Some things to try:
1) Install the firmware I posted above
2) Adjust the extruder tension spring - If you're carving semi-circular divots out of the plastic, you probably need more tension; if you're just kind of flattening it out, then go for less tension.
3) Print the extrusion test piece to get a feel for the capacity of your extruder
4) Consider using less retractions, and printing slower/hotter.
5) Alternative feeders such as Robert's may be helpful.
That's much clearer, Thank you! I'll try those.
The grinding has come back again.
Any feedback from the modified firmware?
Re. Illuminarti firmware:
I finished a print on a newly-cleaned-out nozzle. It sat for a few hours. When I started the next print, I did not prime the nozzle at all. When the print started, no visible priming took place, and it just left a sparse trail of tiny dots on the build plate.
I Aborted it, and primed the nozzle until it extruded, then retracted 8mm. The result was a clean print with no glob when the head raised. Whatever priming took place after the 8mm or retraction only left a trace a half-inch long before the skirt started.
No apparent grinding.
I configured the firmware to perform the priming in two parts; firstly it quickly undoes the 20mm end-of-print retraction, then it more slowly extrudes about 5mm of filament to properly get the flow started. We might want to increase that a bit - especially if the head has leaked any while it has been heating/cooling. I think the 'extra' priming amount should be made user configurable in the GUI.
Bear in mind, however, that one of the purposes of the skirt is to provide a chance for the head to finish priming, so I don't see it as necessarily a problem if it's patchy at the start. Also, I would avoid priming the head manually - or at least increase the retraction distance to about 20mm, since that's what the printer is going to undo when it starts.
"Bear in mind, however, that one of the purposes of the skirt is to provide a chance for the head to finish priming, so I don't see it as necessarily a problem if it's patchy at the start. Also, I would avoid priming the head manually - or at least increase the retraction distance to about 20mm, since that's what the printer is going to undo when it starts."
It was a trail of disconnected dots throughout 14" of skirt and on into the first 12" of the print. Priming and retracting 8mm worked out just about perfect in this print. I'd rather have a glob under the Home position instead of no extrusion and an aborted print...
I totally agree, Rick. The issue is just to try and find the sweet spot of the 'right amount' of priming. If you're only retracting 8mm manually, then the initial fast prime of 20mm is going to be too much, and *might* cause grinding on some newer printers with the weaker extruder springs, depending on the tension setting. Fortunately that doesn't seem to be the case for you.
Theoretically, the best approach if you're priming manually as well would be to retract the full 20, and then have a longer slow prime built into the firmware (or, indeed, just be able to tell the firmware to not make any assumptions about priming, and do it all manually, if that's your thing).
Being able to manually set the prime distance would be a big help in the printer GUI would be a good start.
I installed the modified version of firmware from illuminarti.
Works very good. I only had some strange behaviour on an aborted print. It seems that the retraction that happened when i aborted cause the filament to be blocked somehow, i had to pull the filament out and reload it.
Maybe it's just a coincidence? I had a hard time pulling the filament out because the tip was a bit to large for the bowden tube.
Since then no problems. The priming is nice and not aggressive. No grinding to report.
The bed is perfectly leveled each time. Printed two 10h print with no problems.
Thanks
I think it's most likely a coincidence Didier, because nothing should have changed about what happens when you do an abort. But let me know if you see it again.
I've tried the patched fw on a few prints, it works very well for me, no more grinding 
I JUST got my UM2! yay!
Unfortunately I seem to be suffering from this as well.
When it prints, it prints wonderfully! But half the time, it's stopped extruding about 3mm into the print with the filament grinded down.
I read the thread but I'm not actually sure what the solution is... could someone clarify? Is it to install Robert's extruder? Use an earlier version of Cura? I'm on a stock new machine.
Valcrow, make sure you also aren't suffering from a z homing bug we just now fixed -- the nozzle pressing against the plate can also cause the symptoms you describe. Get at least the 14.06.1 firmware version if you haven't already. See z axis homing inconsistent.
