Automated Wire EDM In Action
From the ground up, this new shop was built around the concept of fully automated, fully palletized wire EDM.
Automated EDM. That is the topic of this article. It is also the name of the shop that is taking this concept as far as it will go--which may be further than any other wire EDM shop so far. Automated EDM Incorporated was formed in Brooklyn Center, Minnesota, approximately two years ago. The two partners who started it, Don Zoubek and Wally Pelto, had a very clear idea about how they were going to set it up to take full advantage of automated equipment for wire EDM (electrical discharge machining).
Sure, lots of shops let wire machines run overnight or over weekends, but mostly these are one-workpiece-at-time operations with substantial downtime for setup between operations. What the Zoubek-Pelto team envisioned was around-the-clock operation with a minimum of downtime--just enough time to pull out a batch of completed workpieces (assorted jobs, almost all one-of-a-kind) and load in another batch.
Today, that vision is a reality. They're doing it, around the clock, and making money at it.
Particularly instructive is what Mr. Zoubek and Mr. Pelto learned from some expected and unexpected bottlenecks. They used these constraints as a growth path. By intent, their policy has been to go as far as possible with automation until they discover what is holding them back. The logical next step is to break that bottleneck and move on to the next.
For example, they knew that programming would be a bottleneck. Many work-pieces would take longer to program than to machine. On the other hand, they hadn't anticipated the impact on their sales force. Now that their machines are up and running, with their capacity to crank out a lot of work over a 24-hour period, bringing in enough business to feed these hungry machines is a real challenge.
Finding and breaking constraints to higher levels of automation has been the pattern for Automated EDM. Don Zoubek calls this "evolution by bottleneck," and it has taken the shop to remarkable levels of productivity.
The Shop In Action
It's not difficult to see how the shop works, although the simplicity is deceptive.
Three GFAGIECHilles Robofil 510 wire machines stand in a row against one wall facing a common aisle. Against the adjacent wall at the end of the aisle stands a four-shelf rack for specially designed stainless steel pallet frames. A DEA Mistral coordinate measuring machine (CMM) is located along the wall between the EDMs and the rack, with a computer station tucked into the corner.
Using a manual forklift, an empty pallet frame can be retrieved from the rack and set down on the CMM. On the granite plate, the frame is tooled and loaded with workpieces. The same clamping and positioning fixtures have been mounted on the CMM as are mounted in the EDMs, so that pallet frames can be transferred yet maintain positioning accuracy and repeatability of two microns.
When all of the workpieces are in the frame and the programs are organized, the forklift carries it to the next available machine. The strategy is to operate in an uninterrupted, untended mode for as long as possible with a minimum of intervention.
The goal for each of the machines is to run 5,000 hours a year. At that rate, these machines together will be as productive as seven machines running one shift a day. The shop has to get very close to this goal in order to justify the additional investment required for automation and palletization.
Don Zoubek and Wally Pelto formulated their concepts for a totally automated wire EDM shop while working together at another, rather progressive wire shop in the Minneapolis area. Not that these plans were made in a vacuum. Early on, the two began talking with an automation consultant, Mike Rogers, of Automation Technologies International (Gray Lake, Illinois), who helped them refine and firm up their ideas. In essence, this is what they decided:
They would be a job shop, going after many different jobs from a range of customers. The partners were convinced that their automated approach would lend itself to production jobs as well as to individual pieces of tool and die work.
They would be highly standardized. All machines would be the same. Standardization would give them the most flexibility in scheduling to meet fast turnaround times. It would simplify programming. It would minimize the variability that works against reliable untended operation. It would maximize machine productivity. Most important, standardization would be the key to palletization. They would solicit only jobs that meshed with their concept of highly automated operation.
They would be fully palletized. Palletization would minimize setup time and maximize continuous "burn time." Palletization would simplify tooling requirements. It would streamline inspection (workpieces could be inspected in the pallet before and after machining).
