This morning I came to work to a perfectly printed set of plates. So I started another instance of the exact same print, went for a swim at the municipal swimming pool nearby, came back to check on it just in case, and it had done the same thing it did on Friday.
This time, nobody was at the office (it’s Sunday) so I know nobody monkeyed with the print. Clearly the plate hasn’t moved. So those hypotheses are out.
The belts look tight - although the teeth feel a bit chewed up, particularly the table belt. But I doubt this is what caused the slip, as it seems to slip randomly in both directions at the same time.
At this point, I’m placing my bet on the print head coming so close to the edges that it hits the limit(s) when it’s unlucky, or it causes the stepper motors’ counters to overflow or something - i.e. it hits a firmware bug. The PrusaSlicer software seems very confident that I can print this close to the edges, and indeed the printer does it, but I wonder if it’s overly optimistic.
So I bunched up all the plates closer to the center of the bed and re-sliced, so the printer never prints less than ¼ inch from any one edge. Let’s see what happens with that.
It’s the PETG. Specifically, it is the softening on the following parts:
- y-belt-holder-R2
- y-belt-holder-tensioner-R2
- x-end-motor-R2
- x-end-idler-R2
I would recommend the following Y-axis mod for the MK4. I am still running this even on the MK4S, even though the Y-axis was modified on the MK4S.
Edit: Print those in ASA and replace them, tighten all the belts as usual, and I think your printer will be fixed.
This is the company’s printer. I’ll have to get the expense approved first.
Assuming it needs servicing of course: I have to keep cranking out these adapter plates as fast as possible right now, and something tells me not going so close to the edges of the bed will help. It wouldn’t be the first firmware bug I hit in this printer…
Thanks for the tip!
Not sure what you need to get approved. Buying a roll of ASA? It’s part of printer maintenance, and making it more reliable in the long run.
And if you don’t have ABS/ASA on hand… why is the printer in an enclosure?
My company is flexible, but ultimately this is not my printer and I want to ask permission to undertake maintenance. For all I know, whoever ordered it in the first place is in fact in charge of it, or maybe they want a 3rd party to do it. It’s just a matter of talking to the boss and making sure what I’m about to do is approved 🙂
Turn this (ramping lift) Off/On or tweak the settings. Maybe that will Help you. Oh and i wouldnt use grid as infill
Turn this (ramping lift) Off/On or tweak the settings
Before doing any of that, I’ll run several prints of the new parts layout that aren’t quite so close to the edges of the bed. The one currently printing is going well so far.
I really have a strong hunch that it’s just a matter of not using quite as much of the bed surface as PrusaSlicer thinks is usable safely.
Oh and i wouldnt use grid as infill
Why is that?
Grid infill is crossing, get a decent blob or buildup and you could have nozzle collision, I personally like gyroid but it is slower.
Had a similar failure on the mk3s, what does the belt tension test return? Stealth mode may help or be the cause, anecdotally I’ve seen mention of motor temps, the old rambo board running stock firmware they got toasty when printing in the enclosure in the summer, stealth helped me limp it along until I did a board swap and changed to klipper. I don’t know if this is an issue with the mk4 as that’s not using the older Rambo based boards, but something to consider as well, had it happen even after I did the first abs rebuild.
Edit: too tight can also cause issues, not necessarily skipping but having it trigger the virtual endstop, prusa has an article for troubleshooting layer shifting. Also probably with checking both axis to ensure they’re smooth and consistent across travel, seen an over tight x carriage back cause too much resistance and have false triggers.
Okay so I’ve readjusted the belts’ tension this morning. The X belt was a bit loose and the Y belt was a bit too tight, strangely enough. Both in the green though. So I set them to the middle of the range. Good thing I checked anyway because all the screws on the X motor mount were so loose they were on the verge of letting go completely.
And since I was at it, I cleaned the entire enclosure and re-lubed the rails and the linear bearings.
However, I don’t think the printer faulted because of any of this: I checked where the hard limit was in X and Y and found that the nozzle came right at the edge of the previous prints that failed on the left and on the top:
At this point, I’m convinced the printer got lucky twice when it printed that print right, and when it didn’t, it was the result of the carriage hitting the limits when the motor(s) overshot the extreme positions a bit. I re-sliced that print to leave some margin with what PrusaSlicer believes are the limits of the printing area and I came to a perfectly printed set of parts today. And the new set I started 2 hours ago seems fine too.
So I think the lesson here is that PrusaSlicer is a bit too optimistic with how large you can print, both in X and Y. It pays not to believe it too much.
EDIT: 6 hours later, another perfect batch. So I think my theory is confirmed.
Grid infill is crossing, get a decent blob or buildup and you could have nozzle collision, I personally like gyroid but it is slower.
I’ve had the extruder collide into blob on solid infills (or perimeters) when the filament was too hot - usually TPU or TPE - but never infill. I’ll give gyroid a spin though.
prusa has an article for troubleshooting layer shifting
That’s a great article. Thanks!
I’ll go check everything tomorrow. The thing is, it’s the first time this happens (well, second time now). The only unusual thing I did compared to previous prints was fill the bed to the brim, right up to the edges as allowed by PrusaSlicer. I’ve corrected that to make sure this isn’t the issue. Other than that, it’s a printer that’s been printing all day every day for a good year and a half. So yeah, it probably needs some TLC at some point…
Says a lot that it can run pretty much maintenance free for a year and a half! I only had issues with my mk3s doing daily enclosed abs prints in the summer, the original petg softened and it ended up killing the idler end of the x axis (idler mount deformed suddenly under tension after like… 1-2 months of that). They may not be the fastest or fanciest but they’re easy to service and in my experience pretty reliable, I repacked the linear bearings after a year or so out of precaution when I did a full rebuild, but I don’t expect needing to do that for a long time.
Here’s another prusa article for infill patterns, the prusa knowledge base is really decent and applicable to a variety of printers, I use my voron a lot but still refer to it.
Add some z hop. A fast move is likely contacting a lifted spot or some ooze. I have had this happen before. It can move the plate or skip steps in the motor which is undetectable unless you see it happen. The belt does not need to slip; only enough force to overcome the motor step fields’ strength is required. During fast movements, it is likely skipping some steps or transitioning from full steps to micro stepping which can create potential vulnerable points where the holding field strength is less than ideal in a compromise to create faster accelerations/decelerations. You have got to remember that 3d printers are cheap largely because they are not absolute position linear systems. All motions are relative to (0,0) home. The (0,0) home location is precise, but it is not accurate at all. Every step the machine makes is only ever precise but is accurate relative to the (0,0) home location. Therefore any skipped steps are catastrophic. The primary issue that causes this is that the steppers are in an unknown position upon first powering them up and they move randomly to whatever field step position happens to be closest. Likewise, all end stop methods do not trigger accurately to within a single step field position. It gets complicated to actually make an accurate linear system for things like IDEx or CNC.
