Product Liability Expert Asses Changing Part Suppliers

Product liability is strongly dependent on part quality. This is a big issue when changing part suppliers, and there are times a product liability expert must be hired to examine parts from the new supplier.

In this case the supplier of a molded nylon part was changed and plastic failure analysis tests showed that the thread strength of the replacement part was inadequate. The possibilities considered were a change in the poloymer, improper glass filling and incomplete thread geometry. The new supplier actually failed on all three counts. He substituted a different polymer, he used shorter glass fibers, and he did not properly mold the part. A failure analysis expert performed a root cause failure analysis which indicated that incomplete molding of the threads was the main cause of the decrease in strength. A failure analysis expert cross sectioned representative parts and found the female threads were incomplete, and these provided inadequate strength. The cross section photomicrograph on the upper left shows the representative threads of a part from the original supplier. Upper right is that of the alternate supplier. One can see that the alternate supplier had formed incomplete threads.