How to optimize pack and hold times for hot-runner & valve-gated molds

Using scientific procedures will help processors to optimize pack and hold times for hot-runner & valve-gated molds. For cold-runner molds, hold times are optimized by conducting gate-freeze study where the part weight is recorded as a function of the hold times. When the gate freezes, the part weight remains constant with increasing time. A second or so is added to the lowest value of time where the part weight stays constant, and this number is taken as the total time for the setting of hold time. Molders need to find an optimized combination of hold times and pressures, and conduct a Design of Experiments (DOE) to optimize the parameters within the available limits.