Electrical discharge machines (EDMs), which use electrical discharges to machine parts, have been advancing for years. Demand for wire and sinker EDMs has increased as manufacturers require more complex parts, which are often made from difficult-to-machine materials.
Makers of EDMs have stepped up their offerings, improving accuracy, speeding cycle times and producing better finishes. New EDMs are also highly automated and easier to operate in order to address the skills gap at U.S. job shops.
“Wire EDM is proving to be an unlikely solution to a current and growing problem facing the U.S. job shop,” said Mark Cicchetti, a sales engineer at Absolute Machine Tools, based at the company’s Mason, Ohio, location. “As I travel around, I see more and more ‘Machinists Wanted’ signs. Skilled labor is harder to find.”
EDMs, despite improvements in speed, are not as fast as other production methods. However, they can be set for long runs. “This is opening the door for automation and the easy-to-use, low-cost wire process,” he added. “Skilled programmer/operators are able to process jobs using wire EDM quickly and then go about running jobs in their mills and lathes and attend to other duties.
“Even though the EDM might not be the fastest process, the job is getting done reliably and at a relatively low cost,” Cicchetti continued. EDMs can perform “jobs that otherwise would be sitting waiting or taking up spindle time. Taking it up to the next level with automation is more possible with collaborative robots like the PR 0B7 with the Mitsubishi LoadMate that combines flexibility with an industrial capacity robot.”
EDMs have benefited from technology such as artificial intelligence (AI) and collaborative robots, or cobots, which can be deployed close to human operators.
“Artificial intelligence allows the operator to be basically a novice that knows nothing about EDM,” said Steve Raucci, Phoenix-based technical sales director and RoboCut product manager for Methods Machine Tools Inc., which is headquartered in Sudbury, Mass. “You can walk up and by answering a couple of questions on the control, the machine will give you everything you need to cut a good part. It’s all in the control and power supply. The control turns a novice operator into a professional user.”
Raucci said simple pickup modes have improved over the years, enhancing their ease of use. One of Methods’ longstanding EDM partnerships is with FANUC, which manufactures the wire EDM RoboCut. In April, Methods added the latest generation of the RoboCut, the a-CiC series, to its product line. The a-CiC series features upgrades that deliver more parts with what the company describes as surgical-like precision, including a taper adjustment for high-precision taper cutting and thermal displacement for increased stability.
At MC Machinery, there is a similar outlook. “On the control and operation side of the EDM process, manufacturers have incorporated many years of pre-established technology databases to take the guesswork out of achieving exacting and excellent results,” said Alan Hallmann, North American sales manager for EDM and machining technologies for MC Machinery Systems Inc., Elk Grove Village, Illinois. “Additionally, packaging easy-to-view dashboard images on the control’s graphic interface, along with intuitive instructions and icons, allow today’s tech-savvy operators extremely short learning curves to master the machine’s capabilities.”
The use of adaptive control and AI self-learning software further enhance the productivity of EDM technology, Hallmann added. “And today’s maintenance has been simplified greatly with the latest models being set up to provide real-time feedback using a number of methods in remote monitoring software,” he said.
EDM improvements go beyond controls. “Today’s high-speed fiber optics and electronics mean faster response times for the control to react to the burn spark and increase the speed while also reducing the electrode wear,” Hallmann said. “These have improved the ability for the software and power supplies to more precisely manipulate the actual spark dynamics to extremely accurate and fine levels. These improvements improve surface finishes and accuracy.”
Today’s job shops are taking more advantage of EDM and the effect it has on throughput, cost, manpower and repeatability, according to Hallmann. “Advanced materials like aerospace alloys, hardened steels and carbide can require many tools and cutters to achieve the final finished part,” he said. “EDM is an excellent, repeatable and reliable process that reduces scrap and tooling costs. EDM does not require mechanical forces to remove the material as the electrical spark removes material efficiently without an electrode ever making contact with the part surface. EDM workholding requirements are more related to accuracy and repeatability, as opposed to additional mass to handle the cutting forces.
“The EDM process is by design a process that lends itself to many hours of unmanned production,” Hallmann continued. “In fact, the more difficult the geometry or the harder the material, the more likely that EDM is the best solution.”
Raucci from Methods commented on recent EDM trends. “It seems like today, things are getting smaller and smaller,” he said. On an EDM “we can use a 4000 or 2000 diameter wire and cut a very intricate small inside corner. We just can’t do it on a mill.
“It’s the speed of the machine, the reliability of letting it run unattended so it can sit in a corner and just knock out parts,” he continued. “Automating EDM has helped us to get into industries that we might not have gotten into before because many EDMs are still considerably slower than, let’s say, a milling process. You have to figure out a way to let it run by itself. Without some of those improvements over the years, we’d have been stuck at first base, for sure.”
Additive manufacturing and 3D printing are new areas where EDM is being used, according to Cicchetti of Absolute. “When a 3D printer builds a part or parts on to the printing base, they need to be removed once the part printing is complete,” he said. “Many times, a common bandsaw is used to separate the parts. The problem is that the quality of the saw cut is not desirable or can even damage the parts. The drawbacks to wire EDM in this case is the price of the machine and, in some cases, the residual powder can be trapped in some features. This can be challenging to deal with from a filtration standpoint, because the finely tuned dielectric system needs to be efficiently run. It is important to find the right supplier that offers cost-effective equipment and the experience and systems to run with the application.”
Said Raucci of Methods, in the 1980s, “EDMs were not a product that most shops wanted to have. They thought of it as black magic. Today, it seems like almost everyone has a use for one, whether it’s cutting out a certain material that is hard to mill or grind, such as small inside corners [and other tight features]. There seems to always be something today that lends itself to really good EDM work.”
As a result, “We’re getting more into production-type jobs because the machines are faster,” he added. “So now we can produce gun, aerospace and medical parts. That’s been another big reason you’ll see EDM in more and more shops than you did 10, 15, or 20 years ago.”
“I can take anyone off the street who’s never seen an EDM and teach them to run this thing in a very short time because the machine does so much for you,” Raucci said. “I can just tell it that I’m cutting two-inch or one-inch or five-inch tool steel or carbide or aluminum and I want this finish, or I want that tolerance” and the machine does the rest.
What EDM improvements lie ahead? One possibility is speed. “For cutting speeds, the line has been almost flat in the last 15-20 years,” Raucci said. “We’ve always said we’re between 28 and 32 square inches an hour. It’s been that way for as long as I remember. So, to me, that would be the next big step to see who comes out with the next best speed improvement. If somebody could make a huge advancement … that would be the next step.”
Why not surface finish? “I can already give you a three- to four-micro-inch finish, which is like a mirror. So I can’t imagine, there’s [a lot of improvement] left, right? You can’t get to zero. It would have to be the speed that could really, really, change the EDM world.”
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