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Maker of Heavywall Bearings Achieves 98% Uptime
Seven Sabre VMCs —two in robot-loaded work cell —boost productivity for Glacier Clevite, world's largest maker of heavywall bearings for large diesel engines
Location: McConnellsville, OH
Established: July, 1952
Products: Heavywall bearings for large diesel engines, thrust washers
Market Area: Worldwide
Number of Employees: 250
Facility Size: 100,000 ft? (9290 m?)
President: William Casey
Cincinnati Sales Agent: Tipton Machinery Co.
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Running five days a week, two shifts per day, the robotic-loaded VMC cell provided Glacier Clevite with 98% uptime in the cell's first full year of bearing production. But the two cell Sabres are just part of a small army of Sabres —seven in all, purchased by Glacier Clevite over the past two years. The company standardized on the Cincinnati VMCs for their versatility, reliability and PC-based CNC. The Sabres have helped Glacier Clevite achieve an eye-opening 5.75 Cpk, quadrupling the 1.33 Cpk industry standard.
The McConnellsville, OH plant opened in July, 1952 as a supplier of bushings for the aircraft industry, and began producing heavywall bearings in 1967. With annual sales now over $40 million, Glacier Clevite is a major supplier to General Electric and General Motors, providing these customers with quality hydrodynamic heavywall journal bearings as well as thrust bearings for large diesel engines.
Glacier Clevite's Heavywall Bearings Division is a one-source manufacturing house, including strip and shell casting facilities, complete machining and forming equipment, and electroplating and babbitt casting facilities. Heavywall bearings are large half shell, full round or specially configured single- or double-flanged hydrostatic journal bearings with a wall thickness of more than 0.250" (6.4 mm) and diameters larger than 6" (152 mm).
Sabre Cell Cuts Cycle Time
Driven by a steady stream of OEM work, Glacier Clevite is always looking for ways to increase production. "And," says Bill Schmidt, manager of manufacturing engineering, "the new robotic-loaded Sabre cell is our latest step toward that end." According to Schmidt, the company decided to go with robotic part loading for several reasons:
* Reduced cycle time. The cell continuously pumps out product much quicker than the previous dedicated-machine setup, and Schmidt couldn't be happier with its 98% uptime. Before, with the four dedicated machines, cycle time was six minutes per part. Now, with the robotic-loaded Sabres, cycle time is 2.5 minutes per part. In addition, where previously two operators loaded four machines, now one operator lightly tends the two-machine cell.
* Reduced scrap. Schmidt had counted on the cell to reduce Glacier Clevite's scrap rate, and the Sabre/robot work cell has not been a disappointment. The scrap rate has been cut by half, dropping from 2.7% to 1.3%, in the first year of production.
* Increased flexibility. Glacier Clevite pumps out 700-800 part numbers in a year in small lot sizes of approximately 200-300 parts apiece, so quick setup and tear down are crucial. The Sabres give Glacier Clevite the flexibility to do this. And since they aren't dedicated machines, Glacier Clevite can now quickly adapt to potential changes in the product line.
Glacier Clevite's Own Foundry Starts the Process
At Glacier Clevite's foundry, bearings begin as strip cast or static cast steel blanks containing a copper-lead alloy. Machining begins by trimming and milling blanks to length at the machine shop, then forming them into bearing halves using a 500-ton (454 mt) mechanical press. Pairs are assembled and inside journal diameter is rough bored, chamfered and grooved. The OD of the matched pair is then turned on a lathe. Each half is then delivered to one of two stand-alone Sabre 750s for milling parting lines (the flat surface where bearing halves meet about the journal). Bearings are finally off-loaded to a conveyor track for delivery to the robotic-loaded Sabre work cell.
Upon arriving at the work cell, the robot removes a part from the conveyor and places it in a test stand to validate previous machining process. Next, the bearing is loaded into the first Sabre for machining locator holes, slots and "mud pockets" which collect debris in the oil. The part is then loaded into the second indexer-equipped Sabre which machines lubrication grooves on the back of each bearing, holding angular tolerances to ±30 seconds (0.0083°). Finish-machined bearings are returned to the conveyor by the robot for delivery to Glacier Clevite's in-house electroplating facility.
Sabres with A2100 CNCs Cut Ramp-up Time
"The common denominator in any manufacturing facility is to make product in as little time as possible, and that is why we brought the Sabres onboard," says Schmidt. "Accuracy, speed and repeatability are what we were after, and that's what we got with Cincinnati's Sabre VMCs." Schmidt purchased eight Cincinnati machines in two years' time: four Sabre model 500s, two 750s, one 1250 and one Avenger 200 Horizontal Turning Center (HTC).
One of the biggest reasons Glacier Clevite went with Cincinnati machines was the helpful Acramatic 2100 (A2100) CNC. "We found it very easy to train people on the A2100 —ramp-up time was minimal thanks to its PC-based layout," says Greg Weaver, manufacturing engineer. "Our operators don't have to stumble around looking for the proper screen, and we can customize our own layout."
Repeatable Accuracy
Two stand-alone Sabre 750s are used to hold the critical ±0.001" (0.0254 mm) tolerance at bearing parting lines. All other milling operations are held to ±0.005" (0.127 mm).
To compensate for offsets and fixturing errors, parts are probed using a Renishaw M12 spindle probe. This ensures that critical features, such as locator holes which locate the bearing in the rocker arm, are in the same position for every bearing. When General Motors representatives asked Weaver how he could guarantee hole location repeatability for each bearing, he demonstrated this in-process probing technique, and they were completely satisfied.
Shooting for 6-Sigma
Glacier Clevites' 5.75 Cpk process capability smashed the industry standard of 1.33 Cpk, but Schmidt's not content to stop there. Glacier Clevite is participating in General Electric Transportation Systems' 6-Sigma program, where GE works with suppliers to develop ways to reduce cost and improve quality. Schmidt says the highly accurate Cincinnati VMCs will be an integral part of this program. "When we achieve 6 sigma, additional work will naturally follow," says Schmidt.