Published 9/1/2009

Optimize Machine Performance with Proper Filtration

There are multiple factors to consider when it comes to operating a wire EDM and filter quality should be one of them. Proper filtration can save EDM users money and time relating to production and maintenance. Buying low-cost filters may seem like an easy place to cut costs, but the truth is, it can be a costly mistake.

Mike Bystrek

Here we see a stack of many of the common types of materials cut on wire EDM machines. Each of these will affect the performance of the filter in both water cleanliness and total filter life. Some materials produce large particles that build up on the filter surface, like tool steel, making for long filter life. Other materials produce a soft gummy sludge, like aluminum, that coats the filter surface quickly stopping water flow. Photo courtesy of Mitsubishi EDM (Wood Dale, IL).

Filters need to be the correct size to achieve adequate flushing pressure, and also must be properly designed to keep EDM particles from being sent back into the cutting zone. Image courtesy of The Consumable Products Group (CPG), division of MC Machinery Systems.

The cutting process of wire EDM vaporizes material from both the wire electrode and the material being cut. These particles will vary in size depending on the type of workpiece material, wire type and power setting being used. Materials such as micro-grain carbide, tool steel and aluminum, as well as the use of plain brass or zinc coated wire, all create different sized particles.

These tiny little things could be causing your biggest problems. Sub-micron particles will rob a wire EDM of its top performance. The perceived cost savings from low-cost filters is actually resulting in bigger expenses by reducing cutting speeds, resulting in low-quality surface finishes, increasing wire breakages and accelerating wear on other machine components.

Filters that claim to last longer than premium OEM filters are actually sacrificing the quality of the work. For example, if a premium 5-micron filter is swapped for a 10-micron filter, the filter life will increase because the particles below 10-microns will not get filtered.

A high concentration of smaller particles that isn’t caught by the filter is then forced into the DI system, which is next in line after the filtration system. If the resin system is now acting as a particle filter, the structure of the resin bed is coated in dirt and cannot do the job it should be doing. This increased contamination results in shorter resin life and production time due to an increased need for machine maintenance and repair.

Once these particles have made their way through the resin system, they are pumped back into the machine. With nowhere else to go, they begin to build up and wear out other machine parts—such as solenoid valves, flow meters, jet nozzles, guides and bearings.

Filter Selection Criteria

Because filters play such an important role in optimizing wire EDM, it is important to use a reliable product. Not only do filters need to be the correct physical size and media size, they must be properly constructed to handle the large amounts of sludge that is generated and to keep the EDM particles from being sent back into the cutting zone.

Premium OEM filters provide several unique designs that pack in more surface area to catch debris, such as expanding linear folds versus equal size radial folds, which increase the total surface area available in the filter. Media size and quality keep the dirt in the filter right from the start and does not require a precoat time before reaching the stated micron filtration level. Precoating allows dirt to pass through the larger media pores for several hours, directly affecting the machine and work quality during that time.

The flow rate of the filter is also critical to its overall performance. A filter that is smaller than
recommended will have to pass the required water volume through too fast, which will not allow time to filter properly. This will cause it to plug up faster, resulting in more downtime and requiring more frequent changes.

Filter construction is also important to proper filtration. Filter systems will push the elements up to over 50 PSI before a change should be required. If the paper media, body construction or adhesive used to glue the media to the end caps is below standard, the filter will fail, allowing dirty water back into the machine’s fluid system and hurting both the machine and the end product. OEM filters are designed to run up to maximum system pressure without failure keeping the dirt where it belongs, not circulating through your machine.