Die Science: Diemaker or dieologist?

If you have ever attended one of my technical seminars, you know that I often use the word dieologist. Don’t waste any time trying to find it on the Internet, because you probably won’t. It’s a word that I made up and frequently use to define a diemaker who uses his or her knowledge of sheet metal physics to derive a solution to a stamping or die-related problem.

There are literally thousands of reasons that a process or die might fail. Trying to find the single source or combination of sources that contribute to failure can be quite an overwhelming task. To succeed, I must have the necessary knowledge not only to solve a problem, but to explain why it worked or didn’t work. In short, a diemaker may perform a certain task or make a certain change in a die because he has had success in the past. A dieologist might make the same decision, but not just because it works. Instead, he makes the decision because he knows why it works. He understands the physics behind the decision.

Example No. 1

A part is splitting, and based on the part and process assessment, both the diemaker and the dieologist come to the conclusion that it needs a preforming operation. Both decide that the fist preform shape should be a dome or bubble. After that, however, their thought processes differ:

•The diemaker’s thoughts—A dome will work. I was taught as an apprentice that a dome is the best shape to use in this situation. It’s what I used on that last job that looked like this. Besides, all of the jobs that we have built in the past started out with a bubble-shaped dome.

•The dieologist’s thoughts—A dome most likely will be the best shape to use in this situation. A dome shape not only will force good strain and stretch distribution of the metal, but it will force the metal to be stretched bilaterally. This will increase the amount of surface area that can be obtained in the preforming operation. As a result, the metal will stretch less in the secondary forming operation, resolving the splitting issue.

Example No. 2

Deep-formed parts made of bright 304 stainless steel are splitting in the drawing and stretching die. The diemaker and dieologist both solve the problem by bagging the blank—putting a thin film of plastic (garbage bags work well) on both sides of the blank before loading it into the forming die.

•The diemaker’s thoughts—When all else fails, bag the blank. I remember using this stuff all the time at the prototype shop where I used to work. The metal really slides when you use the old garbage bag trick.

•The dieologist’s thoughts—Because bright stainless steel has an extremely smooth and shiny surface topography, it fails to hold traditional lubricants on its surface. Applying a thin-film-barrier lubricant to the metal’s surface prevents it from ever touching the surface of the die. Reducing this surface contact results in lower frictional values, allowing the material to feed inward and distribute the stretch more evenly.

Because plastic is made from a petroleum product, it has a low frictional value, so the bag is a good temporary fix. For long-term success, we should consider using a lubricant combined with a wetting agent to help hold it on the surface of the blank. This will eliminate the need for using expensive thin-plastic films.

Example No. 3

A part is splitting in a forming die in a certain press. Every attempt has been made to resolve the splitting issue, but nothing has worked. Both the diemaker and dieologist know that the die performs well in a different press. They both decide to move it to another press, which eliminates splitting.

•The diemaker’s thoughts—That press we were using is a pile of junk. I don’t even think the ram is parallel with the bolster. Besides, the ram speed is too fast to draw this part.

•The dieologist’s thoughts—During metal forming and drawing, too much heat can cause the additives in the lubricant to break down, allowing more friction to be created. This increase in friction can result in diminished feed rates and splitting problems. Installing this die in a much slower press gives the material more reaction time to flow inward. The slower forming speed will also reduce the amount of friction and heat created.

Take the Time to Learn Why

In all three examples, the diemaker and dieologist arrived at the same solutions. However, the dieologist understands why the solutions work and the physics behind them, so he is equipped to make better data-based decisions in the future. After all, as W. Edwards Deming said, “In God we trust; all others bring data.” What a true and unshakeable statement!

Take the time to learn why we do things the way we do. Tool and die is not an art form! We don’t make decisions based on an earlier inspiration.

Please don’t confuse art with creativity, though. As tooling professionals, we do need to be creative in the way we do things. However, our creativity must revolve around a comprehensive understanding of sheet metal physics. When sheet metal meets physics, physics always wins; it doesn’t matter how good of an artist you are. This column is called “Die ” for a reason.