Part removal is the easiest part of the injection molding process to optimize and there is no excuse for basic clamp movement optimization.
While walking the recent NPE 2015 trade show in Orlando, many of the processes were dialed in beautifully where the mold quickly opens and closes while the part is ejected on the fly. Unfortunately, some machine manufacturers had their molds slowly opening and closing, pausing 1 or 2 seconds before starting ejection, and a couple molds even cycled the ejection system multiple times. Many of these processes lost many seconds of cycle time to clamp movement. This poorly showcases a machine at the show, but loses a lot of productivity at your plant.
You should always optimize clamp movements You do not have to slap the mold shut or shake the machine violently as the mold whips open to improve your part removal process. A good basic strategy is as follows:
Mold Opening Fast : This takes place after the initial mold breakaway speed. After the mold components are disengaged, the opening speed should be increased since there are no obstructions. The optimal speed is the fastest speed the machine can safely handle without any awkward movements, machine vibrations.You may need a third, moderate final opening speed if the machine has difficulty maintaining a consistent final mold opening position for robotic part removal.
Final Mold Open : The final mold open position should only be enough to allow proper part ejection.
Eject on the Fly : If a robot is not being used, you should start part ejection before the mold is opened. The fact that the mold is moving away from the part tends to help the part drop downward. This feature typically reduces the total amount of distance the mold has to open when properly set.
Mold Close Fast : Just as with mold open fast, the mold should move quickly when the mold components are not engaged. It is critical that the mold closing speed slows down to a safe speed prior to the mold components making contact for the final mold closing.