Running auto bed compensation at start of print.
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Here are two options:
1. After the G28 command, add G29 to run mesh bed probing.
2. After the G28 command, run G29 S1 to load the height map previously generated by mesh probing. Then use a G1 command to place the nozzle 5mm above bed centre, followed by G30 to probe once and set the Z height.
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OK, thank you David.
I'll try that in a day or 2 (work calls) and get back to you with how it went.
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Ok,
So I decided I'd prefer to go with the first option, and run a full probe at the start of each print.
In the starting script in S3D, I added G29:
G28 ; home all axes
G29 ; bed probingNothing happened at all.
It it homed, probed the center and started the print as usual.
What would be nice would be a homeall script that incorporated the lot….homed x and y, then ran the mesh bed probing and ended up in the center, then started the print.
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Did you define the probing grid using the M557 command in config.g? Were there any error messages on the console?
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Did you define the probing grid using the M557 command in config.g?
No, how do I do that (in laymans terms please)?
I see no M557 in my config.g file.
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OK,
So my config.g file there is no M557 line at all.
In my bed.g file there is this:
; Probe the bed at 5 points
G30 P0 X15 Y15 H0 Z-99999
G30 P1 X15 Y180 H0 Z-99999
G30 P2 X180 Y180 H0 Z-99999
G30 P3 X180 Y15 H0 Z-99999
G30 P4 X97.5 Y97.5 H0 Z-99999 SSo should I be adding to my config.g file the following?:
M557 P0 X15 Y15
M557 P1 X15 Y180
M557 P2 X180 Y180
M557 P3 X180 Y15
M557 P4 X97.5 Y97.5OR, could I enter this and probe more points:
M557 X15:180 Y15:180 S15
And if so, where would I enter these lines? In general preferences below M208?
Is 5 points enough for my 200x200 bed?
What I don't get is why it's already there in bed.g and works when I click the auto bed compensation button in the DWC, but can't be activated in the start script all the same.
Am I actually getting any bed compensation at the moment, or as it is is it just giving me a visual indication of the state of my bed?
I am trying here, but I think it's been well and truly established previously that I'm not the gcode or IT specialist.
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See the link posted by DjDemonD 2 posts earlier.
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See the link posted by DjDemonD 2 posts earlier.
Yes I did thank you, and the question just below was to ask which of the 2 forms offered in the wiki would be best for me, as well as a question that wasn't answered there.
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The first form of M557 (specifying individual points) is no longer supported from firmware 1.18 onwards, so use the second.
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I've set the bed.g file as follows:
; bed.g
; called to perform automatic bed compensation via G32
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; generated by RepRapFirmware Configuration Tool on Sat Oct 22 2016 18:28:19 GMT+1100 (AUS Eastern Daylight Time); Clear any bed transform
M561; Home all
G28; Probe the bed
G29; Absolute positioning
G90; Go to center bed probe point and home the Z axis
G1 X97.5 Y97.5 F4800G30
; Uncomment the following line to lift the nozzle after probing
G1 Z50 F500But the console shows I ran a G32 instead of a G29, and the values are different to the mesh map
6:06:07 PMG32
25 points probed, mean error -0.129, deviation 0.124
Height map saved to file heightmap.csvWhat have I missed here?
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The console will show that you ran G32 because that is the command you sent from the console.
What exactly do you mean by "the values are different to the mesh map"?
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Thank you,
The mesh map graphic screen that comes up at the end of the probe shows these results:
Number of probe points: 25
Probe area: 256.0 cm²
Maximum deviations: -0.312 / 0.104 mm
Mean error: 0.118 mmRMS error: 0.147 mm
Yet the G code console shows this:
G32
25 points probed, mean error -0.076, deviation 0.125
Height map saved to file heightmap.csv
If you look at my bed.g file above, I removed G32 and the 5 point routine and replaced it with G29.How am I still sending G32?
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1. The auto bed compensation button in DWC sends G32. That command runs the bed.g file.
2. You are correct, DWC displays different deviation data from the console:
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in the console, the mean error is just the average height error, which may be positive of negative. In DWC is it the average absolute error, so it will always be positive.