They would buy the most automated machine features and options they could. Automatic wire rethread-ers. Large capacity wire spools. Adaptive control to minimize wire breakages and other disruptions of untended operation. Remote monitoring via a computer network. Of course, this meant a considerably higher up-front investment but the additional productivity acquired would more than pay for itself.
Their management style would be innovative. Machine operators needed to understand and accept the shop's strategy. Palletization, standardization and automation would all live or die on the shop floor, depending on consistent execution and good communication. It takes a lot of attention to run untended.
Finally, they would move forward step by step, fully exploiting each resource before adding more, letting initial investments earn enough to pay for the next step.
The first step, after arranging for shop space, was to choose equipment.
At first, they thought they would need machines with submerged cutting. Cutting under water is usually more reliable on complex parts in the untended mode. However, they reconsidered in light of pallet loading. They decided it was more important to have a stationary worktable with a large door that was accessible with the pallet loader. Moreover, filling and draining the worktank added to non-cutting time. These considerations led them to the Robofil 510 Wire EDMs, the largest models offered by GFAGIECHilles Technologies (Lincolnshire, Illinois).
"We wanted big machines to accommodate pallets large enough to hold a sufficient number of workpieces to go all night or over the weekend," Mr. Zoubek explains. "Wire machines cut so fast now that setup becomes an issue. We also knew we were buying for the future and were determined to have the jobs to fill machines this big."
What's more, these models had all the features they were looking for in an automated setting: a reliable wire rethreader, a 35-pound wire spool, a personal computer-based controller, a compact footprint on the shop floor, and a straightforward design to facilitate maintenance.
Pallets And Tooling
The next step was to acquire the pallets and other workpiece tooling. Before approaching vendors, Mr. Pelto and Mr. Zoubek had a clear idea of the dimensions and features the pallet frames had to have. Unfortunately, no vendor offered ready-made pallets the size they needed. However, Mecatool, a Swiss company with U.S. offices in the Chicago area (Wood Dale), was willing to help design and custom-build them.
Each pallet is essentially an open frame of stainless steel rails. Locating pads mounted to the underside of the frame correspond with matching clamping fixtures mounted on the base of the EDM and on the CMM. This locating and clamping system allows the pallet frames to be located with a repeatability of 0.00008 inch in all three axes.
Dependable, extremely precise repeatability in pallet location is at the heart of the entire palletization concept. It is absolutely critical that a pallet be able to go from setup on the CMM to machine and back again with virtually no loss in positioning accuracy.
As can be imagined, these precision-machined pallets imported from Switzerland were costly. Don Zoubek figures that palletizing a wire machine is more than three times as expensive as tooling a machine with standard items for manual operation. "But less expensive than buying a second machine," he points out.
The number of workpieces loaded on each frame varies from a few larger pieces (which is typically the case) to many smaller pieces. The key is having enough workpieces for extended operation even with the higher cutting speeds that these machines are capable of.
Programming By Modules
Automated EDM faced four critical programming issues essential to their concept of automated EDM. Already mentioned was the sheer quantity of programming that would be required. If automation allows you to double or triple your output on a machine, you'll need two or three times as much programming.
A second issue was adequate preprogramming planning (thinking the job through before generating wire path data). A third was programming in modules to support flexible palletizing on the shop floor. And finally, they had to make sure each programmed module was proven out and error-free before being released to the shop floor.
Many shops might find having one programmer per machine a surprising burden. For Automated EDM, it's a logical extension of their production concept. If an extra programmer permits a shop to get four machines' worth of work out of two, the additional manpower is justified. "But the programmer has to know EDM," Wally Pelto stresses.
As an indication of how important planning is, Mr. Pelto says that planning takes about as much time as actual programming. The key is figuring out how to do as many operations as possible in the untended, automated mode and be able to link these together as a pallet-full of workpieces, so experience with the EDM process is indispensable. The objective is to maximize uninterrupted operation of the wire machines.
