Automotive Design and Production

JUL 2014

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an on-demand state. "If we only need 10% coolant fow, then we're running the motor at 10% of its capacity." The previous norm is to have synchronous motors that are either running or not, so if you needed 10% coolant fow, the motor would still run at 100%. He says they're looking at spindle speeds in relation to axis travel. That is, say there is a long traverse before cutting commences and the spindle needs to be running at 10,000 rpm for machining. Typically today, the spindle is run up to that speed as the axis motors are bringing the spindle to where it needs to be for machining. So what they're doing at DMG MORI is calculating the time for both the time it takes to get the spindle up to speed and the time it takes for the spindle to be positioned for the cut, and then adjusting accordingly: "If the spindle gets to maximum rpm half way through the rapid movement, then we slow the spindle down to save energy without afecting the cycle time in any way." That is, the spindle isn't running at 10,000 rpm when it is still on its way to getting to where it needs to be. Similarly, when it comes to face milling, Hansel points out that when the face mill clears the workpiece, the machining is over. "But," he points out, "ordinarily, the feedrate is constant until the entire face mill not only clears the surface, but moves a distance past the workpiece. If we can calculate the edge of the workpiece, as soon as the face mill is halfway over the edge and it is done cutting, we can go to a rapid feed and pick up a couple of tenths of a second for every pass. It adds up over time." "Anything we can do to shorten cycle time," Hansel says, makes the machine more sustainable." And that's a good thing for everyone. AD&P; > July 2014 > FEATURE > How to Make Machine Tools More Sustainable > Gary S. Vasilash 32 0714ADP FEATURE Machining Tools -- Digital Version.indd 32 6/17/2014 1:10:26 PM

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