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Slicing changes depending on models the models on the build plate.


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Posted (edited) · Slicing changes depending on models the models on the build plate.

I'm trying to solve my issue with inconsistent layer speeds. I noticed when slicing the CHEPCube that the speed changes throughout the layers with that small top and bottom areas and overhangs. I added a plain cube from the calibrations menu and noticed that the layers on the chepcube evened out significantly. When I removed the chepcube, the layers on the plain cube changed, but the speeds were incorrect for all of it. I just can't seem to get consistency and could use any advice. 

Screenshot (6).png

Screenshot (5).png

Screenshot (7).png

Edited by MrLonnie
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    Posted · Slicing changes depending on models the models on the build plate.

    The colour spectrum used for speed changes depending on the speed range that will be used in your print, so you can't do an apples to apples comparison, and in all three of your screenshots it's different - and hard to see because of how the forum crushes image quality:

    image.png.bfa83d8441aaddbe7ddf51b521a35524.png I think that says 16.07 - 80?

    image.png.ad04cd7a6a0c84c16fc566dd70838b99.png 24.65 - 80.14?

    image.png.0abdc91fcdb2460d913cf17bcb051efe.png 25 - 80?

    If you could post the Cura project files of all three of your examples (.3mf, in Cura set it up then go to File > Save Project) that would be great, so we can see if there's anything we can figure out based on them.

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    Posted (edited) · Slicing changes depending on models the models on the build plate.

    Gotcha! Good to know for posting on here. I reduced my outer wall speed by almost half and it kind of fixed it visually in the slicer. I still have the issue of banding along the layers where speed changes in the slicer. I slice under my customsd_alt profile usually, but I saved the change in the temp#2 profile.

    CHEPCalibrationCube.3mf

    Edited by MrLonnie
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    Posted · Slicing changes depending on models the models on the build plate.

    Time for another Slashee Deep Dive™:

     

    So the cause of your quandaries seems to be a combination Cooling > Minimum Layer Time and your acceleration and jerk settings. Minimum Layer Time is is designed to slow down layers that would be especially quick to give the filament time to set. Looking at the file you sent:

    image.thumb.png.be0b4488169c1ba3c9df1285bbb35c3c.png

    The orange lines are because of your inner wall speed is twice your outer wall speed. The blue patches on the inside of the letters are where some skin (top/bottom) is poking through and its acceleration and jerk are lower than the rest of the print. If I reduce your inner wall speed these look good, but it's not a huge issue overall:

    image.thumb.png.10c82e0490836cdd94ffca9ac15d70dc.png

    Minimum layer time isn't coming into effect here because you're printing both cubes, which obviously takes more time.

     

    If I switch to just the regular cube:

    image.thumb.png.7dad075e4b7a1bb5d9ff8947b5782c36.png

    The middle layers are being significantly slowed down so that they take the minimum layer time to complete. The skin layers print at full speed because they need to cover the whole surface, which takes a lot more time.

     

    Switching to the calibration cube:

    image.png.a0485f0339d7445dca473e471387f973.png

    The layers where the walls are printing faster is because there's some skin in there slowing it down. Where there's no skin, they need to be slowed down a little to meet the minimum layer time.

     

    So what can we do about it? Turning down the minimum layer time would make the preview look pretty:

    image.png.c48e8995b55f2b0294f7a94ae53b7f57.png

    But that's ignoring the real problem:

    image.png.4e67a40ed73ec366a6d08732d702927c.png

    Yes, the E3V3SE can accelerate at up to 4000mm/s². But that doesn't mean it's a good thing. Too fast and the filament can end up being dragged behind the nozzle rather than being laid down properly. I never go above 1000mm/s² myself (including travel speed), and even then I've found problems with support (which I print at a lower flow rate so it's a bit easier to remove) being pulled along (and out of position) when the head zooms off on a travel move, resulting in a warped print (so I don't have to slow down the acceleration the whole print I created a post-processing script which lowers the maximum acceleration when it starts printing support until after the first travel move away from the support - but you probably only need to worry about that if you share my level of paranoia).

