CoreXY & 0.9° steppers too much for 8bit ?

o_lampe

CoreXY & 0.9° steppers too much for 8bit ?
February 27, 2017 06:58AM

Registered: 8 years ago
Posts: 5,232

I'm using 0.9° steppers for X and Y axis with an 8bit rumba board and 200steps/mm.
The printhead starts to stutter at speeds above 50mm/s.
I printed a big cylinder in "vase mode". So there are lots of bits to chew...but that's what burn_in tests are for!
At first I blamed Octoprint and USB speed, but when I tried to print from LCD SD card it was the same. Turning the encoder already makes it stutter.

Is there a magic parameter, like delta segments/second I can change to gain speed? ( Marlin RC8 )

Thx
-Olaf

Edited 2 time(s). Last edit at 02/27/2017 07:01AM by o_lampe.

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dc42

Re: CoreXY & 0.9° steppers too much for 8bit ?
February 27, 2017 07:31AM

Registered: 10 years ago
Posts: 14,672

Is the printer missing steps when it stutters? If so, it may mean you are using 12V power and you need more voltage to drive the 0.9deg motors with sufficient torque at high speeds. See [duet3d.com] for how to work out the voltage needed.

If it is not missing steps when it stutters, then I guess you have met some firmware or processor speed limitation. But I would be surprised if it is a processor speed limitation, because 100mm/sec @ 200steps/mm is only a step pulse rate of 20kHz, whereas I have seen 40KHz claimed for Marlin on a 16MHz atmega2560.

Edited 2 time(s). Last edit at 02/27/2017 07:32AM by dc42.

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

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o_lampe

Re: CoreXY & 0.9° steppers too much for 8bit ?
February 27, 2017 03:51PM

Registered: 8 years ago
Posts: 5,232

The Rumba already runs on 24V. It seems the SD-card data stream is still to slow for vase mode.
I've printed another part with lots of 45° infill to test each stepper separately and I could print a lot faster.

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nebbian

Re: CoreXY & 0.9° steppers too much for 8bit ?
March 02, 2017 10:53PM

Registered: 8 years ago
Posts: 916

Which slicer are you using?

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o_lampe

Re: CoreXY & 0.9° steppers too much for 8bit ?
March 03, 2017 01:05AM

Registered: 8 years ago
Posts: 5,232

Slic3er 1.29..
I also have another prob with Octopi and LCD not working at the same time.
I remember, I have defined a feature like " keep_host_alive" that might slow down my printing process and cause the crashes with Octopi. Will flash RC8 again without this option and test again..
Funny sidenote:
I've defined both thermistors as Dummy-thermistors for testing. They fake fixed temps for bed and hotend. But still the board crashes with " HEATER FAULT" failure..

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Pheneeny

Re: CoreXY & 0.9° steppers too much for 8bit ?
March 03, 2017 04:28PM

Registered: 7 years ago
Posts: 41

I think I ran into a similar wall using 1.8 degree steppers, but mine was around 80mm/s. Straight lines look great, curves get random small little blobs where the print head stuttered. Disabling the RepRapDiscount Full Graphic LCD helped a bit, but I would still get blobbing at 80, so i settled for slowing down the LCD refresh.

I have a Re-Arm coming that I hope will help move faster.

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o_lampe

Re: CoreXY & 0.9° steppers too much for 8bit ?
March 04, 2017 02:45AM

Registered: 8 years ago
Posts: 5,232

I tried to print a cylinder with 30mm diameter and 100 facets. I thought it would run smooth, but the printhead still stutters. I'll go for RADDS and RRF.
Good bye 8bit-$hit tongue sticking out smiley

PS: I was able to print straights at 120mm/s, but how should I set the slicer to run fast on straights and slow down in curves? The only thing I can think of is super slow acceleration settings, but that would mess up edges. Also filament temp would be hard to keep stable.
8bit= too many compromises...

Edited 1 time(s). Last edit at 03/04/2017 02:53AM by o_lampe.

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o_lampe

Re: CoreXY & 0.9° steppers too much for 8bit ?
March 04, 2017 07:46AM

Registered: 8 years ago
Posts: 5,232

I changed from Rumba to RADDS board but kept everything else the same. Now I have much more resonance issues than before. It seems the steppers itself causes resonance, not the frame/rails.

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Pheneeny

Re: CoreXY & 0.9° steppers too much for 8bit ?
March 04, 2017 12:27PM

Registered: 7 years ago
Posts: 41

Is this resonance different than the stuttering you had before? Did the stuttering go away after you upgraded?

Edited 1 time(s). Last edit at 03/04/2017 12:37PM by Pheneeny.

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o_lampe

Re: CoreXY & 0.9° steppers too much for 8bit ?
March 05, 2017 03:09AM

Registered: 8 years ago
Posts: 5,232

The resonance with 8bit cpu was around 50mm/s it went away when I moved faster ( straight long lines )
Now with RADDS, the resonance starts at 45mm/s and doesn't disappear at higher speed. But the head doesn't stutter anymore.

I'm afraid the microstepping-switches are not switching to "open" when OFF, so the TMCs are in a different mode. ( No schematics of RADDS available )

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Pheneeny

Re: CoreXY & 0.9° steppers too much for 8bit ?
March 07, 2017 01:36AM

Registered: 7 years ago
Posts: 41

Finally got up and running with the Re-Arm and Smoothies are, and the stuttering is gone. So definitely hitting a speed wall with Marlin.

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o_lampe

Re: CoreXY & 0.9° steppers too much for 8bit ?
March 07, 2017 02:04AM

Registered: 8 years ago
Posts: 5,232

That's weird, since the math behind a CoreXY's kinematic is simple and straightforward. I've checked my code back and forth, if I had some bedleveling active without probing the bed.

I could've tried an old stable Marlin version, but RADDS installation was so much easier. ( especially for Multi-color mixing )

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o_lampe

Re: CoreXY & 0.9° steppers too much for 8bit ?
March 07, 2017 05:41AM

Registered: 8 years ago
Posts: 5,232

RADDS unleashed! eye popping smiley

After finding the reason for the vibrating steppers, I replaced the RAPS128 drivers on X & Y axis of my CoreXY with the CF1-modded TMC's
Not only can I print small circles much faster, but I could also crank up the acceleration from 500 to 2000mm/s²!
The printer almost jumps from the table now grinning smiley

And it is still silent in spreadcycle mode.

Replacing drivers: save ~10$ each ( TMC2100 vs RAPS128 )
Fat grin on my face: priceless

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