While there are many different types of molten metal filters commercially available today for a foundry to choose from, the predominant categories are ceramic cellular/honeycomb, reticulated ceramic foam, and high temperature silica mesh. Having pioneered the development and commercial introduction of silica mesh filter cloth to the foundry industry in 1989, our product research team focused its early efforts on how to improve the basic mechanism of filtration and on developing additional performance traits beyond inclusion removal. Ultimately, we were successful in both.
While the filtration action of most filters is a simple mechanical or "sieving" action, ours was enhanced when using resin treated silica mesh filter cloth in ferrous alloy casting applications through the creation of a "sticky surface" on the fibers of the silica cloth. The sticky surface is a contact by-product of the pyrolytic reaction between the stiffening resin and the molten ferrous alloy that in turn will trap small particle inclusions which are small enough to pass through the open holes of the filter material. Ceramic cellular/honeycomb and reticulated ceramic foam filters do NOT have this capability.
Experimentation and extended validation testing proved early on that by strategically placing flat Flexsil filters with the runner gating, at the ingate, or at the bottom of a riser sleeve, a ready made cleavage plane was created. This cleavage plane makes it possible to break apart gating and knock-off risers with minimal effort and speed, thus saving significant time and cost by eliminating the need for manual cut-off. This valuable performance benefit is unique to Flexsil and CerraFlex, as ceramic cellular and foam filters do not provide for it.