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Abrasive-belt machine gets wheels.

In 1976, Ford Motor Company installed a Hammond rotary multiple-station abrasive-belt polishing machine in the Ford plant in Puerto Rico. The machine was designed to finish to length the end face of a rotor shaft for a power-steering system. Six spindles were located on a rotary table, with two abrasive-belt polishing heads.

The Hammond machine provided a solid increase in production and proved to be cost effective. Within a Year, Ford installed a second machine. Except for start-up adjustments and normal maintenance, the two machines have been operating 24 hr/day-with virtually no downtime.

Grinding conversion

Although the machines served well, Ford's dedication to design and manufacturing improvements through technological developments necessitated even closer tolerances. In January 1989, the machines were retrofitted to meet these requirements. The two machines were modified from abrasive-belt operation to employ bonded grinding wheels and noncontact gaging systems to automatically adjust the heads.

The new features provide capability for closer tolerance of workpiece size and flatness. The retrofit also saved time by eliminating belt changing and manual adjustment to compensate for belt wear.

The new gaging system improved quality by producing more consistent parts, which eliminated hours of manual inspection. Also, two wing-mounted wire-wheel deburring heads were added to deburr the spine and ring groove.

Hammond built a third machine for the Puerto Rican Plant to finish a new input shaft for the power-steering pump. The new part is a hardened piece in a different size, but with the same stringent QC requirements. The new machine incorporates all the technical improvements of the rebuilt machines, except it has seven spindles instead of six, which allows for an automatic unload station. The unload chute orientates the part to a conveyor belt that transfers it to the next operation.

New wheels

Engineers selected Norton SG grinding wheels as the media for all three machines. The SG wheel is a ceramic-coated aluminum-oxide grain specially suited for heat-treated parts. Part size is adaptively controlled by an in-process gaging system similar to the ones installed on the modified machines. The system scans the shaft length and precisely sets wheel position, compensating for grinding-wheel wear (within 0.002 19.

The gaging system allows use of up to 50 percent of the grinding wheel diameter. The wheel oscillates as the workpiece rotates across it, minimizing heat buildup and using 100 percent of the wheel surface. The grinding process is cooled by an air-mist spray system.
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Publication:Tooling & Production
Date:Jul 1, 1990
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