EDM Technology Trumps Offshoring
By Jim Lorincz
Technical advances continue to recommend EDM for applications where the closest tolerances and finest surface finishes are required. Traditional industry applications include aerospace, medical device manufacturing, and large molds and small precision diemaking.
EDM, like other advanced manufacturing technologies, is getting a much-needed boost from the improved appetite for manufacturing in North America, according to Glynn Fletcher, president, GF AgieCharmilles (Lincolnshire, IL). "Reshoring, or right shoring to the US, the trend means that a lot of organizations want to be close to the largest market in the world. That strategic shift in how manufacturers are making their choices gives machine tool builders the opportunity to help manufacturers differentiate themselves from the competition by acquiring productivity-improving technology."
At IMTS 2012, GF AgieCharmilles will have two booths, one in the South Hall where it will exhibit machine tools and services and one in the East Hall where it will promote its Uptime Plus aftermarket products and services. "We have some 8000 machines in operation in North America, and we’ve developed programs to help our customers make better use of the machines they have," says Fletcher. "We have developed high levels of EDM and machining center technology so that when our customers decide to replace equipment, we have what they need available."
Industry Focus Showcases EDM Technology
GF AgieCharmilles’ South Hall booth will be divided into quadrants: Aerospace and Aeronautics; Medtech (medical industry applications); Mold and Die; and Aftermarket. "Mold and die makers who are cutting a lot of carbide stamping dies, for example, should consider a high-end oil dielectric wire EDM machine. The technology prevents leaching of carbide for better surface integrity and a lot less cobalt depletion," Fletcher advises. Other technology advances to be shown include automatic wire changing, on-machine optical inspection for adjustments in the work zone, and laser ablation for creating textures on molds. "We’ll also repeat the e-manufacturing cell done in cooperation with EOS and its additive manufacturing technology, and a Mikron high-speed machining center and an EDM for finishing."
Mitsubishi EDM’s newest MV wire machine features design and engineering improvements, including noncontact cylindrical drive technology, an improved power supply, auto threading, and new methods of reducing operating costs, says Greg Langenhorst, technical marketing manager, MC Machinery Systems Inc. (Wood Dale, IL). "Our wire EDM is introducing Cylindrical Drive Technology, which is using linear shaft motors that feature a noncontact round magnetic shaft that creates a full 360° of magnetic flux in place of a ballscrew drive system. The design eliminates the typical wear and backlash issues of a ballscrew and the normal cogging and cooling issues of a flat-plate type linear drive system, resulting in improved energy efficiency, accuracy, and speed. It’s a very smooth and cool operating system as we have removed all the nonfunctional iron out of the system." The cylindrical drive technology is part of the ODS Optical Drive System that uses an all fiber optics servo control system that is said to be four times faster than a hard-wired system, allowing it to respond faster to the demands of the machine as far as maintaining a continuous spark gap and achieving a smooth finish.
Power Supplies Head List of Advances
The new V350 type 5 power supply with the new digital matrix sensor now shapes each spark pulse to remove more workpiece material while creating less damage to the wire. This results in the ability to slow the wire speed down which can reduce wire costs by up to 60% in typical punch and die type cutting where several skim cuts are used.
"The machine construction, especially in the smaller MV1200 size, has undergone a redesign," says Langenhorst. "It features a split table rather than the compound table movement of our previous model. The table moves in X and the column moves in Y, both mounted to the same base casting eliminating any issues inherent to the stacked table arrangement. The new MV machine combines the speed of a V-type generator with fine-finishing and accuracy circuitry needed for toolroom applications. Also, the new auto-threader is annealing about a 14" [356-mm] long length of wire which reduces the curl to 10% or less and which improves rethreading through the gap, threading through taller parts, smaller holes, and deeper when the tank is submerged," Langenhorst says.
According to Stephen Bond, national sales manager, Fanuc EDM, Methods Machine Tools Inc. (Sudbury, MA), during the last several years much of the technology advancements in EDM were in power supply and software technology to increase cutting speeds. Power supplies have been refined for better finishes in many different materials that are difficult to machine conventionally. Control software advancements have led to increased straightness in taller work, more precise corners and, again, improved finishes. At IMTS, Methods will demonstrate the new Fanuc Wire EDM control and power supply interfaced directly to a tilt/rotary table that makes it possible to produce medical and aerospace parts with virtually no recast.
"Wire EDMing PCD [polycrystalline diamond] has been vastly improved on Fanuc Wire EDMs due to a proprietary power supply specifically designed for this material. The demand for PCD inserts used in both metal and wood cutting tools has more than tripled over the last few years and the ability to cut PCD with no secondary finishing has allowed manufacturers of the these tool to offer quicker deliveries and reduce overall costs to manufacture the tools," Bond continues.
"Wire EDM has been used to cut PCD since the 1980s, but not until software program generation coupled with an improved or refined power supply was generated could these tools be machined competitively on a wire EDM. Now the new advancement in EDM control processors combined with exclusive software and the ability to probe the tool very accurately allows these tools to be machined untended. Methods has delivered several fully automated cells, utilizing Fanuc robots to manufacture PCD tools without operator intervention. Only once the tools are cut complete are they handled by the operator," Bond concludes. ME
This article was first published in the August 2012 edition of Manufacturing Engineering magazine. Click here for PDF.