Plug assist and forming pressure must work as one sequence. If vacuum begins too early, the sheet may seal or freeze before the plug distributes material. If it begins too late, the plug can drive unsupported material into the cavity and create severe local strain.
The correct relationship depends on material, tool design, plug contour, speed, and desired first-contact pattern. A fixed timer copied from another mold is not a reliable starting point.
Establish actual event timing
PLC commands, valve response, plug position, tool closure, and pressure change should be recorded on the same time base. Mechanical and pneumatic delays can make the real sequence different from the HMI recipe.
The process should be adjusted while wall thickness and defect location are monitored. A visually complete part may still contain a harmful thickness shift. Timing should remain stable as air supply, tool temperature, and machine speed change within normal limits.