This study examines the common practice of drilling stress relief holes in aluminum mold frames. While this practice is widely assumed to be beneficial, no systematic evaluation of the effects of this procedure has been previously undertaken. In this study, two specific types of jewelry products were analyzed: a wedding band, and a disc or coin shaped object. All tests were conducted using milled mold frames and standardized mold making, injecting, casting and finishing procedures.

A series of 2-7/8” X 1-7/8” X 1” mold frames were used to mold a wedding band. Stress relief holes from 0” to 1/2” in diameter in 1/16” increments were drilled. A series of 1-1/2” X 2-1/2” X 5/8” mold frames were used to mold a disc or coin shaped object. Stress relief holes for 0” to 1/4” in diameter in 1/32” increments were drilled.

These tests demonstrated that molds made with the larger size stress relief holes had marginally lower shrinkage rates.

Author: Louis Sanchez