Each operation on a workpiece is programmed as a separate file, or "module." When the workpieces are set up in the pallet, programming modules can be arranged to correspond with the order in which the operations are to be performed.
These modules, however, must require no shopfloor intervention.
They have to represent highly reliable "mix and match" pieces that the machine operator can call up on the computer network and plug into the master program for a full pallet of EDMing.
Programmers use GFAGIECHilles' CT Esprit programming system. Because this software is especially written for GFAGIECHilles wire machines, its post-processing capabilities are virtually error proof. This feature really counts in an automated shop because machine operators do not have to worry about editing on the shop floor.
Likewise, Mr. Pelto considers verification of each module an absolute requirement. Verification is accomplished with a simulation system called SIMFIL, a proprietary package from GFAGIECHilles. In essence, it allows a four-axis wire path to be processed on a personal computer that emulates the processor on board the machine's computer numerical control (CNC). The wire path can be displayed in action, making it easy to find potential trouble spots and to correct them from the shop floor.
EDM operators at Automated EDM have a lot of freedom and responsibility. It's largely up to them to manage the logistics of keeping their machines busy based on the jobs that are scheduled.
Operators are responsible for physically loading the pallet frames. This takes place at the CMM, so verifying location and orientation of workpieces is convenient and precise. A computer station a few steps away makes it easy to load the workpiece coordinates and link them with the modular programs, which are already written and verified.
Operators do have to double check the sequence of operations, making sure clearances for tapering moves are adequate, and so on. Shop scheduling is often modified based on their input. Operators are responsible for loading and running their machines, unloading them, handling inspection, keeping records for costing and handling other shopfloor paperwork (which is minimal).
Palletization gives operators a high degree of flexibility, which translates into responsiveness to customers as well as shopfloor efficiency. If a rush job is scheduled, it is not difficult to stop work on one machine and remove the pallet to exchange it for another pallet. Similarly, a pallet with unfinished operations that lend themselves to overnight operation can be pulled out during the day and reloaded before the lights go out. The key to this flexibility is the repeatability of the pallets.
Sales And Marketing
Like the machine operators, Automated EDM's sales force has to understand its operating philosophy and know how to sell this capability. They have to know what jobs to look for and what customers to cultivate. The high throughput of the shop makes this a demanding challenge.
"If you double your machining capacity, then you have to double your gross sales. Keeping the pipeline filled is a challenge when it's a big pipe," stresses Mr. Zoubek. "We recognized early on that a highly automated system does not operate efficiently only half filled. It's a matter of having enough work to keep utilization high."
What It Takes
What does it take to start up an automated EDM shop like Automated EDM? Partners Pelto and Zoubek had experience with EDM technology, insight into its potential, a vision for realizing this potential, a well-thought-out plan of action, and the guts to carry it out. They visited other shops, went to trade shows, looked at all the new EDM equipment they could, and talked to experts in the field. They had the help of a proactive and knowledgeable distributor of EDM equipment in the area, Dan Noonan of the D.J. Noonan Co., who was instrumental in linking them with sources for the various elements of automation they would need. They had the support of some perceptive lenders, a vital part of any startup. They did their homework.
And they listened. They listened especially closely to the people they had working with them in the shop and in the sales office. "These are talented and creative individuals who know a lot about EDM technology and automation concepts," Mr. Zoubek points out. "We learned more from them than from just about any other source--and we made sure they understood what we were trying to do and were a part of each step."
Wally Pelto and Don Zoubek make a good team. They represent a complementary mix of talents and skills. Whereas Wally Pelto is more the systems engineer and programmer, Don Zoubek is more the business manager and administrator; yet both are skilled tool and die makers with roots on the shop floor.
Above all, they share the excitement that goes along with proving a concept and being technology pioneers. Their shop, Automated EDM Inc., is living up to its name.
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