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When you look at the cylinder on injection moulders, for instance on DIY ones on YouTube, they are all thick walled. The piston has say a 20mm diameter and the cylinder has like a 40mm diameter in which plastic is heated to 250C. Could you get away with using a 1" stainless steel pipe with 3mm thick walls?

Lewis Kelsey
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Because injection molding pressures can get very high - typically peaks of 16 ksi , and the hoop stress in the steel is governed by the ratio of bore diameter to wall thickness.

Your suggested dimensions would burst at an injection pressure of around 25ksi if made from very good steel (100 ksi), and less than half that for typical stainless steels.

However real cylinders don't just break because of hoop stress, there are also stress raisers at the endplate, and there are other possible failure modes, not just hoop stress.

Greg Locock
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