Injection Mold Design: Guide [exclusive]

Dr. Aris Thorne stared at the failed part on his desk. The polycarbonate clip had snapped at the boss—a hairline fracture invisible to the naked eye but devastating under load. His production line was down. His client, a medical device giant, was furious. And the problem, as always, traced back to a single, unforgiving origin: the mold.

Location: End of flow path, last 10–20% of fill, behind bosses, ribs.

Uniformity: Keeps cooling rates even to prevent internal stress.

• Cavity (A-Side): The female side; forms the outside shape of the part. Usually mounted to the stationary platen.
• Core (B-Side): The male side; forms the inside shape of the part. Usually mounted to the moving platen.
• Sprue: The channel through which molten plastic enters the mold from the nozzle.
• Runners: Channels that direct the plastic from the sprue to the cavity gates.
• Gates: The entry point where the plastic flows into the cavity. This is the critical control point for flow.
• Cooling Lines: Channels machined into the plates through which water or oil circulates to cool the part.
• Ejector System: Pins or sleeves that push the part out of the mold after cooling.
• Leader Pins & Bushings: Align the two halves of the mold precisely.