Calculating Clamping Force for Plastic Injection Molding

Surface area of mold times pounds per square inch of injection pressure is the amount of force trying to open the mold from the inside. Your clamping pressure must be able to over come this force. Over kill is a good idea for saftey in this area.

I learned mold making from guys who are either retired or should be. They did not have the computerized tools we have today to design their molds. Just to be safe, mold walls were plenty thick. I once saw the side of a mold push out about 1/32" from inside injection pressure. The side of the mold was 2" thick P20 die steel!

Be carefull.

here is the chart i use maybe you can save it and zoom in

let me know if you have translation questions

2 to 2.5 tons per projected square inch is typical

regards

bruce

This range can be from 2 tons of clamping force to 8 tons, depending upon the material used and the surface area of the molded product, runners exposed and parallel to the clamping platens. More likely than not this range will be from 2 to 5 tons for the most widely used materials.

Go to 6-6 of the Tool and Manufacturing Engineers Handbook, Volume VIII, Plastic Part Manufacturing By Tom Drozda, Charles Wick, Ramon Bakerjian, Raymond F. Veilleux, Louis W. Petrounder

Section: "Sizing the Clamp Unit" gives an explanation. You will have to check with each specific material manufacturer for their guided range.

http://books.google.com/books?id=Q4X1ovFVBvoC&pg=PT223&lpg=PT223&dq=mold+clamp+force+on+plastic&source=web&ots=okh9vn0vTm&sig=rammvhICzg3LTfdvnZjImjoeC54&hl=en&sa=X&oi=book_result&resnum=10&ct=result#PPT222,M1

Good luck,

Steve