Flow it Right? or Flow it Left?

Cell Material Flow? Right or Left??

It’s all about perspective… hang on, I’ll explain.

There is a science to production systems layouts. I’m sure you have read about the various “reasons” a cell “must” flow in a counterclockwise manner. The “Leanie purist” is quick to point it out without any reflective thought. But all the reasons a cell MUST flow in this direction are really not that convincing. Let’s explore:

That’s how Toyota does it!

Well, this can’t be considered a fact of science. It’s the old adage of “We have always done it this way!”. Toyota found out that many of their equipment lends itself to loading from the right–process to the left; especially with lathe machines. So that was the “rule” from then on.

Spatial recognition (human perception of space)

It’s all in the brain! Most people being “right” brain folks have better perception using their left eye. Well, this may work well for horses (??) but for a work cell, then logic tells me that in a pull flow cell materials should be coming from the left – the side where I have the best “visual” acuity. Some professor stated he did an experiment where athletes ran faster in a counter-clockwise manner on a track instead of clockwise. He claimed it was due to the right brain - left eye phenomenon. Two logical flaws: an athlete trained in running and banking left would need a prolonged “re-conditioning”, both mentally and physically, to reach equal capability to go the opposite direction. The other issue is that right-handed folks tend to have longer right legs – an ideal condition to bank left on a sustained run.

A South African friend once told me that they teach safari game hunters to always search from right to left because they would be able to pick up more details as they scanned the landscape in search of the game. Try it! We tend to make visual assumptions as we scan left to right, but the brain slows things down as you go from right to left. I believe being aware of what is happening upstream is slightly more important than “seeing” downstream in a pull system – hence flow clockwise. Are you right brain or left brain?

Right hand dominance

This is the most convincing of all the arguments (in a way). For most people, their right arm & hand is stronger than their left. This means that you want heavy stuff to be picked up or pulled (especially if you are sitting) on the right side – hence flowing counterclockwise. Now, ergonomists are taught that picking things up may require less “precision” than the accurate “placing” motion – so we typically want to move and place things with our dominant arm/hand (most of the time the right arm/hand). Now the logic implies we pick-up with our left arm/hand and move-orient-position with our right arm/hand = clockwise.

Now to the question: Why was it ultimately decided to have the material flow through the cells in a clockwise manner?

The answer is “perspective”! Are you looking at the cell as an eagle (way up high looking down) or are you looking at the cell from the operator's point of view?

When I teach about cell flow I do not use the term “clockwise” or “counter-clockwise” – it creates confusion. I simple state:

Flow the production from “right-to-left"

You should never “mirror” a cell: most of all your “standard” equipment, fixtures, and assembly aids become “difficult” to use because they are designed for the “standard” right-to-left cell configuration. Moving operators from one cell to a “mirror” cell drives the operators crazy (analogy: asking the athlete to now run around the track clockwise!). All their “body memory” has to be re-learned.


Quote from Retired Chemical Engineer Harold:

I've often been asked, 'What do you old folks do now that you're retired?' Well, I'm fortunate to have a chemical engineering background and one of the things I enjoy most is converting beer, wine and scotch into the urine. I do it every day and I really enjoy it.

Harold is an inspiration to us all.

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