Lightning-fast mill zaps mold shop's backlog.
Is your mold shop's electrode-machining operation so slow that it's bottlenecking your EDM department? Here's how Reddog Industries Inc, a large mold design and manufacturing firm in Erie, PA, solved the problem.
"About 85% of our machine tools are CNC machines, and we're very efficient when it comes to machining mold steels," explains William M Hilbert Jr, vice president and general manager of the firm. "We would move mold cores and cavities from one machine tool to another on schedule, only to have things come to a halt at our CNC sinker EDMs because the EDM electrodes for the jobs were not ready. Our electrode machining operations were not keeping pace with production."
Reddog's CNC milling department includes a large bank of vertical machining centers (VMCs) used to finish-machine large mold components. "We used one of the VMCs to machine EDM electrodes exclusively, but frequently the one machine wasn't enough," Mr Hilbert explains.
"Most of our electrodes have complex 3D shapes, and the finishing mill could only cut those shapes at feedrates of 10 to 15 ipm," he continues. "When we tried to increase the feedrates, the machine would either skip some points, resulting in an incorrectly machined electrode, or the machine would periodically come to a halt because the system couldn't crunch the numbers fast enough."
The problem affected fundamental decisions about how to process the molds. "Our electrode production was so slow that we decided to mill delicate details, corners, and deep cavities - features that we would have preferred to EDM," Mr Hilbert continues. "We have a sizable investment in modern CNC sinker EDM machines, and we wanted to make full use of their productive potential. The best solution to our problem seemed to be to find a faster way to machine our EDM electrodes."
As a result of Reddog Industries' investigation into high speed milling, it discovered the Creative Evolution CNC, a PC-based, open architecture, machine tool control developed specifically for 3D milling applications by Creative Technology Corp, Arlington Hts, IL. The Creative Evolution control combines the fastest block cycle and servo cycle times in the industry with an automatic, dynamic, look-ahead capability. The combination optimizes the performance of the host machine, enabling it to cut even difficult 3D shapes as fast as the physical limitations of the machine permit without violating the cutter path. Users have reported three- to tenfold improvements in effective cutting speeds simply by substituting the Creative Evolution control for the machine's original CNC.
Reddog decided to retrofit the Creative Evolution control on one of its finishing mills on a coexisting basis with the machine's original control. The Creative Evolution CNC directs all of the machine's axis moves, while the original control continues to govern toolchanges, coolant flow, and similar basic functions.
The retrofitted control improved the performance of the machine - faster feedrates and better machined finishes - to such an extent that its slow (2500 rpm) spindle speed became a serious limitation. Accordingly, a high speed milling head was added that enables the machine to run small-diameter cutters at high rpms.
"With the small-diameter cutters we can make finer cuts with smaller stepovers," Mr Hilbert explains. "Because of the finer stepovers, our toolpaths are much longer with the Creative Evolution control, but the control has at least doubled our cutting speeds, so we finish the job as fast or faster and our cuts are much smoother."
However, the improvements still did not provide the firm with the electrode-machining solution it needed. For one thing, use of even one of the finishing mills for electrode machining reduced the number of machines available for finish milling of steel mold components. Reddog started thinking in terms of a new machine, made especially for electrode machining, that would be located near the EDM department instead of the machining department.
The shop explored the dedicated electrode mills available. It was impressed by their performance claims but appalled by their price tags. About that time, the machine tool distributor that represents Creative Technology in the Pittsburgh and Erie areas and sold Reddog the Creative Evolution control for its finishing mill, came up with a great idea.
The distributor also represents Haas Automation Inc, Oxnard, CA, manufacturer of vertical and horizontal machining centers and other machine tools. Why not, the firm wondered, combine the Haas machining center with the Creative Evolution control to make a CNC mill capable of high speed 3D machining of graphite and steel, yet priced well below the cost of most dedicated electrode mills?
Reddog was so impressed by demonstrations of the "Evolution Series" machine that it bought one for installation in August 1997, and a second unit for installation six weeks later. Both Evolution Series machines are built on the VF-0E, a Haas 15-hp, direct-drive VMC with a 10,000-rpm spindle, and equipped with a dust collector. The machines were up and running the day they were delivered.
The Evolution Series machines, arranged side by side in the EDM department, handle all of the shop's electrode requirements. "These two machines can machine a volume of electrodes that previously required as many as four machines," explains Jeff Wells, Reddog's programmer/operator. "Actually, only one of the Evolution machines runs graphite exclusively. The other also machines small steel parts."
"On the old machines, the fastest we could cut was 10 to 15 ipm," Mr Wells, continues. "Now we're machining electrodes at 200 to 300 ipm. For some applications, say, machining a profile with a ballnose endmill, we've run at 400 to 500 ipm. Because the Evolution machines are so fast, we can program smaller stepovers for machining, achieve better finishes on the pieces as a result, and still be finished much faster than before."
"The Evolution Series machines are not only fast but accurate," Mr Hilbert stresses. "They have a look-ahead capability and one of the fastest data processing capabilities in the industry. That combination enables the machines to always operate at the highest cutting speed that will not compromise the accuracy of the cutter path."
Mr Hilbert explains how the Evolution machines affect the big picture at Reddog: "First, because the Evolution machines provide all of the electrode-machining capacity that we need, all of the finish mills are machining steel again, which has increased the capacity of that part of our operation. "Before, because it took so long to machine the electrodes, we machined details in the mold where possible rather than EDM them," Mr Hilbert continues. "Now, in situations where we have a choice, we can specify the preferred EDM process without having to worry about waiting for the electrodes. With the Evolution machines, our electrode-making operation is so efficient that we have eliminated our backlog."
"Most of our production decisions are customer-driven," Mr Hilbert emphasizes. "Years ago, delivery times of 22 to 24 weeks were common for a fairly large, complicated mold. Today, the customer wants his die or mold as quickly as possible. By adding modern, more efficient equipment and procedures, we have slashed our leadtimes dramatically."
"High speed milling is one of the technologies that will help us to reduce leadtimes further," he adds. Improvements in the CNC milling department will serve the firm's long-term interests in two ways: first, the department will become an even more efficient supplier to the EDM department; secondly, as improvements in milling technology occur that will swing the pendulum away from EDMing and toward greater use of milling in mold production, the shop will be positioned to use those improvements to competitive advantage.
Mr Hilbert confides that within the next 12 months, he hopes to add Creative Evolution controls to the shop's nine other CNC finishing mills. As those machines become obsolete over time, he expects to replace them with new Evolution VMCs.
For more information from Creative Technology Corp, Arlington Hts, IL, circle 382; http://www.creat.com
For more information from Haas Automation Inc, Oxnard, CA, circle 383; http://www.HaasCNC.com
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|Title Annotation:||Evolution Series, Reddog Industries Inc.'s solution to slow electrode-machining operation|
|Author:||Rakowski, Leo R.|
|Publication:||Tooling & Production|
|Date:||May 1, 1998|
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