Y-belt holder and tensioner for MK3 and Bear MK2, MK2.5, and MK3

thingiverse

Motivation ========== There are plenty of great things about Prusa printers, but the Y axis belt line isn't one of them. A 16T pulley on the motor, a 20T pulley on the idler, and an offset going through the belt holder introduce Z axis forces on your bed as it moves along Y. These parts allow you to use a 16T idler and get a perfectly parallel belt line, keeping the bed level as it travels. User [RHDreambox](https://shop.prusa3d.com/forum/memberlist.php?mode=viewprofile&u=42061) designed [replacement parts](https://shop.prusa3d.com/forum/others-archive--f66/fine-tune-your-mk3-y-axis-t13851.html) to fix this on the stock MK3, but they rely on quality assembly to achieve belt tension. These parts provide adjustment via screws. Built for Bear ============= User [pekcitron](https://www.thingiverse.com/pekcitron/about) designed an excellent frame replacement for modern members of the Prusa i3 family of printers. He's also built an excellent replacement [X axis and extruder](https://github.com/gregsaun/bear_extruder_and_x_axis) that makes the belt line parallel, adds a built-in belt tensioner, and improves the extruder itself. Things ====== There are several parts in this "thing". You will need the right set of belt holder, idler slide, and idler mount for your printer. There are a few preassembled kits (zipped STLs) as well. - Y axis belt holder for the mk42 bed - Y axis belt holder for the mk52 bed - Y axis idler slide for Bear users. - Y axis idler slide for stock MK3 users. (Not yet tested; beware!) - Y axis idler mount for Bear users (OpenBuilds V-slot) - Y axis idler mount for almost-Bear users (Misumi T-slot) Additional hardware ================ Bear tensioners --------------- - (2) [M3x0.5 16 mm socket cap screw](https://www.mcmaster.com/#91292a115/) - (2) [M3x0.5 nylock nut](https://www.mcmaster.com/#93625a100/) - (2) [M5x0.8 8 mm button head screw](https://www.mcmaster.com/#92095a207/) - (1) [M3 18 mm dowel pin](https://www.mcmaster.com/#91585a384/) - (1) [16T timing belt pulley](https://www.amazon.com/BALITENSEN-Toothed-Pulley-Printer-Timing/dp/B078SD2XGL/) Stock-MK3 tensioner (not the stock idler!) ------------------------------------------ - (2) [M3x0.5 16 mm socket cap screw](https://www.mcmaster.com/#91292a115/) - (4) [M3x0.5 hex nut](https://www.mcmaster.com/#91828a211/) - (1) [M3 18 mm dowel pin](https://www.mcmaster.com/#91585a384/) - (1) [16T timing belt pulley](https://www.amazon.com/BALITENSEN-Toothed-Pulley-Printer-Timing/dp/B078SD2XGL/) Belt holder ----------- - (1) [M3x0.5 25 mm socket cap screw](https://www.mcmaster.com/#91292a020/) - (1) [M3x0.5 DIN 562 square nut](https://www.amazon.com/Stainless-Steel-Square-Nuts-Thin/dp/B073SB766G/) Updates! ===== 2018-07-29 --------- Feedback told me that the slot-mount holders were harder to center than they needed to be because the screws were behind the slide. Good criticism, so I made mounting ears instead. It was also called to my attention that the naming of the Y belt holder files wasn't quite right. Fixed! I'm also working on an easier-to-use version of the belt holder. 2018-12-25 --------- It's a day off work so it's a day for maker-ing. I've back-ported the belt holders from my ["Serious business"](https://www.thingiverse.com/thing:3122625) mod since the tooth profile is better. I've also modified the Bear version to have a slightly different V-slot profile on feedback that it was slightly too-big. Finally, I added the sight-line to the stock MK3 flavor mount. New Solidworks source is up. It's now the 2019 version. Happy holidays!