This is what I use as a pre-filter. I ordered a couple of rolls and cut them into pieces that fit snugly into the top of the filter case, right on top of the filter cartridge. I use three layers of material for every 1.5-2 hours of cutting/engraving time, then remove and replace with three clean layers of material.
In addition to using pre-filters, I also start the filter about 15 minutes before any cutting /engraving begins, and continue running the filter for an additional 20-30 minutes after all cutting/engraving has stopped. Doing it this way helps to compact the particles that make it past the pre-filters more than normal, and ensures that you get the absolute most use out of the filter’s holding capacity.
I’ve been using the original filter cartridge for almost a year, still have the replacement cartridge I ordered a couple of months ago, sitting on a shelf in the closet, in the original box. I average about 3-4 hours of use per day, changing pre-filters every couple of hours and air drying them after hand washing.
