Baby stepping steps back.
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I am revamping a Prusa i3 I built about 5 years ago with a Duet wifi board and a Geeetech touch probe. I have forgotten most of what I learnt previously it would appear. I am having a problem with setting the z height. I have it adjusted to basically print but on the first layer the print head needs to be closer to the bed. When I baby step closer the head moves down momentarily then steps back to the original position. It wont lower permanently irrespective of the number of steps I make. When I calibrate the Z probe trigger height all goes well but I have a difficulty with para 10 as I dont appear to a have a "config-overide g" file. Any thoughts on where I'm going wrong?
Regards John. -
@johnmaundrell, just a quick thought on this - what is your minimum Z limit? Are you trying to go below that limit? This is what I have in my config.g (note the Z -0.5 part)
; Axis Limits
M208 X8 Y5 Z-0.5 S1 -
@johnmaundrell I reported this year's ago and even provided a video. Deny deny deny...
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@jens55 I dont really understand how the minimum Z value is noted in the code or the relationship between trigger height and minimum Z height. If you could explain this it would help many thanks.
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@jens55 My M208 X0 Y0 Z0 S1
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@johnmaundrell RRF doesn't let you go outside the machine limits. So when you babystep lower than Z0, because your lower Z limit is 0, it won't go any further. Setting it to Z-1 allows you to go below 0
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@jay_s_uk Ok thanks understand that. Can you tell me which command sets the actual trigger height please.
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@johnmaundrell G31 in your config.
There is a process for calibrating the trigger height
https://duet3d.dozuki.com/Wiki/Test_and_calibrate_the_Z_probe#Section_Calibrate_the_Z_probe_trigger_height -
@jay_s_uk I have tried this set up but it appears that after I set it all up it fails to save the data and then reverts back to the original setting. I can also only set it up in the homed position not in the centre of the bed.
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@johnmaundrell M564 S0 dosent disable the axis position
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@johnmaundrell you need to save the probe offset yourself. config.g is never changed unless you're the one doing the change.
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@johnmaundrell I have to go out now but I will try again this evening thanks everyone so far for your help. I will gradually get a better understanding with your help. G31 is a good start.
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@johnmaundrell Ahh I was thinking probe offset was only XY not Z as well!!!
