Print goes haywire at similar point each time  

Re: Print goes haywire at similar point each time

Have I missed the picture?

Joan

Re: Print goes haywire at similar point each time

Ah, something went wrong with the picture attachment. Thanks for pointing that out. The attachment is there now.

I tried again, this time made sure the door to the room was closed the whole time and a heater on, so I'm pretty sure there weren't any cool drafts or anything, and this time it went similarly haywire at about half the depth of what's shown in the image.

Any suggestions very much appreciated!

Re: Print goes haywire at similar point each time

was it sliced between firmware updates?

ive had firmware updates screw with my saved files

Re: Print goes haywire at similar point each time

I don't know if the causes are similar but I recommend to check the extruder path near the layer height where it goes awry. I had cases where Slic3r decided on having very odd and abrupt extruder paths in the middle of a print. Sometimes it would knock the print off the bed, sometimes create a sizeable blob and sometimes just ruin the print quality before returning to behave absolutely normal. Pictures attached of Slic3r pahts and the resulting poor quality at those layers.

I tried updating Prusa edition Slic3r, repaired the stl before slicing and updating, designed and exported the model file again etc etc but for identical designs (not files) I got similar results. I have personally only seen this using Slic3r and not when slicing with Cura but by no means am I an expert and don't want to imply anything.

Re: Print goes haywire at similar point each time

And the resulting print (apologies for the poor quality but I hope the band of poor layers is adequately clear)

Lesson learned: always check if you see any odd extruder paths in the resulting slice before printing... Annoying most of the time, critical sometimes.

Re: Print goes haywire at similar point each time

Thanks for the responses. None of the software (firmware, slic3r, or gcode file) has changed since the original successful prints. I went ahead and re-exported a new gcode file using support material, because some of the issues seemed to arise at the point when bridging was happening, but that print crashed even sooner, because some of the support material started tangling up.

Could this be an issue with the PLA? It's still the original reel of PLA that came with the kit, but does the PLA degrade that quickly (it's been a few weeks that it's been out of the package).

I've tried various temperature settings and being extra careful of atmospheric temp changes (although the first successful prints led me to the impression that they were fairly robust to this).

I'm tempted to open up a new package of PLA and test on that, but it seems wasteful to discard a 3/4 full reel of PLA.

Re: Print goes haywire at similar point each time

The reels only go bad due to water absorption. A few weeks open - yes that's long enough to have considerable effect. A couple days is fine for PLA. A couple weeks, you're going to absorb water. No need to throw out the reel, dry it.

A filament drier is hugely nice. You an create your own or get a PrintDry. I use mine to prep even new reels before use. Regenerates your silica packs too! Every reel gets dried and resealed with a couple silica packs including at least one color indicator silica pack. That lets me check the reel is still dry.

Re: Print goes haywire at similar point each time

Thanks for the tip. I'll look into that. Are the results above typical of PLA that's absorbed moisture?

Re: Print goes haywire at similar point each time

No, doesn't look like a moisture problem to me.

The nozzle is somehow getting into a position that is extruding into mid-air. I'm most suspicious of a layer shift creating the tangles. The location of the tangles isn't necessarily where they were created. The can get dragged around before you catch the problem.

I'm suspicious of anything that might be blocking movement of the print bed, cables or the cables catching against each other. Any of those can cause a layer shift, particularly if you are in stealth mode. Also, a loose pulley, but that's not likely to keep happening at the same point of each print.

X-carriage moves up and eventually gets to a height where a physical interference happens.
THAT is what I would check against.

Re: Print goes haywire at similar point each time

Thanks for the suggestions. I'll be on the lookout for those things. SInce my original post I've had a few more failures and they don't seem to be consistently in exactly the same place, but they all seem to be happening well into an otherwise good-looking print. I'll look closely at the free movement of parts.

Re: Print goes haywire at similar point each time

I had some prints which also started failing higher up and a good clean of the build plate fixed it

Re: Print goes haywire at similar point each time

Update:

I changed to a new spool of PLA, discovered that my first layer with the new spool was printing much too low, so raised the Z in the live first layer calibration. The resulting print was perfect.

Then I tried another print of a slightly different model and got the haywire problem about six hours into the print. I'm re-printing that model now with support material.

At the moment, it feels like luck. I do appreciate all the good advice here though, and I'll keep trying people's recommendations.

Thanks!