How to Calculate Injection Molding Machine Tonnage
What size injection molding machine do I need?
Normally, most plastic injection engineers will rough calcualate the machine`s tonnage with the product`s surface multiply by a index number.
If you are using square inch as the surface, then you can make it 2.5 times (higher flow materials like PS, PE and PP) to 4 times (lower flow materials like PA, PC and PSU) as the index number.
While your are using square cm as the surface, then you should make it 0.48 times (higher flow materials like PS, PE and PP) to 0.72 times (lower flow materials like PA, PC and PSU) as the index number.
What is the formula to calculate tonnage?
Empirical Formula 1
Clamping force (T) = Clamping Force Constant Kp Product Projected Area S (CM CM) * Safety Factor(1+10%)
To properly calculate necessary clamp tonnage, you must first know the projected area of the molded part/s plus any runners.
Area can be calculated by multiplying length times width, A = L x W or A=πr2.