Detail Technologies (Wyoming, MI), a contract machining company, has increased its revenues by retrofitting a coordinate measuring machine (CMM) with a laser scanner to increase its accuracy and speed. The laser scanner can capture almost 15,000 points per second, and the company is still able to switch back to the CMM probe for highly accurate measurements of individual points.
"This dramatic improvement in our reverse engineering and inspection capabilities has helped us generate substantial additional revenues," says Bryan Herrington, president of Detail Technologies. "That's because when we get a reverse engineering job, we typically also get the job to build more parts."
In many ways, a laser scanner retrofit for a CMM is even better than having both machines, he says. Each machine has unique capabilities which, when coupled together, make an extremely strong reverse engineering tool.
"I almost never use just the laser scanner," says John Amos, reverse engineering specialist at Detail Technologies. "The two are a perfect fit. Instead of buying a new CMM, you could purchase a used machine-the mechanics of which have not changed in over a decade-and retrofit it with the latest CMM software, as well as with the laser scanning
The company was founded in 1995 and offers prototyping, limited production and manufacturing services all under one roof. Its customer base includes office furniture, medical equipment, and appliance and automotive manufacturers.
Herrington says that many prospective customers have a physical part but no computer-aided design (CAD) geometry that would allow it to be easily machined on computer numerical control (CNC) equipment. He purchased the CMM so that he could reverse engineer physical components prior to machining additional copies and also to improve the company's inspection capabilities. The ability to capture individual points greatly increased the accuracy with which the company could duplicate its customers' existing parts. "Over time, our customers began to bring us more and more complicated parts and models, many with contoured 3-D surfaces," says Herrington. "A greater number of points need to be measured to evaluate these complicated parts. As a result, the time required to perform reverse engineering on the CMM made it cost prohibitive, and we had to turn down work because it would have taken too long and too much money to create the data."
Herrington heard about laser scanning technology that works by projecting a line of laser light onto surfaces while cameras continuously triangulate the changing distance and profile of the laser line as it sweeps along the surface, enabling an object to be accurately replicated. The probe's computer translates the video image of the line into 3-D coordinates, providing real-time data renderings that give the operator immediate feedback on areas that might have been missed. Laser scanners are able to quickly measure large parts without the need for templates or fixtures, while generating far greater numbers of data points than probes. Because there is no probe on a laser scanner that must physically touch the object, the problems of depressing soft objects, measuring small details and capturing complex freeform surfaces are eliminated.
Retrofitting instead of buying
"Retrofit kits offer the ability to attach a laser probe to a CMM," says Herrington. "The cost is only a fraction of what would be involved in purchasing a complete laser scanner because the retrofit eliminates the need to duplicate the base and motion control system, which constitute the majority of the cost of a laser scanner. I also like the idea of being able to switch back and forth between the laser and CMM probes so as to utilize the best features of both on every
He selected a retrofit package from Laser Design Inc. (Minneapolis). Installation involved integrating Laser Design's encoder interface unit with the CMM motion control system electronics. The CMM's error correction table was translated to the format of the computer used to operate the laser probe. Whenever the probe is mounted on the CMM, its orientation relative to the motion transport must be determined. From then on, the laser controller can develop coordinates on the part surface, combining the probe reference frame coordinates with the motion transport coordinates.
The laser probe can acquire a million points in a little over 1 minute, and the CMM probe can be used to verify the laser scan results. The Geomagic software from Rainbow Geomagic Inc. (Research Triangle Park, NC) provided with the scanner simplifies the process of moving from point cloud to CAD model.
The improved capabilities have led to increased sales. Herrington points to a recent case where a customer provided a shift lever and asked the company to reverse engineer it in order to design a testing fixture that fits perfectly around it. "As our customers began to get the message that we could reverse engineer complicated parts to a high level of accuracy, we began to see an influx of jobs that we would have never gotten in the past," Herrington says.