Ooh that’s clever. And I have just the part to test this - a big clamp that needs to hold a part together in 2 axes and regular breaks on the axis that was printed vertically.

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…

Interesting. I’ll have to try the reverse experiment: I have a roll of TPE that’s been drying in the dryer for at least 3 weeks. I’ll take it out and see how fast it’ll reabsorbs water.

How much weight difference do you see? Do you simply wait for the weight to stop changing?
Good thinking. I didn’t think about that.

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

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?

Yes, it’s obvious. But maybe it’s useful to those who didn’t think about it? Sometimes the most obvious things are the easiest to miss.

I’m sorry you feel so negative about it.

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!

The idler is gripping the filament just fine. I know that because I have to loosen it when I print really soft TPE and I tighten it back up and readjust the idler pressure when I print PLA or PETG - and I did that a few days ago.

The belts might be getting loose though. I haven’t checked them. They look tight but the printer has a lot of mileage, so I guess it’s worth checkout out. But the re-print I just did of the same bgcode just completed fine.

I do have a camera but it doesn’t record.

If it was a nozzle hit, it was a violent one: this was 8 separate parts printing on the same plate and all 8 parts were similarly shifted - meaning the plate itself had shifted underneath, or both motors skipped or lost their origins. So I don’t think the nozzle hit anything.

The filament is PETG, but I don’t think it matters. The prints don’t lift off the bed because I use glue.

The plate does indeed stick very strongly against the bed. The magnets are fine.

The most plausible explanation I have is that someone stuck their hand in the enclosure for some unexplainable reason and the bed hit their arm or something. The only problem with this theory is, there is zero reason for anybody to do that. But I did start the print early enough for a few people to still be at work when it happened.

Other than that, I’ve taken to using glue on the plate lately, because I’ve had adhesion problems. Maybe some leftover glue turned liquid-ish and degraded into some sort of lubricant with the heat (I’m printing PETG with the bed heated at 85C) and it seeped between the bed and the plate. I’ve never felt it was ever slippery though.

Or it was some leftover water that steamed over between the bed and the plate and lifted the plate for a second, air-hockey stylee.

None of this seems very likely though. So I cleaned the bed and the plate real thoroughly, installed the plate tight against the registration pins, upgraded the firmware to the latest for good measure, slathered glue super-carefully all over the plate, making sure it didn’t go overboard, and started the same print once more. I’m watching it remotely through the webcam I installed in the enclosure and it seems to be going fine.

Well, a human being talking random shit won the last presidential election. So why not an AI at this point?

Lada engines don’t have valve / piston interference. They won’t explode. But yeah: the 3D-printed parts won’t last even a trip to the supermarket.

This Youtube channel is all about doing outrageous experiments and mods with old Ladas. Whatever they do really doesn’t have to be reliable 🙂

You were right: after some trial and error, I backed off both idler tensioning screws 2 full turns and then the print went without a hitch. It looks cleaner too. And I don’t know if it’s related (now sure how it would be, but who knows…) the part didn’t warp. First time I get a complete straight TPU part.

Thanks for the tip!

I wasn’t aware. I’ll look into this tomorrow. Thanks!

It’s not clogged: I fished out the mangled piece of TPU and printed something else with it straightaway - several times. Not sure why it starts clicking like that with that filament. Worse: it seems to do it almost always at the same point in that print.

I applied some glue to the sheet and it didn’t increase the adhesion by much, but it increased it enough and the print went through okay:

However, now I have another problem: I tried to print another one with the same material and the head started to make clicking noises mid-print and stopped flowing 😢 I’m not sure what’s going on with this now. Maybe I need to raise the temperature or something.

What have you done to clean the bed?

I cleaned it with water and dish soap. There’s nothing like it for adhesion. Even IPA doesn’t quite get the same results.

Has the TPU been dried?

I left it in the dryer at 55C for 3 days. The internal hygrometer says 13%, I tried drying it hotter than that, but then it seems to have trouble travelling through the silicone tube - like friction or something.

What’s the max speed you’re printing at?

Whatever the default is for the Prusa-supplied preset for this very filament brand and make. I just lowered the nozzle temperature to prevent stringing and material “balling up” on the surface, and I raised the bed temperature to increase adhesion a bit.

In addition to a brim, have you tried adding supports?

There is a ton of support for that part: it’s organic support and it’s growing inside and outside the part without ever touching the part itself. The reason being, it’s basically a thin bellows that’s two layers thick, so I don’t want anything supporting the bellows, or any support growing from the bellows, because it’s super-fragile and it won’t survive removing the support. That’s one of the reasons why we ordered a Prusa XL with 2 heads: one will extrude the part in TPU while the other will extrude the support in PLA, which should fall right off.

So since I told the slicer to avoid touching the bellows with the support trees, there’s a lot of it going around it on the outside. And indeed the bits of parts that I managed to print so far seem quite stiff and nicely supported. But the problem is, the entire thing simply comes unstuck and flies off the bed when it becomes too heavy.