Plastic injection molding process involves the application of plastic, or polymer. The granular polymer is fed in a heated barrel. Also, it is further melted and mixed inside the barrel through the rotation procedure of a screw type plunger, as heat is generated with the friction between polymer granules if the screw is rotating.
The Plastic mold is going to be forced right into a mold cavity with all the required final shape using a nozzle from the screw rotation action. The mold is relatively cold which could have cooling channels run through it. This causes the molten polymer solidifies almost right after the mold cavity is filled. The solidified part with all the final required shape will be ejected out once the mold open again. It will likely be further cooled off with the ambient air.
Plastic injection machine is utilized to hold the mold in position and to melt the plastic and inject it in the mold cavity.
Injection machine is classified by it tonnage. Tonnage is definitely the clamping force that this machine use to clamp the mold during injection molding process. It might be ranged from under 10ton to 5000 tons, depend upon part size and materials.
Another variety of injection machine is whether it is single injection machine or double injection machine. For double injection machine, it can have 2 pair of screw plunger, hoppers and nozzles.
In Medical equipment plastic mold, there injetion many common defect due to 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 better parts design, such defect could be overcome with ease nowadays.