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The optimizing time for injection molds

Edit: Smart Mold Technology Limited    Date: Mar 15, 2016

 

 

All injection molds  need an optimum filling time. The optimum filling speed approached the least pressure which require. However, faster filling speeds are often compromised by problems such as gassing. The burning of the melt front due to entrapment of cavity air takes place. Vents should be cut where the gassing occurs. If vents do exist, and they are properly sized and clean, then reducing the locking force can help with venting and enable faster injection time. But the process should not be compromised because of the poor venting - the venting should be properly engineered to do the job required.


Optimizing filling time;:Probably 95% of all moulds should have a filling time between 1.5 and 3 seconds. If a mould takes longer than 3 seconds to fill, it should be checked again. Small parts with short flow lengths will fill quicker but only very thick parts or those with flow lengths more than 500 mm will need to be filled for more than 3 seconds. Optimizing filling may only make a small time saving, but getting the filling time set at the optimum will enable savings to be made

 

elsewhere. The packing or holding time is a stage in which semi-molten mass in the filled mould is pressurized while it cools to allow additional melt into the mold to compensate for the shrinkage that occurs. With crystalline polymers such as Polypropylene, this can be significant due to  volume shrinkage is high. The packing phase reduces sink marks, improves replication of the mould finish, consolidates welds and controls gloss level. The gate must be sized correctly to remain open long enough to enable a correct packing. A gate freeze check will determine the exact time available for packing injection mold exhibition.

 

 

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