Not Duet but this has me puzzled

  • Link to picture here -
    alt text

    This is a close up of a part I'm printing. I'm using a Diamond hot end so 3 filaments into a single nozzle. For the purpose of this print, I have 2 tools. Tool 0 uses 100% of the white filament and tool 1 uses 100% of the gold filament. Different extruders but the same nozzle, same heater, same temperature. So for every layer both white and gold are printed.

    I don't know how well the issue shows up on the picture but there is what looks like a layer shift of about 1mm on the gold part. It starts at a height of about 3mm above the base, and continues for about 11mm then goes back to the original (correct) position. It seems to be in both X and Z so that would indicate something related to one motor/belt (it's a CoreXY). Possibly a loose pulley or some sort of mechanical issue but it's odd how it shifts then many layer later shifts back again.

    That's kind of freaky but what is really frying my brain is that it is only apparent on the gold part. The white pillars show no sign of this layer shift. So after about 3mm above the base, it prints the gold part slightly shifted, then prints the white part in the correct position, then changes layer and repeats with the gold part shifted but the white part in the correct location. It continues in this vein for another 11mm of height, then reverts back to printing both parts correctly.

    Is that freaky or what?

    All thoughts and donations gratefully received.

  • G-Code issue? Did you checked in a G-Code viewer?

    Or a loose hotend or so, only moving when gold filament is pushing (PTFE not well maintained)?

  • The gold parts are smaller than the white parts, so maybe there velocities are changing quicker resulting in belt flex?

    It also looks like the direction of the print is changing one those shifted layers, so maybe the bed isn’t quite level and the nozzle is dragging in one direction.

  • Good suggestions but it's not the complete height of the gold part that is affected. The first 3mm or so is unaffected then the next 11mm or so has the issue, then the last 6mm or so is unaffected. And of course the white part is unaffected throughout the entire height. That kind of eliminates most mechanical issues that I can think of. Oh and the entire thing is 300mm in Diameter so if the bed wasn't flat or level, I'd never have got the first layer to work. Trust me - it's flat and level within 0.1mm over the entire plate.

    It could be a slicer issue but running through the layer by layer view in Slic3R, I can't see any sign of a shift anywhere. I'll have a trawl through the file and see if I can spot anything but it's a pretty big file -about 55MB and 507 layers in total.

    The other thing is that this is the 4th part I've printed, each one getting progressively bigger. Starting with 150mm diameter then 200mm then 250mm and now this 300mm one. None of the other parts have any sign of anything amiss so I'd be inclined to think that it's not a slicer issue.

  • Just an update to this. I've printed the 350mm diameter version of this object and it's fine - well in truth I had another problem but the gold spindles and white pillars showed no sign anything that looked like layer shift. So to recap, the 150mm, 200mm and 250 mm versions were fine, the 300mm version had a problem part way through but the 350mm version printed latest of all is fine. To me that rules out just about everything apart from the actual gcode. I guess the only way to be sure would be to re-print it to see if it does it again, but it takes 23 hours and I don't have the printer time to spare right now. Thanks to for all the suggestions though.

  • @deckingman Could it be print direction causing the offset? I am still having z-banding nightmares...

  • @bpislife said in Not Duet but this has me puzzled:

    @deckingman Could it be print direction causing the offset? I am still having z-banding nightmares...

    I wouldn't rule it out. Especially with the nozzle geometry of a Diamond hot and the way that filament is presented at and angle. Not sure how I could force the slicer to always make all those small cylinders in the same direction though.

  • @deckingman I know simplify3D has the option to print all in one direction, not sure about others.

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