Kossel Mini bed leveling problem
Posted by tomasf
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Kossel Mini bed leveling problem December 14, 2015 04:22PM |
Hi,
I'm using a T3P3 Kossel Mini R3 (Duet 0.8.5, RepRapFirmware 1.09m+1-dc42) with an IR probe for autocalibration. Yet, I never seem to get a proper bed level. On the side of the bed facing the Z tower, filament is laid out further from the surface. I can adjust the Z offset manually, of course, but then the level is too close on the opposite side. It doesn't matter much for smaller prints, but it gets really problematic for prints with a larger footprint.
Here's a typical example. To the left, the line is squished against the bed. The wavy lines on the bottom get worse towards the right side where the filament loses grip:
What could I be doing wrong? Is there something that needs to be adjusted hardware-wise? Any ideas? Thanks!
Here's a log where I do three G32s and print the M665 and M666 afterwards (in reverse chronological order), in case that's useful info:
I'm using a T3P3 Kossel Mini R3 (Duet 0.8.5, RepRapFirmware 1.09m+1-dc42) with an IR probe for autocalibration. Yet, I never seem to get a proper bed level. On the side of the bed facing the Z tower, filament is laid out further from the surface. I can adjust the Z offset manually, of course, but then the level is too close on the opposite side. It doesn't matter much for smaller prints, but it gets really problematic for prints with a larger footprint.
Here's a typical example. To the left, the line is squished against the bed. The wavy lines on the bottom get worse towards the right side where the filament loses grip:
What could I be doing wrong? Is there something that needs to be adjusted hardware-wise? Any ideas? Thanks!
Here's a log where I do three G32s and print the M665 and M666 afterwards (in reverse chronological order), in case that's useful info:
22:10:45 CET M666 Endstop adjustments X1.28 Y0.45 Z-1.73 22:10:43 CET M665 Diagonal 215.00, delta radius 105.11, homed height 241.53, bed radius 85.0, X 0.49°, Y 1.19°, Z 0.00° 22:10:35 CET G32 Calibrated 6 factors using 10 points, deviation before 0.163 after 0.113 22:09:48 CET M666 Endstop adjustments X1.41 Y0.12 Z-1.53 22:09:47 CET M665 Diagonal 215.00, delta radius 105.12, homed height 241.59, bed radius 85.0, X -0.56°, Y 0.48°, Z 0.00° 22:09:42 CET G32 Calibrated 6 factors using 10 points, deviation before 0.172 after 0.135 22:08:53 CET M666 Endstop adjustments X1.18 Y0.44 Z-1.61 22:08:52 CET M665 Diagonal 215.00, delta radius 105.01, homed height 241.57, bed radius 85.0, X 0.32°, Y 1.14°, Z 0.00° 22:08:34 CET G32 Calibrated 6 factors using 10 points, deviation before 0.350 after 0.088
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Re: Kossel Mini bed leveling problem December 17, 2015 04:21PM |
Thank you for that analysis 
I still have some different endstops lying around so I'll just replace them and then try again. But having a closer look at the state of my endstops I noticed that the mounts seem to have taken some damage in the past, there obviously is some week point where layers started separating; this might be the reason for some inaccuracy. I attach a photo (I only now notice how dusty my setup is ...). I just printed new endstop mounts and will replace them tomorrow while replacing the microswitches.
I had the speeds in all G1 S2 lines set to a lower value -- it's good to know that I can keep high speed for the first run!
My autocalibration only homes before probing the points, I use a modified bed.g from your distribution, with only some probe points modified so that layer cooling fan duct etc. don't collide with anything, here it is:
Is this okay?
I still have some different endstops lying around so I'll just replace them and then try again. But having a closer look at the state of my endstops I noticed that the mounts seem to have taken some damage in the past, there obviously is some week point where layers started separating; this might be the reason for some inaccuracy. I attach a photo (I only now notice how dusty my setup is ...). I just printed new endstop mounts and will replace them tomorrow while replacing the microswitches. I had the speeds in all G1 S2 lines set to a lower value -- it's good to know that I can keep high speed for the first run!
