Plastic Injection Molding vs. Plastic Machining: How to Decide

While not all materials are capable of being injection molded, the ones that are capable exhibit excellent results. Plastic molding is sometimes referred to as injection molding. Make no mistake, machining plastic components and plastic molding is not the same. Consulting a professional is the best way to be sure which process will best fit your needs.

With injection molding, plastic pellets are heated to the point of going from rigid to viscous. Once they reach the point of melting these pellets are actually injected into an enclosed mold or cavity. Once these pellets cool they form to the shape of the cavity that they are enclosed in.

Plastic machining on the other hand involved the whittling of plastic from a large shape to smaller one. It is very similar to whittling wood and making shavings with a knife. Now, plastic machining is far more expensive than plastic molding, but machining parts is cheaper than molding them?

Why; this is due to the cost of the mold. Mold prices can range upwards of $200,000. It all comes down to the complexity of the mold, but even the cheaper ones are $5,000 or more. If you only need a few parts why would you spend that kind of money for a mold? Once a mold has been created it is no easy task to alter it at all. For anyone needing only a thousand or so parts, machining makes a lot more sense, and it offers far more flexibility.

One would think that larger orders would automatically lean towards molding, but there are a few exceptions to the rule. One must think about precision. Plastic machining is far more precise coming within .001” of the requirements needed vs .005” with plastic molding. That is huge in some industries.

Another exception to the rule is the area of uniform smoothness. The process that is required to transfer the plastic into the molds will leave some imperfections on the surface. Injection molding uses runners in an overall process that aids to slight surface imperfections caused by the gate and pins during removal from the mold. This means that machining is better for any project where surface perfection or smoothness is an issue.

Where turnaround time is concerned machining also beats molding hands down. If you have any questions that were not answered here please contact us for a free consultation.