TechFront New Developments in Manufacturing and Technology Honing Technology Conquers Aerospace H


oning was invented more than 70 years ago to de- glaze cylinder bores in early automobiles. Since then, conventional honing has been routinely used to create crosshatch surface finish in bores to enhance oil retention to lubricate and seal sliding/mating parts like pistons, plungers and shafts. New technology has made it a good fit for the most advanced aerospace re- quirements for ultra-precise machined parts. “Computer controls, new tool designs, new abrasives, integrated air-gage part mea- surement and servo-driven tool feed systems and spindles enable new honing machines to produce part bores with 0.000010" [0.00025- mm] accuracy and crosshatched surface finishes targeted to a very narrow range,” said Dennis Westhoff, business development manager, Sunnen Products Co., (St. Louis, MO). “The aerospace industry is constantly tightening the requirements for parts to achieve lighter weight and, particularly, great- er performance from end products—higher power densities, more precise control, tighter sealing, less hysteresis, noise and vibration. “This new generation of honing machines is enabling aerospace suppliers to meet a host of challenges for parts that include ram-air turbine components, fuse pins, turbine hubs/disks, landing gear, hydraulic valve sleeves, accumulators and pumps,” said Westhoff. “Flight control systems are a good example. The ultra-high-performance hydraulic valves in these systems are about 125–250-mm long with a bore of about 12- mm diameter, including numerous lands and crossholes. Honing is used to produce bore diameter tolerances of 0.00025–0.0005 mm. “In fact, some parts are produced to tolerances beyond the measuring capability of many gages. In addition to sizing and fin-


ishing the bore, honing perfects the roundness, straightness and finish of the bore. These valves operate with a clearance of 0.005 mm or less between the valve body and match- ground plunger. The same holds true for the moving parts in the pumps that power these systems. As operating clearances


Piston pumps used in hydraulic flight control systems have clearances of 0.005 mm between moving parts, requiring ultra-precise bore size, roundness and straightness. Piston pump bodies are shown in a multispindle Sunnen honing machine which can control bore size to within 0.00025 mm. The machine is equipped with air gaging stations between spindles.


May 2013 | ManufacturingEngineeringMedia.com 35


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