Injection Units Settings PropertyManager - Pack Tab

The Pack tab of the Injection Unit Settings PropertyManager displays the packing stage settings of the injection process. The goal of the packing stage is to add more polymer material to the filled cavity to compensate for part shrinkage and reduce external sink marks.

To open the Injection Unit Settings PropertyManager:

  • In the PlasticsManager, under Injection Units , right-click the required unit definition, and click Settings .

Pressure Profile Setting

Pressure Profile Setting Specifies a profile for the time-varying behavior of the packing pressure to sufficiently pack out the mold cavity. You can control the variation of packing pressure in terms of packing time, either in percentage or in absolute values.

By default the overall packing time is divided into five sections. Specify more or fewer sections to obtain the required process control.

Machine pressure control (Absolute Control)

Specifies the packing pressure in absolute values according to the total packing time. This is controlled by the machine or as a percentage of the current machine maximum injection pressure (defined in the Fill tab).

Relative to pressure at filling end (Relative Control)

Specifies the packing pressure as a percentage based on the pressure at the end of the filling.

Profile Time

Specifies the time values as absolute time or as a percentage of the Pressure Holding Time.

  Apply Applies the current settings to the curve of the packing pressure profile. This curve controls the packing pressure stage.
You must click Apply to activate the settings.
  Export Exports the Pressure Profile Settings to a .csv file.
  OK Applies the Pressure Profile Settings and closes the panel.
You must click OK to activate the settings.
  Cancel Ignores the Pressure Profile Settings and closes the panel.
  Pressure Holding Time

Specifies the duration of the first stage of packing, during which pressure is applied to the injection locations as the melt in the mold cools and shrinks. SOLIDWORKS Plastics calculates the default value based on part geometry and material properties.

The pressure holding time is the interval between the packing switch point and the packing end point. The control type changes to pressure control after the packing switch point, and the pressure profile of the inlet is then based on the proportion of packing time and injection pressure.

The packing stage automatically ends if the polymer flow rate becomes nearly zero, and any remaining Pressure Holding Time is added to the Pure Cooling Time. The flow rate is considered to be nearly zero when the rate of change of part mass falls below 0.01% per second.
  Pure Cooling Time Defines the time when the pressure is removed from the injection locations and only the temperature of the part is calculated as the freezing completes. The default time for the cooling stage is estimated based on the ejection temperature provided in the material data.

When the part reaches the ejection temperature, the frozen layer is thick enough to eject. The part core may still be in a molten state, and it cools down out of the mold to reach the ambient temperature.

  Residual Stress Calculation

Calculates the residual stresses that develop within the part as it cools down from the melt temperature to the glass transition temperature.

Residual stresses develop because nonuniform cooling and pressure variations occur in the viscoelastic polymer material during molding. A part with high residual stresses might fracture or undergo other physical changes after molding.
Pressure distribution after filling
Pressure distribution after packing