You don’t have to be a yes-man to a large OEM to get the job, but you do have to be diplomatic.
The wide acceptance of e-mail has created the false impression that the sender is entitled to an immediate reply. There was a time when there was an opportunity to think through a response. Today’s rapid-paced environment frequently results in accepting the first idea that seems plausible. That first idea is rarely as good as the third or fourth concept that is more clearly thought out.
The Way it Was
Back in those earlier days, there was enough time to enjoy work. One of the daily pleasures was opening the mail. E-mail barges in all day long and interrupts all other activities. Snail mail, on the other hand, arrives once a day at approximately the same time. Going through the mail was something to plan for and enjoy. There was even more junk mail and advertising back then. There were as many bills as ever, but these were offset by well-thought-out letters, flawlessly typed by a secretary who also cleaned up the grammar, punctuation, and spelling. Most people adhered to the quaint, old-fashioned practice of actually signing those letters. I have to admit that I miss the crisp, solid feel of good-quality, watermarked stationery with a nicely designed letterhead.
If you were lucky, the mail would contain one or more checks from customers. The next best thing to payment of an invoice was a purchase order for new work. Of only slightly less significance was an invitation to quote on a new project. This is the story of a project that started with a quotation request for a prototype mold and samples.
In going through the morning mail I noticed an envelope sticking out of the pile. The logo on the envelope was of a large, well-known East Coast electronic products OEM. I slipped the envelope out of the pile and ripped it open. Lo and behold, it was an invitation to quote. This was great news, as I didn’t have anything else to quote. I really wanted that prestigious company’s name on my customer list. I quoted the project myself in order to avoid any mistakes.
This turned out to be a deceptively simple nylon part called a slider. It had three undercut bosses that snapfitted into holes on a metal plate. Mounting two sliders parallel to each other allowed printed circuit boards to be affixed into the slots running the length of the sliders.
Defining the Problem
The OEM’s design of this electronic component violated the rule of uniform wall thickness with one wall three times thicker than the rest of the part. After the original part design (left) was revised to core out the thick section, the warp was gone and the tolerance was tighter (right).
In studying the drawing I noted that there was a 0.015-inch flatness tolerance on the part. That is a liberal tolerance for a part like this, so I studied the drawing more carefully in an attempt to understand why. That is when I noticed that the section between the three mounting bosses and the slots was three times thicker than the rest of the part. It was a foregone conclusion that this thicker wall would take longer to cool and would shrink more than the other thinner walls. This difference in shrinkage would cause the slider to warp toward the thicker wall, and the nylon’s high mold-shrinkage factor would increase that warpage. I concluded that this part could not be molded as drawn. A design change would be required in order to maintain the 0.015-inch flatness tolerance.
My only contact was the buyer. I phoned him and said I had a problem with the design of the slider and asked to speak with a design engineer. In no uncertain terms I was told that if I couldn’t handle a simple part like this, I should discard the drawing and not bother to send in a “decline to quote” letter. Then he hung up. I should have dropped the project then and there, but I wanted that prestigious company’s name on my customer list.
I went ahead and quoted the job. Realizing the type of person I was dealing with, I was careful in wording my letter: Thank you for the opportunity of submitting a proposal for the slider project.
A single-cavity prototype mold can be built and sampled in 10 days at a cost of $1750.
I have studied this part in detail. In my opinion, the nonuniform wall thickness will cause the sliders to warp along their length.
If the sliders warp beyond the 0.015-inch tolerance, it will cost $500 to modify the part design and the mold to produce straight parts.
I mailed the quote. I had done as much as I could. I did not, however, expect to hear back from that company. Big bureaucratic companies do not look favorably on suppliers who say negative things. They prefer people who only say Yes! Yes! Yes! I was wrong, of course, as by and by I received a purchase order for the slider prototype mold and samples. It goes without saying that the part design still contained the thicker wall.
Told You So
Anticipating problems with this part, we built a laminated cavity with two extra blades located in the center of the thick section. The added blades did not cost me anything as they were included in the quoted mold cost.
The mold was sampled and, sure enough, the sliders warped 0.027 inch out of flat. I sent the warped samples to the buyer with an I-told-you-so letter. He responded with a purchase order for $500 to modify the mold.
The mold was disassembled. The two extra blades were repositioned so that they projected into the cavity. These blades cored out the thick section, giving the part a uniform wall thickness. Sliders from the modified mold were flat to 0.004-0.005 inch.
Sliders from the modified mold were shipped. A few weeks later they ordered a small quantity of additional samples. Thereafter, silence. They paid the invoice, I got that prestigious company’s name on my list of customers, but I never heard from them after that. Perhaps they were too embarrassed to contact me again.
The slider may have been designed on a tight schedule by an engineer who didn’t have time enough to think through the project. This may have been the case, but the fundamental problem with the slider was a nonuniform wall thickness made worse by a bad case of the NIH, or Not Invented Here syndrome that is so prevalent in large companies. They persist in doing things their way even when that is the wrong way.
It is interesting to note that the cored-out sliders used less plastic material and could be molded on a shorter cycle. In other words, it was an improvement in both cost and quality.
The moral of this story is that the customer is always right. It would be unusual, however, for an OEM to know as much about injection molding as its suppliers. Playing the NIH game costs these OEMs many thousands of dollars each year.
About
Glenn Beall Beall owned Glenn Beall Engineering, a plastics product design and development company, from 1968 to 1993, and after retiring from that company, he established and is currently president of Glenn Beall Plastics, Ltd., a plastics consulting business.
