Malcolm Schneer has always been “big” on EDM. Now big EDM, as in a machine
capable of handling extremely large workpieces, is playing a major role at his
shop, Swiss Wire EDM.
According to the Costa Mesa, California-based company, the catalyst for its
recent acquisition of a wire machine capable of cutting parts as large as 3 feet
by 4 feet by 2 feet tall fully submerged in dielectric was a job involving
honeycomb seals for a jet engine. Already acutely aware of the benefits that
fully submerged cutting affords, Swiss Wire EDM realized that the new machine’s
24-inch cutting envelope would enable it to precisely and efficiently cut the
intricate seals. This expanded capacity also held promise for processing other
tight-tolerance aerospace projects.
“There’s a noticeable difference in the ability to cut a large part both
quickly and accurately between attempting to force enough flushing through the
kerf on a non-submerged machine and having it submerged in the DI water,” Mr.
Schneer explains. “There’s always some dielectric present at the point of
erosion so the process becomes inherently more efficient and repeatable.”
How EDM Stacks Up
Walking into Swiss Wire EDM,
one might notice a twinkle in the eyes of Mr. Schneer. Although the origin could
very well be a spark emanating from a workpiece nearby, it’s more likely his
unadulterated zest for electrical discharge machining. The England native first
became enamored of the technology during the 1980’s when Mr. Schneer acquired
the business from Franz Klarer, a Swiss toolmaker who had started up the company
a few years prior. Starting with three tiny EDM machines, the shop has grown
steadily to its present 19 machine capacity.
One distinguishing characteristic of Swiss Wire EDM is that it is clearly not
a conventional CNC shop. Specializing in wire EDM, ram (sinker) EDM and
small-hole EDM, the company produces complex prototype and production work for
the aerospace, medical and commercial industries. Typical parts may have
30-degree angles and corner radii of less than 0.001 inch. Perhaps most notably,
the shop has been able to differentiate itself by machining even large aerospace
components. How large is large? The parts that the shop customarily processes
can be as tall or even as thick as 48 inches, weigh as much as 4,500 pounds and
have diameters as large as 60 inches.
Mr. Schneer has found that many of the exotic materials increasingly
prevalent in aerospace applications such as titanium and molybdenum are more
easily machined with EDM than with conventional machining techniques.
“EDM is wonderful for cutting out contours on 22-inch-thick mold blocks or
19-inch-thick turbine disks,” he explains. “We can run these jobs through a wire
machine instead of milling away hundreds of cubic inches of material, which
would otherwise generate mounds of chips.”
To hold the tight dimensional and positional tolerances—to ±0.0002
inch—required of both the miniature and colossal workpieces that grace the shop,
Swiss Wire EDM has traditionally stretched the capabilities of its existing EDM
equipment. Deeming a submerged cutting environment as the best method to cut
extremely large parts accurately, the shop uses its two FX20 models from Mitsubishi EDM to
hold dimensional and positional control when handling components as large as 14
inches by 19 inches, with 11 inches of submerged Z-axis height.
“Both of these machines have been modified to cut parts as tall as 48
inches,” Mr. Schneer comments. “Even with only the first 11 inches, the cutting
results are amazing.”
|
Company: SwissWire EDM
Problem: Cut challenging honeycomb pattern accurately
Solution: Mitsubishi FA30V wire EDM machine
Results: Machined to 4 decimal
tolerance |
In addition, the company retains its first Mitsubishi wire EDM—a 200G—along
with various Agie and Charmilles models to handle the influx of challenging
projects. Although the shop has found this equipment to be more than adequate
for most jobs, it did not have a way to efficiently machine extremely large or
extremely thick parts—some as thick as 24 inches—fully submerged in dielectric
until recently when it expanded its EDM arsenal.
A Tall Order
In fact, Mr. Schneer, while
always ready to expand operations, was not making any immediate plans until
Rolls-Royce UK approached him to research the possibility of using EDM to trim
large-diameter honeycomb seals. Snagging the actual contract hinged upon
creating a controlled process and passing an onsite audit in which a Rolls-Royce
representative monitored the shop for an entire week.
