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More Accurate CNC Prototypes Make Better Designs, Better Casting

Sept. 9, 2004
Architectural Area Lighting, La Mirada, CA, manufactures outdoor lighting fixtures, and it’s making more attractive and more functional products because it’s found a way to make more accurate CNC prototypes. AAL once made prototypes with hand tools, ...

Architectural Area Lighting, La Mirada, CA, manufactures outdoor lighting fixtures, and it’s making more attractive and more functional products because it’s found a way to make more accurate CNC prototypes. AAL once made prototypes with hand tools, which was time-consuming and often inaccurate. Now, with a Techno-Isel CNC router producing foam prototypes to match the computer-aided design (CAD) files, their models define parts within thousandths of an inch.

The CNC router runs requires no operator attention, and typically takes only about 12 hours to produce each prototype casting. “Having an accurate prototype makes it possible to evaluate the design to a higher degree and also lets us validate the fit and functionality of the part,” says Cory Landefeld, product design manager for AAL. “The new router paid for itself in less than a year by drastically reducing the time and money we spent on prototyping.”

AAL designers have been producing increasingly sophisticated 3D geometries that gain the approval of architects, specifiers, engineers, and building owners. They typically conceive and tweak their designs on-screen. But, while computer-modeling tools provide realistic views, the designs also have aspects that are difficult or impossible to evaluate on screen, says Robert Nankil, product designer.

“Rendering software is good but it can’t perfectly represent the way an object appears under actual lighting conditions. We wouldn’t think of investing tens of thousands of dollars to build diecast tooling until we were able to review the actual part,” according to Nakil. “We wouldn’t think of going into production without being able to view a prototype under different light conditions, put a bulb in the product to light it up, and place it into a real-world setting so we can see how it looks.”

Foam prototypes once were produced on a lathe, and with hand tools, and a complex prototype might tie up a skilled person for weeks. Since AAL has switched to the Techno router, their designs have continued to get more complex, so that it might take even longer to produce some prototypes. Thin-wall designs make accuracy critical for these prototypes.

Hand-built prototypes could never achieve the desired level of accuracy. “According to Andy McMillan, product designer. “There were some cases where we had to make expensive changes to the mold and others where we realized after the product came out that we could’ve made improvements if we had been able to view a more accurate prototype.”

The designers concluded that a more accurate prototyping tool would help them improve their product development efforts. “We considered several different options,” Landefeld said. “Stereolithography is accurate enough, but the machines within our price range did not have the envelope that we needed — 18318 in. We looked at some CNC machining centers, but the ones that were large enough for our parts were, over $100,000, in most cases. Next, we looked at a couple of CNC routers, machine tools with the flexibility and accuracy of a machining center but which are designed to cut softer materials such as wood, plastics and foam.

“We discovered that these machines had the envelope that we need and that the price was in an area that we could afford,” Landefeld concludes. “Of the two that we considered, the Techno machine was superior in terms of the accuracy it could provide. We also liked the fact that the Techno came as part of a complete package that included all of the software that we needed to get up and running. Finally, the price was right, under $30,000 for the full package.”

The Techno machine is constructed on steel stress-relieved bases with hardened steel linear ways. Its shaft-and-bearing system produces smooth, play-free motion. It uses anti-backlash ballscrews with excellent power transmission due to the rolling ball contact between the nut and screws. This type of contact ensures low friction, low wear, and long life. The ballscrews also make it possible to produce wooden parts to the machine resolution of 0.0005 in.

With the new machine, AAL designers can produce prototypes that are as accurate as finished parts. They export the design with IGES, STL or DXF neutral file format. Then, they import the file into the Visual Mill software provided with the Techno router. This package makes it simple to define the surfaces to be machined, and generate tool paths. Normally, the part is completed in two set-ups, one machining the inside and the other the outside. Then, the operator simply sets up the part and starts the machine.

AAL’s complicated parts typically take about 8 to 12 hours to machine. When each one is done, the technician removes it from the machine, performs some clean-up, paints it, and assembles it with other components into a complete product.