innovations CASTING
A Solution to Optimize Large Cast Part Machining
not for everyone. T e generalization ‘parts are parts’ does not apply in this case,” said Ben Belzer, vice president, TCI Precision Metals, Gardena, Calif. “To be profi cient requires commitment to constant process improvement, equipment evaluation and investment. And, to top it off , mistakes are very expensive.” TCI provides contract manufacturing services and produces precision machine-ready blanks from aluminum, stainless steel and other alloys for a variety of industries. Belzer analyzed variables in the machining process that
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directly aff ect quality and consume the greatest amount of time. T e result focused on three key areas: 1. Cutting metal more of the time. 2. Reducing part movement. 3. Maintaining a digital workfl ow.
arge cast metal parts pose unique challenges in ma- chining due to their size and weight, as well as cost and other considerations. Often, tight tolerances are required, along with optimal quality and effi ciency. “Machining large parts, especially castings, is
Jim Edwards, regional metrology engineer for Verisurf
Software Inc., Anaheim, Calif., worked with TCI to imple- ment best practices for each of the three challenge areas. Verisurf provides three-dimensional measurement solutions for model-based, automated computer-aided inspection and reverse engineering. T e core of TCI’s solution was VerisurfX Software running a portable CMM with optional scan head. With a standard touch probe and optional digital scan head, the device performs both point-based inspection and scan- ning to a point cloud data set. Refi ned processes and a fl exible metrology solution solved
all three objectives. Machining large parts such as composite 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 too aggres- sive machining can damage or destroy the tool. T e goal is to keep the tool cutting more often. When a batch of large cast parts are received for fi n-
ished 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. “T e diff erences 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. “T e tool path also can be modifi ed to start cutting specifi c high points vs. cutting air over the entire part.” Moving a large part from the machining center to the
quality inspection room, back to the machining center, then refi xturing and aligning for modifi cation takes considerable time. T e 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 part in the machining center once and remove it only when it is completed and verifi ed,
The software provides color coded and numerical tolerance variances between the design CAD data and the cast part.
48 | METAL CASTING DESIGN & PURCHASING | May/Jun 2013
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