A 2nd Stage Packing study is a critical aspect to optimizing any molding process. You should perform a gate seal test for each of your molds to ensure you are not using wasting energy with excessive packing time.
Gate Seal Time: To determine the time required for the gate to seal requires a gate seal study. To perform this test, you mold a series of parts using different 2nd stage times and weigh each part (without gates and runners). When graphed, you will see the part weigh increase with packing time until the gate seals. Once the gate is sealed, the part weight should stabilize for a cold runner mold. If a hot runner gates directly into the part, the part weight will stop curving and become linear at the time of gate seal.
Packing Time: When gate seal is desired, the optimal time used for 2nd stage packing is 10% greater than the gate seal time. When a non-seal condition is desired, the 2nd stage packing time should 10% lower than the gate seal or less.