Delta calibration problem

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Sep 25, 2020, 2:14:52 AM9/25/20
to Delta robot 3D printers
Hi everyone, I need help with my Tevo Little Monster, I'm about to throw this thing in the trash. I have bought a used Littel Monster. Unfortunately I can not calibrate the printing bed with the best will in the world. In at least one corner the hotend is always too far away from the printing bed or too close to it. In some places the hotend is so close to the printing bed that it scratches the bed and in some places it is about 2mm above the printing bed. I have already tried the following things: I have disassembled the complete printer and built the frame perfectly right-angled, the frame is if I can trust my sensor on 0.05° straight. I tried the "normal" delta calibration and the least squares (David Crocker variant) calibration. Unfortunately I can't check the length of the Delta arms because the previous owner damaged the screw heads and I don't want to drill out the screws until I have new arms. The effector wobbles about 1mm in all directions, could that be the problem? i have already planned the following steps, but i am afraid to waste even more money. Could you give me a hint if my next steps could solve the problem? I would like to exchange the printing bed for a glass plate to have it as flat as possible. I want to exchange the mainboard for a Duet Wifi. I want to install a Duet Smart Effector. I want to install Haydn Huntley's MagBallArms. Could these steps fix the problem? Did I forget important information so you can help me? Please let me know if you need more information.  

John Silvia

Sep 25, 2020, 12:31:58 PM9/25/20
to Delta robot 3D printers
A quick google suggests the arm length is 397.19. Did you mean that you can't confirm that number?
Did your "normal delta calibration" include adjusting the end stops?
When you say "one corner is always too far" etc., is it reproducible?  Always the same corner by the same amount if you don't change anything?
I don't think the effector wobble can be the problem; but your printer is useless until it is fixed.

Since you are talking about replacing just about everything but the frame and carriages, I'd say that will probably fix it. Just check your belts and pulleys.

Edward Simpson

Sep 26, 2020, 12:12:26 PM9/26/20
to Delta robot 3D printers
If the effector is wobbling by that much, then the joints on the existing arms are shot, you'd have to rebuild or replace them at minimum to fix it. Going the Duet upgrade path will definitely fix that issue as long as the carriages and towers are still good, along with adding the bonus of making it self-calibrating.
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