Minimum Mold Sizing
Interpreting Viscosity Curves
As a response to the Fill Time, Viscosity & Molding Economics blog I received this question…
Using Hold Pressure Velocity
I received this question from a frequent blog contributor, and believe it makes a good discussion on decoupled processes…
- A process that uses one injection speed to fill – whenever possible
- The mold fills 95 to 98 percent full during first stage
- All cavities are short shot during first stage
- First stage fill is velocity-controlled and not pressure limited
- Second stage pack is pressure-controller and not velocity limited
- Process uses only 20 to 80 percent of the machine’s available shot size
- The final cushion is approximately 10 percent of the overall shot size
In essence, the purpose of a DII process is to ‘decouple’, or separate, velocity controlled fill from pressure controlled pack. To do this, you should either turn the velocity control off so the pressure control takes prominence.