Burning Questions: Advances in EDM technology
- February 8, 2019
EDM technology gets a little better every day; here are a few of the most recent examples
Maybe you were unable to attend last year’s IMTS exhibition in Chicago. Maybe you were there, but you missed a few things, or simply forgot what you saw. It happens. Whatever the case, if you’re looking for a recap of the latest in EDM technology, you’re in luck. Shop Metalworking Technology has spoken with EDM equipment suppliers to see what’s new, why it matters and how to use it in your shop.
Feel the heat
One of these was Makino Inc., which presented a host of new machine tools and features. For example, if you own an Amazon Echo or similar home automation device, you’ll be excited to learn that you can now talk to your machine tools. According to EDM product line manager Brian Pfluger, the Athena voice command function is available on Makino’s EDM machining centres and EDM equipment, and helps in those situations where your hands are busy with a setup or other types of machine operation. “It’s basically like Siri on your iPhone,” he says. “You can tell it to change screens, run a pickup cycle, thread the wire, as well as display statistics such as machine uptime and other status information.”The new HyperDrive AC motor wire tensioning system from Makino is designed to enhance wire stability and therefore part accuracy, especially when burning very small features. Makino unveiled a new EDM drilling machine, the BX3, an expansion of Makino’s EDBV series that has been “honed and refined” for high production of cooling holes and diffusers in small to medium size turbine blades. But one of Makino’s biggest developments—literally—was the UP6 Heat, a wire EDM machine designed for ultra precision applications.
“The big deal about the UP6 is its one micron precision (0.00004 in.),” Pfluger explains. “There are certainly other machines on the market able to achieve this, Makino’s included, but the UP6 is roughly twice their size. With working travels of 650 x 470 x 320 mm (25.59 x 18.5 x 12.6 in.), it’s on a planet all its own in terms of size and overall accuracy.”
Pfluger says the UP6 is targeted at shops producing large progressive stamping dies—electric motor stators, for example—where pitch accuracy (the distance from one station to the next) is critical. “The UP6 also features the HyperDrive Extreme wire drive system just mentioned, as well as our new Jet-less wire threading capability, which allows you to rethread through the kerf without having to return to the start hole.”
Slugging it out
Slug management was a big topic at the EDM pavilion, although the way in which it’s accomplished varied from vendor to vendor. Fanuc America Corp., for instance, showcased its Core Stitch slug retention feature, while GF Machining Solutions (GFMS) introduced several new features on its CUT P-series machines, among them an automated slug removal system.
“We actually launched CUT P at our open house earlier in the year, but have increased its capabilities since then, with the goal of making it a completely lights-out EDM solution,” says Eric Ostini, EDM product manager. “A big piece of that is slug removal.”
To this end, GFMS has developed an arm that attaches to the machine’s upper head. When the workpiece has been completed, the control tells the machine to cut the wire, raise the head, and swing the arm into place. By applying an air blast to the top of the workpiece, a vacuum is created via the Bernoulli effect, capturing the slug. At that point, the head is raised and the slug carried off to the side of the machine, where it is dropped into a pan.
Other improvements include the company’s rConnect remote maintenance and monitoring system, designed to simplify problem troubleshooting and, by extension, increase machine uptime. Maintenance itself has also become easier—instead of removing a cover from the back of the machine and manually applying grease to the way surfaces, the operator simply pumps the lubrication system once monthly (or convinces his boss to buy the completely automated version).
“We also introduced a robot option for our E-series sinker EDM,” Ostini notes. “This is more of an entry level machine, so it helps shops that don’t have a lot of money to automate their die sinking operations.”
A stitch in time
Joseph Kollar, EDM product manager at Elliott Matsuura Canada Inc., agrees that unattended operation is an important goal for many shops. As noted earlier, Fanuc is addressing one part of this—slug management—through its Core Stitch function, standard on the RoboCut ∂-CiB Series wire EDM, which Methods Machine Tools introduced at IMTS 2018.
“This innovative feature prevents slugs from dropping, saving time and increasing efficiency,” he says. “There’s no need for glue tabs or magnets. Stitch points are set by the operator without any pre-programming, and when the job is done you simply tap out the cores manually without any risk to the machine. It’s an ideal solution for long, unmanned machining and multi-workpiece cutting processes.”
Kollar offers a laundry list of additional new features, all designed to improve accuracy, decrease cut time, or make the machine easier to operate:
Fanuc’s new high speed AWF3 System (Automatic Wire Feed) makes it possible to thread submerged at 500 mm (19.69 in.) workpiece thickness, and automatic wire recovery to 150 mm thick (5.91 in.) when cutting non-parallel plane workpieces.
The iPulse2 Flexible Pulse Control function increases part accuracy through improved pitch error compensation over the entire cutting area. The result is better gap consistency, leading to higher cutting speeds and improved straightness and corner accuracy, while reducing the number of passes and improving surface finishes.
There’s a Simple EDM Data Adjustment function that provides “one touch” adjustments when machining becomes unstable, and an AI Thermal Displacement Compensation feature to monitor and address large temperature fluctuations during cutting.
And the 3D Coordinate System Rotation function reduces the need for indicating-in of workpieces, and allows the operator to measure workpiece flatness and automatically tilt the wire to make it perpendicular to the surface, cutting set-up time.
“All of these features are available on the RoboCut series of wire EDM machines, and are aimed at keeping a customer’s machine productive, predictable, and cost-effective for as long as they own their equipment,” says Kollar.
Absolute Machine Tools Inc. takes a different approach to unattended machining through the use of onboard probing and vision-based inspection systems. EDM technical director Mark Cicchetti says the company recently partnered with Marposs to equip its AccuteX series wire EDM machines with 3D touch probes able to perform a variety of setup and in-process measurement tasks.
A common sight on CNC lathes and machining centres, touch probes allow the operator to quickly find the location of a tooling ball or find reference features on a series of parts during setup. According to Cicchetti, automatic probing systems are roughly 70 per cent faster than the traditional method—using the wire to touch off on part features—and there’s no need to clean and dry part surfaces first. “You can easily pick up half a dozen parts in twenty minutes, all automatically,” he says.
Absolute has also introduced a non-contact measurement option that uses a CCD camera attached to the upper head. It offers three-micron precision (0.0001 in.) and the ability to not only inspect parts, but then send the results to an external metrology system or CAD package for comparison. Says Cicchetti, “with the right tooling, the right CAM software, a little planning, and now with our in-process inspection capabilities, there’s no reason why most shops can’t achieve eighteen hours or more of unattended machining.” SMT