How to Calculate Parting Area of Injection Mold
2026-02-14 11:21:18
Injection Mold
The parting area of an injection mold is the projected area of the plastic part, runner and gating system on the parting surface between the moving mold and the fixed mold. It is a key parameter for calculating clamping force, determining mold size and avoiding flash and mold expansion.
Basic Calculation FormulasFor round products: Area = π × r² or π × d² ÷ 4For rectangular products: Area = Length × WidthFor special‑shaped products: Calculate the minimum enclosing rectangle or measure the area directly in CAD.
Total Parting Area Calculation
Total parting area = Product projected area × number of cavities + runner projected area + overflow and vent area. Only the projection on the parting surface is counted. Generally, a 10%–20% margin is added to ensure safety.
Purpose of Calculating Parting AreaIt is mainly used to select the clamping force of the injection molding machine: Clamping force ≥ Parting area × cavity pressure. It is also used to determine mold size, guide pin position and vent layout, and judge the risk of flash, gas trapping and mold expansion.
Practical Calculation MethodOpen the product CAD, switch to the parting surface view, select the product and runner, measure the area, multiply by the number of cavities, and add a proper margin. This is the most commonly used and accurate method in factories.
Calculation ExampleA rectangular product of 100×50 mm, 2 cavities, runner area 200 mm². Single product area = 100×50 = 5000 mm². Two cavities = 10000 mm². Plus runner = 10200 mm². This is the parting area of the mold.
