Computer-Aided Inspection Promises Big Savings
Emerick, who is a staff designer at the Cedar Rapids, IA, plant of electrical products maker Square D, is using new software that combines the speed of noncontact 3-D scanning with a new level of simplicity for computer-aided inspection (CAI).
Like most companies that manufacture a large number of products, Square D uses 3-D computer-aided design and manufacturing (CAD/CAM) tools that significantly speed up the design process and cut down on development costs. The only part of the manufacturing process that has not been made digital is the critical inspection stage, Emerick says.
The company does first-article inspections on all of its parts, which involves examining every feature and dimension for flaws or deviations from the original model. Traditionally the company has used coordinate measuring machines (CMMs) for the inspections. But that process is slow and expensive, which is why Emerick decided to move to 3-D inspection.
Inspecting with CMMs requires that designers create a 2-D drawing in addition to the 3-D CAD model of a part. The drawing is used to inspect the part at specific locations to verify that it matches the design.
"The dimensions from the 2-D drawing are programmed into a CMM, the part is probed at key locations and a spreadsheet of the probed values is produced," Emerick explains. "The designer then has to look, line-by-line, and decide if the probed dimension is within tolerance, or if corrective action is required." Because some parts require 1,200 lines of dimensions, this approach is time consuming and tedious, he says.
Emerick's research on 3-D inspection tools led him to Geomagic Qualify software from Raindrop Geomagic Inc. (Research Triangle Park, NC). Square D has been testing the product for the past several months and plans to implement it this year as a regular part of its manufacturing inspection process.
Scanning the clouds
Geomagic Qualify processes point-cloud data from a laser scanner or other 3-D scanning device. The software provides a graphical comparison of the manufactured part compared to the CAD model, automatically performing first-article inspection.
"By producing point clouds of the entire part, I can now measure the part everywhere and not be limited to the specific locations on a drawing," Emerick says. "By comparing the CAD database to the CAM-produced part, I can instantly see where differences occur and make an evaluation of the impact or seriousness of the deviation. You don't need to be an expert to use the software -- the user interface is intuitive and follows a simple workflow: align, compare, evaluate and report."
The CAI process saves both time and money for Square D. Depending on workload, the company sometimes outsources CMM inspection work to providers that charge about $100 per hour for the service and can validate six to eight dimensions per hour, says Emerick. That works out to about $12.50 per dimension, a cost that Square D can avoid by using the CAI process in-house.
Square D recently applied the technique to a plastic molded circuit breaker cover that had 1,295 dimensions to be inspected. Using an outside inspection service would have cost about $16,000 to have every dimension measured with a CMM, only to find that just two dimensions were out of tolerance, says Emerick. "With Geomagic Qualify, I can quickly see the two features that don't match the CAD model. I don't have to measure all 1,295 dimensions," he notes. Further, the outsourced CMM inspection method would have required about three weeks, as opposed to two days with the new method, he says.
"This could really change the way things operate here," says Emerick. "We expect this software to save us considerable time and money in our first-article inspection process. Our designers will be able to identify immediately where the part does and doesn't match the CAD database, then provide an on-screen 3-D graphical report back to tooling, which can quickly understand where the problems lie and make necessary changes."
Raindrop Geomagic Inc.
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- The software processes data from a 3-D point cloud from a laser scanner, eliminating the need for slower and more time-consuming CMM measurements.
- The software provides a graphical comparison of the manufactured part compared to the CAD model, automatically performing first-article inspection, tool validation, wear analysis, object alignment, and 2-D and 3-D dimensional analysis.
- On one part with 1,295 dimensions to be measured, the new inspection method saved more than $16,000 and reduced the time required from three weeks to two days.