Plastic injection molding process involves the use of plastic, or polymer. The granular polymer is fed right into a heated barrel. It is also further melted and mixed in the barrel with the rotation procedure for a screw type plunger, as heat is generated from the friction between polymer granules when the screw is rotating.
The Plastic mold will then be forced into a mold cavity using the required final shape through a nozzle by the screw rotation action. The mold is pretty cold which might have cooling channels run through it. This causes the molten polymer solidifies almost once the mold cavity is filled. The solidified part with all the final required shape is then ejected out when the mold open again. It will likely be further cooled down with the ambient air.
Plastic injection machine is used to support the mold in place and also to melt the plastic and inject it to the mold cavity.
Injection machine is classified by it tonnage. Tonnage may be the clamping force that this machine use to clamp the mold during injection molding process. It might be ranged from below 10ton to 5000 tons, depend on part size and material used.
Another variety of injection machine is be it single injection machine or double injection machine. For double injection machine, it can have 2 group of screw plunger, hoppers and nozzles.
In Medical equipment plastic mold, there injetion many common defect due to the process constraint and material properties.
Sink mark, short mold, wrap, silver streak, flow mark, flashes, weld line etc..
With better injection machine, material, skill and parts design, such defect may be overcome very easily nowadays.