Belleville Washers
IMM 10/99

Our company inherited some molds with Belleville washers that shut off the cores that form the inside diameter of the part. Do these washers/springs fatigue, and should they be replaced periodically? Currently, we replace only those that break.

Belleville washers do suffer fatigue from elastic deformation caused during compression. Changing all washers at the same time increases the span between breakdowns, and a light coating of grease applied to each side of the washer cuts down on friction during compression, possibly extending its life. Also, since the molds are inherited, you may want to double-check the washer pocket depth to ensure that the washers have enough room to compress without being over deflected.

-S. Hatfield, Accent Plastics, Corona, CA, (909) 273-7777.