PrusaXL always stops extruding mid-print, any material any speed  

RE: PrusaXL always stops extruding mid-print, any material any speed

have you tried printing with the enclosure doors open
elevated temperatures can cause print failures especially with PLA

regards Joan

RE: PrusaXL always stops extruding mid-print, any material any speed

Can you report the heatbreak temperature when it happens? Sounds like heat creep.

RE: PrusaXL always stops extruding mid-print, any material any speed

Thanks, I'm kicking off the same print now with the top of the sumo enclosure removed. I'll report back to see if there is a difference. 

RE: PrusaXL always stops extruding mid-print, any material any speed

Ok attempted the same print with PLA on both extruders. Sumo enclosure lid completely off with door wide open. Same result unfortunately...extrusion completely stopped on extruder #1 about 30min into the print. Here is the octoprint graph showing temps, @ntdesign is there another temp I should try to get when the issue begins? Also here is what the filament looks like when unloaded, after this issue has occurred. 

RE: PrusaXL always stops extruding mid-print, any material any speed

Attempted yet another print

•  PLA @ 220C
• No enclosure hood, doors open
• Ambient temp 26C

I changed the print to start with  many layers initially on extruder 1 before any tool changes occur. Layers before the tool change print perfect. As soon as tool changes start to begin, after a few changes, extruder 1 stops extruding and is slipping on the filament as shown in my earlier picture. 

I agree with @ntdesign, this seems to be heat creep, building up when the tool is parked. Maybe I need to change my ooze prevention settings?

Currently using the default settings

• Ooze prevention enabled
• -110C  temperature variation

Anyone have other ideas? 

RE:

These are the tool temps, I meant the temps from the heatbreak sensor. If that one goes above nominal for the used filament, you'll get heat creep blockage. I don't use Octoprint, so don't know if you can track the heatbreak sensor there.
It's on the front panel under "Info", but you can also access it during prints. Possibly you could also put it in the configurable info that is shown while printing. Get the temp when it idles, during normal operation, and when the problem starts.
There are many possible reasons why this can happen, we have to narrow it down first. Does it happen only on that tool? It could be something as simple as too much idler tension, a slightly broken fan/obstructed airflow or a damaged nozzle. If the holding screw is torqued too tightly the upper part of the tube can get kinked, which creates resistance.

RE:

I've had the same thing happen to me.  Printing fine for months then add an enclosure (enXlosure in my case) and I see this problem on longer prints.  (Even with doors and lid open on the enclosure.)  One theory is that the filament lever parts (that hold the filament against the drive gear) are distorting with the higher ambient temps of an enclosed printer.  This causes the drive gear to chew into the filament instead of pushing it toward the nozzle. 

(I was able to get better results when I tightened the screws to increase the pressure on the filament, but that's likely a temporary fix as the PETG parts are likely to only distort more.)

Prusa seemed to be aware of this very early on when pre-release beta machines were sent out.  Feedback resulted in Prusa perforating (with hexagons, of course) the steel cover behind the tool heads to improve air circulation around the parked tools.

This theory has bee boosted by the just released Prusa enclosure.  It addresses this problem by having you replace the filament lever parts (original printed in PETG) with PC-CF versions (which I assume are supplied in the kit).  I've printed those parts myself in PC-CF and will be installing on my tool heads in the coming days.  

Fingers crossed.

RE:

So it softens and the gear only rubs over the filament surface? Didn't think of that one. OP you could test this theory by leaving the case open as you did and directing a fan into the case to flush out the heat.
Still beats me why they didn't print these things out of PC to begin with. Especially since they did the corexy parts in PC. Sure, it must have saved a little cost but now everyone getting the official enclosure will be annoyed. Not looking forward to taking apart 5 toolheads. I really hope they throw in a few of the tubes that go around the screw, I'm fairly sure I'll wreck a couple.

RE: PrusaXL always stops extruding mid-print, any material any speed

I suspect once the PETG parts are 'overheated' and distort, the damage has been done.   

The process to replace the lever parts only requires minor disassembly of the tool head and should only take 10-15 minutes each.   I plan to compare the original (now distorted?) parts with my newly printed parts.  Will I be able to see or measure some distortion?

