Horizontal lines during print
Hello Prusa fam,
My spouse and I have been designing and printing purses. And the XL 2T has been an absolute workhorse (has a print time of over 120 days in the last 11 months). Lately it has started causing some printing issues.
As we start approaching the top part of the purse, it creates these horizontal lines across the entire layer. What could be causing this issue? My gut instinct tells me it could be something with the Z-Axis, but since it takes almost 24h to get to this point, I am not really sure how to check.
More details in the images attached. (The silver one could be just due to moisture)
Thank you all
RE: Horizontal lines during print
Are the lines appearing on both toolheads, or happening on just one?
I've seen similar lines occur when the nozzle was being temporarily starved for filament, or when newly-laid filament was sticking to the nozzle after more filament was picked up elsewhere and being dragged around the print pulling little bits of fresh filament with it.
My issue was exclusively with certain spools of PETG, and I've apparently solved by making spool supports using bearings, by improving the z-lift parameters, slowing down my print, and better managing the temperatures and flow rates. These ended up making my nozzles less likely top leave little blobs or raised bits that the nozzle would run into and stick to the nozzle building up blobs to drop elsewhere, and making the filament deposition a lot more stable.
I ask this as I can see little voids on the red material on the left side of some of the ridges bordering the flatter areas. This suggests to me that there's something causing that gap, either a lack of deposition at that point, a pulling of printed material away from that point or (a distant third) the slicer pushes the print head into the piece at that point (an accidentally-by-design thing) and the larger gap is simply where things have cascaded and blown up a bit. The fact that the print "recovers" at some point after the larger gap does point to the failure mode being non-catastrophic. As obvious as that is, it's a useful data point.
I would also caution about correlation and causation with the Z-axis position specifically. It may also be related to the time since the start of the print, or a heat-soak factor with more hot mass of plastic creating currents of warmer air around the printing area than at the start of the print, or a friction-in-tube thing that would more often appear after a few hundred meters of filament have passed through, or a friction-at-spool thing that takes hours to build up enough heat to start becoming sticky causing micro-jams and voids.
There's a reasonably small list of possible reasons for the effects you're seeing, but the unfortunate thing is that the troubleshooting will take time for each iteration.