Plastic injection molding process involves the usage of plastic, or polymer. The granular polymer is fed into a heated barrel. Additionally it is further melted and mixed from the barrel through the rotation process of a screw type plunger, as heat is generated with the friction between polymer granules if the screw is rotating.
The Car color plastic mold will be forced into a mold cavity with 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 using the final required shape will be ejected out if the mold open again. It will be further cooled off through the ambient air.
Plastic injection machine is utilized to keep the mold into position and also to melt the plastic and inject it in the mold cavity.
Injection machine is classified by it tonnage. Tonnage is the clamping force how the machine use to clamp the mold during injection molding process. It may be ranged from under 10ton to 5000 tons, depend on part size and materials.
Another variety of injection machine is whether it be single injection machine or double injection machine. For double injection machine, it will have 2 set of screw plunger, hoppers and nozzles.
In Medical equipment plastic mold, there injetion many common defect because of 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 could be overcome with ease nowadays.