RE: PrusaXL always stops extruding mid-print, any material any speed

It would be great if you could snap a foto of the old & new parts next to each other. Or put them flat on a scanner.
You're right, probably it will deform for good since it's under load when it happens. PETG is definitely not a good material for this, even when not hot it has a lot of flex.

RE:

So, my 10-15 minute guesstimate is way off.  That PC-CF is really tough.  Trying to insert the bearing pins and the sleeve is proving difficult.   The one screw that holds the two halves of the lever together was slow going.  That screw doesn't use a nut, it is designed to cut its own threads into its other half.  It took determined pressure and torque to get the screw into the part.  A tap would have been helpful, but by using the tapping technique of advancing the screw a bit and then backing it out repeatedly I was able to get it seated.  PETG would have been easy to do.  For the bearing pins and the sleeve I may need to use a small C-clamp to press those parts in.  (I'd normally used pliers but holding the parts perpendicular is not possible with the angled jaws of pliers.)

I did compare the original PETG parts with my printed PCCF parts.  I couldn't get any consistent measurements but it appears to me that the hole at the bottom of the part (that holds the sleeve of the hinge) has been stretched very slightly into an oval.  The metal sleeve can wiggle a bit in that hole now.  It makes sense to me that that is a weak spot of the part.

I'll post again when I make more progress.

Comparison photo, my PCCF part is on the left, original PETG part is on the right.   

RE: PrusaXL always stops extruding mid-print, any material any speed

Heat break temps w/o enclosure hood, while tool is parked are 43C for a PLA print. I'll install the enclosure hood, and measure on the next print to see what the difference is. 

I printed the idler level in Overture PC on my mk4 (also in an enclosure, no issues with that one) and swapped them in for the PETG one's that shipped with the printer. The original ones look slightly warped, and as @evillebill reports, the sleeve hole is a bit of an oval. 

Note, the overture PC didn't have the self tapping issue that @evillebill mentioned with the PCCF, the screws went it without much trouble. 

I just kicked off my first print, so far it's cruised past the usual point of failure! Very exciting! 

You all are amazing! Thanks!

RE: PrusaXL always stops extruding mid-print, any material any speed

I completed the PCCF upgrade to my #1 tool head and tested successfully (at least to basic functionality).  I needed another pair of hands to insert the bearing pins and the metal sleeve, so thanks to my wife for lending a hand.  A small vise would be helpful to seat those parts while you keep the parts aligned.

When the mod was completed I discovered that the suggested initial setting of the tensioning screws is REALY TIGHT, so tight that I couldn't snap the level closed without reducing the tension significantly.  Does that mean that the original parts had distorted enough that much?

Time will tell how well this addresses the problems encountered when printing within an enclosure.

RE:

Did you print the replacements with Prusa's recommended settings (assuming they are documented somewhere)? If they come untapped I really hope they throw in a couple of spares with the enclosure, or at least some filament to print more.

RE: PrusaXL always stops extruding mid-print, any material any speed

I printed these parts from the latest Prusa XL printable parts download.  The included .pdf suggested PCCF parts be printed with 0.20 Structural, 4 perimeters, 30% grid infill when using a 0.4 nozzle.  Which I used.  
To assemble and install the lever parts I followed the instructions for assembly/installation of the Prusa XL Enclosure.

Assembly using these PCCF parts will take determination and patience.  The bearing pins and especially the metal sleeve can be damaged by during assembly and while Prusa sells the relevant parts printed with PCCF the metal parts are not listed for sale separately.

RE: PrusaXL always stops extruding mid-print, any material any speed

Thanks. So we can expect the parts that come with the enclosure to have the same issues as your printed ones. Great...

RE: PrusaXL always stops extruding mid-print, any material any speed

@mturner1721, did the Overture PC you used have carbon fiber?  Perhaps the PCCF I used made it much harder to fit the metal parts.  Did you happen to notice an increase in the clamping pressure after installation (assuming you returned the tensioning screws to their previous position)?  

RE: PrusaXL always stops extruding mid-print, any material any speed

No CF, this is the PC I used https://www.amazon.com/dp/B0BQRC3JDH. So far I've successfully completed 3 prints after swapping in these PC parts.

RE: PrusaXL always stops extruding mid-print, any material any speed

Here with the same problem….

i printed the parts and installed..  one batch works good, second batch fails again,

Looks like all the problem is just on then extruder 1, the number 2 is working properly,