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Daniel Schaeffler Daniel Schaeffler
President

Gemba Walks: In Battle of Theory vs. Reality, Reality Always Wins

March 31, 2021


The Japanese term “gemba” means “the real place.” In the context of manufacturing, the production floor is the gemba, or the actual place where manufacturing occurs. The commonly-referred-to “Gemba Walk” originated with Taiichi Ohno, called “the father of the Toyota Production System” and just-in-time production. Oodles of references exist that describe how factory management can use Gemba Walks with great success during lean-manufacturing and Six Sigma exercises, to explore value streams for waste and to uncover opportunities for improvement. 

For those new to the metal forming industry or who spend too much of their time behind a desk looking at or creating spreadsheets and analyses, getting onto the plant floor—for Gemba Walks or other purposes—can provide invaluable perspectives into the nuances of the work.

For example, trying to learn about steelmaking or aluminum production only in the classroom will rob people of an awareness for high-volume production. Take a walk and gain an appreciation for melting and casting. In the case of integrated steel mills, a blast furnace runs 24/7 for years at a time, producing a new 300-ton heat every 45 min. Ask yourself, what would happen to that constant flow of molten metal if the continuous-casting equipment failed? 

Walk the path the slab takes and see the hot-rolling operation. You will notice hot bands moving at speeds to 30 miles/hr. As a new slab enters the hot mill rolls, think about what happens if it misses the roll bite, where the gap is around 1 in. tall. Known as a cobble, the hot sheet metal goes everywhere except where it is supposed to.

More amazing than seeing red-hot metal spewing above, under and to the side of the mill, watch the speed at which the trained workforce removes the sheet metal ribbons and damaged work rolls and swaps in a fresh set of rolls. Continue walking the line and realize that in the production of a coil of 1-mm-thick mild steel, the equipment and processes are robustly engineered,―capable of producing thickness tolerances of ±20 microns across the width and down the length of what might be a mile-long coil.

Many readers are familiar with metal forming simulation tools. While these tools typically succeed at what they claim to do, simulations do not always accurately predict reality. Some limitations are baked into improper assumptions, such as having uniform friction across a panel or selecting the wrong hardening law for the chosen grade of material. Other limitations arise from running the simulation based on an out-of-date part design. Material flow changes once a grinder touches the tool, and binder and press tonnages impact splits and wrinkles. However, many production floors lack tonnage monitors connected to every press.

In addition, while a simulation may capture how a metal forming process behaves at room temperature, when stamped at production rates the same parts can become too hot to handle. Everything―changes when tooling heats up. Clearances change, affecting sheet metal flow. Stress-strain curves vary with temperature, as does lubricant performance. Lubricant additives designed to work at room temperature may not activate at the actual stamping temperatures. And, applying lubricant using a drenched mop further thwarts accurate material-flow predictions.

Walk the production floor and watch the blank-destacking process. The tackiness of the lubricant on the material may cause the destacker to pick up multiple blanks. In addition, while the lube may excel in helping formability, it might result in extra welding or painting challenges if not sufficiently cleaned. Also remember that if you’re stamping highly formable sheet metals for Class A applications, these grades should perform well in stamping but could lead to higher warranty claims for dents and dings. To protect the material from damage in cases where operators perform die work in close proximity to the press or to coil- and blank-storage racks, set up a curtain to prevent grinder sparks from landing in the press or on the sheet metal (I’ve seen this occur more than a few times).

And, let’s not forget that the most valuable company assets on the plant floor—the production-team members who may have decades of experience performing magic day in and day out. While some of them may not know the reasons why they take the actions that they do, what they do usually works. Walk the production floor and have genuine discussions with them. Ask them about the actions they’re taking when they run into specific issues, such as splits and wrinkles. Discuss any automation and lube-application challenges. Then take that real-world knowledge and incorporate it back into the simulations and spreadsheets. And, of course, take the time to thank them for their insights and wisdom. 

We all have important roles to play in creating value-added products. Do yourself and the people who rely on you a favor and spend some time in the place where manufacturing actually occurs. You’ll walk away with fresh insights that will help throughout your career and make you a more valuable contributor to the team. MF

Industry-Related Terms: Case, Die, Forming, Run, Thickness
View Glossary of Metalforming Terms

 

See also: Engineering Quality Solutions, Inc., 4M Partners, LLC

Technologies: Materials, Quality Control

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