July 14, 2022

Injection mold parting surface

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What is the injection mold parting surface?
Generally, injection mold has two major components: the movable halve and the fixed halve, during injection molding process, these two halves are pressed tightly and form a sealed hollow to avoid the melt flow leakage and maintain certain holding pressure, the pressed surface are called parting surface, usually parting surface are the biggest projection outline of the part.

Types of parting surface
Types of parting surface
Flat parting surface (see figure a)
Parting surface tilt (see figure b)
Stepped parting surface (see figure c)
Curved parting surface (see figure d)

Parting surface design principles
Parting surface design directly affects the product quality, ease of construction and operation of the injection mold, the mold design is one of the key factors to success.

Design parting surface should follow the following principles:

  1. Design the injection mold structure as simple as possible. Avoid or reduce side parting as much as possible to reduce the complexity of mold making.
  2. Ease of de-molding. As far as possible, for instance, the plastic parts should stay in fixed halve of the injection mold and ejected by ejection system, avoid side de-molding action.
  3. Ensure the dimensional accuracy of the molded parts. Try to make the parts with similar dimensional accuracy requirements in the same module to reduce manufacturing and assembly errors.
  4. Ensure appearance requirement of the molded parts. Flash or mismatch occurs usually on parting surface, so the parting surface should not be designed on any high quality requirement surfaces.
  5. Ensure adequate venting. If possible, parting surface should be place at the end of the mold flow. This is going to be a good advantage of filling and venting.

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