CASTING INNOVATIONS Reducing Maintenance, Downtime in Finishing
Large cast metal parts pose unique challenges in machining due to their size and weight, as well as cost and other considerations. Often, tight tolerances are required, along with optimal quality and efficiency. “Machining large parts,
especially castings, is not for everyone. Te generaliza- tion ‘parts are parts’ does not apply in this case,” said Ben Belzer, vice president, TCI Precision Metals, Gardena, Calif. “To be proficient re- quires commitment to constant process improvement, equipment evaluation and investment. And, to top it off, mis- takes are very expensive.” TCI provides contract manufactur-
ing services and produces precision machine-ready blanks from aluminum, stainless steel and other alloys for a variety of industries. Belzer analyzed variables in the ma-
chining process that directly affect quality and consume the greatest amount of time. Te result focused on three key areas: 1. Cutting metal more of the time. 2. Reducing part movement. 3. Maintaining a digital workflow. Jim Edwards, regional metrology
engineer for Verisurf Software Inc., Anaheim, Calif., worked with TCI to implement best practices for each of the three challenge areas. Verisurf provides 3-D measurement solutions for model- based, automated computer-aided inspection and reverse engineering. Te core of TCI’s solution was VerisurfX Software running a portable CMM with optional scan head. With a stan- dard touch probe and optional digital scan head, the device performs both point-based inspection and scanning to a point cloud data set. Refined processes and a flexible me-
trology solution solved all three objectives. Machining large parts such as com- posite mold tooling for aerospace, or large castings for oil and gas, typically involves large surface areas. Compensating for high spots on a wing mold or variances between castings can result in cutting air for hours, days or even weeks. Miscalculation or
modification takes consid- erable time. Te part can be damaged and there is a risk of injury associated with moving large parts around the shop. “If you can place a large
The software provides color coded and numerical tolerance variances between the design CAD data and the cast part.
too aggressive machining can damage or destroy the tool. Te goal is to keep the tool cutting more often. When a batch of large cast parts
are received for finished machining, a sample group of the parts are “painted” (scanned) using the CMM with scan head. Verisurf Reverse Software captures the data as a point cloud and converts it into a precise CAD model. “Te differences between the as-cast
part is compared digitally to the as- designed part, allowing the machine tool path to be optimized to cut metal more of the time while avoiding tool crashes,” Belzer said. “Te tool path also can be modified to start cutting specific high points vs. cutting air over the entire part.” Moving a large part from the ma-
chining center to the quality inspec- tion room, back to the machining center, then refixturing and aligning for
part in the machining center once and remove it only when it is com- pleted and verified, you will save considerable time and effort,” Belzer said. “Machine operators will remain focused on com- pleting the part at hand
and avoid distractions associated with switching out parts, refixturing, alignment and all the potential for error that goes along with it.” Part movement begins with align- ment and fixturing the part to the table. Te software can tell the machine the exact placement and orientation of the part on the table after the user samples a few relational points on the physical part with the portable CMM, using the probe tip instead of the scanner at- tachment, and runs a simple alignment routine. Once the machining process is complete, the portable CMM and Veri- surf software is used to quality inspect the part, in process. Closing the loop on digital
workflow is the key to improving the quality inspection and reporting process, according to Belzer. Verisurf Software accepts virtually all
Placing a large part in the machining center once and removing it only when it is completed and veri- fied saves considerable time and effort.
June 2013 MODERN CASTING | 43
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