DME University

Learn About Stress In The Plastic Industrial Molding Industry

All plastic parts have some degree of internal stress molded in. Molded stresses are concentrated around holes, gates, inside sharp corners, large transition changes in cross section, and weld lines. Unfortunately, many molded parts are not tested for stress, and fail in the field. (Stress relieving after molding will reduce stress caused by the molding process). Non-destructive and destructive tests may be conducted to determine the stress condition of a part. Stress Solutions:

  1. High mold temperatures increase crystallinity and lower the resistance to stress cracking. Therefore, lower mold temperatures if possible.
  2. Keep the temperature differential across the entire mold surface as small as possible.
  3. Slow injection fill, pressure, and cycle time will decrease part stress.
  4. If required, test for stress, or stress relieve after molding, if absolutely required.

(Unfortunately, many factors that reduce part stress increase cost.)



Page 18 of 21

Share On Linkedin