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Technology in Action Te concept of zero defects is very literal, and the mandate is


well enforced. So, aerospace shops continuing to be successful and competitive, such as Christopher Tool, are those now pro- ducing perfect parts that are always within specified tolerances. “Tese days, aerospace OEMs will refuse any parts that devi-


ate from tolerance,” said Patrick Christopher, president of Chris- topher Tool & Manufacturing Co. “All parts must be to print and documented with the proper paperwork, and shops must take initiatives and have corrective measures and benchmarking in place to ensure any past mistakes will not be repeated.”


Te large-size milling machine features linear motors on


its main axes and optimized direct-drive motors for its B and C axes. Both the GF AgieCharmilles milling machine and wire EDM incorporate glass-scale positioning that provides Christopher Tool with extremely high precision and superior part surface finishing capabilities. In addition to its involvement with the Joint Strike Fighter


program, the shop has a worldwide customer base and supplies components to all the major aircraſt jet engine builders. And while over half of the shop’s work is in aerospace/defense, it also manufactures components for the oil and gas industry, does prototyping for diesel engines and provides parts for robotics. Production levels are low-to-medium volume, job lot sizes


average between 30 and 50 pieces, and between 400 and 500 jobs are shipped per month—with 60% of those being recur- ring work, the rest new. In aircraſt and aerospace work, the shop typically produces the prototype components and then gets the job to manufacture at production volumes. Aerospace jobs can entail parts for pumps, actuation sys-


Hansen VP of Operations Craig Peck (left) and Machinist Bob Macho, two champions of the shop’s “zero part defects” initiative.


All of this “mandatory continuous improvement,” he said,


has significantly changed the aerospace industry landscape. Quality is paramount and must be maintained for parts that grow increasingly more complex. To fulfill these requirements, the shop constantly invests in expanding its technological capabilities—two recent examples being full simultaneous five-axis high-speed machining and rotary axis wire electrical discharge machining (EDM). Because of these two machines, the shop can now process


previously farmed-out parts in-house as well as shorten cycle times for many of its existing components. But most impor- tantly, the machines make it easier to achieve better surface finishes and much tighter tolerances. Propelled by its heavy involvement with the Joint


Strike Fighter program, Christopher Tool added a GF AgieCharmilles HSM (high-speed machining) Mikron 600U LP full five-axis milling machine and Cut 200 wire EDM to its existing 35 or so pieces of CNC equipment. With a tilt/rotary table design, the milling machine delivers +30/-110° B-axis travel and 360° in C. Te shop’s Cut 200 wire EDM features a rotary fourth (B) axis specifically for complex part geometries. Te HSM 600U LP’s high-speed comes from a 36,000-rpm


32-hp (24-kW) spindle and rapid traverse speed of 196 fpm (60 m/min). And for continuous production, it is equipped with an integrated pallet-changing system.


68 Aerospace & Defense Manufacturing 2013


tems, fuel control systems and auxiliary power units for both defense and commercial aircraſt. Most part sizes fall within a 10" (254-mm) cube, and they are machined from both raw stock material and castings. Christopher Tool defines part complexity based on its


geometric intricacy and tolerance requirements. Te shop routinely works in true position tolerances between 0.0002 to 0.0005" (0.005–0.0127 mm), flatness/squareness toler- ances to within 0.00005" (0.00127 mm)—some parts even 0.00002" (0.0005 mm)—and to Ra


2 surface finishes. Adding


to the challenge, all parts are made from exotic and tough- to-machine Nickel alloys and hard to machine steels with low coefficient of expansion. Such materials include Monel, Hastalloy, titanium, carbide and powdered metal (CPM 10V) as well as precipitation hardened materials (17-4 and 15-5) and some high-speed steels such as T1, T15 and M2. And with all of its experience, the shop definitely catego- rizes itself as an expert in machining these materials and in constantly holding extremely tight tolerances in every part it produces. Te shop also has turning machines, vertical and horizon-


tal machining centers, grinders and a coordinate measuring machine (CMM). But with the five-axis machine and rotary- axis EDM, many jobs previously done on the shop’s other CNC machines have been moved to these two newer machines. “In addition to the impellers now machined in-house, we


are processing several other parts on the HSM 600U LP, and doing so in single setups, allowing us to access all necessary part surfaces to shorten cycle times and further improve preci- sion,” explained Craig Peck, vice-president of operations at Christopher Tool & Manufacturing Co. “Many of these parts previously required several different machines with multiple setups and operations. And with the rotary fourth-axis on the


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