Two of the three linear rails for my Kossel 3D printer were not good so I ordered some 3/32" ball bearings which I had hoped would fix them. When I originally measured the bearings that were installed in the carriages from the factory, I noted they were undersized, so it was not super surprising that the the new ones did not fix the "crunchyness". However I bought enough spare 3/32" bearings that I was able to sacrifice some to the gods of automation by using them, with some Clover lapping compound to smooth out the races in the carriage and the rails. To do this, I first removed the original bearings and set them aside so they would not mix with the new bearings. Then installed the new 3/32" bearings with some superlube and a bit of clover mixed in. Then I cycled them probably a hundred times until I could feel things smoothing out. After that I cleaned the heck out of the carriage and rails and discarded the bearings which were pretty much ruined by the clover. After that was all done, and I had things thoroughly cleaned, I installed the old bearings (and packed them) to see and noted it was a bit loose feeling but it probably would have been fine. I did not like the looseness however and replaced the old bearings again with the new 3/32" bearings but initially they snug, but after cycling a couple dozen times with a good amount of superlube, they smoothed out considerably. So now that the worst bearing seems usable, at least until I get the replacements, I am starting to assemble the printer.
The first step was to install the rails on the 3 structural posts for the printer. This should be easy, and is, however there is some fine tuning since there is some variance between stops on the parts I received, which I decided is not a problem. However when installing the rails on the square tubing I decided to try and get them centered as best as I could. For this a vernier caliper is a necessity. Since the tubes are 20mm and the linear rails are 12mm, I set it for just a shade under 4mm, and used the end that extends from the back of the caliper as a gauge to center the rails, top and bottom, then tightened everything down. Not a big deal, but hopefully something that could avoid some issues down the road. I would have liked them to include some tips in the manual on improving the build since it seems like any additional accuracy that can be built in will only help, but it seems that the manual is focused on just the basics of constructing the printer. I have some ideas where to focus on accuracy however:
1. squaring the vertical tubes to the top and base
2. verifying the length of the rods from the carriages to the printhead is consistent and correct
3. checking for excessive play in the end joints for each connecting rod
4. verifying the bed is level and perpendicular to the rails - or as close to it as possible.
For these, I will try and make adjustments as needed, though at some point I will just get it done regardless. I am setting this aside for the next few days, but will update when I get some more time to complete the printer.
The first step was to install the rails on the 3 structural posts for the printer. This should be easy, and is, however there is some fine tuning since there is some variance between stops on the parts I received, which I decided is not a problem. However when installing the rails on the square tubing I decided to try and get them centered as best as I could. For this a vernier caliper is a necessity. Since the tubes are 20mm and the linear rails are 12mm, I set it for just a shade under 4mm, and used the end that extends from the back of the caliper as a gauge to center the rails, top and bottom, then tightened everything down. Not a big deal, but hopefully something that could avoid some issues down the road. I would have liked them to include some tips in the manual on improving the build since it seems like any additional accuracy that can be built in will only help, but it seems that the manual is focused on just the basics of constructing the printer. I have some ideas where to focus on accuracy however:
1. squaring the vertical tubes to the top and base
2. verifying the length of the rods from the carriages to the printhead is consistent and correct
3. checking for excessive play in the end joints for each connecting rod
4. verifying the bed is level and perpendicular to the rails - or as close to it as possible.
For these, I will try and make adjustments as needed, though at some point I will just get it done regardless. I am setting this aside for the next few days, but will update when I get some more time to complete the printer.
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