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Marlin 1.1 RC2 Auto Calibration help

Posted by nebbian 
Marlin 1.1 RC2 Auto Calibration help
November 18, 2015 11:19PM
I've been printing with my Kossel Mini for a couple of months, it's working really well for me.

However the calibration is completely manual at the moment. If I notice that the skirt is printing a bit thicker on one side, then I do the paper test in 4 places and adjust my endstop screws until it prints flat. This system only takes a couple of minutes to do, and is accurate enough to work well.

What I would like to know is how to get the marlin autocalibration to work.

I have a working Z probe, with repeatability of better than 0.02mm.

Typing "G29" into Pronterface makes it deploy the probe, probe the whole bed in a grid pattern, then retract the probe. However I'm not sure that this process then adjusts its internal representation of the bed to print on it properly. I've spent two days searching for this information but it really isn't obvious to me what I'm supposed to do.

To be honest I don't need any more than three points, my bed is flat enough as it is and manual calibration works well enough so that I just want to avoid having to do the paper test occasionally.

Can anyone who has automatic bed levelling on a delta using Marlin please let me know what commands to send, to get Marlin to reset where it thinks the bed is, based on the probe?

Thanks in advance.
Re: Marlin 1.1 RC2 Auto Calibration help
November 19, 2015 12:15AM
G29 auto LEVELing

You run a print and you add g29 after g28 in your gcode file.
That way it will probe the bed and build a new plane of what the bed is.
Then it will use that as Z 0.

Now G30 A is auto calibrate. This probes the bed and adjusted end stops, rods, raduis etc.. . Which woukd be the same as manual calibrating the printer.
Re: Marlin 1.1 RC2 Auto Calibration help
November 19, 2015 03:35AM
AFAIK G30 A is not part of Marlin 1.1.RC2, but RichCattels branch.

G29 levels the bed and has to be send every time you start a print. The important part is the z-probe-offset, which allows you to adjust the nozzle height.
I've seen no difference with or without G29 on my delta, because I had trouble with a leaning tower. Now I'm rebuilding it with robotdigg aluminium corners. ( fingers crossed )
Re: Marlin 1.1 RC2 Auto Calibration help
November 19, 2015 08:11AM

Yes you are correct. It slip my mind since i only use RichC for delta type printers.
Re: Marlin 1.1 RC2 Auto Calibration help
November 19, 2015 09:02AM
Thanks guys.

I had a good play with it tonight, and it looks like it does actually take note of the probe points when it does the G29. For some reason I'm getting better results when manually calibrating rather than using G29, but I haven't really gotten it dialled in yet.

Thanks again for your assistance.
Re: Marlin 1.1 RC2 Auto Calibration help
November 19, 2015 03:19PM
Consider switching to Rich Cattells marlin and then you can use g30 A to auto calibrate. Its quite good and saves a lot of messing about. If it fails to resolve a solution then you have something loose/bent/poor probe reproducibility etc...

Using this I get excellent results which I wasn't getting from manually calibrating. If you are not sure if g29 makes a difference put something like a thick coin under the probe when it probes a certain point, then when it's done move to that point you'll see the nozzle lift. I've had it accidentally mark one probing point as 30mm above the bed, it's quite interesting to watch it rise above this point when printing.
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