Plastics Machining vs. Injection Molding

A question we are sometimes asked is, “Should I have my part machined or injection molded?” The short answer is, “It depends.” In this blog we look at some of the factors you should consider when deciding between machining or injection molding as a means of production.

What is plastics machining?

Machining of plastics involves the production of finished parts using a computer controlled (CNC) router or milling machine. Using this technology, plastic materials can be cut, shaped, drilled, contoured, surfaced, etc. with the use of precision tooling under computer control.

What is injection molding?

Plastic injection molding refers is a process in which plastic pellets or powders are fed into the hopper of an injection machine, where they are melted under heat to maintain a flowing state. Under pressure, the molten plastic is then injected into a closed mold though the injection nozzle and the runner system of the mold. After cooling and shaping, the molten plastic is solidified into the desired plastic part.

Plastics machining vs. injection molding

An advantage of injection molding is that it supports large scale production. While this feature is attractive when producing large quantities of parts, the up-front costs tend to be higher due to design, testing, and tooling requirements. Therefore, if you are going to produce parts in high volumes using injection molding, you want to make sure you get the part design right the first time.

When production quantities do not justify the high up-front costs of injection molding, plastic machining offers the following advantages:

  • Lower initial costs. Because design, testing and tooling requirements are reduced or eliminated with machining, initial costs are much lower.

  • Fewer material limitations. Not all plastic materials can be injection molded. On the other hand, most currently available plastic materials can be machined.

  • Tighter tolerances. Achieving and maintaining a tight tolerance can mean the difference between a good part and a defective one. Machining allows for tighter dimensional tolerances than can be achieved with injection molding.

  • Greater part consistency. Depending on how well process parameters are maintained during injection molding, part consistency can sometimes vary. Because there is less variability in process parameters, machining tends to produce parts with greater consistency.

At CRG, we can support your needs for industrial or automotive parts produced by either plastics machining or injection molding. Because there are a wide variety of plastic materials and grades available the marketplace, CRG can provide guidance on selecting the best material for your application.  The CRG team will support you across all aspects of the product realization process, from design and prototyping, to final part production.

If you want to learn more about our plastics machining or injection molding services, please contact our sales department for assistance at