Started printing this filament shrinkage test and had to leave the house. When I came back, the whole upper half of the part had shifted after the first few layers, and it left two solid blobs attached and one ball of spaghetti. The magnetic bed doesn’t appear to have moved. Part is still solidly adhered to the print bed. How did this happen, and how can I keep it from happening again?

    • amminadabz@sh.itjust.worksOPEnglish
      2·
      3 months ago

      Not entirely sure what “cold pull” means. I unscrewed the nozzle while the machine was powered off and the hot end was room temperature. Blasted the living hell out of the nozzle with a small torch, scrubbed it inside and out with a brass bristle brush, ran one of the bristles through the end of the nozzle. With the nozzle and ptfe out, I heated the hot end to 60 C to loosen the remaining chunk of filament and pushed it out the bottom with the handle of a needle file. It came out in one solid piece. Shined a light through both hot end and nozzle individually and it looked clear.

      • ffhein@lemmy.worldEnglish
        2·
        3 months ago

        Did you hot tighten the nozzle while putting it back? Don’t think it caused your current failure, but cold tightening can lead to more clogs in the future.

        I think layer shifts can be caused by many different things, but the first thing I’d check is that the bed carriage can move freely and there isn’t something mechanically blocking it, like a wire or a misplaced screwdriver. The second thing I’d check would be the belt and gears, so that the bed can’t move without the stepper motor also spinning.

          • abcdqfr@lemmy.worldEnglish
            1·
            3 months ago

            Thermal expansion is real. Have experienced loose nozzles when only cold tightened. Also as others have said, ensure belts are tight. If they’re floppy enough to skip teeth on the steppers you’ll definitely get layer shift from a light breeze. Monitor the next test and let us know how it goes!

      • marcos@lemmy.worldEnglish
        1·
        3 months ago

        Not entirely sure what “cold pull” means.

        You unscrew your extruder, heat the hotend up until you can barely push the plastic across (~170ºC for PLA, ~180°C for ABS), push a bit of it and then pull it out.

        Cut the end of the filament and do it again, a few times.