[Alan Rooks]

MicroEDMing has made major strides in recent years, both in terms of the equipment used to perform it and the quality of parts shops are able to make using the process. MICROmanufacturing asked several experts for their thoughts on the most important improvements made in microEDMing over the past 5 years. They identified several, from machine design to electrode materials to wire-threading capability.

Mechanical changes in EDMs have enabled more-accurate machining. The ability to cool the EDM casting with dielectric liquids, in particular, keeps the temperature of the work area and the machine body constant, enabling more accurate cutting, according to Gisbert Ledvon, business development manager for GF AgieCharmilles, a machine builder based in Lincolnshire, Ill. This helps the EDM head hold position throughout the work envelope. Ledvon said GF AgieCharmilles developed its cooling capability with microEDMing in mind. Also, newer sinker EDMs offer higher C-axis accuracy, which is especially helpful for micro applications. GF AgieCharmilles makes EDMs using an Accura C-axis and a positioning accuracy of 3.6 arc seconds.


A Makino UPJ-2 EDM after automatically threading a 20µm wire through a workpiece. The workpiece is mounted to an Erowa workholding pallet, which in turn is clamped into an Erowa automatic chuck. A video of the wire-threading operation is available in the online version of this article at www.micromanufacturing.com. Image courtesy Makino.

Ledvon also noted that better electrode management has improved microEDMing operations. He pointed to new generator board technology that can reduce electrode wear by up to 60 percent. “This is critical for micro applications because those electrodes are difficult and costly to make, so you want to preserve them as long as you can. The IQ technology from GF AgieCharmilles allows for more-precise control of the spark and smaller spark gaps. The smaller spark gap allows use of an electrode that is slightly larger in diameter without affecting the cavity or part size. “If your electrode is very thin, it can start to flex, so if you can increase the diameter of the electrode by a couple of tenths, you make the electrode more stable,” Ledvon said.

Another improvement is that shops are choosing higher-quality electrode materials when microEDMing, according to Jason Kaczmarek of EDM distributor Belmont Equipment & Technologies, Madison Heights, Mich. “There are some consistent hurdles when [sinker] microEDMing, one being corner wear,” he said. “With smaller details come tighter tolerances, so retaining sharp corners on electrodes is vital.” When microEDMing with fine-grain electrode materials, shops typically use fewer electrodes than in the past to make the same number of parts while obtaining crisp corners and correct part geometries. He pointed out that high-quality electrode materials are also capable of imparting finer surface finishes. According to Kaczmarek, high-grade graphite used for electrodes has a grain size range of 1µm to 5µm; mid-grade from 6µm to 15µm; and low-grade from 16µm and up.

Threading for success

Advances in EDM wire threading have been one of the key developments boosting micromanufacturing productivity, according to John Bradford, micromachining R&D team leader at Makino Inc.’s technical headquarters in Auburn Hills, Mich.

“We make parts on a daily basis, and better wire threading has made our lives much easier,” he said. “We commonly deal with start holes as small as 25µm in diameter, and having a machine that can automatically feed wire through those holes—which you cannot even see unaided—is big. If you had eight start holes and you had to manually feed them, it would take the balance of a day to make those holes.”

Bradford reported that Makino’s UPJ-2 horizontal-wire EDM with a wire-threading option can thread a 30µm start hole with 20µm wire and finish the hole in 1 to 5 minutes. (To view a video of this wire-threading operation, go to the online version of this article on www.micromanufacturing.com.)

The automatic wire-threading capability facilitates lights-out machining. “We have a pallet magazine on the machine so we can fully automate the production of multiple parts containing multiple start holes,” said Bradford. “We never even have to touch the machine once we hit cycle/start. It’s a linchpin of cost-effective parts production.”

Ledvon agreed that better EDM wire-threading systems facilitate mass production of microparts. He pointed to a new GF AgieCharmilles wire-threading technology that has enabled threading of 0.0008" wire. “It’s impossible to thread wire that thin by hand. With automatic threading, shops can run microparts lights-out,” he said.

Cycle time is also being reduced by using high-precision, integrated workholding. MicroEDMing still frequently involves multiple steps, including removing the part for inspection and process adjustments, according to Bradford. He pointed to integrated workholding systems, such as those manufactured by Erowa, System 3R and Hirschmann, which have locating systems that allow a workpiece to be quickly fixtured, removed, reattached and requalified with submicron repeatability. “We couldn’t operate without that capability,” he said. µ

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Better measurement enables smaller EDMed part production

EDMing small parts has not been a problem for EDM Department Inc., Bartlett, Ill. Measuring them has been. According to Mark Raleigh, founder and president of the company, maintaining reproducible tolerances when microEDMing is challenging, but it is improving with better measurement capabilities. EDM Department is a contract manufacturer that focuses on flexible manufacturing.

“When you make something, you must be able to check it and qualify it,” he said. “That’s been the problem with micromanufacturing; elements are getting smaller, but the tolerances have not followed.”


The Alicona InfiniteFocus 3-D optical metrology system. Image courtesy Alicona.

To remedy that situation in his operation, Raleigh uses InfiniteFocus, a measurement device utilizing the FocusVariation technique developed by Alicona GmbH, Austria. The device moves the small depth of focus of an optical system, combined with modulated light, over the object with continuous vertical scanning, producing a topographic 3-D data surface model. As the distance between the object and objective is varied, the variation of sharpness measures 3-D depth information.

“We have integrated that technology into our manufacturing process,” he said. “Before, we weren’t able to see or measure our parts with sufficient accuracy. We were using destructive testing; we would have to dissect a part to expose elements that normally were not exposed. Now, with InfiniteFocus, we can effectively measure parts without destructive testing.”

EDM Department has used this new capability to produce smaller and smaller elements on the parts it EDMs. Operators can make measurements down to 0.5µm, and the shop has produced elements on an experimental basis as small as 8µm. It has developed “stable and capable” manufacturing processes, measured with the Alicona unit, for elements 50µm and smaller, with tolerances of ±1.7µm, according to Raleigh. By the end of the year, it expects to be stable and capable at the 40µm level, with tolerances of ±1.0µm. The goal is to make 30µm elements.

“We can now clearly see and measure what we are making,” Raleigh said. “That’s a major improvement in microEDMing.”

—A. Rooks