S-curve in marlin 2: seems like a huge quality improvement.



  • https://github.com/MarlinFirmware/Marlin/blob/bugfix-2.0.x/Marlin/src/module/planner_bezier.cpp

    When I heard marlin 2 was in beta and worked on the sbase, I immediately switched over. Still figuring out why the sd card wont work but I was blown away by the improvement in movement from smoothieware. Much less vibration & noise with seemed to translate over to much higher quality surface finishes. Trying to see if I could up the acceleration & jerk settings I noticed the config had a feature called S-curve acceleration turned on. Looked it up and it seems to explain why I'm getting such nice movements.

    I like my duet a lot (seriously nicest user interface out there. you guys are awesome) but my large delta 300x650 is pretty limited in speed because of the extra weight of a flying extruder & from what I've read S-curve acceleration is great for moving heavy effectors around.

    I'm just a beginning coder... how hard would it be to hybrid over their s-curve code?




  • administrators

    @warbunnies @dc42 is looking at adding s-curve or similar improvements to a future firmware release. My understanding is that the version 2.0 (RTOS) build needs to be released as stable before new features are added.



  • Might also consider getting a lighter extruder like a zesty nimble



  • @bendiesel said in S-curve in marlin 2: seems like a huge quality improvement.:

    Might also consider getting a lighter extruder like a zesty nimble

    I have a flex3drive on my Kossel XL which is pretty light and it still suffers from ringing. I can reduce the ringing by reducing acceleration but then I get fat corners. So it would be nice for me if this alternative acceleration scheme is implemented and it does actually perform as well as people say it can. I'll certainly be trying out any betas if/when they appear.



  • @burtoogle said in S-curve in marlin 2: seems like a huge quality improvement.:

    I have a flex3drive on my Kossel XL which is pretty light and it still suffers from ringing. I can reduce the ringing by reducing acceleration but then I get fat corners. So it would be nice for me if this alternative acceleration scheme is implemented and it does actually perform as well as people say it can. I'll certainly be trying out any betas if/when they appear.

    What acceleration are you using? My k800 xl did not have much issue at 1400mm/s acceleration. Now I'm considering jumping up a lot higher... it just prints so darn good with marlin 2.



  • @bendiesel said in S-curve in marlin 2: seems like a huge quality improvement.:

    Might also consider getting a lighter extruder like a zesty nimble

    Nothing I've seen from the zesty nimble has really impressed me. Their prints have always looked just "ok" even though they were printed on a delta.

    This is what I expect from a delta with a decent extruder: https://imgur.com/a/PAoU2

    This is what I see outa a zesty delta: https://www.youtube.com/watch?v=BMq88tPxU2s&t=84s

    Thats pretty horrible by comparison. Especially because they are using the awesome duet smart effector & those high precision mag rods. My machine uses some shitty rods that i had to adjust to be the same size and have much more play than the mag rods.

    I'm currently working on making a dc motor / encoder extruder which should be a much better option. Same weight range as the zesty but none of that slop.



  • @warbunnies said in S-curve in marlin 2: seems like a huge quality improvement.:

    @burtoogle said in S-curve in marlin 2: seems like a huge quality improvement.:

    I have a flex3drive on my Kossel XL which is pretty light and it still suffers from ringing. I can reduce the ringing by reducing acceleration but then I get fat corners. So it would be nice for me if this alternative acceleration scheme is implemented and it does actually perform as well as people say it can. I'll certainly be trying out any betas if/when they appear.

    What acceleration are you using? My k800 xl did not have much issue at 1400mm/s acceleration. Now I'm considering jumping up a lot higher... it just prints so darn good with marlin 2.

    I'm currently using 3000 and putting up with the ringing. I prefer some ringing to having fat corners.



  • @warbunnies said in S-curve in marlin 2: seems like a huge quality improvement.:

    This is what I expect from a delta with a decent extruder: https://imgur.com/a/PAoU2

    The model you are printing is curved so the low acceleration probably doesn't really matter. You can see some rounded corners on the support but it's hard to tell in that image how bad they are.

