uneven surface finish

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  • Have you compared the target extrusion thickness to actual? Backing off on the extrusion multiplier helped me get better vertical walls recently.

  • @doctrucker
    photos are currently with extrusion set to 90%
    steps /mm are correct so I don't want to go more than 10% off, which is a lot

  • I made a test with 1mm nozzle, extrusion multiplier 70%, extrusion width 0.7, layer height 0.5, outline speed 20 mm/s
    this is the result...so strange
    1_1531434384669_IMG_20180713_0020101.jpg 0_1531434384668_IMG_20180713_0020041.jpg

  • I have had the same uneven finish from my coreXY printer as pictured in your first post when using volcano with 0.8 mm nozzle. I tried everything I could think of to ferret out the source and could not. If you look at the corners under a microscope, they appear to stack up just fine, so it isn't the precision of the mechanism. I suspect it's the behavior of the cooling plastic. What I think is happening is that as the previously deposited layers of plastic cool and shrink, they distort the wall slightly and cause the new line to land a bit off-center on the previous line. The long straight vertical wall is the worst case scenario. If you print a cone, the effect almost disappears. I suspect the curvature resists the warping force created by the shrinking, cooling plastic better than a straight wall does, so the layers have a chance to stack up properly.

    When you start printing other things with that nozzle, you'll find gaps at the start/end of layers/lines, especially after travel moves. With a lot of messing around, you can tune them out for a specific part being printed, but as soon as you try to print multiple parts on the bed, or even a different part, all bets are off. With a 0.4 mm nozzle, the gaps are controllable/nonexistent, with a 0.6 mm nozzle they are starting to become a problem, with a 0.8mm nozzle they are severe. There is a plug-in for Cura called "scalable extra prime" that varies the extra extrusion upon unretract as a function of the travel distance. It helps, but is not a cure for the gaps.

    The second photo isn't strange at all. You're trying to print a line that is thinner than the nozzle diameter. That's what happens when you do that- you're under extruding. It's like the water coming out of a slow running faucet- if there's some distance to the sink, the stream pulls itself into discrete droplets. In this case, the droplets form before the plastic cools enough to stiffen. I'm pretty sure that's a result of surface tension, just like the formation of water droplets.

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