How to use Injection Molding Clamping Force Calculator
- Enter Single part projected area (cm²) and adjust the options as needed.
- Run the tool and inspect its results, evidence and limitations.
- Copy or download the result, then verify it against the actual website, source data or business records.
Try a concrete example
Single part 180 cm², 4 cavities, 15% runner allowance: total mold parting projected area is 828.0 cm². With ABS resin and standard wall thickness, average cavity pressure is 40.0 MPa (400 bar), generating 3312 kN mold opening force. Applying 1.15x safety margin yields 388.5 metric tons (3808.8 kN). Recommend a 400 to 450-ton injection molding machine (tie-bar spacing >= 730x730mm, mold daylight 350~750mm).
How to interpret results
Clamping force counters parting line opening forces generated by high-pressure polymer melt injection. Insufficient tonnage produces severe parting line flash; excessive tonnage crushes parting vents and causes plastic mold fatigue and bent machine tie-bars.
Frequently asked questions
Why must the runner system projected area be included in clamping force calculations?
In multi-cavity tooling (8, 16 cavities) or cold runner systems, sprue and runner channels are subjected to peak melt injection pressure. Runner area adds 10% to 25% to overall projected area; omitting runners underestimates required tonnage, causing immediate parting line flashing.
Why does part wall thickness have a decisive effect on cavity pressure?
Polymer melts exhibit non-Newtonian shear behavior. Thinning walls from 3.0mm to 1.0mm escalates flow resistance dramatically. High injection pressures (120~200 MPa) are required to avoid freeze-off, driving transmitted cavity pressures to 60~85+ MPa and doubling required tonnage.
What severe damage occurs from running small molds on excessively oversized clamping presses?
Clamping a 100-ton mold in a 500-ton press concentrates force over a small platen area, permanently coining parting surfaces, crushing 0.02mm air vents, causing diesel burns, and bending tie-bars from non-uniform platen deflection.
How does polymer melt flow index (MFI) determine cavity pressure?
High-flow polymers (PP, PE) fill smoothly with 25~32 MPa cavity pressures. Medium engineering resins (ABS, POM) require 35~45 MPa. Stiff-chain resins (PC, PMMA, glass-filled PA66) present heavy viscosity, requiring 55~75+ MPa cavity pressure ratings.