Shenzhen Alu Rapid Prototype Precision Co., Ltd.

How to calculate injection pressure in injection molding?Injection pressure is the force per unit area applied by the injection molding machine to push molten plastic into the mold cavity. It is typically measured in units like psi (pounds per square inch), bar (1 bar ≈ 14.5 psi), or MPa (megapascals). This pressure is essential during the filling, packing, and holding stages of the molding cycle:

Fill pressure: Fills the mold to 95-98% capacity.

Pack pressure: Packs material into corners to compensate for shrinkage.

Hold pressure: Maintains contact with the mold during cooling to minimize defects like voids or warpage.

The required injection pressure depends on factors like material viscosity, mold design, part geometry, and machine capabilities. Too low, and the mold won't fill completely (short shots); too high, and it can cause flash (excess material leakage), part stress, or mold damage. Typical ranges are 40-200 MPa, but aim for the minimum needed for quality.

Step-by-Step Guide to Calculate Injection Pressure

Calculating injection pressure involves both the machine's delivery capability and the process requirements. Here's a practical approach:

1.Determine the Projected Area (PA) of the Part

2.Estimate the Required Force (F)

3.Calculate the Injection Pressure (P)

4.Account for Losses and Viscosity

5.Validate and Adjust

Tips for Optimization

Use pressure transducers for real-time monitoring to visualize the pressure curve (fill peak should be sharp, pack/hold steady).

For viscous materials like glass-filled nylon, expect higher pressures (up to 150 MPa).

Always prioritize cavity pressure over machine pressure for consistent quality—it's the true indicator of part integrity.

For complex parts, consult simulation tools or material datasheets.