Many parts and components of injection molding is made by CNC, e.g., sliders, ejectors, runners, etc.
Plastic injection molding is the most commonly used manufacturing process for the fabrication of plastic parts. A wide variety of products are manufactured using injection molding, which vary greatly in their size, complexity, and application.
The custom injection mold process requires the use of an injection molding machine, raw plastic material, and a mold. The plastic is melted in the machine and then injected into the mold, where it cools and solidifies into the final part.
Injection molding produces parts by forcing molten plastic into a mold where it cools and hardens. Granular plastic is fed by gravity from a hopper into a heated barrel. As the granules are moved forward by a screw-type plunger, the plastic is forced into a heating chamber, where it is melted. As the plunger advances further, the melted plastic is forced through a nozzle into the mold cavity. The mold remains relatively cold so the plastic solidifies almost as soon as the mold is filled. Custom steel tooling is required and adds to the initial cost but is quickly amortized.
Injection molding provides low cost at moderate to large quantities. This method of making plastic parts is an extremely versatile process for producing a wide range of parts with an excellent finish. Almost any 2D or 3D shape can be achieved. However draft is required in most cases as the shape must allow ejection from the mold. Side holes and even threaded holes are possible though they complicate the tooling.