EDM Filtration – TAGUTI
Traditional Filtration Media
Filtering is necessary to remove the contaminants that the wire-EDM process leaves in the dielectric fluid. If left in the fluid, these contaminants can interfere with the electrical discharge between the wire and the workpiece, reducing the quality and the speed of the cut. Unfortunately, these contaminants pose a threat to humans and the environment in the form of groundwater contamination; therefore, there are few safe places to put them once they have been removed from the fluid.
The EDM wire itself is the source of much of this hazardous contamination. One analysis of the contaminants produced when an A-2 tool-steel workpiece was produced found that about 48.5% of the waste was copper and zinc eroded from the EDM wire. The disposal of materials such as copper and zinc is regulated by local and state laws, because these materials can leach out and poison an area’s groundwater if they are disposed of in a landfill improperly. Because dielectric-fluid contaminants pose a threat to both the EDM operation and the environment, EDM shops must consider how much it will cost to both remove and dispose of the contaminants when they evaluate their filtration needs. EDM shops use a variety of different media types and particulate-retention capabilities in search of the holy grail that is EDM filtration. Every shop is searching for an acceptable balance between filtration efficiency and cost.
Most knowledgeable EDM users would agree that clean water is essential for fast, high-quality cutting. Generally, shops have considered a filter that can remove particles down to 5µm or 10µm in size sufficient to get their water clean. However, many applications produce smaller particles and could benefit from the use of a higher quality filter with a rating of 3µm or better. The EDMing of D-2 tool steel is an example of such an application. One analysis found that 81% of the particles produced by such an operation were less than 5µm. Generally, finer filtration will produce the most dramatic improvements when used with machines capable of finer finishes. These machines typically produce smaller particulate. Also, the cleaner water produces fewer false voltage readings that cause the machine to back up in applications where a smooth, steady servo action is required to produce a good surface finish.
Additionally, the use of dirtier than normal dielectric fluid or dielectric fluid filtered through media larger than 5µm will reduce resin life, because the resin (which is designed to remove soluble particulate) also is an excellent filter for the finer solid particulate that passes through many of the conventional filter cartridges on today’s market. By using a system that filters particulate down to 3µm, a shop can extend resin life by 200% or more. Because the finer filtration produces cleaner EDM water to start with, less particulate is trapped in the resin filter columns, which are really designed to deionize the water, not filter out contamination.
But despite the advantages that can be gained through finer filtration, such a quality level is neither practical nor cost effective when traditional pleated cartridge elements are used. The finer the retention rating of the filter, the more expensive it is to purchase. Filter cartridges capable of fine retention also drive up the operating cost of the equipment, because these filters get clogged easily and need to be replaced more often. In addition to the cost of the media itself, the user must consider the cost of the nonproductive time that accumulates as the machine sits idle during filter change out and the labor cost required for this routine maintenance.
Shops find it a daunting task to assess the total financial impact their choice of filter-media type and filter rating will have on their operation. As a result, many shops accept their filtration expense as a necessary evil, which they pay for on a filter element-by-element basis; they never track what they are paying for the elements or for any associated costs. Some shops can tell you what they are paying for filter media, but they haven’t analyzed any other costs.
It is usually the more experienced shops with multiple machines that have determined what their total filtration expenses are, including their costs for such elements as media, machine downtime, and labor. Shops with multiple machines are more concerned with costs because they usually operate these machines closer to their full capacity, running two or three shifts six to seven days a week. Not only are their filter costs higher, but the cost of machine downtime and the labor required to change filters and perform the extra maintenance to keep the machine dielectric tanks clean has a greater impact on their profitability. With machines that can earn $50 to $80 per hour, shops with multiple machines place value on a “hassle-free” solution.
If you are running a wire-EDM operation and you haven’t analyzed your filtration needs or explored alternatives, your filtration costs may be unnecessarily high. You might be able to reduce your maintenance costs, increase machine uptime, and work with cleaner dielectric fluid (which would help you produce parts with better finishes in less time) by replacing your paper-cartridge system with a different solution.
To know for sure, you will have to conduct a thorough investigation to answer these questions: Do you know what your current filter costs are? Do you know what it will cost you to stick with the OEM filtration system that came with the machine? Are you paying for 10µm capability when you really need 5µm results (or better).
Filtration Advances
In the past few years, the EDM filtration media has been greatly improved. Higher precision paper is normally adopted, and even the surface material is also being improved. Some advanced filter manufacturers have adopt the plastic ones to produce a EDM Filter. TAGUTI filter use the pained iron ones as their filters’ surface and all TAGUTI filter adopt Japanese paper and glue. This is a powerful guarantee of the quality and its service life. So as a leader in china’s filter market, TAGUTI has continuously conducted research and development. Now, TAGUTI´s product portfolio includes EDM Filter, Air Filter and Powder Filter Cartridge.