     

    However my bigger problem:

    image.png.3589ae6f623a369be93d5237f335f016.png

    Umm... holy cow. I never print with jerk above 8mm/s, and go as low as 2mm/s if I'm printing something complex or likely to fall over. Jerk is how much the head is allowed to instantly change direction at corners. In an ideal world, the print head would move to a corner, come to a stop, then start to move in the next direction. In the real world, that would result in a blob at the corner, so it has to slow down a bit to approach the corner, and then at the corner instantly change direction and start accelerating in that direction. High jerk - and I'd call this ridiculously high - can also result in the print head or build plate slipping and moving a step or two out of alignment due to the vibrations. This causes layer shift, which is when layers start printing out of alignment with the ones below. It can also make the filament cut corners, seeing it's being dragged behind the print head and it'll just get pulled along and follow the print head using the shortest path possible (which will be a diagonal because it doesn't have time to set before getting dragged along).

     

    If I disable jerk control (which will make it print with the printer's default jerk settings, which are much lower than 40mm/s) then the preview in Cura doesn't actually change, but that's because it doesn't depict acceleration along a move, just the print speed for a line.

     

    The solution: firstly, lower your jerk or turn off jerk control. This doesn't actually make the previews look any different, but it'll immensely help the print process. Trust me. Slow print > bad print.

     

    As for how the previews look... it's working as intended. You're printing very quickly and your layers don't have much in them. You could try lowering the minimum layer time to something like 1 second and that will make it print at a consistent speed, but that setting is there (and has a default of 10 seconds) for a reason. Feel free to lower it so it doesn't slow down a print and test it, and if it works for you, go for it. Small scale testing is your friend. Just try and remember it if you're trying a more detailed print later and having problems.

     

    Personally I'd also turn off acceleration control (or lower it to 1000mm/s²) so the acceleration is a more reasonable pace. It's not going to change the speed in the preview, and yes it will make it take longer, but again: slow print > bad print.

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    Posted · Slicing changes depending on models the models on the build plate.

    I knew I was way off something, I'm still pretty amateur at this. 

     

    I didn't even know about the "minimum layer time" setting, I'm playing with that and it seems to resolve most of the speed consistency issue. I turned off acceleration and jerk control and the prints quality suffered significantly, so I kept acceleration on, which helped. I'm going to dial in acceleration and layer time to get the quality back. 

     

    I noticed that the acceleration in the gcode from standard default slicer settings uses 1800 - 2400 acceleration. I'm just printing in a standard quality expectation right now, so I will play around with lowering everything for higher quality prints.

     

     

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    Posted · Slicing changes depending on models the models on the build plate.
    8 hours ago, MrLonnie said:

    I turned off acceleration and jerk control and the prints quality suffered significantly, so I kept acceleration on, which helped. I'm going to dial in acceleration and layer time to get the quality back. 

    Can really depend on the models you're printing. I use acceleration control to lower it to 1000mm/s² for PLA. Even lower for TPU, but TPU loves to go slow (I get the best results printing at about 20mm/s).

     

    I've read reports of the E3V3SE sometimes ignoring the values in the gcode and just doing it as fast as it wants. You can prevent this by using the control panel on the printer to turn down the maximum acceleration and speed values.

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    Posted · Slicing changes depending on models the models on the build plate.

    Your advice actually helped me print the cleanest benchy I've ever printed. After months of trial and error, I have the best profile I've ever had. I've been printing almost perfect models all day without changing anymore settings. My acceleration is now 900mm/s and jerk is 10. Inner wall = 40, outer = 25. Minimum layer time is around 6 - 6.5 There were other tiny tweeks, but nothing substantial.

     

    The Cura default profiles try to use almost max speeds for my printer. It made a lot of noise and the quality was never close to as good as my new settings. The only thing I only hear now is the fan. Thanks a ton!

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    Posted · Slicing changes depending on models the models on the build plate.
    2 hours ago, MrLonnie said:

    The Cura default profiles try to use almost max speeds for my printer. It made a lot of noise and the quality was never close to as good as my new settings. The only thing I only hear now is the fan. Thanks a ton!

    No problemo! Always love to have a happy customer 😄

     

    Whenever someone has a problem and they have an E3V3SE I should probably just start my posts with "The profile that ships with Cura for the E3V3SE is trash." (Believe it or not, in newer versions since it was first added they've actually made it worse)

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