Manufacturing by the removal of material may be among the oldest of human endeavors. In fact, the Stone Age takes its name from the process of chipping away unwanted rock to yield useful tools. Obviously, that process was completely manual. Even though it has become far more sophisticated, machining has continued to be labor-intensive and therefore challenging to use in the manufacture of prototypes.

By the late 20th century, manual drafting had given way to computers and CAD software, and manual machining had evolved into computer numeric controlled (CNC) machining. But between those automated processes, there remained two very labor-intensive steps. The first of these was reviewing the design from an engineering standpoint and determining a price quote. The other was the conversion of the model from its original paper or electronic form to the machine code (toolpaths) that instruct the CNC machining equipment in the production of the finished part.

Both of these were time-consuming, painstaking processes that could cost hundreds or thousands of dollars and take days of trained professionals’ time, even with the use of high-end computer aided manufacturing (CAM) software tools. The cost and delay could be tolerated, if grudgingly, when a large number of copies were needed. But they made it difficult or impossible to justify the use of the CNC machining process to produce a small number of prototypes. That was particularly unfortunate for the plastics industry, since machined prototypes, being made from blocks of engineering grade resins, could do an excellent job of representing injection molded parts for the functional testing required during product development.

Of course, developers still had the option of using non-CNC machining, but that, too, was costly and slow. Instead, they turned to the emerging technologies of additive rapid prototyping (RP), which used software to control the process of layering plastic materials to produce a physical facsimile directly from the 3D CAD model. But while the additive rapid prototyping processes were fast and inexpensive, they could only use a small number of resins, and they produced parts with rough surfaces and reduced material properties due to the layering process. This was a distinct disadvantage compared to the solid construction and wide variety of resins available using CNC machining, but prototype parts could be obtained quickly via additive RP, so it was seen as a reasonable tradeoff.

The obvious answer was to computerize toolpath generation for CNC machining, but this required more sophisticated software and an enormous amount of processing power. First Cut Prototype, a division of Proto Labs, Inc., has developed software that runs on a high-speed 1.9 teraflop compute cluster that can generate toolpaths in minutes instead of days, all without the need for CAM programmers.

This system supports the automated preparation of FirstQuote® web-based quotations, on-line ordering, and the manufacture of CNC-machined “subtractive RP” parts in as little as one business day, essentially providing all of the advantages of additive RP processes without the associated limitations.

The end result is that, today, subtractive RP can produce “injection molding equivalent” prototypes even faster than additive RP processes can produce prototypes of lesser quality, so there is simply no reason to settle for less.

www.protolabs.com

MPF