Under $30 easy Prusa mk3 linear rail mod

thingiverse

# Linear Rail Mod for Prusa MK3 This mod uses 300mm MGN12 linear rails. I opted for the Chinese version, which costs under $15 each. No rail cutting is required. The parts are designed to match the original build height (Z) and Y movement spaces, preserving the build volume and avoiding firmware modifications. The self-test calibration will pass without issue. Setup is straightforward; the springs keep the bed secure while allowing for block alignment. You'll need to modify the PSU holder if you have an old silver-PSU (not necessary in rev2). A demo video is available at https://www.youtube.com/watch?v=MpT0MBIkZBg. ## Change Log ### 2020/04/21 - Updated Rev2 * Adjusted square nut slot and bolt hole size. * More compact and stronger tail and bridge mounter design. * All parts can be printed without support. * Compatible with both older silver and newer black PSU without modifying the PSU case. ## Why The Chinese linear rail is a cost-effective option, offering stability and quiet operation superior to smooth rod-bushing combos. The linear rail also provides a neat appearance. ## Q&A Q: But the Y rod is 330mm; your rail is only 300mm. A: Refer to the last picture for clarification. ## Parts List ### Bolts and Washers * 2x 300mm MGN12 rail * 3x MGN12C block * 2x M3x10 bolt * 10x M3x12 bolt * 4x M3x15 countershunk bolt * 6x M3 washer * 12x M3 spring washer * 4x 4x10mm spring (or cut from a ballpoint pen spring) * 4x M3 nut * 4x M4 nut * 4x M4 washer * 4x spring washer * 4x M4 T-nut * 8x M3 T-nut * 8x M3x15 bolt * 8x M3 square nut ### Printable Part Rev2 * 2x head mount * 4x node mount * 2x tail mount (mirror in slicer) ## Installation * Install M3 nuts (Nylocs recommended) into the tail printed parts. * Mount the printed parts to the printer frame using M4 bolts for the tail parts. * Install the rails with M3x10 bolts. Avoid over-tightening, which may deform the part. * Install 2x MGN12C on the left side and 1x MGN12C (or MGN12H) on the right side. * Secure the Y carrier to the left block using M3x10 bolt, washer, and spring washer. Ensure it's tight. * Use M3x15 countershunk bolt, 4x10 spring, and M3 washer to secure the Y carrier to the right blocks. Leave some space for alignment. * Refer to the pictures for further details.