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EDM Molds a Smart Future

Built-in intelligence allows machines
to cut finer small and large molds

 

By Jim Lorincz 

Senior Editor 

 

EDM, both wire and diesinker, is generally regarded as a mature technology in applications for which it is especially well-suited. Innovations have been incorporated over the years in literally every facet of the process to provide competitive advantage to the end user and the supplier. EDM technology itself has gotten smarter, capable of producing finer surface finishes—especially needed for micro molds—and has enjoyed growth spurts both in the smaller and larger moldmaking applications. Using EDM in combination with high-speed hard milling offers processing solutions for automotive, consumer product, and aircraft components for parts production and for mold work and graphite electrode machining. It’s quite common for the major suppliers of EDM equipment to offer the latest high-speed hard-milling technology and to support both technologies with the necessary tooling, supplies, and training.

There’s no doubt that with all the advances that have been incorporated into EDM machines over the years, today’s machines are more efficient, more capable, and more energy-efficient than ever before. The challenge to technology suppliers and users alike is to match the right technology to the proper applications, especially as more opportunities in moldmaking, in particular, begin to filter back onshore. Photo Courtesy of Exeron GmbH and Methods Machine Tools Inc.

“We’re seeing more EDM diesinker business staying in the US, Canada, and also in Mexico,” says Bob Ianitelli, president and COO, Belmont Equipment and Technologies (Madison Heights, MI). “What we’ve seen lately is actually a large upswing in our orders and quotations on large EDM machines, particularly our larger two-headed MX-196HD EDM diesinker, which is a gantry-style machine. The table doesn’t move, and a lot of customers actually leave the work tank down and overhang the table if they want to set up a large tool and use framing to balance it on the table.”  

Typical large-tool applications include automotive bumper fascias and instrument panels (IP). “A lot of the IPs are done in sections so you don’t need as large a tool. In other cases, there may be three or four inserts, and the moldmaker wants to do the EDM work after everything is assembled. It might be that medium-sized workpieces are milled and then put into the die sets or mold sets, and they’ll do the EDM work as a one-piece mold. It’s all part of the trend in which moldmakers are becoming more creative in using their diesinkers,” Ianitelli explains.

Belmont Equipment equips its diesinkers with its AL (adaptive logic) circuit, which maximizes the cutting speeds that can be obtained without arcing that can occur from smaller ribbed electrodes. “AL allows us to get some burns that others can’t do, or can do only on machines with a fairly high price differential. We add the AL circuit to the machines ourselves, along with our CNC capabilities and vector orbiting for angular cutting for large tools,” says Ianitelli. 

Belmont is a full-service supplier of EDM consumables, supplies, electrode fabrication, and EDM equipment, including high-speed graphite milling machines and cutting tools. "When a customer asks why Belmont, we tell them that our biggest advantage comes into play after the sale is made. We specialize in after-sales support to help the customer in materials selection for the EDM machine, electrode fabrication, whether machined by us or our customer, and advice on settings required for cutting conditions. Today, they may only be doing ribs, but six months later another opportunity may present itself, and we can help by giving them suggestions concerning process requirements and capabilities,” Ianitelli says. And there is a lot of opportunity. “There’s a lot of plastic used in automotive, consumer products, and aircraft. Behind all that plastic in an airplane there are support ribs to keep everything from collapsing.

“EDM diesinking has always been something of a black art, because nobody knows what’s going on underneath the bubbling oil," Ianitelli explains. "Wire EDM is geared around setting a number for this material and this thickness. EDM diesinkers have worked more of this type of knowledge into the machines. So we train customers about how to get the most efficient cutting, particularly by adjusting flushing conditions. Our goal is to educate the operator to what the settings mean. Different flushing conditions can have a definite impact depending on whether you’re cutting a deep rib or a rib that is broken out on the side and has a long wall. Our role is to educate the customers whether we’re talking about a consumable EDM product or an EDM machine itself. We lay out the options. A lot of what we do is to go in from the processing side and make suggestions—about cutters for graphite mills, or settings for EDM, whether the equipment is ours or not—to help the consumer be ready when business comes back to them.”

GF AgieCharmilles (Lincolnshire, IL) is building intelliegence into its diesinkers with its dynamic process control (DPC) technology and adding probing and optical measurement onto its EDM machines. “There are two main trends that I see,” says Eric Ostini, product manager, “putting more smart knowledge for production control in the machine’s control and greater use of probing and optical measurement in the machines. With DPC technology in our new diesinkers, we are adding the expertise and ability to adjust hidden cutting parameters so that less knowledge is required on the part of the operator. To get the accuracies and finish required for LED molds, for example, there’s a lot that can be done. All the operator has to do is select from a list of applications, and the generator will automatically be set up, including the undersize and the power setting to cut the type of material required for the job.” 

  

“We’re seeing more EDM diesinker business staying
in the US, Canada, and also in Mexico.”

