Production Machining

AUG 2014

Production Machining - Your access to the precision machining industrial buyer.

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Go to the Light A demonstration of Green Light Strategy in action can be found at RFM Inc. of Brighton, Michigan. Te company is a wholly-owned subsidiary of Mitsubishi Materials. RFM manufactures high quality, indexable insert cutting tool bodies including shell mills and end mills. Te manufacturing process uses multiple turning centers, including two Mori Seiki NL2500s and an Okuma LB3000MY lathe. All of these machines are equipped with a bar feeder. "Prior to 2006, we used standard three-jaw chucks; but, as our tolerances tightened, and we looked for more efciency in change-over, we realized we needed to fnd a better method," says RFM's plant manager, Tim Barnes. "We typically rough machine the body of our tools on the back end, then transfer the part to another lathe to machine the other end. Te part is then sent out for heat treating and subsequently placed in a chuck with center drive for fnishing operations. Unless your chucks are extremely accurate, moving workpieces between machines can cause real problems. Tis is especially true when the tolerances go from 0.005 inch in the roughing operation to 0.0003 to 0.0005 inch in fnishing." Another factor demanding improved workholding capability is the material used. Although many parts are machined from 4-foot bars of 4140 and 4340 steel, special orders demand harder materials that require increased gripping power. Mr. Barnes says, "Te chucks we now use employ a parallel clamping design that allows the engage- ment of 85 percent of the diameter—signifcantly more than a standard three-jaw chuck. Tat results in 25 percent more gripping power." A major reason to incorporate improved workholding is change-over time. "Our part runs vary widely," Mr. Barnes says. "I would say our longest runs are from 400 to 500 pieces, but we frequently do lots as small as 5 to 10 units. When you calculate the dollar value of the time involved in change-overs with conventional chucks, you're talking about a large fnancial burden. "Te quick-change feature enables us to load and lock diferent collet sizes quickly and easily without sacrifcing quality and accuracy," he continues. "In fact, we are now able to machine surfaces in-house that we used to have to send out for grinding, and our change-over time is 35 to 40 percent faster." In his 22-year career at RFM, Mr. Barnes has progressed from the shop foor to his current position of plant manager, a transition that enables him to see the business from both a technical and a managerial standpoint. "Improving workholding capability, like any capital improvement, demands an investment of both time and money and has to :: Going from OD to ID to three-jaw chucks is accomplished in a matter of minutes. 34 PRODUCTION MACHINING :: AUGUST 2014 WORKHOLDING

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