Bondtech BMG for the Cocoon Create Touch

thingiverse

Geared Bondtech Extruder for Cocoon Create Touch/Wanhao I3 Plus This geared extruder uses the existing heatbreak, in my case the Micro Swiss all metal heatbreak. I wanted to try the geared Bondtech drive without purchasing another heatbreak, as I had already installed the Micro Swiss all metal heatbreak. I used this Thingiverse model for the existing printer: https://www.thingiverse.com/thing:2669164. The Bondtech models and dimensions were measured using CAD files from here: https://github.com/BondtechAB/Bondtech_Prusa_i3/tree/master/CAD-Files Hardware I used gears and bearings from inside a Bondtech BMG extruder. The Zaribo Pancake Extruder Motor is recommended for this application; it's available here: https://zaribo.com/electronics/126-zaribo-pancake-motor-by-ldo.html. I believe this motor is equivalent to the LDO-42STH25-1404MAC, or the Stepperonline 17HS10-0704S. A 3mm thick aluminum spacer for the heatsink was used; trace around the side of the heatbreak cooling block for dimensions. A PC4-M10 Straight Pneumatic Fitting with an M10 thread (I had a 1/8 NPT version) was used, along with a 4mm OD Capricorn Bowden PTFE Tubing between the heatbreak and just below the drive gears. One PEM IUBB-M3-1 heat-set insert was required; I used an Lulzbot Heat-Set Insert Tapered, M3-0.5mm Internal Thread, 3.8mm L. A longer heat-set insert would be better. The filament path in the model is 1.75mm diameter, which needs to be drilled out to 2mm after printing. I used a reamer to get the bearings to fit nicely as my printer was printing the holes too small. Use a 4mm drill to clean out the holes for PTFE tubing, and a 4.2mm drill for the heat-set insert hole. Depending on your printer's calibration, you may need to drill other holes to size. If you use the hinge pivot shaft from the Bondtech extruder, shorten it so that it doesn't protrude past the outside face of the case; I used a piece of 3mm shaft from an old CDROM drive. The white Bondtech gear protrudes out the back of the extruder; check the clearance between the gear and the x-axis bearing screws. You may need to slide the heatbreak towards the front or shorten the x-axis screw for proper fitment. Using a specified pancake stepper will result in about 5mm less X travel, while using an existing stepper will result in more lost travel distance. UPDATE: I have now tested the Stepperonline 17HS10-0704S with a 1.8 degree step angle and can see no differences in print quality compared to the Zaribo Pancake Extruder Motor. The Stepperonline motor has the same pinout as the original stepper motor supplied with my printer, so I reduced the current to below 0.7A and set Vref to 0.5V. Set steps/mm to 415. The 0.9 degree Zaribo Pancake Extruder Motor requires swapping the outside two wires on the cable and inverting the extruder motor pin direction in firmware; do not change motor current from original settings. On my printer, Vref was set to 0.8V with a steps/mm of 830. Additionally, I had rosc shorted out on my A4988 driver.