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.
I was in a local restaurant the other day looking at the way the waiters went about their tasks. It soon became obvious that some were more efficient that others. Some had time to chat to the guests, while others appeared to be rushing around. I looked at the number of guests and tables they were serving. That appeared to be in balance. I looked at the various stages the meals were at, again all appeared to be reasonably balanced.
The difference was really was quite simple, some waiters were optimising their movements. Every Time they returned to the kitchen, they would clear a table, or at least not return empty handed. The ones that were running around did not. They were having to make twice as many journeys. One to being food out to the guests and a second process to clear plates. Simple.
So in this case improvement is a simple matter of a little training, yet why had it not been spotted and the waiters retrained?
I think the answer is that we get blind to what we do as we go about familiar tasks. Sometimes it makes sense to stop, watch and understand what is going on.
Supervisors and managers in particular need to make time to observe day to day activities and reflect on simple improvements that can be made. This type of improvement activity costs little, but done on a regular basis can overtime significantly improve processes.
Try it. Watch a familiar day to day process and see what you can see.
The concept Poka-yoke was originally developed as part of the Toyota productions system by Shigeo Shingo. it is a Japanese term that means “mistake-proofing”. By interestingly it was originally named “baka-Yoke”, which has the meaning “Fool-proofing”, but this was quickly changed to the less offensive form.
The name is derived from two Japanese words, Poka meaning “Mistakes” and Yokeru meaning “avoid” and really is applied to any mechanism in a lean manufacturing process that helps an equipment operator avoid making mistakes. Its purpose is to stop the process at the point where a defect occurs. This has two effects. Firstly and most obviously, it stops the defect from being passed on the other processes further down the
line. But also, secondly it allows an error to be investigated at the very point and time the defect originated. This makes problem solving much easier and allows ‘counter-measures’ to be put in place, thus improving quality.
There are 3 main types of Poka-yoke device:
- Contact type, which is designed to identify defects by testing the product’s shape, size, color, or other physical attributes.
- Fixed-value type, which is designed to alert the operator if a certain number of movements are not made.
- Motion-step (or sequence) type, which tests if the prescribed steps of the process have been followed.
Poka-Yoke and its use is not reserved for business. Examples can be seen in everyday life. Here’s just a few:
Fill a car with Fuel. Look at the area around the Filler flap. There are at least 3 examples of Poka-yoke devices present.
- The size of the nozzle varies depending on the type of fuel to stop unleaded being put into a diesel. But you can make the error the other way around, so this is not a perfect example.
- When you take the fuel cap off, the cap is tethered to the main body, stopping the motorist driving off having left the cap on the roof!
- The Cap is fitted with a ratchet to prevent over tightening.
Circuit breakers in houses are designed to prevent electrical overloads . When the load becomes too great, the circuit is broken.
Computer Leads, Look at the back of any computer and you will see a plethora of leads. All of the leads have different type plugs on them to stop them being fitted into the wrong socket.
ATM Machines, return your card before your cash is dispensed to stop you forgetting it. This one works on the basis you are unlikely to forget your cash !!!
In the UK 240v/50Hz electricity is used. This can injure people so electrical plugs are designed so that live electrical pins are never exposed. Two forms of Poka-yoke are used here:
- The ‘3 pins’, Live, neutral and earth are positioned and orientated are such that the plug can only fit one way in the socket.
- The pins are insulated near the plug body so that electric shock is not possible when the plug is being pushed in, this also means that if the plug is not fully inserted the current will still pass, but electric shock is not possible since only the insulated portion of the pins is exposed.
Of course there are many more, but I hope this gives you a few examples you can use in lean training courses, or just impress people at a party with your knowledge of Poka-yoke !
This is a great exercise to break the ice at a training session, although you will require a few old T-shirts.
Kids love this one as well !
or if you would like to see it in English try this link