How to Calculate Injection Molding Machine Tonnage Most people in plastic moulding industry may have the same question: how to calculate injection moulding machine tonnage or how to calculate clamping force in injection molding? This is a very common question if you are in the plastic inejection molding industry. So how do you calculate injection molding tonnage?Get more news about second hand ppr mold,you can vist our website! Before answering the question about clamping force calculation, we should make it clear for some basic definition of the injection machine`s molding tonnage and how it comes from and what it supports during the injection molding process. What is tonnage in injection Moulding machine? The “tonnage” is the maximum of clamping force that a injection molding machine can offer to keep the the injection tool tightly closed during the injection process. This clamping force ensure the mold won`t apart or getting loose and having products with sharps.The tonnage size is one of the most important factor when you want to select a injection molding machine. As it will determinate what kinds or size of plastic products you can produce with this molding machine. We normally use the tonnage size as the main index of a injection moulding machine. You may heard some of these sentence: I have a 200 ton injection machine, the mold will need a 300 ton molding machine,is the product can be produce with a 120 ton moulding machine? 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.