Printing problem with the duetwifi gcode interpretation?



  • So when I was testing the duet wifi I got some layers that appeared not to extrude any plastic, I was thinking it was a filament jam that had magically cleared itself, but it was very precise/clean….

    Then I got 2 30hour prints failed at the exact same layer....

    Then over the last 2 days I have been trying to print a cheek piece three times and got the same symptoms. Ive never had this with this roll of filament nor the others while the mainboard was Wanhao's So this "starvation" happens as the same layer and repeatedly across the 3 attempts, it cannot be a filament jam. This cant be a feed jam, so a result of either a corrupt G-code from Cura? or the duetwifi is "mis-reading" the G-code?

    The layer changes per part. In this case about 30mm up and it repeats.

    https://postimg.org/image/5bnhopoql/865a18c0/

    In the past Ive had it and the missing layers have been messy this is so clean. Since its happened across several models sliced with cura with the only change being the duet wifi I am scratching my head. I mean fault finding logic tells me its a problem that only occurs when one thing has changed, its that one thing.

    confused…...



  • The missing layer is different on other prints I mean. for the two 30 hour prints it was up around 160mm high. This time about 30mm.

    Suggestions on how to fault find this please?



  • What is the amp setting for your extruder stepper? 800? You might try 1000 (1 amp)
    Good luck!



  • Already at 1000mA, you think it might need another 100mA?

    Kind of strange that it occurs at what seems to be the same layer height, but its possible I suppose.


  • administrators

    @gzcwnk:

    Already at 1000mA, you think it might need another 100mA?

    Kind of strange that it occurs at what seems to be the same layer height, but its possible I suppose.

    What is the rated current of the extruder motor, and is it direct drive or geared?



  • Looking at the images, it seems to continue to print OK after the "problem layer". So I'd tend to agree that it's unlike;y to be a filament jam which magically cures itself. More likely a "temperature thing" that prevent that layer from adhering to the previous layers. Does it coincide with a part cooling fan coming on? Take a look through the gcode file that Cura has generated and see if you can spot any temperature or fan commands that occur around that layer.



  • ABS so no fan.



  • The extruder stepper is a nema 17, direct drive but it isnt marked so I would guess its about 1.5 maybe 1.7amps nominal based on its frame size. In the wanhao firmware it was set to 1000mA and ran for 4 months without this symptom, so I copied it across and ran if for 150hours+ No symptom. I have swapped out the ribbon cable feeding the hot end / extruder possibly its breaking down going open circuit and the extruder is stalling? kind of odd its at what looks like the same layer. Temps looked ok at 240C, I will try a full test tomorrow with the new ribbon cable. Otherwise I am really stumped.



  • @gzcwnk:

    ABS so no fan.

    Appreciated. But if it always happens at the same layer and continues on OK after that layer, it would indicate something amiss at that particular point in the print which is why I suggested you check the gcode file just in case Cura has inserted a fan command (even though you may not want a fan command) or a tool change or anything else that could drop the hot end temperature or otherwise screw things up. A bad connection, faulty motor, or anything similar would tend to behave in a more "random" manner (although stranger things have been known to happen).



  • I have seen this issue before and it turned out to be an issue with the original STL File don't really know the ins and out it was a friend of mine and may even have been a specific slicer/FW issue he was using Ramps IIRC and may have been Cura or Slicr at that time and some of the Preview software you can use picked up that the slicr missed a layer totally don't think we ever got to the bottom of why tho

    Doug



  • I thought of that and I re-stl'd it.

    It has happened on more than one part though and only since I swapped in the duet wifi. So this suggests to me a hardware issue. Being intermittent its going to be a piggy to find 😞

    I will go googling see if there is a gcode viewer tool? I can look with.



  • Ive upgraded to cura 2.x from 1.6, doing a test print. Loading the g-code I can see lines in it, I assumed it is / was a video artifact as my graphics card is so old and never was an issue pre duet…. So I might try this on my son's decent PC.

    I hopefully have the original gcode for the original part, I'll upload that as well if the above fails. That was a prefect print in fact I did 4 of them all perfect, if 1.5mm too high. If that fails I think i will try a different ABS as 3 of the 4 were Wanhao, 1 noname. Failing that I'll assume a hardware issue. but just what will be the Q. My only idea is a bad joint in the cabling to the stepper, so I will replace that entirely, leaving the stepper, wire and duet as the three components. Oh, hmm also the PSU.....I should make sure its hasnt started to volateg fluctuate or something, given its usual wanhao quality. 😕

    Sorry if I am rambling...trying to figure this yet another intermittent fault......I must have a Friday 13th machine or something....



  • still doing it 😞



  • rhand part done in October so original g-code, lh part tried just now same g-code, I think its severe under-extrusion? the Q is why and why periodically? odd…

    https://postimg.org/image/qlzwvps6h/3ac3f196/



  • Check the filament on the spool. I had a periodic under-extrusion due to the filament was jamming up on the spool at random times due to a crappy wind.



  • I am watching it do it before my eyes…but I dont see why, its like its dropping too much on Z.



  • I have just checked the Z drive, looks Ok. I have a I60 which is called the "idle" is that the % of the movement mA used to hold the Z axis in place? I have up'd Z to 1000mA and I80 to see if that fixes it.


  • administrators

    The idle current factor only comes into play when no motor has moves for 30 seconds.

    Is there any sign of the extruder skipping steps?

    Do other prints show the same effect at the same height? Could the Z axis be binding at that point?



  • What would be the sign of the Z skipping steps? nozzle digging in? noone of that. Its almost like its dropping too far. I had a good look at the Z axis and ran it by hand. What I did notice was I could fairly easily over-power the stepper. I also ran it up and down by hand, I could feel no binding at all. At the moment its on 1000mA up from 800mA and looks OK so far so maybe I had it set right on the edge ie too low. Not sure yet, I am sitting here in front of a 4 hour print watching it, it hasnt missed yet I can see….I will keep watching, rather boring, LOL.



  • So I just completed The old "October" gcode after uping the Z current to 1000mA from 800mA, I wackd it with a hammer pretty hard and its didnt separate so it seems a good print. Doing a "new" gcode print and it looks OK so far. Anyway I also talked to the D6 group and one person replaced the Z axis as he was having issues and on stripping the ball found the ball bearings worn out. So I am guessing that I have a worn ball as I noticed that the Z axis seemed a lot easier to turn than I remember, so a part to replace soon I guess. 😕


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