Anycubic i3 Mega conversion to linear rails

thingiverse

Due to very noisy linear bearings, flexing rods and massive play, I decided to convert my i3 Mega to have nice and sturdy linear rails instead of the original steel rods with linear bearings. From this Aliexpress shop ( https://www.aliexpress.com/store/1760039 ) I ordered some SGR10N rails and roller blocks ( https://www.aliexpress.com/store/group/SGR10N-series/1760039_510602243.html ) This seller is really nice and helpfull, on request they cut the rails to any lengnth you desire. So I let the Y-rails cut to the i3 Mega's 370mm. The build platform: (Y-axis) Unfortunately I mis-ordered three 4-roller blocks instead of three 3-roller blocks for the Y-axis. But I just cut and machined them to fit the available 120 mm below the print-bed. Installing the rails on top of the i3's base case is straight forward. Just measure well and accurate and drill and tap the holes carefully and precise. Since the case's wall is only 1mm thick, I put additional nuts to prevent the thread in the case top-sheet to break out. After installing the rails and adjusting the preload on the roller-blocks (they should slide by them selves when the rail is tilted 45 degrees, but not race to the end) the print-bed base-plate needs some new holes. I had to drill some additional ones, because of the wrong blocks. the 3-roller blocks would have fit perfectly on the existing holes. Note that you will need a 4mm spacer between the blocks and the bed, to prevent the belt-holder to touch the base-case. After this, re-assemble the whole -printbed, including the Ultrabase. When drilling and assembly was precise, you should now have a stable (no bending) and smooth running build platform with zero play in any direction. Then for the gantry-carriage: (X-axis) I used two 300mm/3-roller blocks stock items ( https://www.aliexpress.com/store/product/High-quality-Aluminum-Square-Roller-Linear-Guide-Rail-1pcs-SGR10N-Length-300mm-1pcs-SGR10N-3UU-three/1760039_32796707704.html) To mount them instead of the steel rods with linear ball-bearings, I used two pieces of 30x30x3 aluminium T-profile. Cut it to length, cut out the space for the X-axis stepper, and mounted the linear rails on to the profiles. The profiles themselves are kept by a number of M3 screws, held by tapped thread into the profiles. Then the profiles + rails are dialed in on the i3 Mega's gantry, still with the original rods attached ( for copying the spacing between both Z-axis bearing-and-guide assemblies ) The holes to be drilled are copied from the dialed-in hole positions in both profiles. Then drilled into the steel assemblies and tapped with M3 thread. On the side of the extruder, two 5mm holes are drilled, to let the extruder's mounting M4 screws to pass. Finally it's just a matter of removing the rods and re-assembling the gantry with the newly constructed profiles and rails. The Hot-End mounting plate fits back onto the roller blocks. Only 2 screws per block are used and are enough to make a sturdy connection between upper and lower rail. As both X- and Y-axis limit switches do not fit their original positions/mounting anymore, both are re-located. For the Y-axis, a long M3 screw was put in the build-base-plate, for the X-axis a new mounting bracket was made and screwed under the lower profile, kept by two M3 screws. Have fun looking at the pictures and here: https://youtu.be/YPMQjcqoc24 you'll find a short movie ;) Note: the attached .STL has nothing to do with this project, just was required to publish this post :) It's the fan-cover seen on the first photo by the way ;)