Over twenty years ago, the first Wire EDMs were imported to the U.S. - creating a machining revolution!  First they changed the entire tool & die industry's methods and now, the latest breed of fast cutting machines promises to do the same in the production machining area.  With cutting speeds that were  never even dreamed of in the 70's, and the ability to create three-dimensional shapes, the Wire EDMs are replacing the "chip-makers" in ever-increasing numbers.

In reality, the Wire EDM machine is a chip-maker, but because of the early model's low cutting speeds, the chips could be forgotten about for quite a while - until the filter cartridge finally needed changing.   Higher cutting speeds however, became a double-edged sword.  They cut the time to produce the parts, but they also cut into the productivity and profits due to filter inadequacies and the resulting high maintenance costs.  Fortunately for the EDM users, there are companies like Ebbco Inc. of Sterling Heights, Michigan, who take the art of filtering very seriously and constantly strive to perfect it.  Recently Ebbco embarked on a project to improve Wire EDM filtration by extending the life of the filter cartridge.  They were successful in accomplishing their goal by adding a new "twist" to cartridge filters.

Analyzing Wire EDM Filtration

During Ebbco's research into prolonging the life of the cartridge, they also discovered other areas that required attention and decided to take the complete systems approach to dielectric improvement.  The operative word here is "filtration".  It is widely used, but it is most definitely a misnomer, since in reality, overall dielectric quality is the important factor.  In order to operate a Wire EDM machine at top efficiency, water with the following qualities is a necessity:

1. Water free of particulate (down to 3 micron).  This is where the work "filter" comes into play.

2. Water free of total dissolved solids (T.D.S. or conductivity).  This is where the D.I. resin enters the picture.

3. Bacteria-free water.  This is the missing link in the complete system.  Ever since "day one" in the Wire EDM business, bacteria has bee fouling both filters and resin beds and before now, had not been identified as the villain it really is.

In order to properly address the whole problem, Ebbco produces complete systems which solve all three problems.  They have accomplished this without endangering the environment - a fact that becomes more important with the passage of time.

Filtering Out The Particles

A modern fast-cutting Wire EDM produces large quantities of particles in the one-to-ten micron range.  One micron is .000039" (39 millionths of an inch).  The shear volume of these particles produced can overwhelm many filters, however Ebbco has developed a reusable cartridge filter which can remove up to 25 lbs. of contaminant and still deliver crystal-clear water.

Traditionally, manufacturers use pleated filter media to increase the square footage available within a compact configuration, usually a cylindrical shape.  In theory this appears to be effective, but upon closer inspection, it was discovered that often "pleat pinch off" occurs.  This is when two or more (often as many as four or five) pleats are squeezed together, thus reducing the amount of usable filtering area.

In their new Hurricane II filter design (above), Ebbco has virtually eliminated "Pleat pinch off" by employing two of their patented ideas.  First, the velocity of the liquid being pumped into the filter is directed into a circular flow path which causes the pleats to open up, thereby exposing 100% of the media to the liquid flow.  Next they have further enhanced this action by introducing a slight twist to the cartridge which results in the pleats leaning directly into the liquid flow path causing them to open even wider.  An additional benefit tot he EDM user is Ebbco's patented "up flow" design employed in the Hurricane II.   This unique construction eliminates the dumping of many gallons of dirty water into the "clean tank" when changing filter cartridges.  By containing the dirt and keeping it out of the "clean tank" this eliminates the necessity of having to physically clean out the tank before draining it down, a mandatory environmental requirement.

The new "twist" in the cartridge helps to open the pleats for more efficient filtering.

The Second Concern Is Total Dissolved Solids (T.D.S.)

In order for a Wire EDM machine to function, the water must be free of dissolved solids.  When it contains dissolved solids, water takes on the ability to conduct electricity which precludes its use as a dielectric fluid.   An EDM machine cannot function properly and will DC arc if the dielectric fluid is conductive.  The undesirable T.D.S. are removed by passing the water through a container filled with a mixed bed of resin beads supplied with the Wire EDM machine.   This container must be manually emptied and refilled with fresh resin on a regular basis.  It is no longer allowable to discard the used resin beads along with the regular trash, they must be disposed of according to EPA regulations.

Ebbco provides the EDM user a system which addresses this situation.  Their D.I. resin is packaged in a one cubic foot capacity bag and is simply removed.  A fresh one is replaced in the vessel as needed.   The EDM user then returns the used bag of resin to Ebbco's EPA-approved regeneration site.  It is regenerated and returned to the shop.  The waste products are disposed of properly and the EDM user has not only followed EPA regulations, they have also practiced conservation by recycling this valuable resin.

The Third Concern - Bacteria In The Water

This is an area that had not been previously addressed in Wire EDM filtering systems, but seems to be a source of problems.  Over the years, Ebbco has on occasion, been confronted with a fouling of resin beds and premature failure of filter elements.  The filters would appear to be generally clean, however they had run for just a few hours before shutting down.  After much investigation, Ebbco discovered what "cooling tower experts" had known all along - that recirculating water systems form an ecosystem in which bacteria can flourish.   It shows up as a dark slime on the tank and hose walls and the water is slippery to the touch.  When bacteria-laden water is pumped through a filter or resin bed, it coats the surface and causes premature failure.  The initial reaction would be to add a biocide to the water, however this would alter its conductivity rendering it useless as a dielectric fluid.  Ebbco's solution turned out to be rather simple, they added an ozone generator tot he system - much the same as found on many spas and some small swimming pools.

Ozone - What It Is And How It Works

Ozone is a three atom form of oxygen and is a normal trace element in the earth's atmosphere.  Ozone is the strongest commercially-available oxidizing agent.  Because gaseous ozone is highly reactive, it readily oxidizes organic matter and has a variety of uses including a bactericide and an algaecide.  Ozone's presence can be detected by its distinctive sweet odor, even at very low concentrations.  Ozone will not contribute to the total dissolved solids, but in fact, acts as a micro-flocculent to bind tiny, non-dissolved solids together so they can be filtered, or settle out.  The goal of ozone oxidation is to treat the water without the addition of chemicals.  Any chemicals added to the water will react with the ozone and create an added demand on it.  This raises the amount of ozone required to accomplish the treatment objectives.

Summing It Up

As environmental concerns and new discharge regulations shift the burden of compliance to the users of industrial water treatment systems, industries are being forced to practice new methods of water treatment to comply with ever-tightening discharge limits.  In many cases, ozone-oxidation will allow water that is being currently discharged to be recirculated and not reused in the process.   That not only eliminates the environmental exposure, but often results in a sizable savings for the industry.

So there you have it - a three part approach to what appears to be a singular problem:

1. A reusable cartridge filter that holds 25 lbs. of contaminant.

2. A resin-regeneration package that is environmentally sound and conserves precious resources.

3. A non-chemical bactericide that lengthens the D.I. water's life and is simple and inexpensive to use.

All of this totals up to one COMPLETE system!

EDM Today would like to thank Ed Bourgeois, President of Ebbco Inc., for this very interesting story about how his company improves the total quality of a Wire EDM machine's dielectric water.