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Manufacturer uses laser scanner to get the perfect fit.

Hensley Industries, Dallas, builds ground engaging tools for the construction and mining industries. One of the greatest challenges for Hensley in building replacement parts is creating teeth and adapters that fit perfectly with the installed base of existing equipment. For a new product line, Hensley engineers wanted to verify that its mating geometry was the same as that of its previous product line, which has been demonstrated over years to deliver a perfect fit with all the equipment the company supports. But the earlier product line was designed without the benefit of solid modeling, so the company did not have a definitive record of its geometry. The patterns for the molds used to cast the previous product line were hand-made by pattern makers and fine-tuned over the years.

In the past, the company would have addressed this type of measurement challenge with a touch probe coordinate measuring machine, where a solid model of the new product is used to generate a surface model in the IGES neutral file format, and 12 to 15 data points are created to represent important areas of the geometry. The IGES file is used to control the touch probe and measure the same data points on the existing product, which takes several hours. With this approach, only a small number of data points are captured, so it would have been impossible to obtain the complete geometry of the teeth and adapters.

So, Hensley engineers looked into laser scanning for a more complete reverse engineering of their previous product. Laser scanning systems work 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, enabling the object to be accurately replicated. The laser 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. Instead of collecting points one by one, the laser scanner picks up tens of thousands of points every second, so reverse engineering complicated parts can often be accomplished in an hour or two.


"Since this was our first project, it didn't make sense for us to purchase laser scanning technology," said Damian Castillo, CAD and administration manager for Hensley. "We weren't sure if we had enough work to justify the investment, and we were also concerned about the risk of technological obsolescence."

The company hired NVision, Southlake, Texas, to use its laser scanning systems to reverse engineer the eight castings in the product line. The parts were scanned in two days, and the NVision technician stayed onsite for two more days processing the data. The error map that resulted from the scans showed that in defining the geometry of the new product, engineers had accurately duplicated the old part. Hensley engineers then used the solid model as the master to produce the patterns using CNC geometry.


"This project demonstrated the viability of laser scanning both for reverse engineering our existing product line and for first article inspection," Castillo said. "In both areas, laser scanning provides far more accuracy than a touch probe, so it saves us a considerable amount of time that we previous had to spend tuning and modifying our product based on field test results. Soon after finishing this product, we made the decision to purchase the NVision laser scanner and have begun using it as a regular part of our product development process."

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Title Annotation:New Product
Publication:Modern Casting
Date:Oct 1, 2008
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