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.