Modern Machine Shop

JUL 2018

Modern Machine Shop is focused on all aspects of metalworking technology - Providing the new product technologies; process solutions; supplier listings; business management; networking; and event information that companies need to be competitive.

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Machining's Role in Camera Production Modern Machine Shop 89 inside these large parts to machine difficult- to-reach areas such as the pockets in the back f lange. Shrink-fit tooling supported the long tools necessary to reach some of the pockets, and Keller milled with a very light depth of cut to ensure good surface finishes in these areas. The shrink-fit tooling also reduced vibration, resulting in more accurate and smooth cutting. A workholding scheme that held the f lange up off the table (using a combination of stan- dard clamps with blocks and aluminum cutoffs from waterjetting to hold and elevate the part) allowed for better machining access. This arrangement plus the f lexibility of the five- axis head made it possible to machine the back f lange in just two setups. The company may use a similar strategy for the camera housing, where the ram and spindle will be inside the part to machine internal features. To program the camera parts for the Parpas machining center, Keller started with Mastercam from CNC Software Inc. "There are a couple hundred operations on these parts," says Mr. Steggs, who programed both LSST parts for the machining center. "It takes prep time to make sure we're good out of the gate, and Mastercam is really our first line of defense not just for lights-out, but also successfully completing one-off or first-article jobs," he notes. Once the program is created and initial simulations are run, Mr. Steggs moves to Vericut from CGTech for a comprehensive simulation of the toolpath motion and material removal process, including the guards, spindle, tools, clamps and fixtures. For complex parts such as the camera housing in which the spindle will need to operate deep within its inner diameter (ID), achieving an accu- rate simulation is especially important. Keller has also found that verifying dimensional accuracy and optimizing the tool paths in advance leads to better finishes on surfaces and edges. Close Up After machining, both parts require polishing to a No. 4 dairy, or sanitary, finish. This standard is commonly used in the food industry (including dairy equipment) because the surface created resists harboring potentially dangerous bacteria. Polishing is a core competency at Keller, because many of the vacuum chambers it makes require polishing around the seals. The slightest cross- hatch can create a void and allow leakage, so it is To inspect the back flange, Keller used both the touch- probing and scanning capabilities of its Global Advantage CMM. The company also had an added resource during this step: representatives from SLAC were present during the inspection of the part. SLAC partnering with Keller allowed for clarification and adjustment of tolerances on the fly. Photo: Keller Technology

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