Advertising in MoldMaking Technology offers
Issue link: https://mmt.epubxp.com/i/544238
TIP 64 MoldMaking Technology August 2015 Achieving Efficient Filtration EDM By Fabian Maier The EDM process generates various amounts of dirt particles, whether the material being cut is aluminum, platinum, titanium or gold. It is important to collect and filter these dirt particles so that the finished cut does not result in a rough and uneven surface. An EDM filter and its media can effectively col- lect this dirt, and their construction are key. Each material being cut can be classified by its dirt extrac- tion efficiency (dirt size particles and consistency). For exam- ple, aluminum generates large dirt particles (10-20 microns) and requires an EDM filter that can hold larger particles without clogging. Unfortunately, no official filter efficiency classes currently exist that would help to ease the filter selec- tion process. However, there are two important factors any manufacturing company should take into consideration: filter media and pleating technology. Both are important for high dirt-removal efficiency and long filter service life. Determine the appropriate filter media. An EDM filter consists of pleated (folded) filter media constructed with a cel- lulose or synthetic fiber material whose structure permits the separation of dirt particles from the dielectric fluid during the cutting process. Filter media with cellulose fibers (paper-based raw material) require an impregnation of phenolic residue to enhance their mechanical stability during filter installation and while in the dielectric fluid. On the other hand, this exact impregnation causes an increase in conductivity due to ion exchange. This has a negative influence on the process, per- mitting rust to form more easily. An optimal solution is a filter with a media that has no neg- ative influence on the dielectric fluid, such as one consisting of fully synthetic fibers that do not require any impregnation to ensure mechanical stability. Additional advantages of a syn- thetic filter media include its minimal thickness (0.25 micron), which yields slow resistance against the flow and therefore lengthens the filter's service life. Integrate the appropriate pleating. The smaller the parting (space) between each pleat in the filter, the greater the total fil- tration surface area that can be realized. However, every filter media and pleating structure has a specific minimum spac- ing that ensures the pleats do not clog with dirt. To achieve optimal filter service life, it's important to determine the right amount of filter area with the ideal pleat partition correspond- ing to the given installation space. Different EDM filter solutions include single-bellow, double- bellow and progressive triple-bellow filters. Triple-bellow EDM filters with progressive pleating actually feature one bellow consisting of three segments. This allows for an enlarged filter surface area and results in very high dirt- holding capacity and long filter service life. Combining this triple-progressive-pleat geometry with a synthetic media yields an EDM filter with a service life as much as 60-percent longer than a standard filter media with a single pleat (see image). Filter media (cellulose and synthetic) and bellows technolo- gy (single-bellow, double-bellow and triple-bellow) can have an impact on the efficiency of the EDM process. Some manufac- turers are working toward establishing industry-standardized efficiency classes that would address specific requirements and applications for EDM filters. Such classes would ease filter selection for EDM users and help to determine true filter life and cost. FOR MORE INFORMATION: Mann + Hummel Purolator Filters LLC / 919-926-4164 marianne.guldberg@pureoil.com / mann-hummel.com CONTRIBUTOR Fabian Maier is manager of the engineering business segment for industry and energy at Mann + Hummel. Images courtesy of Mann + Hummel Purolator Filters LLC. Combining triple-progressive- pleat geometry with a synthetic media yields an EDM flter with a service life as much as 60-percent longer than a standard flter media with a single pleat.