Edit: When you say "3 mm into the print", do you mean "3 mm of x/y travel"? I was thinking you meant that, in which case it could be the nozzle mashing the plate. But if you instead mean "3 mm of layers built up vertically" before the grinding starts, then that's not the z homing bug, and it's not a priming issue either.
Either way, go get at least 14.06.1, or illuminarti's version above, which is based on 14.06.1 and fixes some of the priming bugs folks are discussing in this thread. And do try his recommendations -- I was going to mention some of those but he summarized better.
Valcrow, make sure you also aren't suffering from a z homing bug we just now fixed -- the nozzle pressing against the plate can also cause the symptoms you describe. Get at least the 14.06.1 firmware version if you haven't already. See z axis homing inconsistent.
Edit: When you say "3 mm into the print", do you mean "3 mm of x/y travel"? I was thinking you meant that, in which case it could be the nozzle mashing the plate. But if you instead mean "3 mm of layers built up vertically" before the grinding starts, then that's not the z homing bug, and it's not a priming issue either.
Either way, go get at least 14.06.1, or illuminarti's version above, which is based on 14.06.1 and fixes some of the priming bugs folks are discussing in this thread. And do try his recommendations -- I was going to mention some of those but he summarized better.
I'm on 14.03 I'll update to the new one.
for the 3mm question, I meant 3mm of layers built up. so layer 30, if at 0.1mm/layer. I'm printing relatively slowly and a pretty small layer height so I don't think I'm hitting my extrusion limit. (35-45mm/s @ 0.12mm/layer)
This firmware thing... I looked into it, but it's a Hex file? I have no idea what to do with that...
Installed and used a few times the firmware of illuminarti. Fantastic! No more troubles. My appreciations.
Now, the UM must release the fix officially, since we can only imagine how many people who performed only the automatic upgrade now suffering from the grinding and filament being stuck in the Bowden tube.
This firmware thing... I looked into it, but it's a Hex file? I have no idea what to do with that...
Hook your printer up to Cura, like you're going to do a regular firmware upgrade. But then, instead of picking the 'Install Default Firmware' option, pick 'Install Custom Firmware' and then point it at the hex file.
Installed, first print was better. Thanks!!
Hook your printer up to Cura, like you're going to do a regular firmware upgrade. But then, instead of picking the 'Install Default Firmware' option, pick 'Install Custom Firmware' and then point it at the hex file.
Thanks, I almost never have it attached to the computer... I've installed the new firmware and so far so good! need to do more in-depth testing, but the first print so far was a success!
Daid mentioned that he uploaded a new version this morning. This should fix the issue. It was a bit delayed due to his vacation.
Yes, uploaded Cura 14.06.1, which has UM2 firmware 14.06.2 (sorry for the confusing numbers)
Thanks illuminarti for the nice patch to fix this and a few other minor issues in the firmware.
Let me know if there is still a problem after this. If there are no problems then I'll update the "latest version" information and everyone will get popups about a new release on Cura startup. (14.06 did not have this popup, as I always delay this a bit to catch possible mistakes like this one)
I made two comments on github; I think there are a couple of things that need cleaning up still.
I made two comments on github; I think there are a couple of things that need cleaning up still.
I noticed. But the latest changes should at-least correct some problems. (Better to have a partial fix out there then a fully broken one)
Is this affecting UM1 too or just UM2?
Just UM2
Is it recommended to level the bed again after installing the updated cura & firmware?
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I JUST got my UM2! yay!
Unfortunately I seem to be suffering from this as well.
When it prints, it prints wonderfully! But half the time, it's stopped extruding about 3mm into the print with the filament grinded down.
I read the thread but I'm not actually sure what the solution is... could someone clarify? Is it to install Robert's extruder? Use an earlier version of Cura? I'm on a stock new machine.
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