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injection moulding process - explanation & Video

The injection moulding process involves heating & injecting plastic material under pressure into a closed metal mould tool.

 

The molten plastic cools & hardens into the shape inside the mould tool, which then opens to allow the mouldings to be ejected or removed for inspection, delivery or secondary operations.

 

A schematic view of the injection moulding process
injection moulding process - stage 1injection moulding process, help with injection moulding, moulding process, help with, help, toolcraft plastics, stage 1 Material granules from the hopper feed into the heated barrel & rotating screw.

Material melted by heat, friction & shear force is forced through a check valve to the front by the rotating screw.
injection moulding process - stage 2injection moulding process, help with injection moulding, moulding process, help with, help, toolcraft plastics, stage 2 Having been moved backwards by the shot of material at the front, the screw is forced forward by a hydraulic ram.

This action injects material into the mould cavity in the closed mould tool.
injection moulding process - stage 3injection moulding process, help with injection moulding, moulding process, help with, help, toolcraft plastics, stage 3 The tool is held closed under pressure until the plastic material cools & sets hard in the mould tool cavity.

This is often the longest part of the injection moulding process
injection moulding process - stage 4injection moulding process, help with injection moulding, moulding process, help with, help, toolcraft plastics, stage 4 The screw starts to move back for the next moulding. The tool then opens & the finished plastic part is ejected.

The tool is closed and the injection moulding process starts again at 1.

 

For more information, you can also watch our injection moulding video:

 

For more injection moulding advice, have a look at our plastic moulding advice pages.