An EDM design that reduces energy output, lowers wire consumption, speeds set-up and achieves high cutting and finishing accuracy through several innovative machine features will be prominent on the stand of MC Machinery Systems at IMTS in Chicago, Sept. 10-15.
MC Machinery, in Wood Dale, Ill., a Mitsubishi subsidiary, is introducing the MV Series machines, which include these features along with an innovative drive system. But the MV machines aren’t entirely new. Greg Langenhorst, MC Machinery’s technical marketing manager, says an early version debuted at the biennial IMTS in 2010 as the NA series, which had been developed and sold by Mitsubishi in Japan.
Cylindrical Drive Yields Smooth, Friction-Free Movement
The most innovative feature of the MV Series machines is a cylindrical drive motor, which Langenhorst says is unique to Mitsubishi. The cylindrical drive is comprised of a linear shaft motor that controls movement in the X, Y, U and V axes. It replaces flat-plate linear magnetic drives, ball screws and iron-backed mounts in conventional EDM systems.
The device operates with round permanent magnets, or as Mitsubishi calls them, “buttons.” The buttons, loaded in a cylindrical stainless steel tube wrapped in coils, function as ball screws. When energy is applied to the shaft, the buttons generate a 360-degree magnetic flux, which pulls the shaft in a non-contact path from magnetic field to magnetic field along its axes of movement.
“This is a much more efficient way to move further, faster and more accurately with less energy,” Langenhorst says. “It eliminates the excess energy needed to pull an iron-backed drive system from one mount to the next.”
The cylindrical drive is so efficient, he notes, that after a day of operation it is barely warm to the touch, owing to lower heat buildup.
The drive design also overcomes problems associated with conventional flat-plate linear motor drives and ball screws, according to Langenhorst. These include tracking heat along the iron-backed mount, susceptibility to magnetic shop dust interference, cogging, backlash, pitch-error compensation and ball-screw wear — the latter necessitating replacement and machine downtime. And with no ball screws, there is a reduction of lubrication needs.
Fiber-Optic Sensing Is Among Other Features
Langenhorst says, in fact, that the machine series’ planned introduction to North America was delayed by a year as Mitsubishi added other capabilities. These include the Optical Drive System, which uses fiber optics to provide four times the sensitivity and communication speed of hard-wired systems, and enhancements to the power supply, monitoring circuitry and wire-threading system, Langenhorst says.
A digital matrix sensor in the V350 Type-V generator shapes the electrical pulse to minimize wire wear and vibration. “When we do rough cuts and skims, we’re seeing a 60 percent reduction in wire consumption, which is huge,” Langenhorst says. “This cuts operational costs significantly, with no loss in speed, accuracy or finishing capabilities.”
Mitsubishi, in fact, says these enhancements make the MV Series machines extremely precise: Pitch accuracy and machining accuracy are ±2 µm, while straight-line accuracy is ±5 µm. A finishing ratio of Rz 3.5 µm/Ra 0.45 µm is achievable in three cuts, and a ratio of Rz 2.0 µm/Ra 0.28 µm can be done in four cuts.
Another upgrade in the MV Series is Intelligent Automatic Threading (IAT), which can be set to match workpiece shape. With IAT, upper rollers travel with the Z-axis, maintaining a constant distance to the upper guide. Mitsubishi says that up to 14 in of annealed wire can be threaded and the wire-curl ratio can be reduced to 10 percent or less. IAT reportedly improves threading reliability on tall parts and permits threading without the jet stream to facilitate operations on small parts.
A redesigned lever-activated head permits installation of a flat-plate power feeder that simplifies indexing during operations. Mitsubishi claims significant time savings for indexing the power feeder with the new design — 1 min per head versus up to 10 min on previous machines.
Supplier Says Machine Achieves Major Energy Savings
When combined, these features, along with the energy savings that accompany them, can lower operational costs by 40 percent, Langenhorst says. They also contribute to faster machining of workpieces, which reduces cycle times.
Such benefits are in line with trends he sees in the market. “Everyone is trying to improve cutting speed — not just in inches per minute but in the number of passes needed to finish a part and in how fast workpieces can be taken off a machine,” he notes.
The MV series, Langenhorst adds, can help make shops more competitive and profitable. And they won’t break a budget. They are “competitively priced” with other EDMs, he advises, and their premium is “less than $10,000” compared with the Mitsubishi machines they replace.
The machines also have what Mitsubishi terms the Natural User Interface — a user-friendly control that is designed to keep operations simple and minimize the learning curve.
MV Series machines come in four types: the MV1200R and MV2400R, and the MV1200S and MV2400S. The MV1200 models have respective X, Y and Z travels of 15.7 by 11.8 by 8.7 in (400 by 300 by 220 mm), while MV2400 models have travels of 23.6 by 15.7 by 12.2 in (600 by 400 by 310 mm).
There are some engineering differences between the two, but similarities include direct-axis, independent mounting of the X and Y tables to a T-shaped base casting for greater rigidity, smoother movements and improved cutting, Langenhorst says.
MC Machinery is replacing all of its wire machines with the MV Series. Its sinker EDMs, though, will still use ball screws rather than the cylindrical drive.
The company will show all four MV Series models at IMTS.
Here is more about the Mitsubishi MV Series EDMs and the cylindrical drive technology: