Ride of Wire EDM | Why Wire EDM

Wire EDM cuts a new path - electrical discharge machines - Emphasis : Electrical Discharge Machining

Andrew White

This job shop knew it had to change direction and offer more than just precision milling and turning if it wanted to keep its current customers and attract new ones. Adding wire EDM gave the shop a new range in capabilities along with a better balance in its operations.

When an electrical discharge machine (EDM) is introduced to a conventional mill-and-turn job shop, it can't just take up floor space. It has to earn its keep, and the machine will be under the scrutiny of many skeptical eyes to do just that - and to do it quickly.

So when a wire EDM made its way to the pine woods of northern Massachusetts and settled into a far corner of the work floor at Lavelle Machine, Inc., the staff of 40 looked on with keen interest. Would this machine become a problem-solver, or just a headache-generator?

For 30 years, Lavelle Machine has grown steadily and quietly, building up customer trust in its capabilities as a precision milling and turning shop. By diligently focusing on the areas it knows best, the company has been steadily rewarded with contracts to handle prototype machining assignments as well as small production runs for medical, military and commercial applications.

But the management team at Lavelle sensed they couldn't live forever tightly burrowed within this niche. Often the programs on which Lavelle worked required that the company subcontract out secondary operations such as laser welding, EDM, or product assembly. Some projects requiring additional processes weren't even being offered to Lavelle by existing customers for bid.

"We knew we had to increase the scope of our capabilities," said Ed Lavelle, Jr., vice president and general manager. "We needed more things to ask a customer to let us bid on."

A Strategy Emerges

To get that additional business, he decided, the company needed to bring new production capabilities in-house. Assembly work seemed to be the least intrusive to the shop's existing operation, so a portion of the shop floor was set aside for limited assembly work, and flexible staffing arrangements were made so that the company could handle product assembly on an "as needed" basis.

Getting into EDM was a tougher decision. From its earliest years, EDM has had a reputation for "black magic," of being more of a science than a technology - one that also required large capital investment and specially trained personnel. While Lavelle certainly was not wary of advanced technology - its shop floor is comprised almost totally of high precision CNC milling and turning machinery - it had heard enough stories of other machine shops getting in over their heads with EDM.

For Mr. Lavelle, though, a little time spent researching today's EDM equipment showed a pleasant surprise: The industry has changed dramatically in recent years, primarily due to truly quantum leaps in control technology. While computers have simplified processes in countless fields of industry, the gains are most apparent in the more delicate and complex of production operations. Such is EDM. It now seemed possible to run a small EDM operation using existing plant labor - without the expensive and specialized operators and programmers of days past.

One Lavelle employee who last worked in EDM over a decade ago, machinist Harry Haynes, agreed to become the company's EDM supervisor. When he saw the state of today's equipment, he said, "I was literally blown away.

"Programming [an EDM machine today] is a breeze, using plain English and minimal keystrokes. While the job is underway, the display can show the operator a diagram of the cutting path, and then continually show exactly where the cutting is being performed throughout the job."

For Mr. Lavelle, two major factors in the decision-making process were when he learned that most EDM equipment has decreased in price in recent years - even though the control and cutting technology has dramatically improved - and that one of his most trusted machine tool suppliers had recently begun marketing a line of wire EDMs. If we are going to get into this, he thought, now is the time.

Setting Up For EDM

Lavelle already had strong relationships with several customers producing medical components, and often served as primary contractor for jobs requiring EDM operations. The jobs varied in the complexity of EDM work required, and Mr. Lavelle realized his shop would not be able to perform all of the EDM work that might be required with just one machine on-site. But acquiring two EDM machines was out of the question at this early running. Narrowing the decision to either ram-type EDM or wire EDM, the company chose the latter for what amounted to an utterly practical reason. "With ram EDM, you have to make your own electrodes," Mr. Haynes said. "With wire EDM, all you need to do is buy a spool of wire."

Not interested in making their first EDM experience more complicated than it needed to be, the Lavelle managers determined that a control unit that was powerful yet still easy to use would be the major factor in their purchasing decision. They gave the nod to a Fanuc flushing-style wire EDM. Familiar with Fanuc CNCs, they felt confident that the control unit of the new EDM would live up to expectations. Likewise, managers had the additional reassurance of working with a machine tool supplier, Methods Machine Tools of Sudbury, Massachusetts, from whom they had acquired other machines in the past. Methods distributes the Fanuc line of wire machines in the United States but what was important to this shop was confidence that they would receive the appropriate support, training and service as they got started.

"We found the EDM control easy to understand," said Peter Oberto, operations manager. "It wouldn't be unreasonable to expect even an inexperienced operator to be programming and cutting within days."

The machine was placed in the company's prototype department. "It was a cleaner environment in there," said Mr. Oberto. "And in the beginning, at least, we expected most of the cutting we did would be for prototypes or for our own tooling."

Harry Haynes programmed his first job: a modification for a carbide collet used on a turning center in-house. The operation was completed successfully on the first try. "I knew we were on our way," he said.

As the shop began to use wire EDM for prototypes and for small runs, Mr. Haynes and the supervising staff in the shop were especially surprised to find the finished parts not only measured well within specification, "but visually they looked terrific," said Mr. Haynes. EDM has a history of being a less-than desired production method when it comes to producing parts that must be visually appealing. But today's generation of digital AC power supplies, such as that on the model that Lavelle had acquired, greatly reduces discoloring and tarnish by supplying the charge through a non-electrolysis method.

"When we saw the quality of the output," Mr. Oberto said, "we knew the range of potential jobs for this machine had just been greatly expanded." Since much of Lavelle's work is in the medical field - where a highly polished, unblemished finish is required for instrumentation - this unexpected benefit of using EDM appeared to be a godsend.

Discovering Production Efficiency

Turning its attention now to obtaining larger work orders for its new capability, Lavelle management suggested to its customers that they could achieve some excellent economies of cost and time by keeping their total job - from milling to turning to drilling to EDM - within a single shop. In addition, job accountability, responsibility and overall quality assurance would be tighter - all key benefits for precision machining jobs.

"It makes sense for our customers to funnel their work into a single shop they know and trust," said Mr. Oberto. "It's better for both the customer and for us."

The customers seemed to agree. One project brought into Lavelle early on, a surgical inserter made from 303 stainless, required four precise operations - milling, turning, EDM and laser welding. The handle for the inserter was milled on a Matsuura CNC vertical machining center. Meanwhile, the shaft was turned on a Nakamura-Tome CNC lathe. Before the two could be laser welded together, however, the handle needed an extremely precise cutting operation to provide three narrow slots. On the prototype, these slots were cut manually with a circular slitting saw. This was an extremely labor-intensive and expensive process. Plus, "we would have needed to do significant deburring on every piece in production," said Mr. Oberto.

With what Mr. Haynes called "a minimum of set-up," the wire EDM took care of the slotting process for four pieces set on a fixture in one cycle, with a cutting time of three minutes for each part. No skim cuts were needed, the accuracy level was 0.0002 inch, and the finished pieces required no deburring or polishing.

Another medical application, a mini-anchor assembly made of 17-4 PH, would have proved even more daunting without secondary EDM capability. Here, the required processes included turning, milling, welding, EDM, assembly, passivating and laser marking. For a machine shop to handle only the milling and turning in-house and then send the other processes outside would have created a nightmare of logistics and quality control issues. But with Lavelle's newly added capabilities including EDM, the only process that needed to be handled out-of-shop was the passivating. Again, the EDM work required for the part was primarily to create three precision slots. On the new wire EDM, the single-cut operation took four minutes per part, with 24 parts per cycle.

For a bushing for a computer printer that had the most demanding specs yet, a blank was turned out of tool steel using a Nakamura-Tome six-axis dual spindle turning center, which also performed a secondary milling operation to create the flange. After heat treatment, the part was brought to the wire EDM, where a rough cut followed by a series of skims took the ID to within a tolerance of 0.0001 inch.

The new EDM received its most vigorous test when Lavelle Machine was asked to produce a prototype for a medical sliding gripper block. The job called for a complex mix of milling, turning, EDM, heat treating, passivating, laser marking, hard coat anodization, and manual assembly using 300 series stainless steel. The most critical operation was the precision cutting of angular teeth 0.040 inch in height that required an extremely sharp point - yet also needed to be absolutely free of burrs for use in holding human tissue during surgical operations. The wire EDM succeeded in meeting the specs, and upon completion of the prototype, the company was assigned a production run for this component.

