The Value of an OEM Assembly Plant Trial

Posted on 11/7/2017 10:01:59 AM By Dan Daley

“Always bring donuts” might have been the motto of an HB Fuller adhesive salesman that I spent time with early in my career. He would usually pick up a dozen for each stop of the morning. I was thinking about him one day in the early 1990s.I was sent to one of our assembly plants, and did not think anyone would be happy to see me. Driving in, there were small piles of rubber molding laying along the highway into town. All the new trucks going in the other direction had this material flapping in the wind getting ready to make its own little pile. It is something to see your work literally strewn across the highway.

The last stop on our journey from selecting an adhesive to testing is to see the bonding process start production. As the above example shows, it is wise to conduct a robust plant trial as a final evaluation of the product. In the above case, the application was in a relatively large program, which included new aerodynamic body color chassis skirts with rubber accent moldings. Material selection and testing had required some work, but in the end, had gone well.  It was a straight-forward application with no real problems. No worries.

Then, we littered the highway.

Figure 1:  IHC International 9400 Truck with External Air Intake (1987-1996)


Figure 2:  1st Grille Prototype, designed & fabricated by MDI, in place on a prototype hood in the Navistar design studio

Source:  Montgomery Design International

Two things went wrong. First, I had made initial material selections for the adhesive and rubber for cost and quoting purposes. I had just spent considerable time developing an elastomer for fuel tank strap lining which had similar cosmetic and fuel staining requirements, although these were not bonded. I figured the adhesive would be an acrylic PSA (pressure sensitive adhesive), no real choice here, a wet application would not be accepted. I had argued that this should be a film rather than a rubber extrusion but that was not seriously considered by the styling team.

During development and testing the adhesive had to be significantly changed to bond well – the plasticizer and fuel resistance had to be improved. The elastomer required improved processing to better retain the plasticizer. Unfortunately, during sourcing both changes were rolled back in favor of the original materials due to an increase in cost. Controls and communication are much more robust than when this took place – but still, this should not have happened.

The second was the assembly process. It worked well in the lab but did not translate well to the plant. The expectation was that proper pressure application would be as specified. I had naively assumed that the manufacturing team would take this seriously. Even with the correct adhesive the material did not reliably bond corners of the moldings. It was difficult for the operators to reliably apply pressure to the molding corners. This was better than falling off barely out of the plant but not good enough. So, we corrected the adhesive and added fasteners.

Well, there was one more mistake I made. There was not a plant trial. At least not one that I attended. I am sure there were builds and pre-production pilots. But I was not invited and did not hear of any issues. A plant trial is an essential step toward a successful adhesive production launch. So, the first and only recommendation is:

Do the plant trial!

I have come to realize that whenever I have said aloud or to myself that this is easy, no problem those materials always bond, or things really cannot get any worse – that I am just challenging God to prove me wrong. If you are changing something, run the plant trial.

A plant trial, run with production material, would have caught the material change and the fixturing/tooling issue that kept the corners from getting enough pressure. Time for tooling or just having the fastener fix lined up would have saved important time and trouble.

Good luck on your trial and eventual start of production. Just one more thing for your trial, just in case, bring some donuts – it can’t hurt.