Low Friction Feed for keeping filament dry

thingiverse

According to https://www.youtube.com/watch?v=ACRh51hdBxo, successful printing of flexible filament like TPU hinges on two essential attributes. First, keep the filament dry at all times. Second, feed it into your Extruder with the lowest possible friction. The Roller Holder is a dual-part system featuring four Skate Bearings that support the roll of filament. This setup is standard practice, but I believe leaving the surface of the rollers flat and constraining the lateral position of the spool by the sidewalls of the printed supports is acceptable. Different rolls of filament have varying rim-to-rim spacing, so the Roller Holder (comprising parts A and B) boasts an adjustable spacing with detents to maintain a constant spacing while in use. A Top Roller designed specifically for the Prusa MK3 printer is included. It's not a snug fit, making it unsuitable for stiff filaments like PLA or PET, but it works well with flexible TPU filament. To keep the spool of filament dry during printing, I place a 2-gallon (8 liter) ziploc bag around the spool and include an old sock filled with about a cup of oven-dried crystal kitty litter (silica gel) to control humidity. To prevent the bag from dragging on the spool and creating friction, I fashioned a wire frame that supports the bag without allowing it to touch the spool. I initially made a mistake regarding the length of the m3 bolts, but this issue has since been corrected.