Shenzhen Alu Rapid Prototype Precision Co., Ltd.

Clamping force in injection molding is the compressive force applied by the clamping unit of the injection molding machine to hold the two halves of the mold securely closed during the injection, packing, and cooling phases of the process. This force counteracts the high pressure exerted by the molten plastic as it is injected into the mold cavity, preventing the mold from separating or "flashing" (where excess material leaks out), which could lead to defects in the final part.

Why It's Important

Mold Integrity: It ensures the mold remains tightly sealed, maintaining part dimensions, surface finish, and structural quality.

Machine Sizing: Clamping force is often measured in tons (tonnage), and it determines the appropriate machine size for a given mold—insufficient force can cause incomplete fills or parting line issues, while excess force may damage the mold.

Process Efficiency: Proper clamping reduces cycle times, material waste, and energy use by allowing consistent, high-pressure injection without interruptions.

How It's Calculated (Basic Overview)

Clamping force is typically calculated using the formula:

Clamping Force (tons) = (Projected Mold Area × Cavity Pressure) / 2  Projected Mold Area: The surface area of the part(s) perpendicular to the mold's parting line (in square inches).  

Cavity Pressure: The estimated pressure inside the mold during injection (often 4–8 tons per square inch for thermoplastics).

This is a simplified estimate; actual values depend on material properties, wall thickness, and machine specifics.