By Jon Miller | Post Date: August 17, 2006 11:32 PM | Comments: 0
The topic of takt time and specifically "how does it apply to me?" seems to be a popular one, based on comments left by readers at this blog entry. The latest from John asks for advice on the environment where TAKT time is ideal and where it is not applicable.
Whether you choose to write it TAKT time, Takt time or takt time (but not tact time with a "c"- that would be time for careful consideration of feelings and value of others, which is also important in Lean manufacturing, but a topic for another discussion) it is essential to Lean manufacturing. Takt is a key building block of Just In Time (Takt Time, One Piece Flow, Downstream Pull). Just In Time in turn is one of the pillars of the Toyota Production System (the other is Jidoka). Takt time is one of the three elements of Standard Work along with work sequence and standard work in process.
Takt time is a must, but it is not ideal in many environments. However takt time production is an ideal to strive for. The aim of takt time is to synchronize the speed at which work flows with actual customer demand. There are many things that make immediately converting to working to takt time (customer demand) impractical for many businesses.
For example, John describes his workplace where they are considering takt time production. They manufacture aircraft structures such as the fuselage, rear fuse, front fuse, fin, etc. The products may not lend themselves to takt time production at first glance. The realities at John's aircraft structure production company are:
- Tight tolerances
Converting to operating at takt time does not solve all problems, and exposes many more clearly. Measuring the cycle times of each individual process and balancing the work to takt time is a big improvement but only the first step.
If as in the example above the parts can not be made within tolerance each time the first time, meeting takt time will be difficult because there will be rework and the cycle time will not be repeatable. Kaizen effort should focus on making the process repeatable and stable. If this is not possible, you can still flow one piece at takt time by allowing extra stations (takt time pitches) based on the degree and frequency of variation in cycle time due to parts made out of tolerance. This of course will waste some space and is not ideal.
Low build rates are not a problem in takt time production, except that it becomes harder for people to gain a feeling for takt time or the "takt image" as it is sometimes called. If the production rate is 50 per year (approximately 1 per week) then 20% of the work needs to be completed each day over a five day week. It is much easier to have a takt image that is minutes or hours per unit complete, rather than days.
Pitch lines and other visual makers can be used to show progress or delay against takt time, when takt times are long and flow too slow to be felt while working. In any case extra effort will be required, including physically pulling the product at the speed of takt time. This can be done several times during the day to progressive work stations or ideally a constant slow motion. In the case of large aircraft parts this can be a challenge, but this is done at Boeing with wings and even entire aircraft so the "we don't make automobiles" excuse is gone.
Just in time production can not really be achieved without a certain degree of heijunka (averaging of both production volume and product mix). If the constant swings are too great, changes in takt time and work content due to the different number and mix of orders will make staffing and resource calculation difficult. Basically you will have to staff for the peak volume and complexity of work content or you will need the ability to flexibly add capacity during spikes. Takt time is best calculated based on an averaging of demand based on heijunka. True customer demand fluctuates too much in practically every industry. The image used for the role of a strategic finished goods buffer based on heijunka is that of a wave breaker between a raging ocean and the shore.
Suppliers as a cause of shortages is another topic entirely, and will be a problem whether you flow at takt time or flow at a batch pull. A Supplier Development partnership is highly recommended where opportunities can be identified to improve the flow of information and materials together. Proving a schedule based on heijunka and working to a pull should solve some of the problems, but it is best to go on site to understand the issues at the supplier.
Takt comes from a German musical term and means rhythm or beat. In an orchestra if the instruments are playing at different speeds, it sounds terrible. When they play at the same speed it sounds good. In the same way, if the material and information in a manufacturing company move at different speeds rather than at one speed, takt time - the pace of customer demand, the result is a higher total cost and a longer lead-time.
If your production is high volume with little variability in demand, very stable quality, a strong supply chain and a simple product, it may be easier to implement takt time production but I would not say ideal. No business of this type has come asking us for help, in any case. The environment where takt time is ideal is any process where you have challenging problems you want to solve.
I believe there is no environment to which takt time can not apply. It may not always be the place to start when doing kaizen. Just as nature has its rhythms and cycles, all takt time does is to harmonize the rhythm of customer demand with the rhythm of production.Comments are moderated to filter spam and inappropriate content. There may be a delay before your comment is published.