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Tech Front: Honing Technology Conquers Aerospace

Honing 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 requirements for ultra-precise machined parts.

"Computer controls, new tool designs, new abrasives, integrated air-gage part measurement 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, greater 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.  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.

"In fact, some parts are produced to tolerances beyond the measuring capability of many gages. In addition to sizing and finishing 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 between moving parts shrink, honing can tightly control the bore’s surface finish to retain a lubricating film of oil.

"Similarly, the bores of hydraulic accumulators are honed to eliminate any surface flaws that could propagate into cracks under stress. The bores of fuse pins, used at the attachment points of engine pylons, are honed to precise size and finish tolerances to ensure they shear under the correct level of stress. Multiple components in ram-air turbines are honed, as are the boltholes in turbine hubs and disks. The bores of gears used by Airbus, Boeing, Cessna, and NASA are honed for similar reasons," said Westhoff.

In production honing, process capability with small variability and high Cpk are essential. Tool expansion to achieve the desired results and final size is programmed based on rate of time. The tool feed system performs the same way on each cycle, starting with touch-off, sensed through spindle load or the force sensed on the tool feed system. Cycle time is always the same. However, when a batch of parts comes in with a different heat treatment, distortion, or variations, the operator must intervene to prevent the tool from expanding too quickly for part conditions and being damaged, or expanding the tool too slowly with a softer than normal workpiece, resulting in glazing of the honing stones, which won’t self-dress if the cutting force is too low.

New tool feed technology that servo-controls the force in the tool feed system enables the machine to sense and compensate for variables like heat treatment, distortion or size variation replacing the need for operator intervention. "The new Controlled-Force feature, which works in concert with the machine’s standard rate-feed system functions like cruise control to maintain the optimum cutting load on the honing abrasive throughout the cycle, regardless of the incoming part’s hardness, geometry or size variation. In effect, the machine detects what is happening in the bore when the abrasive contacts it, whereas with rate-feed alone, the machine feeds the tool per the program, not according to the real conditions the part is experiencing," said Westhoff. ME

For more information from Sunnen Products Co., go to or phone 314-781-2100.


Multidirectional Radio Touch Probe Compact high-speed TC62 multidirectional touch probe from Blum LMT achieves speed, precision and shop-floor versatility, along with operator convenience, using innovative BRC radio technology.

Compact high-speed TC62 multidirectional touch probe achieves speed, precision and shop-floor versatility along with operator convenience using innovative BRC radio technology. "The TC62 completes Blum’s range of metrology products with a radio probe that is used when a permanent visual connection to the receiver during measurement can’t be guaranteed," said Jon Kulikowski, president, Blum LMT (Erlanger, KY).

Compared to probes with IR transmission, the TC radio probes are effective when used on large-scale machines, five-axis machines or when the probe has to be immersed in the workpiece. The TC62 is the compact little brother to Blum’s TC60 probe that is mainly used in standard and large-scale machines and was introduced at 2008 EMO. "The TC62 with its compact size of just 40 mm in diameter is perfectly applicable for smaller machining centers and excels through extremely fast and robust data transmission," said Kulikowski. 

Instead of the usually applied channel-hopping method or channel assignment, this probe is transmitting the data collected to the receiver via the BRC technology. The advantage of this technology is based on each single bit of the radio signal running across the entire frequency bandwidth, thus making transmission particularly resistant to interference. The data is transmitted to the radio receiver RC66 quickly and securely. Multiple measuring systems, for example a tool setting probe and a touch probe, can be used, without problems with the BRC technology. Up to six measuring systems can be controlled with one receiver.

"Design of the touch probe allows considerably higher measuring speeds than comparable systems. Other systems measure at a speed of 16–20 ipm [400–500 mm/min] and often require two touchs, while the TC62 can measure with up to 80 ipm [2 m/min], offering significant reduction of measuring time. The probe also features the proven rotational symmetric measuring system which measures precise in all directions without the lobing effect which traditional probes have. Trigger signal generation of the Blum probe is initiated opto-electronically by shading a miniature light barrier, guaranteeing precision and reliable measurements," said Kulikowski. ME

For more information from Blum Laser Measuring Technology, go to, or phone 859-344-6789.


3D Projection Maps Aero Part Assembly

ProjectionWorks is 3D projection technology that is a key component of the Fastener Insertion Live Link System (FILLS) that automates assembly line fastening of large workpieces. FILLS was developed by a team of aerospace companies, including Variation Reduction Solutions Inc., Delta Sigma, Lockheed Martin Aerospace, and Northrop Grumman Aerospace Systems under a Small Business Innovative Research Grant from the Air Force Research Laboratory to automate data input and compare data against original specifications for fastener assembly.

FILLS digital thread process automates hole measurements that are done on the assembly line, stores the measurements in a database, and creates a list of fasteners that are brought to the assembly line. A color-coded map shows where the correct fasteners are to be installed and in what sequence. The map is projected onto the workpiece with part numbers, installation directions and access to an encyclopedia of information.With FILLS, mechanics on the assembly line see the most recent information relative to any aircraft or product they are working on in order to install the right part in the most efficient and accurate manner. Dozens of mechanics on the F-35, P3, C-5, and C-130 production lines, for example, are using Delta Sigma’s ProjectionWorks 3D technology to project assembly instructions directly onto aircraft parts.

As a result, FILLS is credited with saving more than 200 hours per plane and a potential $111 million for the F-35 program alone, according to David See, project manager for the Air Force Research Laboratory. "FILLS will revolutionize how we assemble, maintain and repair our fleets from jets to submarines to ships to satellites," said See.

The FILLS team’s accomplishment is developing improved "digital thread process" in which digital information collected by a computer is directly linked to the factory floor. "FILLS automates the hole measurements that are done on the assembly line and stores the measurements in a database," said Roger Richardson, director of business development for Delta Sigma. "FILLS then automatically creates a list of fasteners that are brought to the assembly line. ProjectionWorks then projects a color-coded map showing where the correct fasteners are to be installed in the sequence they are to be installed. The 3D map includes part numbers, directions and access to an encyclopedia of assembly information."

For their accomplishment, the FILLS team members received the 2012 Defense Manufacturing Technology (ManTech) Innovation Award. ME

For more information from Delta Sigma Co., go or,or phone 770-575-5100.


This article was first published in the May 2013 edition of Manufacturing Engineering magazine.  Click here for PDF

Published Date : 5/1/2013

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