Cavity Balance
Pressure Drop
Process Window
Gate Seal
Cooling Study

Procedure to estimate Gate Seal

  • Set the injection speed to the value obtained from the viscosity curve experiment.
  • Set the process at the center of the process window from the process window study.
  • Set the cooling time to a value to ensure that the part is cooled before ejection. 
  • Drop the holding time to zero and start molding. Mold approximately 5 to 8 shots. 
  • Increase the holding time to one second and collect a shot.  
  • Increase the holding time to two seconds and collect a shot. Similarly collect shots at increments of one second.
  • Weigh the shots and plot a graph of part weight versus time similar to the graph in the picture.
  • Determine the gate seal time.  

The figure below shows a typical Hold Time curve that as generated at the molding machine.


How to use this information: 
Once the graph is generated, choose your holding time, such that you are just beyond the time where the part weight is constant. In the above graph, the part weight is constant after 8 seconds. Set the holding time to 9 seconds. 
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