Honeycomb cell structures are frequently used as seals for rotary components
in jet engines. In this case, the seals were to be used in Rolls-Royce’s Trent
1000 jet engine for a 787 Dreamliner aircraft. (The cell material of choice is
often stainless steel or another high temperature metal alloy, sometimes
titanium.)
The job involved cutting both the ID and OD for the round seal. The
structures could contain absolutely no burrs, rips or inconsistencies. They also
required a pure edge with extreme dimensional accuracy.
 |
| A technician inspects high-volume production tooling for EDM
of small medical parts. |
Having been a Mitsubishi EDM
customer since 1986, Mr. Schneer was well acquainted with the manufacturer’s
products. Taking into account the similarity of programming among the Mitsubishi
machines and the material thickness range of the machine—it can cut pieces as
thick as 26.5 inches—Mr. Schneer was confident that the shop would gain
significant benefits by having one of the company’s FA30V machines on its
floor.
Greg Langenhorst, technical marketing engineer at Mitsubishi EDM, explains
how the machine’s submerged cutting envelope facilitates fast, precise cutting,
particularly when handling intricate components such as honeycomb seals:
“Often aerospace parts are pre-machined pieces with complicated geometries,”
he says. “There may be many nooks and crannies, varying widths, gaps and so
on.”
“In a non-submerged machine, you only have two columns of fluid from upper
and lower flush cups keeping the wire wet,” he continues. “Cutting ‘dry’ doesn’t
allow the entire workpiece to get wet at once. Therefore, you have to slow down
to keep some kind of water in between the wire and workpiece so it doesn’t
break, as hot sparks can jump onto a dry surface and easily break the wire. In a
submerged environment, however, you have more liquid to work with, meaning that
you can use more power behind the wire and cut the workpiece faster.”
To distribute ample power throughout its machining range, the FA30V uses a
V500 power supply. In addition, its programmable fluid control system is
designed to enhance fast machining. Machine features such as these have allowed
Swiss Wire EDM to meet the tolerance requirements of the honeycomb project
without having to resort to extreme measures.
 |
| The submerged environment ensures that fluid is present
between the wire and the workpiece.This is critical to applying enough power
behind the wire to accelerate cutting. |
“One of the beauties of EDM is that you can cut honeycomb quickly and
burr-free at the same time,” Mr. Schneer explains. “Whereas conventional shops
might have to take exotic measures, such as freezing water in the honeycomb
cells to bolster the structure during cutting, we need only use a wire or an
electrode to cut them efficiently.”
For Lightweights, Too
Aside from its
heavyweight projects, Swiss Wire EDM is equally engaged in producing
near-microscopic components, each of which can weigh merely a few grams.
Burgeoning applications in the medical sector have brought about production
challenges in terms of accuracy and surface finish requirements, as well.
So exactly how does this West-Coast shop efficiently process parts at
opposite ends of the size spectrum? Moreover, how does the company consistently
uphold Mr. Schneer’s mandate for economic, accurate and efficient production
while tackling these projects? Simply put, aside from having a high level of
quality assurance and certifications, including ISO9001, AS9100B and NACAP,
Swiss Wire EDM immerses itself in and continues to rely on the technology that
has served it well for decades. As confirmation of this philosophy, the company
is an approved vendor to not only Rolls-Royce, but also to GEAE, Boeing,
Lockheed Martin and Northrop Grumman, to name a few. Aersopace represents one of
Swiss Wire EDM’s many specialties. For instance, its Mitsubishi 90 HAs are
employed to produce a cannula tube used to biopsy breast cancer. The shop
processes 7,000 to 8,000 of these tubes per month for one customer alone.
“Regardless of how small or large a component is, wire EDM offers accuracy,
favorable surface finishes and material economy,” Mr. Schneer concludes.
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