My autocalibration only homes before probing the points, I use a modified bed.g from your distribution, with only some probe points modified so that layer cooling fan duct etc. don't collide with anything, here it is:
; Auto calibration routine for delta printers ; Before running this, you should have set up your zprobe Z offset to suit your build, in the G31 command in config.g. M561 ; clear any bed transform, otherwise homing may be at the wrong height G31 X0 Y0 ; don't want any probe offset for this G28 ; home the printer ;*** Remove the following line if your Z probe does not need to be deployed ;M98 Pdeployprobe.g ; deploy the mechanical Z probe ; The first time the mechanical probe is used after deployment, it gives slightly different results. ; So do an extra dummy probe here. The value stored gets overwritten later. You can remove this if you use an IR probe. ;G30 P0 X0 Y0 Z-99999 ; Probe the bed and do 6- or 7-factor auto calibration G30 P0 X-66 Y-30 Z-99999 ; X tower G30 P1 X0 Y-66 Z-99999 ; between X and Y towers G30 P2 X66 Y-30 Z-99999 ; Y tower G30 P3 X46 Y42 Z-99999 ; between Y and Z towers G30 P4 X6 Y62 Z-99999 ; Z tower G30 P5 X-56 Y28 Z-99999 ; between Z and X towers G30 P6 X-36.8 Y-21.25 Z-99999 ; half way to X tower G30 P7 X36.8 Y-21.25 Z-99999 ; half way to Y tower G30 P8 X0 Y42.5 Z-99999 ; half way to Z tower G30 P9 X0 Y0 Z-99999 S6 ; centre, and auto-calibrate 6 factors ;*** Remove the following line if your Z probe does not need to be retracted ;M98 Pretractprobe.g ; retract the mechanical Z probe G1 X0 Y0 Z150 F15000 ; get the head out of the way of the bed
Is this okay?
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Re: Kossel Mini bed leveling problem December 19, 2015 06:15AM |
Nr. 4 (mostly) was it for me, thank you!
I first noticed that indeed the bearing spacing at the carriages was approx. 0.4mm less than the bearing spacing on the effector (strange, because all parts came from the same vendor). However, as this was the same over all three rod pairs, I suppose this can't be the problem.
Although I could not find any play while trying every single screw and joint, I decided to put rubber bands between the rods and hold the bowden tube with a sling so that it enters the effector as vertically as possible. This made a huge difference. I still have some slight differences, but the situation is MUCH better now. I will continue going for the other aspects to see if there is still room for improvement, but large pieces should not pose a problem anymore
Thank you very much, dc42!
I first noticed that indeed the bearing spacing at the carriages was approx. 0.4mm less than the bearing spacing on the effector (strange, because all parts came from the same vendor). However, as this was the same over all three rod pairs, I suppose this can't be the problem.
Although I could not find any play while trying every single screw and joint, I decided to put rubber bands between the rods and hold the bowden tube with a sling so that it enters the effector as vertically as possible. This made a huge difference. I still have some slight differences, but the situation is MUCH better now. I will continue going for the other aspects to see if there is still room for improvement, but large pieces should not pose a problem anymore
Thank you very much, dc42!
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Re: Kossel Mini bed leveling problem December 19, 2015 02:18PM |
Hi. OP here again.
Thanks for your helpful tips, David! I've done a lot of testing, and it took me a while to reply because I wasn't sure what to make of the results. Before, I was convinced the bed surface wasn't the problem, because I had the same bed level problems a while before I even started using PEI. But after doing some pretty conclusive tests, I have to admit I was wrong, as it definitely seems my PEI surfaces are at fault.
Printing on blue tape (on top of glass), my test prints look fine. The level isn't perfect, but not far from it, and compared to the PEI results, it's night and day.
I have two PEI plates, both attached to glass plates with 3M adhesive tape (the adhesive is the pattern you see in the picture), and both behave the same way. I then tried sanding one with a rough sandpaper to make it more opaque, but that had the opposite effect; the IR probe did not detect the surface properly at all and the nozzle buried itself into the bed. Sanding it further with finer grit sand paper helped somewhat, but it still smashes the nozzle into the bed sometimes, so it's still worse than the non-sanded surface. And yes, there's a black sheet of paper between the glass and aluminium.
Here's a good example, printing a test spiral on PEI (non-sanded) and blue tape.
PEI:
Blue tape:
I had such high hopes for PEI. Prints stick so well and detach so easily when done, and there's almost no need for much maintenance. But I guess I need to go back to something else
Edited 2 time(s). Last edit at 12/19/2015 03:13PM by tomasf.
Thanks for your helpful tips, David! I've done a lot of testing, and it took me a while to reply because I wasn't sure what to make of the results. Before, I was convinced the bed surface wasn't the problem, because I had the same bed level problems a while before I even started using PEI. But after doing some pretty conclusive tests, I have to admit I was wrong, as it definitely seems my PEI surfaces are at fault.
Printing on blue tape (on top of glass), my test prints look fine. The level isn't perfect, but not far from it, and compared to the PEI results, it's night and day.
I have two PEI plates, both attached to glass plates with 3M adhesive tape (the adhesive is the pattern you see in the picture), and both behave the same way. I then tried sanding one with a rough sandpaper to make it more opaque, but that had the opposite effect; the IR probe did not detect the surface properly at all and the nozzle buried itself into the bed. Sanding it further with finer grit sand paper helped somewhat, but it still smashes the nozzle into the bed sometimes, so it's still worse than the non-sanded surface. And yes, there's a black sheet of paper between the glass and aluminium.
Here's a good example, printing a test spiral on PEI (non-sanded) and blue tape.
PEI:
Blue tape:
I had such high hopes for PEI. Prints stick so well and detach so easily when done, and there's almost no need for much maintenance. But I guess I need to go back to something else
Edited 2 time(s). Last edit at 12/19/2015 03:13PM by tomasf.
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