I built my 3D printer a couple of months ago, but I can’t get it to print sharp corners. The corners in the picture should be 90°, without any fillets:

During this test print, I played with multiple parameters: speed, temperature, acceleration, junction deviation, linear advance. All of these were also individually tuned previously. Nothing seems to make a difference.

Could this be a issue with the construction of my printer? I’m beginning to think my hotend isn’t rigid enough, but then I would at least expect better results at low speeds.

  • rambos@lemm.ee
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    9 months ago

    Id like to see a single wall cube print like 30x30 mm. Corners on the picture look rounded too much, but wall thickness is only 1.35 mm (right?). In ideal world you would have R0.225 on each corner so the flat part would be only 0.9 mm. Thats super small, you probably want smaller nozzle for details like that. But yeah, maybe it can be improved by tuning settings or reducing play in your XY gantry

    • elDalvini@discuss.tchncs.deOP
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      9 months ago

      This is a 40x40 cube printed in vase mode:

      The corners look pretty okay on that:

      But I don’t see these kind of results on real-world parts. I guess I have to print some more test parts to narrow down the problem.

      • rambos@lemm.ee
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        9 months ago

        Cube looks good, but corners are rounded bit too much I think (at least the one on 2nd pic)

        • rambos@lemm.ee
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          9 months ago

          Your design CoreXY reminds me on belt issues. Do you have a pic? It doesnt have to be mechanical issue, but belts must be tight and parallel/perpendicular to linear motion system.

  • KillerTofu@lemmy.world
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    9 months ago

    What printer, what slicer, what settings, what filament would help people give you assistance.

  • FuglyDuck@lemmy.world
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    9 months ago

    So, 3d prints will always have a radius on corners that is roughly equal to half the extrusion width. This is because the nozzles are circular, and the plastic comes out in a circular cross section.

    From what I can tell on the picture of your part, you have a relatively wide extrusion width set up. what’s the sliced width? what’s the size of your nozzle?

    If you want very sharp corners, you’ll need to drop down to a smaller nozzle diameter to maintain other aspects of print quality- generally extrusion widths should be at least the width of the nozzle. The reason being is that your printer relies on getting good ‘squish’ to keep the layers adhering stronger, and the way a printer gets narrower extrusion widths is by ‘stretching’ the filament along, which kind of weakens things.

    If you’re using prusa slicer, it’s a simple matter to reduce EW specifically on external perimeters and get a nice print without sacrificing too much in the way of strength, but if the difference between internal perimeters and external perimeters are too large… things may go wonky. at that point, it might be prudent to drop down to a smaller nozzle diameter. (which prints things slower.)

    A minor word of warning, however. Fillets and chamfers are important aspects of design. having sharp corners looks good, sure, but putting a fillet or chamfer on an internal corner makes a stronger part.

    • elDalvini@discuss.tchncs.deOP
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      9 months ago

      The part is just pretty small, I have the EW set to 0.45 mm withe 0.4 nozzle. But I will try turning it down further.

      The rounding looks much more extreme than what I would expect or have seen on other printers I worked with (mostly Ultimakers).

      • FuglyDuck@lemmy.world
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        9 months ago

        Huh. Maybe it’s just the perspective, it looked maybe closer to .6mm.

        Just to verify, you’ve checked that the printer extrudes .45mm of width when called? (Tuning extruder esteps and extrusion multiplier, and double checking filament diameter,)?

        As a sanity check, I’d compare the overall width of the part to what you were expecting.

  • Fuzzypyro@lemmy.world
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    9 months ago

    I can only add 2 things that I know of here that could help.

    #1.Try a linear advance tune. That alone should give you sharper corners and more consistent details at higher print speeds.

    https://marlinfw.org/docs/features/lin_advance.html

    #2.A direct extruder can help with getting very precise sharp corners but from what I understand it will hurt with accuracy on curves. Also there is the whole fact that there is a motor on top of the hot end so weight and whatnot will hurt speed.

    Anyway just check out #1. It should help with your issue. If not that then a feed rate tune would solve any over extrusion problems.

  • Shdwdrgn@mander.xyz
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    9 months ago

    One thing that concerns me for the inside corners along the side… Why is your slicer cutting an angle across that corner instead of making a sharp turn (see the yellow lines in the slicer image)? Most prints draw the inside lines first and the outside perimeter last, so if you have a diagonal line sitting there already then there’s no possible way to force a square corner there.

    Sorry for the lack of terminology, it’s been awhile since I fired up my printer, but I know in Cura under the speed settings there are parameters to set how fast the head goes from zero to full speed, and if you disable this then the head doesn’t have time to slow down at the corner before launching off in another direction which causes rounded outside corners like you show on the end of your print. I’m sure someone else can jog my memory about what this is called, but it would be worthwhile to check this in your Prusa settings as well.

    Regardless, you’re not going to get ‘sharp’ corners. My printer has a 0.4mm nozzle and even with decent settings and a slower speed I still get corners roughly twice that diameter, so don’t expect your print to match what’s drawn on the screen.

    • silentknyght@lemmy.world
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      9 months ago

      I’ve only used prusa slicer, which is what it looks like OP is using, and it results in printing perimeters first, then inside.

      • Shdwdrgn@mander.xyz
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        9 months ago

        Ah interesting. On Cura you can change whether you do the perimeter or infill last, but I always found doing the perimeter last creates smother detail. Makes me wonder why Prusa decided to go the other direction, but I guess whatever works…