Production Machining

OCT 2017

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

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Page 38 of 59

I n the grand scheme of things, machine tool-wise, the inverted vertical turning lathe is a relative newcomer. Traditional VTLs have been making chips for well more than a century and still are well applied for applications that turn large-diameter blanks that are too large and heavy for horizontal turning. Over the years, the fundamental design of the VTL hasn't changed much. A base unit carries a spindle to which a workpiece blank is held. A gantry mounted tool carrier is able to bring the machining axes into the cut like a vertical machining center does. e spindle base can be as large as neces- sary because gravity is working as its workholder. e traditional VTL capability has undergone refinements over the years with the addition of milling and drilling capabilities as well as CNC servo control of the axes. Even so, its basic configuration has remained fundamentally the same for more than a century. However, in the early 1990s a new wrinkle on the VTL configuration hit the market with the introduction of a concept that inverted the vertical turning center. It is gener- ally accepted that EMAG LLC (Farmington Hills, Michigan) was the first company to market with this concept. With the inverted spindle design, the spindle axes are mounted on a slide where the traditional tool VTL carrier was mounted. In that position, coupled with the mobility afforded by the slide mount, the spindle is able to serve the dual purpose of loading and unloading the machine while presenting the workpiece blank to the cutting tools that are now in the position where the traditional table was—effec- tively inverting the iconic VTL 180 degrees. Why 180 Degrees Makes a Difference e machine operator on a traditional VTL who spends many hours a day sweeping or blowing off chips is just one person who appreciates the inverted vertical design. With the machine spindle mounted on its carrier and the cutting tools arranged below, chips fall away from the spindle into a conveyor in the machine base and out of the workzone. On a traditional VTL the chips fall on the workpiece needing to be cleared periodically to prevent recutting. Locating the part blank above the cutting tool elimi- nates this issue. On the EMAG design, all of the spindle :: A self-contained conveyor system, which can be customized for the application, delivers workpiece blanks to the spindle and discharges completed parts. ways, actuators and scales are located on the slide rail, outside the cutting zone, away from chip and coolant contamination. ere are limits to the size of workpiece blank that the inverted vertical can effectively handle. EMAG's line of inverted verticals accommodate chucks from 200 mm to 1.2 meters in various models. However, there is a significant amount of chucked workpiece blanks that fall between those sizes. Another inherent advantage of the vertical turning design, within EMAG's working range, is a small machine footprint relative to horizontal turning centers of similar capacity. Conveyor systems can be arranged around the machine to carry workpiece blanks into the machine and finished parts away to create stand-alone production cells or machines are linked together into engineered produc- tion lines. With the spindle's ability to load the blanks and discharge the finished parts, the entire system is compact and flexible. One-Stop Hard Turning and Finish Grinding Turning and grinding have been linked together as comple- mentary processes for a long time. Turning's relative speed is used to rough a workpiece, while leaving a small amount of stock, before it is heat treated. Once it is hardened, the part is finished to size on a grinding machine. roughput time for this multi-step Programming for Inverted VTLs :: 37

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