Igus 8mm bushing and SC8UU compatible housing by MKSA

Last crawled date: 3 years ago

The bushings are made from Igus filament (size 8X12X12), the housing can be PLA, ABS whatever. Igus supplies stl files for their standards press fit bushing but these are too thin. The one I designed are thick enough, a bit oversized so you can bring them to the correct sizes and finish and are to be press fitted too. You have to finish the exterior with abrasive or files but for the inside, better to use a reamer or eventually a good sharp drill bit once installed to get the proper diam and finish. Done properly will lead to virtually no play, yet a smooth travel.
For linear motion, the bushing with groves works best.
They are smaller, shorter, lighter than the chinese LM8UU series yet are better and can be used with cheap SS rods. These don't last long with ball bearings as they are too soft.
The housing is compatible with the SC8UU, just shorter, only two screws. Use self tapping screws, 3.2mm is OK, bigger may require drilling the holes. Regular M3 or M4 are OK too, not really needed to tap, just drill as required before tapping (diam minus pitch).
No messy lubrication required. Note that you need to properly align the bushings. Use the smooth rod to help. This is always true. The way LM8 are installed in most 3D printers is just the opposite of good engineering practice (split housing, tiewrap) but required because of poor design and alignment. The elasticity of the assembly will cope with it.
On the pictures, you can see them installed on my Geetech Prusa Al Y table (the housing is a previous non press fit design) and integrated in the X carriage of my own. For the X, I used two, one at each end.
To get a pretty good alignment, you can heat the housings once installed with a heat gun to relieve the stress. I did it for the Y table. Not required for the X carriage as I reamed the two bushings in one go with a long reamer once installed.
You can see the grooves left by the LM bearings ! Was time to phase them out.
They have been running for a few months now, a couple 1kg spool.
The Y table is more than 150g lighter than the original and my X carriage plus extruder, hot end etc is about 250 g, less than the weight of just the supplied MK8 Nema 17 motor !
Note that an added advantage of these bearings is they somewhat dampen vibration and are silent contrary to the LM bearings that rattle so much they can drive people crazy. (if they don't rattle it means they are stressed because of misalignment and will soon fail :) )
PS:
-Igus supplies drop in bearings (Drylin) similar to the LM, SC series used in 3D printer. They are fine but lead to bigger, heavier parts. Longer too wich is unnecessary here due to the light loads and they have therefore more friction. And what about the fun to do your own ?
-Standard bronze bushing (8X12X12) can be used instead of the printed Igus bearing.