EDM And JIT

For Mr. Haynes and Lavelle's EDM operators, the time and cost benefits gained from their EDM setup go beyond the simplified control and ease of use. Several jobs can be left within the control's memory at any given time - and the tooling and fixturing for those same jobs often can be left set up within the machine's working area even while another job is underway. This means a setup for a job that is in frequent production on the EDM can be left intact while another job or two jobs are run during a break in the machine's production schedule. These benefits can be significant ones on a hectic shop floor.

"Our shop has a strong JIT emphasis, and this EDM fits in perfectly," said Mr. Oberto. To keep production changes moving quickly, the Fanuc machine is hard-wired to the shop's central DNC computer, and programs can be downloaded quickly for jobs.

For classically trained machinists like Harry Haynes, there are other enjoyable benefits to EDM. "If I set up a job for 1000 pieces, I'll never have to change the offset number," he said.

It didn't take very long for Lavelle's new EDM to be booked solid for its two daily shifts and beyond. At the end of the day's second shift, the operator often sets up an "overnight job" and programs the controller to wait until the early morning hours to start the cycle. This way, the job is finished shortly before the first shift operator arrives at 7:00 a.m., and the finished pieces are not sitting wet for an extended period. The first shift operator unloads the finished job, and goes on to prepare the next cycle.

Once the setup is complete and the run button is pushed, the EDM operator rarely needs to stay near the machine. "I can set up 25 parts for a two-hour cycle," said Mr. Haynes. "I can walk away for those two hours and have confidence that everything is running smoothly."

If he does decide to wander back to the machine to check the status of a job, all the details of the progress of the run are displayed on the control monitor.

"The nice thing about the control is that it graphically shows what I'm cutting at any given moment," said Mr. Haynes. "I always know what path my tool is following."

To create an even greater level of automation, the Fanuc control can be programmed to use its own artificial intelligence capability. The machine can be set so that the controller can be allowed to make its own "decisions" about how to adjust cutting conditions and operations. These guidance functions also can be applied to automatic power recovery, restarting, and even machine maintenance.

At Lavelle Machine, typically the machine's primary operator is working nearby at the shop's laser marking machine, which requires continual operator attention. When the EDM cycle is finished, he simply shifts over to the Fanuc to unload and prepare the next job.

"The two machines complement each other well with their cycle times," said Mr. Oberto.

The EDM also allows Lavelle to maintain flexibility among staffing assignments. The company has several veteran CNC milling and turning machinists who have found little difficulty stepping in to operate the EDM - simply by using basic machining principles. The control unit on the EDM is similar to the controls they're already used to working with, and a quick look at the display during programming or at run time shows the data they require to get the job done.

Bringing "Balance" To Operations

Lavelle Machine has always held as one of its goals the objective of being a balanced job shop. In recent years, Ed Lavelle had sought to create such a balance by installing the equipment and recruiting and training the staff necessary to handle complex jobs involving conventional as well as third and fourth axis milling, along with turning capabilities ranging from the conventional to multi-spindle, multi-function operations. "But I had always been eyeing EDM as well," he said. "We wondered if it might be the missing link."

"If we were sending the EDM operations on a job out to an EDM shop," said Mr. Oberto, "we had to contend with time delays and quality issues. Jobs were costing more due to our additional administrative and management time. And we were not fully in control."

Now that Lavelle Machine has been up and running with EDM capabilities for over a year, Mr. Lavelle and Mr. Oberto note that they are able to quote lower costs and shorter deliveries on their job bids. They have better control over the jobs that are in the engineering stage or in production, and they have reduced the chances of running into unhappy surprises from outside vendors.

And, they say, they have once again confirmed what they have always believed to be a fundamental tenet of the business: that a machine shop can make itself more versatile and responsive to its customers' needs when it has a broad range of capabilities. "We never want to be in a situation where we cannot accommodate the customer," said Mr. Lavelle.

The customers have noticed. Mr. Lavelle said his company has solidified its relationships with its existing customers as well as opened up new avenues of business in recent months.

"In today's market, the company that is going to be the most successful is the one that is the most self-sufficient," said Mr. Lavelle.

One measure of success is growth, and at Lavelle Machine plans are underway for a 10,000 square-foot expansion to the facility, which Ed Lavelle said will certainly include significant additional EDM capability.

And no longer is anyone at Lavelle Machine casting a wary glance at the little white machine in the corner.