Self-Destructing Printer
I have noticed on occasion a few issues with the x-axis. At first, it was layer shifting, which is still a problem, but I no longer believe it's a belt tension issue despite there being no way of checking that without having a fully functioning printer. Now, I've encountered more severe problems that have resulted in the printer seemingly trying to kill itself.
1) It sometimes has issues moving right, stuttering and causing a crash, but moving left is fine. Moving by hand sometimes results in the same resistance, sometimes not. Once it is forced in the direction with resistance for a certain distance, it will then slide across that distance easily in both directions.
2) It has crashed into the right side of the printer, thinking zero is wherever it was on startup. During this crash it also pressed right into the bed, bending it, when executing auto-home. A couple restarts later, it was back to normal without any adjustment.
3) It has lost a piece of black stuff on the rods or the bed two times. I have attached an image of the second piece. It is rubbery. I assume it is from a bearing.
4) The PrusaSlicer g-code preview is not accurate relative to the print bed. It is shifted to the right by about 3mm. This means something utilizing the advertised print volume cannot be printed.
I followed the assembly instructions exactingly, finding them to be incredibly deficient in detail, English proficiency, and acknowledgement of widespread issues. I have been able to print three times, generating four small things, but I seem to have very big problems every other print attempt. I am starting to think I made a bad, irrevocable decision buying this printer.
It'll keep getting worse
Sounds like ignoring a simple bearing-over-tightened problem in the beginning is starting to add up to more and more damage. At this point I would recommend a tear down of the X and Y axis, remove and replace the rods and the linear bearings, which appear to be ruined at this point. If the bed has bent because ignoring the assembly issues early on has turned the extruder body into a hammer, there are probably more things bent as well.
If this is still under warrantee, you may be best served engaging support. I would recommend if you choose to fix it that you not ignore critical part failures such as the bearings being over-tightened in the X and or Y carriage. It is also possible that the pulley has slipped - based on your "mispositioned" statement. I assure you, the prusa slicer is not off by 3mm. You are probably ignoring the skirt.
RE: Skirt, "Ignoring"
Over-tightening is difficult to measure without torque values. "Not too tight" is a laughable substitute. The pully doesn't slip when I check with the suggested method. How is doing something exactly as instructed ignoring anything? What signs would exist when everything is OK according to the instructions? The Y-axis is perfect and exhibits no issues.
It is not under warranty. I found the contact address buried somewhere. I will try to ask for help anyway.
I removed the skirt. It would prevent printing the part and is unnecessary with the amount of supports it is going to print. The PrusaSlicer is simply not showing the print as it ends up appearing in the x-axis. It prints outside the white line boundary when it does not appear that way in the slicer.
Reach out to support
Over-tightening is difficult to measure without torque values. "Not too tight" is a laughable substitute. The pully doesn't slip when I check with the suggested method. How is doing something exactly as instructed ignoring anything? What signs would exist when everything is OK according to the instructions? The Y-axis is perfect and exhibits no issues.
That may be true, but the guidance in this forum is that you should leave the screws in the back of the extruder loose to the point where they're just about falling out. That being said, even fully tightened I can't see this causing the havoc you're describing. You seem to have so much friction on the X axis that the belt is jumping teeth. If anything slips here (for example, not having the X axis motor gear being improperly screwed down (FIRST the flat edge, then the other set-screw) or a very loose belt, then the extruder isn't where the printer thinks it is and that will not go well.
For support: go to https://shop.prusa3d.com/en/ - "Chat now" will appear in the lower right corner.
And remember, we realize you're frustrated with these problems, but we're just users. I've had a bunch of really good results with mine, and some train wrecks. I've tuned the printer to the point where it's far more reliable than my last one.
Understandable
I was completely unaware of that guidance. I assumed incorrectly that the official instructions would be enough. Information related to the problem is valuable and I appreciate it. Assuming what I did or did not do is counterproductive.
I screwed the motor gear on exactly as instructed. I tested the belt tension as instructed and could not get it to jump teeth no matter how hard I pulled. I can't imagine I'd be weaker than the stepper motor, but I never looked up its specification. I have been told to ignore the values in the software, and that seems fair, as the numbers would indicate the belt is actually too tight even when purposefully loosened.
I don't really have a choice but to get this printer working, so I will definitely be chatting with the company soon. Thanks.
Prusa support response
They said I needed new bearings. They will not replace them because I put together the machine too long after I bought it. I guess support at least confirmed what the forums have already stated, so it's not totally worthless. Still, it stings to have to buy replacement parts for a printer I've barely used at all.
Easy link
Here's what I use instead of linear ball bearings https://www.amazon.com/Printer-Solid-Polymer-LM8UU-Bearing/dp/B06XPRCMJS?pd_rd_w=5RfMB&pf_rd_p=5bc65336-a8b0-4888-9e70-4d4ce2f6bd59&pf_rd_r=AVY7DY5D63B4EQETJHYZ&pd_rd_r=dca47523-d49e-4432-8247-a26f2ddb7755&pd_rd_wg=mJrYD&pd_rd_i=B06XPRCMJS&psc=1&ref_=pd_bap_d_rp_13_t
I'll try them
I don't really have a choice since Prusa's ordering system won't let me buy the LM8UU bearings.
You may need to be logged into eshop to order printer parts
That's one of the quirks of e-shop. They only sell parts to verified owners.
Verified
There was an error on their side with my account. I can order now.
Spares online
I contacted Prusa by chat the other day to buy spares for a secondhand printer. I was expecting some song and dance around serial numbers and photos, but the extremely fast and helpful CS guy just said "okay I've enabled purchasing". Whole interaction took about 60 seconds.
RE: rods
OP, in case you haven't checked this, see if both X-axis rods are straight and go all the way within the 3D printed part.
The printer will trigger a message anyways if the rods aren't properly in place but you never know.
I have seen posts where an "out of the box" rod was damaged.
Regarding X and Y, the problem might have been me but I couldn't figure out that MK3S+ belt calibration system, plus ghosting headaches.
I have printed X and Y-axis customs parts to solve that and to stop be Y-axis bearings from hitting the backplate and twisting the bed to set "Y-axis position 0"
It has crashed into the right side of the printer, thinking zero is wherever it was on startup
This happened once with me, after turning the printer on I forgot to call home first before moving the axis around, it has no idea about the XYZ position.
After "calling home", everything was as it should.
I couldn't understand that rubbery part, the closest I can think of is the thermal cables cover.
I checked my printer and couldn't find anything close to that.