I started my career in the spring business pressing springs and operating several stress relief ovens. I worked another 13 years doing just about everything there was to do, including an eight year stint in a hot coil plant. After I changed employers to seek work in CNC coiling, I got the chance to work at Monticello Spring Corporation in Monticello, Indiana.
Monticello Spring was started in 1970 by a German engineer named Horst Pimmler. Now retired, he was a learned and prepared engineer who knew his product well. His knowledge of springs, spring application and materials is vast. In 1990, he gave me the chance to learn spring engineering after he had hired me as a cost estimator. This was a brave new step for a former shop rat.In due time, he offered me the position of engineering manager, and I gladly accepted. Mr. Pimmler was, in true German form, a meticulous detail man. He could calculate any result with a calculator because he knew every formula by heart. He stressed the need for nursing the details and making certain every parameter was given consideration. There was no such thing as worrying about something later! He focused on making certain that the part was able to be manufactured within the capability of the production machines. If this was not possible, he let customers know by way of an “exception” report what was feasible and what wasn’t.
I was already inclined to do things right the first time, but Mr. Pimmler’s approach honed it to a ritualistic habit. His daily thought process was centered on capability: “Could the floor operator make the part repeatedly with the same result?” Unlike some of my past experiences, his daily mantra was to be certain the production people were given a fair shake by negotiating changes that would prove to be a win-win for everyone. That was the only thing that made sense to him, and he was right.
It made no sense to attempt a solution if you knew from the start it would fail. You had to define clearly what you could do, or determine what you could create to make a needed design feasible.
Because I had floor experience, he didn’t have to explain to me the negative result of unreasonable tolerances. That result was something I’d dealt with as a coiler when tolerancing was next to impossible. Instead of having the grace to use the allowed tolerance to adjust for rate and load, I had to hold diameter and/or free length tolerances that were too stringent for a given design.
Now before I give the impression that all problems can be easily solved, let me qualify my remarks. Many springs are manufactured as precision components and cannot be short-changed. There is no increasing tolerances or making referenced dimensions because the application requires a great deal of, for a loss for a better word, “perfection.” This situation, however, is not the typical spring requirement and many designs have just never had the tolerances scrutinized. Guidelines such as the SMI standards provide a point of reference. After that, the application dictates what is truly needed to make the spring perform within its functional system. The real world function will always define tolerances and limits. Once the use is defined, processes are developed to determine capability.
Overall, there are three points of contact that need to work together to achieve the best part for the job. This includes the customer, engineering and the shop floor. The customer must define what is needed. Engineering must define a process and associated costs. The shop floor must determine what can be made or what would need to be designed or purchased to create a required design. Any detail not defined and refined will cause delays and less than favorable results, which impacts the bottom line and overall customer satisfaction.
My advice is: don’t sweat the small stuff of life in general. But when the subject is an engineered component that works with other components as a functional whole, the details become an all-important link between success and failure. Capability of process and repeatability are the all-so-important aspect of true control of the finished product. Ask questions, educate and be educated, because little things can be connected to larger things and they all need to play well together.
By: Randy DeFord, Engineering Manager Mid-West Spring & Stamping