Generally, you will need 1 ton of clamp force for each square inch of part area. So, all you need to do is anticipate the largest part you will mold and size accordingly.
To answer your question simply, there is a formula. You must identify the material to be used. For example TPU thermo plastic urethanes take between 4-5 tons per square inch whereas PP can take 2.25 tons per square inch. I hope that you get the picture.
The formula is simple multiply your square inch area calculation by a given multiplier and there you have the tonnage calculation.
Remember to allow for the runners and sprue area and subtract any hole areas. You get the projected area of your product looking down on the part perpendicular to your parting line.
A good resource for material specs is matweb.com . Look up any given material and check the clamping tonnage needed. All suppliers can be asked this question directly and are normally very obliging with their answers.
Plastic molding process
Re: Plastic molding process