    Anyway, I am happy enough with the flex3drive in terms of print quality.



  • I'd love to see photos showing the improvements made from S-curve acceleration.



  • @burtoogle said in S-curve in marlin 2: seems like a huge quality improvement.:

    @warbunnies said in S-curve in marlin 2: seems like a huge quality improvement.:

    This is what I expect from a delta with a decent extruder: https://imgur.com/a/PAoU2

    The model you are printing is curved so the low acceleration probably doesn't really matter. You can see some rounded corners on the support but it's hard to tell in that image how bad they are.

    Anyway, I am happy enough with the flex3drive in terms of print quality.

    Yes I agree. That comment wasnt about s-curve. BenDiesel was talking about using a different extruder and I was arguing that the flex drive was just a drop in quality from a normal bowden/direct drive.



  • @bot

    What photo would you like to see? Marlin 2 with & without s-curve or smoothieware vs marlin 2? I'm a bit busy this week but I can set up the firmware and make something during my lunch breaks.



  • @warbunnies I'd be more interested in a video of it in motion comparing S-curve and non, all else being equal.



  • Videos would definitely be better, but often lack the perfect angle and lighting to show the differences in extrusion.

    Yes, photos showing before and after, and indicating which speed/accelerations were used and possibly even print times.

    We need to compare the time spent and quality of the prints. If the prints are of the same quality, but they're faster with s-curve, that's an improvement. If they're better looking with s-curve but with no speed benefit (as would be evident with actual print time) then s-curve still has a benefit. Etc.



  • Great to know that's on dc42's whatchlist



  • @bot

    I'll do my best. I've only done video editing once and only have my phone... so I'll probably stick to pictures. But I got the firmware baked at work today so I should be able to make some simple calibration cubes after work. I upped my acceleration to 3000 so it should force the ringing to be more visible. I'm not sure I'll have time to check print times but will definitely try.



  • @warbunnies don't bother with video editing take your smartphone and push it to YouTube 🙂



  • Okay I'm doing more testing but I am honestly a bit confused with my initial results...

    With an acceleration of 3000:

    Turning on the S-curve feature does not seem to do anything. Anything!
    The prints are so similar that the camera on my phone cannot pick up any difference & asking friends to blindly rate has produced indeterminate results.

    Even more perplexing is that both prints took almost exactly the same amount of time. The s-curve was faster by 5 ish seconds over a 1hr50ish min print. If anything I would have assumed it would have been slower because the acceleration is not constant...

    They also produced the same amount of noise.

    My conclusion is the the marlin firmware (with or without s-curve) is just better than smoothieware. 1400mm/s use to be a hard cap for my printer but the 7000mm/s acceleration im testing now suggests I can tune my printer much higher. I'll let you know if the 7000mm/s produces artifacts worth taking pictures of. I may also try increasing the jerk value to see if it has any effect.

    Also my small delta may be a poor candidate to test these features. The effector is less than 100g total & its a relatively small machine 260mm D x 361mm H & overkill structure so there's just nowhere near enough weight moving around to tell if the s-curve is helping. If it was easy to do/ i had more free time, I would stick it on my large delta 325mm D x 680mm H with the added weight of a flying extruder and see if the s-curve helped. If anyone has a heavy effector and some free time, I'd love to see if it does anything.



  • @warbunnies said in S-curve in marlin 2: seems like a huge quality improvement.:

    My conclusion is the the marlin firmware (with or without s-curve) is just better than smoothieware.

    I probably shouldn't comment because I've never been hands on with smoothieware on a delta. However, I have used Marlin 1.6.6 and above quite a bit on Delta's, and from reading about smoothie... well... I believe your conclusion is probably spot on.



  • @danal

    I actually think I found the issue. The name was recently changed from #define BEZIER_CURVE_SUPPORT to #define S_CURVE_ACCELERATION

    & whoever did that missed 1 part of the code that still used #define BEZIER_CURVE_SUPPORT

    That's what you get for beta testing. I'm trying the firmware with both defined and should actually be using the s-curve feature.


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