Work out the clamping force

Clamping force has to hold the die shut against the metal being pushed into it. Get it from the projected area and the specific pressure for the alloy — then pick the smallest machine above that figure.

Alloy

Projected area (cm²)

Area of the part plus runner and overflow, seen from the die face.

Specific pressure (MPa)

Typical: Al 50–100, Zn 13–20, Mg 40–70, Cu 80–120.

Safety factor

Inserts in the part?

Cavities

Required clamping force

— kN

Smallest machine in range —

The formula, and what it ignores

F (kN) = A (cm²) × p (MPa) × 0.1 × safety factor

1 MPa acting on 1 cm² is 0.1 kN, which is where the 0.1 comes from. Multiply by the number of cavities if the die is multi-cavity.

The formula tells you the clamping force. It does not check whether the die physically fits: tie-bar spacing, die height, platen size and shot position all have to be checked as well, and on small machines the die often does not fit even when the tonnage is right.

Send us this and we will confirm

Part drawing or a photo with a scale
Alloy and part weight
Projected area (or let us calculate it)
Inserts: yes / no, and what the insert is
Target cycle time and annual volume
Destination country — it affects documentation and electrical configuration

Send the details