Wire EDM: How Much Better Is Bigger?

Originally published at: https://edmproud.com/wire-edm-how-much-better-is-bigger/

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Large-diameter wire for EDM has been around for decades, but just recently it has taken the market by storm. To understand how and why this is happening I will go back to my personal experiences as a WEDM operator.

In 1976, the industry-standard wire diameter was .008″; this was for three reasons:

1. The power supplies were 5-10 amps, and the rate of cutting was around 1″ square. Any larger wire would have needed more power and better flushing—technology that was unavailable in the mid-1970s.

2. The primary use of the WEDM was punch and die making, which needed sharp corners both inside and out to replace the process of fitting sections of blocks together for the small, intricate shapes that were being stamped.

3.  We did not care so much about speed because there was no other way to produce these components. We were happy just to have the ability.

In the late 1970s, the need to produce die components faster was driven by the demand for this new technology. If you had access to WEDM, and the die shop you were competing with did not, you could outbid your competition by building the dies faster due to the 24/7 operation of the machine. So now, the faster the machine could cut, the more you could produce. Next, we made bigger power supplies of 15-20 amps and utilized the increased surface of .010” diameter wire to cut faster. This change in diameter gave us speeds near double the 1″ per hour rate. Then we just had to work around the .001″-.002″ increase in our corner rads, which was an easy trade-off.

In the early 1980s, we started seeing new uses for WEDM because of the increase in speed. The first change was in the thickness of the part we could cut due to the increased amperage we could utilize from the .010″ wire. We also coined a new term: “production EDM.” One of the slowest machining methods in our industry was now becoming a process considered by a larger sector of manufacturing. The saying “if there’s any other way to make it than EDM, then that’s the way to do it” was becoming less common.

In the mid 1980s, EDM manufacturers realized they could expand the market thanks to the versatility of adding speed with the larger wire diameter. This increased metal removal rates to the point of taxing the flushing and amperage available from the machines—so the industry made the next jump to .012″ diameter wire and added more power and higher flushing pressures. Now the speeds were in the 20″-square hour range and the WEDM was becoming a go-to process for an even bigger market sector, all due to the larger wire diameters. At this point, we were pushing the envelope of many parts of the EDM machine technology: servo, abnormal discharge detection, thermal distortion, just to name a few. Then the progress in technology flat-lined in speed. Many manufactures went to .013″ and .014″ diameter wire, but the increase in speed was minimal and the cost of the wire outweighed the time saved.

The flat-line in speed remained until 2019 when .016″ diameter wire came to the market. Although only a few machines have the capability to use this larger-diameter wire, the speed and performance is worth looking at. An example based on book technology is outlined below:

  • 4″ thick D2 Tool Steel
  • .010″ Brass wire avg. machining speed is 14.25″ square
  • .012″ Brass wire avg. machining speed is 17.35″ square
  • .016″ Topas H.E.A.T. EXTREME by bedra wire avg. machining speed is 33.05″-square

Given this kind of increase in performance, there’s a trade-off in cost and accuracy. So, what is the cost for this speed?

  • Wire Job Test Punch: .010″ Brass wire, workpiece 4″ steel; shop rate $60.00
  • Inches of cut linear = 28.5″, cutting rate 14.25″-square per hour; total cutting time 480 minutes (8 hours)
  • Wire consumed = 4800 meters; other consumables, water, electricity, filters, $5.50 per hour

TOTALS FOR PUNCH TEST WITH .010″ WIRE

Wire used cost @ $6.50 lb.                    $26.35

Consumables used                                   $44.00

8 hours shop rate                                   $480.00

                                                 Total         $550.35

  • Wire Job Test Punch: .016″ Brass wire, workpiece 4″ steel; shop rate $60.00
  • Inches of cut linear = 28.5″, cutting rate 33″-square. per hour; total cutting time 207 minutes (3.45 hours)
  • Wire consumed = 1036 meters; other consumables, water, electricity, filters, $5.50 per hour

TOTALS FOR PUNCH TEST WITH .016″ WIRE

Wire used cost @ $12.14 lb.                    $23.12

Consumables used                                     $19.00

3.45 hours shop rate                                 $207.27

                                                 Total           $249.40

From this example, we can see bigger did not cost more, but in fact cost less in both time and money. Two parts for near the same cost and time as one.

This example was just one of the applications where we could see advantages with the larger wires. Another advantage to the larger wire would be cutting off metal-printed parts where the spark is interrupted, or parts mounted in such a way that there is a large gap between the head and workpiece. It should be noted that these applications are not the only reason but, just the ones I have studied to date. We will also see applications that will not be a good fit for this technology. But if machines have the mechanical and the spark technology to be versatile enough to cut with .003″ diameter wire to .016″ diameter wire, we will see many more opportunities to use WEDM. As the wire manufactures and the machine builders better their products through competition, we all benefit.