Strange Ringing artifacts on coreXY

[kuhnikuehnast]

So seems that I could go for a 350 mm/s speed until the torque starts to drop with the stepper motors I own... The videos linked in the first post are performed at a speed of 6000 mm/min (100 mm/s)

[makerdise]

@kuhnikuehnast

[Neoxio]

Hi,

try:

M201 X1000 Y1000 Z250 E600
M203 X12000 Y12000 Z1800 E3600
M204 P1500 T2500

and try to print a test cube @ 30mm/s max. 40mm/s, show some pictures.

Greetings

[kuhnikuehnast]

Started printing. But The M204 seems to be very fast for my Z-axis? As I own a Nimble (30:1 ratio) i left the M201 at 120 as recommended by zesty.

[Neoxio]

U mean M203? there is no Z parameter for M204... The Z parameter is from your config u posted before I would set it to Z680 or 720 depends on your Z axis setup, weight of the heatbed ect... Using pressure advance u schould set your jerk min. to 600 so mayby try to turn off pressure advance too.

[kuhnikuehnast]

With M204 you set the travel acceleration. Isn't this also then used for the z-axis?
I also tried prints with Pressure advanced off before...
This is the "cube" I printed in vase mode at 40 mm/s:

Results are almost the same:
:

[Neoxio]

Do you have quality 3M belts or china? How about your hotend mount is it stable or wobbly.

[deckingman]

@neoxio said in Strange Ringing artifacts on coreXY:

Do you have quality 3M belts or china? How about your hotend mount is it stable or wobbly.

Check his OP - seems he's tried them.

[Phaedrux]

I had very similar ridges on my corexy and the solution for me was to replace the toothed idlers with smooth bearings and do a belt flip so the smooth side rode on the bearings. It seemed that the diameter of the idler was too small or the profile of tooth and belt mismatched enough that it wasn't meshing smoothly.

Also, I recall a thread from not long ago where using very low steps per mm was causing motor movement to be less smooth.

Just some thoughts

Here's an example of what I had.

[whosrdaddy]

Could be an extrusion problem.
Add some pictures of the complete printer so we can have a better idea...

[mrehorstdmd]

@whosrdaddy

I second the vote for extrusion problem. Try changing the extruder motor current up or down 20% and see if the pattern changes.

I've seen this in direct extruders with no gear reduction and relatively large filament drive gears.

What kind of extruder is on the machine?

[makerdise]

@whosrdaddy @mrehorstdmd @kuhnikuehnast did test a bowden setup as an alternative, while currently running a zesty nimble (which sounds like a hot candidate having a non concentric part or imprecise worm drive etc.)... This was also one of my first ideas (inconsistent extrusion). However, the pattern remains nearly the same on both setups. The distance between the "waves" is very consistent so this could only be caused by a part moving around in circles with a non-concentric bore or wrong clamping (in theory).

Damn.

@mrehorstdmd - are you the guy with the belt driven z-axis printer, do I remember right? If so, respect.

[kuhnikuehnast]

as @makerdise already told: at first, I was "hoping" to have an extrusion problem... But as I tried 2 different types of extruders and also with 2 different stepper motors, the problem persisted. And if you watch the video, you can also se the "sine wave like" spinning on the axis. These videos were made by just "printing" a g-code like:

G21
G91
M564 S0 H0
G0 X300 F6000
G0 X-300 F6000
G0 X300 F6000
G0 X-300 F6000
...

So all the possible interfering factors were eliminated.

[Neoxio]

Does it get worst when u print @ 0.1mm layer hight? (does the "ringing" changes, increase?)

[T3P3Tony]

@kuhnikuehnast, @makerdise It looks like you have carried out a detailed investigation so far. To try and isolate the problem to a subsytem (electronics/mechanical) can you try changing:

1. Movement axis interpolation this line in config.g "M350 X16 Y16 Z16 E16 I1 " change so that X and Y are not using interpolation:
   M350 Z16 E16 I1
   M350 X16 Y16 I0

2. As a seperate test, try different microstepping for movement axis:
   "M350 X64 Y64 Z16 E16 I1 "
   You may need to reduce the print speed. Also make sure you follow the documentation about how the microstepping and steps/mm interact. https://duet3d.dozuki.com/Wiki/Gcode#Section_M350_Set_microstepping_mode

[whosrdaddy]

I had a look at the videos, it seems that X axis has issues (20 micron range is a lot).
Could be something simple as binding or a bad bearing.

[kuhnikuehnast]

Would be great if it was that simple... As I only wanted to use high quality parts I installed Misumi long bearings... Bending isn't a probleme I think.

Steppings:
Already tried switching off interpolation and tried from full step to 1/32. But I will give a second try later (just out for dinner)

[makerdise]

@kuhnikuehnast - I am unsure if we did test the M350 X16 Y16 while setting the I flag to 0 explicit...

@T3P3Tony - for sure we did test a lot and discussed a bunch of common and uncommon things. It seems to be more complex in this case. I was focused on the mechanical subsystem since we did some tests today. As written in the OP, the belts, pulleys were changed, so they are out. We measured the rods, the movement was ~0.05mm. There's no measurable bending or movement of the frame. So we continued debugging within the XY frame, by measuring if the Y carriages does bend in x direction while moving x, and they didn't. The only measurable movement within a linear x move(as seen in the video) is into the y direction (+-0.2mm = 0.4mm). You can clearly see this sinus wave like pattern with a ball pen mounted on the x carriage painting on paper. In conclusion, we have to find all factors that can cause kind of a stuttering in the motors. As the motors were changed, it can be related to soft- or hardware issues.

I thought about an issue with M669 which was introduced in RRFW 1.1.9 - are there potential collisions with M667 or known issues related to CoreXY?

Maybe @dc42 can join the discussion to bring in some light into the darkness

[mrehorstdmd]

@makerdise

Yeah, I have the belt lifted Z axis. I recently put a Volcano and 0.8 mm nozzle back on it to print some structural parts and ran into some Z axis banding problems that I am starting to think are due to the gears in the worm drive that lifts the Z axis. I'll probably do a post on it to see what other think is going on.

Older prints made with a standard heater block and 0.4 mm nozzle in 0.2 mm layers don't seem to have the problem, or have it to a much lesser, more acceptable extent.

I have a CubexDuo with a relatively large diameter filament drive gear that produces little ridges in the walls of prints and seems to be related to the microstepping causing the motor to pulse enough to create the ridges. For some reason, changing the motor current changes the spacing/angle of the ridges.

[makerdise]

@mrehorstdmd - this is a real nice project. I like the worm drive, in my research I only found a very few ideas to stop the unwanted z movement and this is the best implementation.

OMG, another complex issue For sure, feel free to post it by pm or here. Did you thought about a PID related issue? Is it possible that the block itself is bending cause of this and the vertical alignment? Did you ever tune the PID's after changing the block? Are you using the volcano sock?

Do you have any detailed information on the motor pulsing, this seems to be interesting...