Unable to print PLA
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@wouldstain About the only other thing I can think of which would cause the print to fail so quickly due to lack of filament movement, is if the nozzle is so close to the bed that it is preventing the filament from exiting. But if that is the problem, then it should be the same for both PLA and PETG.
Suggest you try increasing the Z offset by at least a layer height or even more. It might be that the print will fail because it won't adhere to the bed, but even if it's an "air print", if the extruder continues to run, it will prove a point.
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@deckingman Agree.. that was one of the first things I looked at. Sadly, if I raise the head any higher (+.05), filament does not stick to the bed and just gets dragged around. This was true on PEI and is now true on garolite w/ elmers glue stick. I havent tried it on garolite w/ bed weld but that may be next.
In the mean time, I'm going to tear down hotend again, clean out the boron nitride paste and apply white thermal grease. Seems like it shouldnt make a difference but I think restoring it to as close to the condition it was in the last time I was able to successfully print PLA is the way to go.
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@deckingman replaced heat-damaged heatsink fan and added higher cfm fan. no improvement.
I'm thinking of moving to a mosquito hotend and ditching the E3D V6 at this point but if that doesnt work that leaves only the extruder and the Duet board as possible problems. -
@wouldstain Have you tried a different thermistor? Even good quality thermistors can be highly variable...I've seen them vary by +/- 20C from device to device. What you think is 190C might actually be 210C...
The other thing I'd check is if the idler force on the extruder drive is actually too high. People often think that gripping the filament more tightly is a solution, but that rapidly loads up the drive bearings and can often deform the filament to the point it cannot feed through rest of the filament path.
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Thank you for responding!
I actually had to replace the thermistor at one point, and this problem was already present when I replaced it and still persists.One thing I did find today was that I was using the wrong beta value for it. My base config came with 4750. The E3D documentation specifies 4267. I do not know how significant that change is, but I did make it hoping it would resolve the issue.
To set the idler tension I screwed it all the way in (w/o filament) and then backed it out 3 full turns. I was advised that this is the right tension setting for the Bondtech BMG. It seems to work quite well for PETG and TPU. I have not had anyone tell me that idler tension should be set differently for PLA but I am always open to suggestions!
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@wouldstain You didn't try the "air print" I suggested earlier which is a pity because it would have given us a data point. As a general rule, all metal hot ends are more prone to blockages than PTFE lined ones. The downside is that the PTFE limits the maximum temperature you can use to around 200 -220 Deg C (depending on who you believe). Before you shell out money for another all metal hot end (although I am a huge fan on Slice Engineering's designs), you could try the "lite" version of the V6 heat break with PTFE liner.
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@wouldstain
I always start trouble shooting by taking any idler tension out and then just pushing filament through by hand. I don't know if that's possible with the BMG, and not being able to see the pinchwheel while its running doesn't happen.
PLA is harder than PETG or TPU so might be breaking away on the teeth of the wheel, when the others just deform a little. What does the filament look like when you back it out of the extruder? Can you take a picture so we can see how deformed the wheel has left it?It does sound like you have tried replacing most things. Have you been going through changing just one part before testing, or changing a bunch?
And I would echo what @deckingman says. Its worth trying the PTFE lined version of the E3D. Most all-metal hotends of that design have a very small window of being able to work with PLA. The PTFE lining greatly improves that.
Isolate, substitute, verify.
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@deckingman I did not run an airtest as you suggested as it seems to extrude freely when the build plate is nowhere near the hot end, even at slow feed rates.
I looked at the mosquito and the pricetag and realized that for that amount of money I could get another E3D plus extruder and all the trimmings and set up a dual system so... I've sort of ruled that out for the time being as just too expensive.
I MAY have identified the problem. It's looking like its something VERY small having a very big impact.
Running more tests and will report back with results.
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@theruttmeister been replacing parts one at a time... slow going.
same thing for changing settings.... one at a time. print.. see what happens...filament has minimal deformation aside from teeth marks from the drive gear.
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Possible solve...
I may be speaking too early on this but it's looking promising.I've been super focused on what could cause the filament to start a phase transition
in the wrong location and I THINK I've got it.The short of it is that the PTFE tube connecting the extruder to the hotend may have been a hair or two short of seating solidly against the heatbreak.
Long version...
The way this probably came about is, because the PTFE collet on the bottom of the extruder is not visible from above (I have a Railcore 300ZLT so it's pretty tall and sits on the floor), I'd gotten in the habit of leaving the collet on the extruder and removing the one on the heatsink coupler and just pulling the extruder and tube out in a single step. When reassembling the extruder after cleaning it, I probably seated the tubing as far into the extruder as I could, leaving a small gap between the heat break and PTFE tube. Clearly I must have cut the tube a bit short.This was literally the only thing I could of, so I tried re-seating the tube all the way down inside the heatsink, reassembling everything, and I'm suddenly able to complete a test cube out of PLA.
Going to run a few more tests before I call this one resolved but this sort of fits what I've been seeing and is consistent with your advice about what could cause this.
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@wouldstain thanks for the update. how has it progressed?
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@t3p3tony It's looking like the PTFE tube was in fact the issue. I've successfully printed out a few items in PLA now with zero stops. I've also dialed back the MFM parameters so it's no longer wide open and still no problems.
I have to pull the tube out and measure it to see just how short it was (build docs call for 91mm) but the only things I can attribute this to is my being a creature of habit. I've pulled that tube many times while yanking the extruder for cleaning and repeated the same error by installing it in the extruder first.
I'd say mark this one as resolved but I'm going to run some longer prints in PLA just to be 100% as there was an element of randomness to it.
Props to @deckingman for getting me focused on the right thing and thanks to everyone who responded!
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@wouldstain Sounds like you've got it sorted. PLA can be temperamental and prone to blockages in and around the heat break area due to it's very low Tg.
TIP - always use Bowden clips at the hot end to prevent the PTFE liner being pushed up. If you start printing with highish melt rates, the back pressure can dislodge the PTFE liner resulting in the gap that you've seen. I generally exert pressure on the tube to keep it seated while lifting the ring on the Bowden fitting and then slide in the clip. In my case, the extruders are mounted on a separate gantry above the hot end, and I cut the Bowden tubes slightly long so that they are always under compression (but I still use clips as well).
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@T3P3Tony
Sadly, I thought this was resolved. I did manage to get a few small prints out of this, however it has started happening again.I reached out to E3D support and they have me messing around with print speed and temp settings. As part of this exercise, I returned the hotend to its original configuration, which included switching out the nozzle.
I ran the PID tuning routine (going from brass to tool steel) for the hotend and it stopped on phase 3 and allowed the temp to return to ambient with no console output over a period of about 30 minutes. This happened twice before I was finally able to get a result.
Is it possible there is something wrong with my Duet board or firmware?
I'm still running 3.4b5+1. -
@wouldstain said in Unable to print PLA:
Is it possible there is something wrong with my Duet board or firmware?
I'm still running 3.4b5+1.Either try 3.3 or 3.4b7
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@phaedrux installed 3.4b7+3 and I've had two consecutive successful prints of a file with no stops! crossing fingers....
just read b7 notes and it looks like PID tuning got some love!
thank you!
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@phaedrux sadly failed on the third try.
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@wouldstain said in Unable to print PLA:
@phaedrux sadly failed on the third try.
I've got five different printers running 3.3 on Duet 2 and Duet 3 hardware.
They all work fine.
Try 3.3
Frederick
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@fcwilt had same issue w/ 3.3
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@wouldstain Have you done the obvious thing and checked the previous cause? You said before that the PTFE liner wasn't correctly seated and when you rectified that, it cured the problem.
