Mold parting line.
Where mold splits.
Visible feature.
Parting line design for injection molding and casting. Where mold halves meet. Visible flash, feature consideration.
Key principles.
Major decision
Where mold splits. Affects ejection, draft, flash visibility.
Slight
Plastic squeezes between mold halves at parting line. Visible flash.
Avoid parting
Cosmetic surfaces should not contain parting line.
Hidden
Place parting line on edge or hidden seam.
Avoid parting
Side actions/inserts avoid parting line on visible faces.
Affects gates
Parting line position affects gating, weld lines.
FAQ
Where to put parting line?
On edge or hidden surface. Avoid cosmetic faces. Discuss with tooling engineer.
Flash size?
Sub-mm flash. Most flash deburrable. Significant flash indicates mold issues.
Side actions?
Mold inserts that move sideways for ejection. Avoid parting line on visible features. Increases tool cost.
Two-shot parting?
Two-shot molds have two parting positions. Each requires careful placement.
Cost impact?
Standard parting line no premium. Side actions add 30-100% to mold cost.
Documentation?
Mold flow analysis predicts parting line behavior. Specify acceptable flash on drawing.
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