Recently, a tier one automotive supplier asked Hunt Machine and Manufacturing to build a mold to produce an enhanced version of an existing interior trim component that sits on the top of the airbag module in an instrument panel. “The challenge came from the fact that we were given this task without any historical data that anyone felt comfortable with.” Hunt said. The part was so soft and flexible that it would have been impossible to use a contact measurement method to determine its geometry. It would have been possible to measure the mold using a contact measurement method but this would have created the challenge of somehow backing out the shrinkage allowance for the original material and adding the shrinkage allowance for the new material. In addition, there were intricate cursive graphics on the part that would have been nearly impossible to reproduce using a CMM.

Hunt looked for an alternative method of digitizing the part. “I was particularly impressed with the NVision people,” Hunt continued. “They seemed to have the best technology and the deepest talent.” “We reconstructed the instrument panel in our facility so we could mount the part exactly as it would be in a vehicle,” said Bill Bonner, Director of Sales and Consulting for NVision. “We scanned all sides of the part with our handheld scanner in only one day.” The result was a point cloud consisting of over 1,000,000 points. NVision separately scanned the lettering using handheld scanner which has even tighter resolution with a 50 by 35 millimeter scan range. NVision used surfacing software to automatically generate surfaces through the point cloud.

Hunt Machine provided the resulting CAD file to a design firm that converted it to Pro/ENGINEER CAD format, performed modifications requested by the customer and provided an IGES surface model file to Hunt Machine. Hunt Machine engineers read the file into their Unigraphics CAD system, converted the surface model to a solid model and produced a prototype using a stereolithography system. The customer examined the prototype and request several additional modifications. The goal of these changes was to improve the fit of the part with the rest of the instrument panel. Hunt Machine made these modifications and provided a new prototype. The customer said they were happy and Hunt Machine engineers then began the process of designing the mold to produce the new design. “We took the solid model that was approved by the customer and applied shrinkage factors to it,” Hunt said. “We also changed the design of the lifters and slides in order to make the mold less expensive to build and run faster in production.”

“Laser scanning provided substantial time savings while also improving accuracy on this job,” Hunt concluded. “We prepared an estimated timeline for this project using traditional CMM methods and using laser scanning. It showed it would have taken 28 weeks to do the job using CMM compared to the 16 weeks that was actually required with laser scanning. Another advantage was that we were able to produce a more accurate mold because the million-plus points generated in laser scanning made it possible to produce a solid model that accurately reflected the contours of the part.