Using Screws to Fasten into Plastic

Reprint from China Fastener World Magazine, Vol. 53

Very early in my career I worked on a very interesting project. In the U.S. after a new car is assembled, it is either loaded into a truck or onto a train for delivery. In this case, our customer’s new model vehicle was loaded onto a train car for shipment across the country. When it arrived on the other end of its journey the cars would not start and could not be offloaded. It did not take long to discover that the glove box doors were opening in route, causing the glove box light to come on, and the battery to drain down. When the root cause of this problem was investigated it was quickly determined that the plastic ABS bosses which accepted the screws that held the glove box door assembly together were completely cracked and broken. The Type AB screws that had been used exerted so much radial stress on the plastic ABS bosses that they had destroyed them causing the plastic to fall away, the doors to flop open, and the new cars to arrive in an inoperable state.

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