The Toyota production system then requires the team to religiously perform checks to find out the answer, as a matter of priority.

If the answer is yes, then the fix from the original problem is put in place in all locations that a similar potential problem, thus preventing a future issue occurring.

This is done, even if there is a cost or time implication, because the cost of a further breakdown or quality issue would be far greater in the long run.

The question is asked every time by managers at problem reviews. Importantly, no blame is apportioned; the philosophy is ‘to find a problem once, is good, it’s an opportunity to improve. But to find it a second time means the system has failed.’ The focus is on prevention of re occurrence.

When an A3 report is used, the final two question boxes as ‘does this issue exits elsewhere’ and has ‘Yokoten’ been completed. Only when these two questions answered, is the problem considered closed.

Yokoten is also strengthened through the regular  departmental and Production Working Group meetings, which is made up of representatives of all plants and reports directly to top management, with careful attention paid to “Best Practice” at all the facilities.

This level of the use of Yokoten helps to ensure that all plants “level up” to the best performance in the group.

A very powerful tool to quickly improve a processes reliability, but it requires great commitment and discipline.

 

Develop a Deeper Understanding of Waste

If you are familiar with the principles of Lean then you will be aware of the fundamental principle that there is waste to some degree in every single activity we perform, whether it is at work or in our day to day business.

You will also be aware that in general waste is split in 7 types or categories. Defective products, Waste incurred during transportation,
overproduction, over processing, holding inventory, Waiting and excess motion.

But my question to you is. Did you realise that this is only part of the big picture in understanding ‘waste’ its effects and how to address it.

To  understand this we need to go back a step and really look at some of the core fundamentals of Lean. Let’s start at the very beginning and understand why the removal of wastes within processes is judged so important.

The single most important factor in developing a lean process is the ‘Voice of the customer’. Understanding what the customer needs, in what volume, and when it is needed.

Having understood this, the next step is to develop a system that will deliver to the customer needs on time, to the correct quality, in the right
volume. Sounds simple but this is where the problems start. If the process is not flexible enough to meet the changes in customer demand inefficiencies creep in and hence level of wastes within the process grow.

This is where most peoples understanding (including many lean practitioners) of waste starts to break down.

You may have heard the term ‘Muda’. Muda translated from Japanese is Waste. However this is only part of the story.

When Taiichi Ohno Sakichi Toyoda, and Kiichiro Toyoda, originally set out to develop the Toyota production system, they recognised that the root causes of waste in a process were much deeper than many consider today.

They defined 3 types of waste, MUDA, MURA and MURI

What has happen is that Muda has been given much greater attention since over time it has been well defined into the 7 categories I mentioned earlier.
Because of this, many Lean practitioners have learned to see just Muda they fail to see in the same prominence the wastes of Mura (unevenness) and Muri (overburden). Normally whilst they are focused on getting their process under control they do not give enough time or consider the impact of the other two types of waste.

So let’s take time to consider both Mura and Muri.

Mura or unevenness occurs at a number of levels within a process and needs to be considered when Just in time it being put in place. Consider this, what happens when we reduce or remove inventory (one of our 7 classic wastes). Well, now that the safety buffer has been removed, the process will be put under strain to deliver in a much more responsive way. The entire value chain will be asked to flex up and down in speed. The impact of this change can be devastating to the organisation. Manning levels have to be adjusted (If cost and efficiency are to be maintained), Suppliers will be asked to change deliver schedules at short notice. Maintenance schedules may need changing, in fact a whole plethora of issues arise and all takes time to manage. Also, because of the need to produce at peak volume at any time in theory, equipment, workers, inventory and all other elements required for production must always be prepared for peak production. This is adds both cost and waste.

Unless systems and processes are put in place to do this, waste starts to creep back into the process.

Toyota considered this in the development of the Toyota production system and took it into account with the concept of Heijunka or production smoothing. The concept of Heijunka may at first appear to contradict the Just in time and lean production philosophies, however it must be
remembered that done correctly well small amounts of well managed strategic stock will both aid efficiency and lower overall cost.

In the general concept of Heijunka is to try and smooth the production rate within acceptable limits. There are a number tools and tricks to this which are again linked to the original thoughts behind theToyota production system.

For example. Toyota’s final assembly line never assembles the same automobile model in a batch. Production is levelled by making first one model, then another model, then yet another. The pattern or order of the 3 models is the adjusted to smooth the daily rate based on customer demand (takt time). This flexibility is one of the key reasons for having a mixed model process. But in order to achieve this Standard work must be well defined and implemented otherwise the waste of ‘MURI’ will be the issue.

Muri or overburden, generally occurs when Standard work is not well defined or when addition tasks have been placed upon someone through a process change without consideration to their over workload or line balance.

Within most companies it is the case, but the importance of Standard Work cannot be underestimated. A smooth process with well trained people has a number of other benefits. When everyone knows the standard condition, and the standardised work sequences, heightened morale is seen along with improved quality improved productivity and reduced costs.

So when you are next observing a process for waste, look a little deeper. Look for the all three forms of waste, not just MUDA.

Think of the 3 M’s consider MURA and MURI as well as MUDA