RE: Why does Prusa not recommend lubricating the bearings for MKS3+?
I understand what you're saying, and I can tell you that I was *very* careful about that, and can tell you that I didn't lose any when putting the bearing on the rod as I inserted it gently.
In any case, I did get the issue. Now, is it possible that the bearing was defective from the beginning? Could be, but there is no way for me to tell now
wear/scour marks on the bottom X-axis rod
It's hard to be certain but I get the impression that rod scatches are more often the result of knocking balls out of the bearing during assembly.
Cheerio,
RE:
Any mechanic can tell you, if you have bearings which are not mechanically retained in place with a cage or some such, that packing them with grease (even if they allegedly come pre-greased) prior to assembly will tremendously improve the odds that they will stay in place during said assembly. 🤣
... but that the process of packing, especially if overdone, can also dislodge ballbearings...
Cherio,
RE:
Bringing this thread back from the dead just to report that despite frequently lubricating all rods, the top X-axis is now scored (upper back) and needs to be replaced. It started with lubrication (SuperLube) turning black. The bottom X-axis is also turning the lubrication black. It's not yet scored, but I am guessing it's only a matter of time.
I should have disassembled and re-packed the bearings properly to begin with, but I didn't feel like all that extra work when I had just completed the assembly process.
Other rods seem fine, and the lubrication stays clear on those. So maybe the problem was made worse if somehow alignment was off. Everything was sliding freely during assembly though.
RE: Why does Prusa not recommend lubricating the bearings for MKS3+?
Bearing killers are conditions that could damage a bearing system and prematurely end its life. The four most common causes are:
Improper lubrication, dirt, overload, handling and installation.
In any case, the lifetime of the bearings is significantly reduced by unsuitable or missing lubrication.
Even if they are quality bearings, they are still wear parts with a limited life cycle.
wbr,
Karl
Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen.
RE: Why does Prusa not recommend lubricating the bearings for MKS3+?
Hi Karl.
Since the other rods are all fine and running smooth, it appears the shipping lubrication has been sufficient for those. So why has only the top X-Axis rod scored..? Not exposed to dirt, and frequent lubrication every few prints. Perhaps I tightened the backplate of the hotend carriage too much, putting pressure on the top bearing, so much it deformed slightly. Oh well, I won't spend too much time speculating. I'll just replace the two X-Axis rods and corresponding bearings, and this time clean out the shipping lube and re-pack with SuperLube before installation. And make sure not to over-tighten the backplate.
Cheers, --Karl.
RE: Why does Prusa not recommend lubricating the bearings for MKS3+?
"And make sure not to over-tighten the backplate..."
I would also do it this way. Before using the new bearings, it would be recommended (my opinion and experience) to clean and lubricate them with NLGI 2 lithium soap grease.
much success!
Karl
Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen.
RE:
The End of This Story: I have received a replacement X-axis rod and 3 bearings from Prusa. While waiting for the replacement parts, I did the following:
- Disassembled the Y-axis assembly, cleaned, and re-lubricated those bearings. They were perfectly fine and had no black residue.
- Loosened the extruder assembly backplate screws significantly.
- Rotated the scratched top X-axis rod 45 degrees so all bearings run on undamaged steel.
- Thoroughly cleaned the rods, applied thin bearing oil, and moved the head back and forth several times until all gray/black residue disappeared.
- Then I continued to print without any issues whatsoever while applying SuperLube (PTFE) a few times.
Note: Prusa no longer supplies authentic Misumi bearings, like those that came with the printer kit (Sept/Nov 2022). Sometime soon I will disassemble the X-axis assembly as well, clean, and re-lubricate the Misumi bearings. I will not install the non-Misumi bearings unless the Misumi bearings appear damaged.
There is no indication running the printer with the Misumi bearings without cleaning off the transportation lubrication, while relatively frequently applying PTFE grease, caused any problems. The problem was likely that the extruder assembly backplate screws were too tight causing bearing misalignment for the top X-axis. I would still recommend cleaning off the transportation lubrication and re-lubricate all bearings with proper grease, for everyone building a kit from scratch, or replacing bearings.