Mold Gate Location Optimization Analysis Theory

The injection molding process is heavily affected by where the mold gate location(s) are placed on the mold cavity.  If the right gate location(s) are not selected the part will have quality issues during the mold trial process.

Wrong gate location will cause Problems including but are not limited to the following:

  • Incomplete cavity fill (short sot)
  • High shear rates
  • High shear stresses
  • High molded in stress
  • Difficult to vent air traps
  • Objectionable weld lines

The worst of the above problems is got short shot.  The other problems are objectionable but an incomplete part is unacceptable.  In larger plastic parts this is a big risk.  Most plastics will only flow between 150mm and 450mm for a part of about 2.5mm thickness.  There are many factors that affect how far a plastic will flow in a mold cavity. Other critical parameters tested  by the gate analysis are as follows

  • Part flow length
  • Part thickness
  • Thickness transitions
  • Part material
  • Location of mold vents
  • Mold temperature
  • Melt temperatureMold gate location

A gate location optimization analysis investigates various, practical gate locations and numbers to assure that the above factors are within an acceptable range. With the knowledge of what gate locations form an acceptable part, the most economical location can be chosen before the tool is built.  Most gate optimization analysis consist of three to five gate location configurations.

Other critical data that is obtained by running a multiple gate locations analysis include:

  • Location of weld lines
  • Clamp tonnage requirements
  • Injection pressures
  • Location of high shear rates
  • Location of high shear stresses

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