Kossel calibration problems
February 19, 2017 09:24PM
Hello! First time posting on the forum smiling smiley
I am having an unusual (and frustrating) problem with my Kossel from RenRen3D.
The first layer print is uneven, with parts of the print with the nozzle far from the bed, and other parts where the nozzle is too close to the bed, as seen in the photo.

I have ran G32 with M500 and G29 in the GCode. The G32 and G29 work fine, there is no issue with it.
I thought the issue was caused by carriage wobble, but after fixing that, the problem still persisted.

M501 is below:

echoconfused smileytored settings retrieved
echoconfused smileyteps per unit:
echo: M92 X100.00 Y100.00 Z100.00 E150.50
echo:Maximum feedrates (mm/s):
echo: M203 X999.00 Y999.00 Z999.00 E999.00
echo:Maximum Acceleration (mm/s2):
echo: M201 X9000 Y9000 Z9000 E9000
echo:Acceleration: S=acceleration, T=retract acceleration
echo: M204 S3000.00 T3000.00
echo:Advanced variables: S=Min feedrate (mm/s), T=Min travel feedrate (mm/s), B=minimum segment time (ms), X=maximum XY jerk (mm/s), Z=maximum Z jerk (mm/s), E=maximum E jerk (mm/s)
echo: M205 S0.00 T0.00 B20000 X20.00 Z20.00 E40.00
echo:Home offset (mm):
echo: M206 X0.00 Y0.00 Z0.00
echo:Endstop adjustement (mm):
echo: M666 X-1.12 Y0.00 Z-1.69
echotongue sticking out smileyID settings:
echo: M301 P22.20 I1.08 D114.00
open | download - P_20170218_2240361.thumbnail.jpg (112.7 KB)
Re: Kossel calibration problems
February 19, 2017 09:39PM
Looks to me like a combination of frame twist, wrong diagonal length in firmware (or wrong steps/mm), and poor geometry.

To start with, measure your diagonal rod length from the centre of one ball, to the centre of the other ball, and put that into the firmware.

Then go through your frame with a set of calipers, and ensure that the distance between towers is all exactly the same (to within 0.05mm, measured at both top and bottom of the towers).
Then get your bed at exactly 90 degrees to your towers.

Then, go here:

and run through a calibration. If you don't have a probe you'll have to use a piece of paper to figure out your nozzle height.

That should keep you busy for a little while smiling smiley

Edited 1 time(s). Last edit at 02/19/2017 09:40PM by nebbian.
Re: Kossel calibration problems
February 23, 2017 08:53PM
Thanks for the very detailed post smiling smiley

It's been a long week of troubleshooting for me, so far I've fixed:
the belt slipping over the bearings at the top of the frame
Minor twisting of the frame
A loose bed
wobbling carriages causing the effector to tilt

The issue still persists, though, and when I used the program, I got the result in the image that the printer could not reach the points specified
open | download - IMG-20170224-WA0001.jpg (110 KB)
Re: Kossel calibration problems
February 23, 2017 09:11PM
Hmmm, those numbers look OK to me. Perhaps it might be that the code can't handle negative endstop corrections? Try adding 3 to all endstop correction values and see if the calculator works. Either way, email the auther (DC42) for help.
Re: Kossel calibration problems
February 23, 2017 10:36PM
I think I got a value wrong - the printer radius is the distance between the start of the diagonal rod and the carriage (horizontal distance), i was measuring from the centre of the printer to the smooth rod centre
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