CUTTING LEAD TIMES AT CAMBRIDGE
Sturman Moore has some firm ideas about where his industry is heading. "The prime strategic imperative in the die/mold business today is to shorten leadtimes," says Moore, Production Manager for Cambridge Tool and Die Corp.(Cambridge, OH), a 60-person firm that builds plastic injection molds for automotive and other customers. "We at Cambridge realized that using new technology was the only way to do that. "In April, 1995, Cambridge acted on that belief, installing a GN2012, one of Makino’s newer vertical machining centers. With its table reinforced for heavy loads and its spindle constructed for tackling hard materials, the GN2012 is designed with die/mold applications in mind. Even more important, from Cambridge’s perspective was its high spindle speed and feed-rates, and its Super Geometric Intelligence (SGI) Servo control software, designed to maintain accuracy during high-speed contour milling.
"Our intention was to speed our 3-D work while simultaneously achieving better surface finishes," says Moore. Did it work? "Many of the cores that we are cutting now require no benchwork," says Moore. "In fact, we’ve had parts that came straight off the GN2012 and were accepted by the customer. The cavities, of course, normally require additional benchwork, but much, much less than we experienced before implementing this system. We’ve probably cut out 80 to 90% of the benchwork time with this new approach to machining." Shortly after purchasing the GN2012, Cambridge elected to bring the same sort of productivity improvements to the EDM side of their operation by adding a Makino EDNC156. "The EDNC156 has opened up a whole range of new possibilities for us," observes Jim Mercer. Mercer, the EDM Coordinator for Cambridge, has nearly three decades of EDM experience. "The machine’s tank size has allowed us to take on larger capacity molds, and its unattended operations capability has helped our productivity."
Cambridge is running the machine 24 hours a day, says Sturman Moore. "The finishes we’ve been getting from the EDNC156 have been so good that it helps us further reduce bench time," he adds. "Burning ribs in molds is always a big, big expense," Moore continues. "The new machine has done a good job burning ribs—in some cases so good that we don’t have to bench or second polish them. That’s been a big help."
New Ways of Working
Later in 1995 Cambridge added a third piece of Makino technology, the SNC64 graphite mill. "Like a lot of companies, we used to have a graphite room," says John Douglas, an EDM operator at Cambridge. "It was a 12 by 12 room with two mills, two grinders and a saw. Normally we had three or four people back there at all times, squaring graphite and fixturing graphite so that it could be contoured. Graphite dust was a constant problem. Now, because of the SNC64’s speed and accuracy, we have dismantled that graphite room completely. We are cutting 95 to 98% of our electrodes on the SNC64. In most cases the guy running the EDM also machines the graphite, so the reduction in hours spent on electrode production has been tremendous."
Douglas notes another good feature about the SNC64: "It’s sealed. We’ve had no problem with graphite dust leaking out into the surrounding area, which is a big relief for all of us involved with EDM."