I don’t normally do this, but I’d like to revisit a past article I wrote about why u-shaped cells often flow counter-clockwise.
Specifically, I’d like to share an excellent comment from Bryan Lund of Training Within Industry Service fame. Here are Bryan’s thoughts on the matter. Thanks for sharing Bryan!
Another more practical reason may exist…but we must consider the origin of workcells at Toyota. It may be that when Ohno, or a supervisor, experimented with flow in his machine shop he encountered a problem never faced prior to workcells: all lathes have their headstocks on the left side of the machine requiring operators to load stock with their right hand and tighten the chuck with their left. In a workcell manufacturing to JIT; parts were unloaded – the left hand placing the finished part in the bin to the left while picking up the stock for the next cycle with his right. My guess this efficiency in loading materials, (until auto bar loaders and through spindles replaced a machinists hands) was proliferated throughout Toyota and its keiretsu of suppliers. Counterclockwise workflow was the countermeasure for eliminating extra fumbling of the part between hands during load/unload cycles.
Often something that is innocuous becomes conventional wisdom. I literally have seen and heard lean consultants state that workcells MUST go counterclockwise for the right hand reason. It is almost taboo to suggest anything but U-shaped and counterclockwise. But I think most people, except those posting comments here, dismiss the taboo attitude and forget to understand why counterclockwise exists in the first place. Since the workcell is the most copied lean concept born from TPS than it only makes sense that something so copied for so long has evolved into a sacred cow in North American lean literature and practice.
The fact that the majority of the population is righty and may be a convenient and viable reason for not trying to make our workcells flexible, but how to explain right hand people doing things with their left hands everyday? Rolling down the driver side windows, typing, opening door handles, tying their shoes, using utensils, or juggling?
Don’t believe me? Give your toddler who is learning to use utensils – toddler SAFE utensils please – a knife and fork. Watch them struggle with their non-dominant hand. Then you do the same and marvel at how easily it seems to you, how you don’t even think about it. Try to think about it as you cut your steak, slice a cooked carrot with ease between the tines of your fork. You can’t even think about it as it comes so naturally, right? The fact is, people can LEARN to use their left hands as well as their right and vice versa – with practice and discipline.
Of course, I don’t think I can prove any of this, it is just an educated guess based on experience, but I think its a pretty good guess. What do you think?