Need Help with large scale printers tuning!
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@Machoo566 said in Need Help with large scale printers tuning!:
I have tried changing the microstepping to 64 instead of 16 but I never could get it to work properly,
Leave it set to x16 with interpolation to x256 enabled and set our steps per mm accordingly for x16.
For me to get rid of the vertical banding on my corexy I had to have two belt flips so that the smooth side of the belt was always riding on a smooth idler. The only teeth in contact with the belt ever is at the drive pulleys.
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Okay so where do I set the interpolation to x256? I'm just wanting to make sure I'm understanding what I'm changing exactly because I have never really messed with the interpolation at all.
Also what I think i'm understanding what you are saying is that these type of idlers could be causing some issues?
I have the belt running over these in three spots. What I have herd is you don't run the toothed part of the belt across a smooth idler so how exactly do I do the belt flips you talked about properly?
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@Phaedrux said in Need Help with large scale printers tuning!:
Leave it set to x16 with interpolation to x256 enabled
@Machoo566 said in Need Help with large scale printers tuning!:
Okay so where do I set the interpolation to x256?
You set it to x16 with interpolation enabled. Like so (this is from a coreXY):
M350 X16 Y16 I1 ; Set 16x microstepping for axes. I1 = Use interpolation.
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@Machoo566 said in Need Help with large scale printers tuning!:
I have the belt running over these in three spots. What I have herd is you don't run the toothed part of the belt across a smooth idler so how exactly do I do the belt flips you talked about properly?
Tooth belt to tooth idler, as in your photo, is OK (assuming same pitch and type). Smooth belt to smooth idler (not in photo) is also OK.
Tooth belt to smooth idler is not. Do you have that anywhere?
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Okay so I guess I just leave the Interpolation the way it is because this is how i have it set.
M350 X16 Y16 Z16 E16 I1I don't have any toothed belt to smooth idler anywhere. I took special care not to do that.
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@Machoo566 said in Need Help with large scale printers tuning!:
M350 X16 Y16 Z16 E16 I1 ; Configure microstepping with interpolation
You had it correct in your first one.
@Machoo566 said in Need Help with large scale printers tuning!:
I have the belt running over these in three spots.
Originally I had smooth idlers everywhere with the belt teeth running on them. Then I swapped to toothed idlers like you have. It didn't solve the problem. Maybe they weren't a good match to the belt teeth or maybe the bend radiius is too tight. Not sure. The ridges became a bit less noticeable but they were still there. So then I swapped back to smoother idlers and flipped the belt.
The belts are flipped going from the motor 180 degrees and go around the back side and then flip again in reverse on the return to the motor again. The flip is only on the belt lengths that stay a fixed length.
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Maybe this illustrates better.
Ignore the white belts. They were replaced with gates.
I don't even use actual idlers either, they are just flanged bearings. The idlers have tiny bearings and we're constantly seizing.
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I have a cartesian printer with a very heavy Y axis. I notice a very faint repeatable vertical pattern exactly as you see, only on surfaces printed with pure Y moves (and perhaps to some degree on angles close to it). My X axis does not seem to show it.
I think what this is, is the steppers only holding full step positions. All positions in-between are lost. Though, maybe it can do half-step positions, or even quarter positions, but it's not holding EVERY possible commanded position.
This might also explain "corexy cogging," especially of the cogging effect is prevalent during print moves involving only one motor, while moving the entire gantry.
The effect on my printer is only visible under magnification. This is, IMO, because I have 0.9 degree steppers, 16 tooth pulleys, and 2:1 gear reduction, meaning an effective 8 tooth pulley drive resolution. This would allow the full (or half, or quad) step cogging to be sufficiently small as to be not very noticeable.
Perhaps you could increase your motor current, lubricate axes more for smoother motion, lower weight on axes, decrease acceleration, jerk, and top speed on moves requiring smooth surfaces, etc. See if that helps.
Edit to add: Though, I think what dc42 and Phaedrux are saying is more related to, basically, inaccurate toothed idlers adding unwanted motion to the toolpath. This might indeed be the case, even for my printer, as my Y axis has more toothed pulleys, and perhaps it's simply the addition of toothed pulleys that causes this, but since my addition of toothed pulleys is before the gear reduction, it appears "halved" as compared to the belt pitch.
*not actually a robot
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The diameter of the pulleys makes a big difference in two regards. You can use smooth idler pulleys with belt teeth touching them if the diameter is sufficiently large. I use stacked F608 bearings (22 mm dia) for pulleys in my corexy printer and get no print artifacts. I read somewhere (Gates literature, I think) that the recommended minimum number of teeth in contact with a smooth pulley is 9. The 22 mm diameter pulleys just meet that spec with a 90 degree wrap of the belt. Those 3D printer pulleys with 3 and 5 mm bore have very tiny balls in the bearings that put a lot of contact force on the races due to belt tension. That causes the bearings to wear out quickly. Larger bearings have larger balls and that reduces the contact force they put on the races, resulting in longer life and smoother rotation.
I have some of the smooth versions of the 3 mm bore pulleys in my sand table (800 x 1660 belt space) and some of them wore out after only about a year of sporadic operation. I'm in the process of redesigning the printed bearing mounts to accept stacked F625 bearings.
If you change the pulley diameters you have to reposition their axles (and maybe the motors) to keep the belts parallel to the guide rails or you'll create more problems that you solve.
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@bot I've long thought that it might be possible for steppers to have a tendency to "jump" to the nearest whole step under certain conditions. It's more of a gut feel than based on any testing or analysis. But I have a suspicion that too high a belt tension can exacerbate the problem.
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@deckingman I have definitely had my belts too-tight to the point of preventing smooth motion of the axis before. I could easily see a situation where the motor couldn't even move reliably, much less skipping microsteps. Skipping microsteps is basically fundamental behaviour, which is why I geared down my axes 2:1 and got the smallest drive pulley possible. I am only assuming full step microstep resolution is a thing, anything else is just for quietness and smoothness.
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@bot said in Need Help with large scale printers tuning!:
...................... I am only assuming full step microstep resolution is a thing, anything else is just for quietness and smoothness.
That seems perfectly reasonable to me. I keep toying with the idea of doing the gearing thing with "remote" motors - one day I'll find the time........