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in the console, the deviation is the RMS deviation from the mean, so it is the deviation after subtracting out any error in the average Z-0 position. It is a measure of how flat the printing plane is, and will be zero if the bed is perfectly flat, even if probing detects that the Z=0 positions is out. In DWC ii is the RMS height error, so it is not a measure of flatness of the printing plane because it also includes any general area in the Z=0 position.
I'll discuss this with chrishamm, the author of DWC.
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Did I inadvertently stumble upon something there?
I've got the start script in S3D successfully running G29 now, and as the whole reason for wanting to do it was the varying bed temps I'm running, I'm happy to do it at the start of each print.
Thanks very much for the points as I get my head around the whole Gcode thing.
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Ok, so this has made a great improvement in my first layer.
In the starting script (in S3D) I added this, which is exactly the same as my bed.g file:
G29 S2
G28
G29
G90
G1 X97.5 Y97.5 F4800
G30
G1 Z5 F500I am now getting PERFECT and consistent first layer thickness right across the print, and have reduced my slicer Z offset from -0.25 to -0.1.
Mechanically my bed is leveled perfectly, but despite using cast ally precision plate there is still some runout which I've been struggling with.
While I didn't quite understand the explanation above regarding the difference between in the deviation data from the console, I can see quite plainly that (for my setup) this works and the other doesn't.
I'm also very happy with this method, as when using a different bed temp/material/profile, you're getting a bed compensation directly related to the exact bed conditions caused by that profile.
One weird thing though is that longer free movements between printing points are now jerky, short movements are unaffected.
I've touched nothing else but the bed.g file and added the same file to the slicer start script.
I strongly suspect that these jerky movements are the same 40mm long distance that I entered as the probing points.
It's had no bad effect so far, but is a little annoying.
Any reason this would happen?
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The reason for the jerky movements is the changes in Z speed due to mesh bed levelling. Increasing allowed Z jerk in the M566 command will get rid of it, if it doesn't cause the Z motor to skip steps.
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The reason for the jerky movements is the changes in Z speed due to mesh bed levelling. Increasing allowed Z jerk in the M566 command will get rid of it, if it doesn't cause the Z motor to skip steps.
Thanks David,
That was it, the lowest jerk setting I got it to work at was 1250, up from 900.
I took it up to 1400 with no skipping, but didn't like the feel of the machine at that setting. Less is more.
I had also took the XY steppers up from 1000 to 1100mA thinking that was the problem before that, but have left them there and all feels good.
This is working very well on all materials, and I would recommend others try this in their start script, as it's got to be more accurate than saving a mesh map at one bed temp then using it at a completely different temperature.
I'll leave it all as I have it set up now regarding bed leveling, thanks all for the help.
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I would recommend sending your head to 00 or better a negative position if possible then extruding 15mm of filament at the end of your start script this will make sure that when your print starts it is flowing and has a clean bed
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I would recommend sending your head to 00 or better a negative position if possible then extruding 15mm of filament at the end of your start script this will make sure that when your print starts it is flowing and has a clean bed
I'm not quite sure what that means, but I have my first layer at 150% height and 120% width, so my Z offset of -0.1mm is putting my first layer at 0.2mm with a bit more extrusion stuffed in there.
I'm running 2-4 rounds of brim in the first layer, depending on the size of the printed piece, and am having no problem with the nozzle being primed or bed adhesion at all.
First layers are pretty nice, bordering on beautiful, with a very minor elephants foot and stuck nicely to my printbite surface.
Nozzle zero height is set exactly as per the wiki instructions, and bed is leveled very carefully with a feeler guage.
If you're meaning something else, sorry please explain further, but I'm pretty happy with the result I'm getting here regarding my first layer.
**Sorry, you're meaning to but the nozzle hard onto the bed then extrude some plastic to "pressure it up" before printing?
Only concern I'd have there would be marking the print surface. Contrary to what they say, Printbite can be damaged by a hot nozzle pressing on it.
But sure, please give me an example of the script you'd use to do that and I'll try it.**
