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Auto level does not seem to be working

Posted by StlLooking 
Auto level does not seem to be working
August 23, 2018 07:00PM
Hi All,

It is the latest Smoothie version from GitHub, edge-24da5ce

The pic is what I got. It's a glass bed on top of shiny aluminum so please ignore the double images.
The important part is the thinning at the back. The glass is perfectly flat. And, yes I do have the M375 command in the GCode file.

Am I doing something wrong with the sequence below?

This is what I did with micro-switch probe.

PROBE LEVELS
G28 (Home XYZ)
 1:    G32       Calibrate the machine
 2:    M500      Save probe results
 3:    G28       Home XYZ and the Jog down and Touch Bed
 4:    M306 Z0   Set and Save the Z-Offset
 5:    M500      Save homing offset
 6:    G28

GRID MESH
 1:    G28       Home XYZ
 2:    G31       Probe the grid
 3:    M374      Save grid to SD card
 4:    M500      Save probe results
 5:    M375      Add Grid command to SD card
 6:    G28       Home XYZ and the Jog down and Touch Bed
 7:    M306 Z0   Set and Save the Z-Offset
 8:    M500      Save homing offset
 9:    G28

Edited 2 time(s). Last edit at 08/23/2018 07:05PM by StlLooking.
Attachments:
open | download - smoothie-01.jpg (43.8 KB)
Re: Auto level does not seem to be working
August 24, 2018 07:48AM
This could simply be something with how the probe measurements are done, interracting in a weird way with your machine geometry. Can you try changing ( increasing or reducing ) the grid resolution and seeing if it changes the effect ?
Re: Auto level does not seem to be working
August 24, 2018 11:44AM
Thanks for th reply, I am redesigning the probe to give a more direct switching motion for the micro-switch.

The current version uses a sliding rod to trip the switch. I am now mounting the switch directly at the bottom of the probe and that will contact the glass directly.

Will try again when new mount is done and get back you.
Re: Auto level does not seem to be working
August 28, 2018 02:29PM
Quote
arthurwolf
This could simply be something with how the probe measurements are done, interracting in a weird way with your machine geometry. Can you try changing ( increasing or reducing ) the grid resolution and seeing if it changes the effect ?

OK, it might have been partly the probe as I made a rigid mounted micro-switch version using a special Omron switch designed for such probing use. Like the one shown in this assembly.
[www.amazon.com]

Anyway, the leveling improved a little but the first layer is still thin in the rear as the OP-pic showed. It is definitely not the glass as I checked that on my granite surface plate. The only thing that changed when using different grid resolutions etc was that the thin section rotated slightly (about 5-deg) to the right or left.

For it to be thin over such a short section -and- rotating slightly left/right, seems to indicate the algorithm.
Re: Auto level does not seem to be working
August 28, 2018 06:01PM
Well, the algorithm is known to work perfectly on perfect surfaces.

It might be over-reacting to something barely detectable though, maybe due to some lack of luck with how the grid aligns with the physical thing ? Maybe .. it's all speculation really, I can't really think of anything obvious.
Re: Auto level does not seem to be working
August 30, 2018 02:32PM
Thanks, about ready to give up on the Deltas. Time to experiment with the CoreXY. Seems like it might be the best of both worlds for Delta-speed and Cartesian-accuracy.
Re: Auto level does not seem to be working
August 30, 2018 02:47PM
I think the effect you are seeing is really the result of an extremely small height difference, and if you just increased your initial layer height by a very small value ( maybe 0.05mm or even less ) you wouldn't see it anymore and you could print just fine. Sometimes "a bit less than perfect" is good enough smiling smiley
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