Creality Ender-3 Y-Axis MGN12H Linear Rail Mod (Older Style)

thingiverse

Human: *Note:This is for older Ender-3 printers with flat/z-shaped front Y idler bracket.* [Here's the mod](https://www.thingiverse.com/thing:3058382) for newer style with U-shaped front Y idler bracket.* [The original design](https://www.thingiverse.com/thing:2914034) placed belt too close to frame, causing severe belt misalignment. This could be due to early model unit, poor QC or other reasons, so I moved holes for belt retainer blocks out 4.6mm. I figured I wasn't alone in my endeavor to fix wobbly bed, so I wanted to make this remix available. A **HUGE** shoutout goes out to [goopyplastic](https://www.thingiverse.com/goopyplastic/about) for doing most of heavy lifting on this design. Don't forget to degrease rail & carriage. Pre-lube everything if you want to do it now or save mess & wait until its mounted. # BOM * 1 x Ender-3 * 1 x 300mm MGN12H linear rail * 2 x M4x20mm screws * 2 x [M4 t-nuts](https://www.amazon.com/s/ref=nb_sb_noss_2?url=search-alias%3Daps&field-keywords=m4+tnut) * 2 x M4 washers * 12 x M3x8mm screws * 12 x M3 t-nuts * 4 x M3x25mm screws * 8 x M3 washers * 4 x M3 locknuts # Instructions 1. Remove all four bed leveling knobs & lift heated bed & springs out of way. 2. Loosen screws on front idler to give Y belt some slack & slide belt off Y plate. Remove four screws & v-wheels holding Y plate to extrusion. 3. Once all hardware is removed from Y plate, use **ydrillguide_remixed.stl** to drill 1/8" (3.2mm) holes by aligning it in holes where vslot wheels were mounted. 4. Mount **yretain.stl** & **yretain-mirror.stl** blocks to Y plate using 4 x M3x25mm screws, 8 x M3 washers and 4 x M3 locknuts. 5. Mount 300mm MGN12H rail to extrusion using 12 x M3x8mm screws and 12 x M3 t-nuts & at least 2 x **Linear_Rail_alignment_helper_MGN12_+_V-Slot_2020.stl** as alignment blocks. 6. Relocate Y-motor mount (leave motor attached) & front idler assembly to opposite side of extrusion & re-mount with existing screws/hardware. 7. Relocate Y-axis limit switch using **ylimitspacer.stl**, 2 x M4x20mm screws, 2 x M4 washers and 2 x M4 t-nuts to opposite side of extrusion. 8. Reuse stock Y belt and attach it in same insert-into-slot fashion as stock. 9. Add your favorite oil or grease to rail (you degreased brand new one, right?) 10. Do the reverse of Step 1 & re-level bed. 11. Move z limit switch up a few mm's/until nozzle doesn't crash into bed when homing. 12. Print away! Video: https://youtu.be/IBlSbVZZRGk Any feedback, questions or comments are welcome!