Part design guidelines on double injection molding

In this article, we will show you from three aspects to be taken into consideration when designing plastic parts for double injection molding so we can save our customers time and money in the long run.


Mechanical structure

Double injection Consideration
Double injection Consideration
Part Design
Part Design



Surface Contact

  • Adhesion is depending on materials compatibility, process temperatures, surface contact area, molding sequence and designing of mechanical interlock systems. If design not allows enough contact surface area, Tooling can make up like
  1. Make-up 1 : Increase expose surface byincreasingroughness.
  2. Make-up 2 : Employ interlock

Contact Surface

Wall Thickness

  • Utilize 2nd shot to get more uniform wallthickness

Wall Thickness

  •  Reinforce the 1st  and 2nd shot(transparent) by structure design such as “H” section etc. Thin but high rib in 2nd short.
  • First shot thicker than 2nd shot. 2nd shot should be as thin as possiblewhen flow and weld line is not a issue.
  • In MP case, 1st shot 0.6mm, 2nd shot 0.6mm was made
  • Avoid sharpcorner

Wall Thickness

  • Make a stronger tuber if it is necessary in 1st

All three plastic part design consideration listed in the article make up just some of the good practices that HS Mold has accumulated over years. Keep them in mind when designing plastics parts to be mass manufactured by means of  2K injection molding.

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