We recently completed a handbook on additive manufacturing. It will appear in the August issue of Design World. One of the things I became reaquainted with from working on this project is just how many options you have for rapidly prototyping (or manufacturing) your designs. It’s easy to get caught up in the idea that all we have are 3D printers, especially with all the media coverage this part of the industry is receiving today. But you have more options, including subtractive prototyping and rapid injection molding.

Under the broad umbrella term of rapid prototyping (or rapid manufacturing) you can choose additive technologies such as 3D printers, subtractive technologies such as CNC machines, and rapid injection molding (RIM) systems.

Each of these choices is available to you as either an in-house operation (with the purchase of the equipment) or as an outsourced option to a service bureau. The choice, of course, depends on the application.

With all the attention 3D printing is receiving, though, you might want to reacquaint yourself with the subtractive and RIM options.

Subtractive technologies usually use CNC machines. But CNCs are not the machines of the 1950s or 1960s. Vendors have been continually upgrading the design and operation of them so that you can simply push a button, walk away and come back to evaluate the result. Roland, for example, makes CNC machines that do not require programming in G code. And the price of some of these systems ranges from $20,000 to $60,000.

Rapid Injection Molding (RIM) involves injecting thermoplastic resins into a mold, just as is done in production injection molding. What makes the process “rapid” is the technology used to produce the mold, which is often machined from aluminum instead of the traditional tool steel used in production molds. Molded parts are strong and can have excellent finishes.

RIM is also the industry standard production process for plastic parts, so there are inherent advantages to prototyping in the same process if the situation allows. Almost any engineering grade resin can be used, so you are not constrained by the material limitations of the prototyping process.

So, when you are investigating rapid prototyping, remember to think in “threes.” One will be right for your prototyping or production needs.