  

In addition to LED molds, applications for which DPC have been developed include cell phone molds, and cavities for micro and nano applications. “For micro and nano applications where you are dealing with very small cavities with very fine finishes, it’s important to tweak details so that the electrode doesn’t wear out and remove the detail from the mold,” Ostini explains. “It’s not so much the functionality of the machine, it’s the hidden elements. You can easily add a function to the Photo Courtesy Belmont Equipment & Technologiesmachine, but it’s technique that counts when optimizing its operation.” 


GF AgieCharmilles has also added Renishaw probing compatibility and optical measurement systems directly on the machines to hold tighter tolerances in measuring cycles for both wire and diesinking EDMs. “This will provide the operator an easy way of removing the part, checking it, putting it back on the machine and locating it for a second burn or subsequent milling operations,” says Ostini. “Sometimes, parts have to be taken off the EDM, especially in the micro mold area for milling and then put back on the wire EDM or diesinker for further processing. Consequently, the part has to be picked up correctly. Otherwise, a very small mold isn’t going to be correct,” Ostini comments. 

What is important today as much as any time in the past is satisfying the customer’s production requirements with regard to cost, quality, and process stability. “Everything is so price-conscious today that technology advantage, which should still the most important aspect in buying an EDM machining solution, may not be sufficiently considered in the decision-making process,” states Greg Langenhorst, technical marketing manager, Mitsubishi/MC Machinery Systems Inc. (Wood Dale, IL). “It’s important for us to tell our customers that we build application-specific technology into our wire and diesinker machines, with a lot of features that can help them meet their quality manufacturing objectives. In our wire EDM machines, these capabilities take into account materials, thickness, speed, accuracy, and surface finish, among others. Cutting solutions are developed in our own lab here in the US. It’s important for us to elevate the machine’s performance so that the end user simply has to plug in condition numbers to get the right part, the right finish, and the right accuracy,” Langenhorst says. For diesinkers, Mitsubishi EDM offers the Roku Roku high-speed graphite mill with a 30,000-rpm spindle for efficient milling of electrodes.

Mitsubishi EDM’s NA Series wire EDM is particularly well-suited for high-end carbide die making and punch and die for stamping, because of its digital FS (fine surface) power supply, Langenhorst says. “It can work with wire down to 0.002" [0.05-mm] diam and achieve surface finishes down to 2.5 µm Ra, like a polished mirror.” The machine blends the V500 high-speed generator with a standard AE3-HS generator on one machine that can be used for both production work and high-end tool and die work, eliminating the need to buy two machines, one for each type of application.

   

“There’s a lot of plastic used in automotive,
consumer products,
and aircraft, for example.”

 
According to Steve Bond, national sales manager, FANUC RoboDrill, RoboCut and EDM products, Methods Machine Tools Inc. (Sudbury, MA), “the merits of graphite have spilled over into the European market,” which has long preferred copper for electrodes for diesinker EDM. European machine manufacturers recognized the advantage of graphite’s high melting temperature to obtain zero percentage wear, which is important, because the quality of the surface finish of an electrode directly translates to the mold  At the same time,  “the need to reduce both the size of the machine’s power supply and to decrease the amount of energy consumed during erosion” was explored. This has benefited all those involved in diesinker EDM machining using graphite. Renishaw

According to Steve Bond, national sales manager, FANUC RoboDrill, RoboCut and EDM products, Methods Machine Tools Inc. (Sudbury, MA), “the merits of graphite have spilled over into the European market,” which has long preferred copper for electrodes for diesinker EDM. European machine manufacturers recognized the advantage of graphite’s high melting temperature to obtain zero percentage wear, which is important, because the quality of the surface finish of an electrode directly translates to the mold  At the same time,  “the need to reduce both the size of the machine’s power supply and to decrease the amount of energy consumed during erosion” was explored. This has benefited all those involved in diesinker EDM machining using graphite.  

R&D in this area has resulted in developing new power supplies that are compact and still capable of generating the same amount of cutting amperage. Exeron GmbH (Oberndorf, Germany) introduced the exopuls+ liquid-cooled generator technology, which is designed to reduce electrode wear during roughing and finishing, resulting in more accurate parts. “The new generator reduced graphite electrode wear during roughing and finishing by about 35%, while machining efficiency increased, providing faster burn times. In some cases when using electrodes with fine details, the burn times were reduced by as much as 18% over previous power supplies,” says Bond.

The efficiency enhancements resulting from the new liquid-cooled design have netted dramatic power reductions. It has been found that under a  full 60-A burn, power consumption went from 537 kW-hr to as low as 2.8 kW-hr in the same erosion applications. Power dissipation was also reduced from 3000 W to 600 W, Bond reports. 

“Advancements in this area of EDM machining have continued with an examination of the machine’s logic to further enhance burning, especially in poor flushing conditions. The newfound efficiency of the power supply allowed for smoother power setting transitions (1 A increments), which, in turn, allows the CNC diesinkers to produce the same results with less setting changes,” Bond concludes. The exopuls+ liquid-cooled generator technology is available from 60 to 240 A, and is standard on Exeron diesinker-type EDM machines, available in North America from Methods Machine Tools Inc. ME 

 

 

This article was first published in the October 2011 edition of Manufacturing Engineering magazine.  Click here for PDF

 


Published Date : 10/1/2011

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