Molded side hole with side action
- Higher tooling complexity
- Flash and shutoff maintenance on slides
- Good repeatability at volume
DFM
Side Holes: Injection Molding Design Rules
Side holes need side actions, special cores, or secondary ops because they fight mold pull.
DFM
Side holes fight the primary mold open direction
Any hole whose axis is not parallel to pull needs a plan.
Side holes typically require side actions, angled pins, or secondary machining.
Designers sometimes replace side holes with split housings and assembly screws.
NetProto DFM flags side holes early so tooling scope is honest on the quote.
DFM
Quote this rule with your CAD upload
NetProto DFM review flags these geometry patterns before steel is ordered.
- Call out draw direction and cosmetic faces on the model.
- Note resin family even when the grade is not final.
- Tighten tolerances only on mating features that need them.
Strategy
Side hole in mold versus post mold drill
Pick based on volume, tolerance, and cleanliness.
Post mold drilling or ultrasonic
- Simpler mold steel
- Secondary operation per part
- Useful when hole count is low or axis is awkward
Related rules
Design guide
Jump to sibling rules before you freeze CAD.
Design guide hub
All DFM topics on one route.
Design guide hubDFM article
Long form engineer guide.
DFM articleSide actions
Slide tooling context.
Side actionsUndercuts
Related pull conflicts.
UndercutsSecondary operations
NetProto secondary scope.
Secondary operationsVisual reference
Molding context for this rule
Images from the Forge media library illustrate typical programs.
Injection molded part design review on CAD
Injection molded part design review on CAD
Plastic housing with ribs and bosses
Plastic housing with ribs and bosses
Engineer measuring molded component
Engineer measuring molded component
FAQ
Side hole questions
Can side holes be avoided?
Often yes with clamshell design or hidden parting tricks.
Are side holes always side actions?
Angled lifters or collapsible cores are alternatives on some geometry.
Who validates side hole axis?
Upload CAD views with hole axes shown relative to draw direction.
Next step
Mark hole axes on CAD views
Show draw direction and every hole axis that is not parallel to pull.