Stress Relief

Minimization of stresses is an important enclosure engineering criteria; but some stresses are inevitable while others are extremely hard to eliminate or even to minimize. However, stress minimization is the primary vehicle to solve the cracking problem. There are two main classes: part and process induced stress minimization. Parts can be stressed from a variety of different sources, such as loads and environment induced. The environment is responsible for thermal, ultra violet (UV) and other radiation, vibration, chemical resistance and many others. Process induced stresses include assembly related and plastic process related stresses. Injection moulding creates thermal, shear and recombination stresses. This last stress is often called weld line strength and appears unavoidable if the melt flow needs to recombine after a hole, boss or other feature in the part. However, this stress can be minimized to solve many of the mysteries of a cracking or breaking plastic part.