Idler for Direct Drive Extruder

thingiverse

This idler is designed for 1.75mm filament and works well with Makerbot mk7 and mk7 Drive Gear, though it was created for a spur gear from SDP-SI (S10T05M020S0505). It includes clearance on the bearing side so you can print a mirrored idler for dual extrusion use. Drawing inspiration from the overhead lever design of Thingiverse's item 15718, this idler incorporates a filament guide that is missing in the original design. However, it has been noted that the idler bearing may contact at slightly wrong position during printing. The body of the idler was inspired by Thingiverse's item 13727 with one important difference - this design does not protrude on the idler side, allowing for use in dual extrusion setups. However, the force required to operate it can cause the lower part of the base to flex due to the slight bounciness of the spur gear. The hinge design from the original inspiration was also found superior, but unfortunately could not be incorporated into this design. After about a year of use, the pivot arm on the original print may require a larger spring for continued functionality. A replacement with at least 40% infill is recommended. Parts required include two M3x18 flat head screws to secure the base and the arm to the stepper, one M3x10 flat head screw to hold the bearing, one R2 (US size) or 623 (Metric) bearing, and a fairly strong spring. To print this idler, print one plate normally for single extrusion and mirror and print again for dual extrusion. Remove built-in support from the curve meeting the stepper, the idler where the bearing goes, and the hole where the bearing screw goes. Some holes may require cleaning with a 2mm drill depending on your printer. Tap the bottom side of the bearing screw for M3 and secure the bearing. Mount the base to the stepper using the leftmost screw, pinch a strong spring between the base and the arm while securing the right-side screw. The spring can also be inserted afterwards.