Page 31 - MetalForming September 2011

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• Nickel Silvers • Stainless Steel • Zinc Strip Alloys 800.356.7923
line. Material comes to Voss Taylor as 20- ton steel coils from Interstate Steel Co., Elk Grove Village, IL, which contracts Voss Taylor to apply
the dry lube; blank-
ing the coated coils is A drawn compressor housing is ready for performed by Heidt- post-processing—a conveyor will carry
the drawn part to a shear trimmer, a man Steel Products, piercing unit and then to a wash station.
Toledo, OH.
Bristol allows a liberal range on coating thickness (or
weight) of 400 to 800 mg/sq. ft., and Voss Taylor has no problem meeting that range, says Ed Sikina, director of qual- ity assurance at the toll processor.
“We routinely apply the Tru-Chem product at 300 mg/sq. ft. to a tolerance of ±100 mg/sq. ft.,” Sikina says, “with a 1.33 or bet- ter Cpk. We run 6000 to 7000 tons of steel/month through the coating line, of which Bristol accounts for about one-third.”
Application and QA Processes
Voss Taylor’s coating equipment mounts on rails to allow it to be moved into and out of the pickling line quickly and efficiently. The process begins by leveling the coil prior to the material entering the acid bath. A rinse station follows the pickling process, then the material is dried and the dry- lube coating applied. An accumulator builds up 100 ft. of the coated steel to allow it to dry before recoiling.
Quality-assurance technicians at Bristol inspect incoming coated blanks before they make their way to the press lines. They test both sides of two blanks per every fifth lot of blanks; lot sizes range from 360 to 500 based on blank size. A techni- cian also inspects blanks periodically throughout each shift.
To test the blanks for proper lube application, a technician lays a weighted rubber ring in the center of the blank and applies an indicator solution inside the ring (0.1 percent bromophe- nol blue). He then deposits drops of 0.01-percent hydrochlo- ric acid into the ring until the indicator solution changes color. The amount of acid required indicates coating weight.
Tru-Chem’s T.C. 1800-3 comprises a water-soluble powder applied as a solution. Die buildup, peeling, powdering and sticking “are virtually eliminated,” says the company, “leav- ing no lubricant marks on drawn steel parts.” Compared to applying lube at the press, Bristol Compressors enjoys a much cleaner, safer process.
Prolonged Draw-Ring Life
“Not only are we holding the tight fitup tolerances required for welding the housings,” says Counts, “but we’re also more than quadrupling draw-ring life, running our draw rings for as long as 3 yr. This is due in part to the consistency of the dry- lube coating, as well as recent change in draw-ring radius. We went to a longer, softer radius on the rings to prevent the lube from being wiped off during the forming process. MF
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