Artefacts on walls

Veti

Anybody got a suggestion where these could come from? you can not realy feel them but can see it in light reflections.

the top one is printed at 80mm/s the bottom one at 40mm/s

my printer is a corexy (hevo fusion) with linear rails.

Phaedrux

There's been a few good threads about troubleshooting issues like this. Search for vertical ribbing, or banding, or waves.

Usually it's a mechanical issue. Something loose. Belts not meshing with pulleys smoothly. Toothed side of belt running on a smooth idler. Oblong pulley, or not running on center. Bad bearing. those are the things I would check first.

DocTrucker

Here's my recent thread:

https://forum.duet3d.com/topic/9222/part-wobble-formerly-need-gates-gt2-belt/23

Mostly mechanical, but in my case motor choice/swap helped. I've not finished yet. Dampers, pulleys, and tl smoothers (note: I'm running v0.6/0.8.5, v2) are due over the next few days.

DocTrucker

Looks like the wobble on your parts are about stepper major step size?

Presume a Duet Ethernet/WIFI?

Veti

Its a duet maestro.

it could be the stepper major size.
i will try swapping my x and y stepper motors with the z ones.

DocTrucker

Alongside the already popular polymer dampers there is also mass inertial dampers to consider. That said I've not heard of these being used on printers yet and would limit the max accelerations the steppers could achieve without stalling. Whether that effects the accelerations and instant speeds used in printing is another question.

DocTrucker

Are you already running on the current limit of the Maestro or 80% of stepper max current whichever is smaller?

Veti

I am currently running my steppers at 67%

I can give 80% a try.

Veti

after a long time of testing and adjusting

chaining to different motors -> Still there.
switching to 16 tooth pulley -> Still there but small ripple distance decrease
using Spreadcycle instead of Stealthchop -> Still there , just more motor noise
chaning all toothed idler to smooth ones and twisting the belt -> Still there.
modifying some parts for better belt alignment -> Still there.
upping the current -> Still there
relubricating all the rails -> Still there.

i then rotated the part by 45 degrees. this causes the part to be printed by only one motor at a time.
-> The ripples decreased in distance.

So i guess i will some 0.9 degrees steppers and combine them with a 16 tooth pulley and see if that helps

Phaedrux

What are the motors?

Veti

Model 17HS8401
Step Angle 1.8 (deg)
Motor Length (mm) 48
Rated Current (A) 1.8
Phase Resistance (Ohm) 1.8
Phase Inductance (mH) 3.2
Holding Torque (N.cm) 52
Detent Torque (N.cm) 2.6
Rotor Inertia (g.cm2) 68
Lead Wire (No) 4
Motor Weight (g) 400

dc42

What type of printer is it, which firmware version are you running, and what is your extruder steps/mm ?

Veti

its a Hypercube Fusion CoreXY with linear rails.
Duet Maestro with Firmware Version: 2.02(RTOS) (2018-12-24b1)
Extruder Steps are 415 for Bondtech BMG

dc42

I'm not and expert on CoreXY machines. I've seen a number of threads about similar artefacts on CoreXY machines. AFAIR the pitch of the artefacts generally matches the belt pitch, and the cause is generally friction. Using non-toothed idlers may also contribute.

Until you resolve this issue, I suggest you use spreadCycle mode for the X and Y drivers, also run them at higher rather than lower current.

Veti

the steppers havent arrived yet.
but this seems to be a common problem
see these benchys from a prusa.
https://youtu.be/FAXUjZZER5E?t=563

Phaedrux

@veti said in Artefacts on walls:

the steppers havent arrived yet.
but this seems to be a common problem
see these benchys from a prusa.
https://youtu.be/FAXUjZZER5E?t=563

That looks like plain old ringing to me though.

Veti

ok my 0.9 stepper motors arrived.

Looks ok from this angle

Same Cube, different angle, but still a lot better than before

However now i am getting layer shifts (as seen at the bottom layer), so i have to do some more tuning.

Veti

the layer shifts were due to the lowered stealthchop -> spreadcycle switchover.

its not that important but i think it would be more consistent to specify the V Parameter in M569 as mm/s rather than clock cycles

dc42

@veti said in Artefacts on walls:

its not that important but i think it would be more consistent to specify the V Parameter in M569 as mm/s rather than clock cycles

Then we would need to reprogram the stepper drivers when you set the steps/mm. So I compromised with setting the TPWMTHRS value but reporting the corresponding speed too. Also bear in mind that these are belt speeds, which for CoreXY, delta. SCARA| etc. printers are not the same as head speeds.

Veti

so i bought an ender 3 on sale and was surprised to find the same artefacts on the wall. I have not done much tuning on the machine yet.
This is using a board with marlin 2.0

so am i beeing to picky and there are inherent artefacts for 3d printing?

dc42

I can think of three likely causes of artefacts like that, that go all the way across the face (not just at the leading edge, which is symptomatic of ringing):

Belt issues. If that's the case then the pitch will be related to the belt tooth pitch and will not vary with layer height or extrusion width. A possible cause is the use of smooth idlers instead of toothed ones.
Motor issues (least likely). In this case the pitch of the artefacts will be a multiple of full motor steps, most likely it will be 1, 2 or 4 full steps.
Extruder issues. In this case then the pitch will decrease if you increase layer height or extrusion width. A possible cause is the use of an ungeared extruder with low steps/mm. Remedies include increasing extruder microstepping, changing from a 1.8deg to a 0.9deg motor, or changing to a geared extruder.