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on BREP (boundary representation) associative surface-technology soft- ware from Tebis, designed to support the creation, adaptation, repair and optimization of CAD surfaces.
“The surface created by the mesh data is essentially like the pattern on the surface of a soccer ball—a series of pentagons,” notes Tebis West Coast sales manager Michael Thiessen. “As a result, you can’t generate highly accu- rate curves. In addition, when you scan an item with sharp corners you may discover some built-in inaccuracies. Scanners, for example, can’t identify sharp corners due to the triangulation of the data. Instead, they approximate with small radii and the Tebis software then creates a sharp corner.”
Adds Tadday: “BREP creates high- quality surfaces and clean curves, and sets them to the desired tolerances. The final product is data that I can open up in any CAD system. In addi- tion, the mesh creates surfaces that can be very ‘heavy’—using many small-
er surfaces. This added ‘weight’ can be a problem when generating toolpaths, and especially when trying to put springback or coordination moves back into the tool. A BREP surface, by com- parison, is ‘light,’ which makes it easi- er to do a lot of things, including put- ting these modifications back into the original tooling.”
Atlas takes the surfaces created by BREP and transfers them into its Uni- graphics or Catia systems, followed by the generation of the needed machine- tool programs.
“BREP is integrated with the Tebis CAD and manufacturing software,” Tadday says, “so that the entire process—from working with the ini- tial scan data to CNC program cre- ation—could be handled in Tebis, but we decided to go with our Unigraphics and Catia software because we have been working with them for many years. It’s all seamless because Tebis has excellent conversion into Catia and Unigraphics.”
A Growing Trend
Thiessen notes a trend in the North American tool-and-die landscape toward increased die reengineering. “Die shops are making fewer new builds because so many large cus- tomers have chosen to cut costs by having their dies built overseas,” he says. “That, however, doesn’t mean there’s a shortage of work. The demand for reengineering has increased because tools returning from overseas often are missing engineering changes that have been requested. In other instances, changes may have been made in the building process that may, in fact, be beneficial, but are not reflect- ed in the documentation. Also, there may be quality issues that need to be addressed. In situations like these, shops use sophisticated tools to evalu- ate the current state of the tool and identify the necessary modifications in order to complete the work.”
Tadday adds that “sometimes cus- tomers send us dies that not only are
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