G32 doesnt save after True Bed Leveling

[johny]

@droftarts i think finally i understood what you said, you say that the points on both Z leadscrews are at the same position relative to Z0 and leveled but they are not, the bed is 0,6mm off on the right. How should it look like my bed.g and homeall.g ?

@infiniteloop custom-made BLV cube

[droftarts]

@johny said in G32 doesnt save after True Bed Leveling:

but they are not, the bed is 0,6mm off on the right.

No, that's not quite right.

Leadscrew adjustments made: -0.649 -0.645, points used 2, (mean, deviation) before (-0.647, 0.001) after (0.000, 0.000)

-0.649 -0.645, points used 2: The first set of points is the measured variation from Z=0 for each point
(mean, deviation) before (-0.647, 0.001): This is the average (mean) of the two points, and the amount each is off (deviation) from this average.
after (0.000, 0.000): The "after" shows the average, and the deviation from average, it is after the correction.

So it is not off 0.6mm on the right. As far as the firmware is concerned, these two points are level with each other. They just happen to be 0.64mm below (or above, I can't remember which way the signs go) Z0 in the middle of the bed.

Like I said, do a bed mesh. It may be enlightening.

Ian

[johny]

@droftarts Will do it and record a video as well because after the first iteration only the right motor gets calibrated.
I will create another macro without G28 to see.

[jay_s_uk]

@johny thats typically the way RRF works. The first z motor remains static and the rest of the motors are adjusted to match the first

[droftarts]

@johny It applies a rotation around the origin ie X0 Y0 Z0. If your origin is front left, then yes, most of the movement will be on the right hand side. If your origin is in the middle, the adjustment is usually equal.

Ian

[infiniteloop]

@johny said in G32 doesnt save after True Bed Leveling:

custom-made BLV cube

Thank you. I just thought of the faint possibility of the Z-steppers loosing microsteps, but after all, I think @droftarts is on the right track.

[fcwilt]

@droftarts

I don't know if G32 behaves differently with two Z steppers but on my three stepper printer, which has 0,0 in the middle of the bed, it appears that the 1st Z stepper is not used during leveling.

I know when doing it on my printers with three "thumbscrews" for leveling, the adjustments have always called for on the 2nd and 3rd thumbscrews.

Which makes sense since the outcome will be the same as adjusting all three steppers/thumbscrews.

Frederick

[fcwilt]

@johny said in G32 doesnt save after True Bed Leveling:

@droftarts Will do it and record a video as well because after the first iteration only the right motor gets calibrated.
I will create another macro without G28 to see.

From the current docs on G32 and bed leveling:

If your bed is not perfectly flat or the gantry sags a little when the head is over the middle of the bed, the process will cause a small shift in the Z=0 position. To correct this, if you are using the Z probe to do Z homing, you can just re-home Z at the end of your bed.g file.

Based on that you want to keep the G28 Z

I don't home with the probe but I have always re-set the Z=0 Datum after leveling the bed.

Frederick

[johny]

What about G32 using absolute position instead of relative?

[droftarts]

@johny said in G32 doesnt save after True Bed Leveling:

What about G32 using absolute position instead of relative?

What are you trying to achieve? I don't think switching G32 to relative moves will make any difference, or it will produce an error, though I've never tried.

Ian

[johny]

@droftarts Just trying to be able to print correctly the first layer on the entire 300mm bed
I made a new macro and its correct, without the g28 it doesn't correct anymore.
How do you suggest starting the print? Like this?

G28 XY
M561 ; Clear any bed transform
G1 X1... Y... ; Move Probe to middle of bed
G30
G29 S1

[fcwilt]

@johny

It's just possible that using G28 Z is the source of the problem because, in addition to invoking homeZ.g, it first marks the axis as un-homed.

As I mentioned I don't home with the Z probe but I do set the Z=0 Datum after bed leveling by doing a G30 at the center of the bed, but it doesn't changed the homed state of anything that is already homed.

Maybe the un-homing that occurs with the G28 Z causes the firmware to "forget" the adjustments made during bed leveling.

Just thinking out loud here.

And since you are supposed to set the Z=0 Datum using the same XY position when creating the height map and when loading the height map you can follow the bed leveling with a G30 to set the Z=0 Datum and then load the height map and all should be fine.

It has always worked for me.

Frederick

[droftarts]

@johny That start should be fine. The G30 is setting Z0 at the bed centre anyway. And you are loading a bed mesh. What does your bed mesh look like? Maybe share a picture of the printer.

@fcwilt said in G32 doesnt save after True Bed Leveling:

I don't know if G32 behaves differently with two Z steppers but on my three stepper printer, which has 0,0 in the middle of the bed, it appears that the 1st Z stepper is not used during leveling.

I just tried it on my centre origin machine (with two leadscrews, left and right of the bed), definitely both leadscrews get adjusted around the centre, ie the origin.

@fcwilt said in G32 doesnt save after True Bed Leveling:

Maybe the un-homing that occurs with the G28 Z causes the firmware to "forget" the adjustments made during bed leveling.

As far as I can tell, there is no adjustment, just that both the probed points are -0.64mm from the Z datum sent at the bed centre. There's nothing to 'forget'. One way to test would be to run G32 with no Z homing or G30 after, and see at what height the nozzle hits the bed in the centre.

Ian

[fcwilt]

@droftarts

The screen shots the OP posted shows there were adjustments. The fact that they were the same doesn't mean the firmware wasn't turning the steppers trying to get both sides to read "0".

It is pretty clear that, as you mentioned, the bed is simply higher in the center than at the edges. So re-setting the Z=0 Datum in the center is going to once again make the edges read low.

You got it right early on - good job.

Frederick

[johny]

@fcwilt after several iterations and tryouts the problem is still there.
I can’t calibrate the first layer, the difference in the bed is very high… I dunno if it’s the compensation or something else. That’s why I was saying that the calibration wasn’t saved. I can post a picture of the printed 1st layer…
The mesh didn’t help btw @droftarts

[droftarts]

@johny Can you please at least post a picture of the bed mesh? As there's nothing else saved, ie there is not calibration with G32, it just levels the gantry with the information it gets from probing at the points you tell it to, there's very little else for us to go on. Maybe a picture of your machine that shows the whole bed, with an indication where it is probing. And yes, a picture of the first layer if you want.

Also, when you make a bed mesh, make sure any previous bed mesh is cancelled.

Ian

[fcwilt]

@johny

When I look at the screen shots you posted of the results from G32 I can see that it is making very nearly identical adjustments on both steppers.

That means for the two points being probed there is very little difference in Z height.

You observed that if you home Z after the leveling and then did the leveling again the results were the much the same.

That says to me the difference in Z height between the two points probed by G32 and the point probe by G30 differ by appx 0.64.

Given the location of those points it must be that your bed is "bowed" upward from the edges with the middle being appx 0.64 higher.

Please create a height map of, say, 10 x 10 and post a screen shot of what is looks like.

Frederick

[johny]

@fcwilt
Screen of the 1st layer of a small cube. In the center it’s ok, 1 corner too far away and the other too close 

[johny]

@droftarts the mesh

[fcwilt]

@johny

Your bed is not as flat as you would like.

And as you can see it does "bow" up in the middle which is consistent with G32 having no apparent effect when you follow it with homing Z.

Here is a height map from one of my flatter printer beds:

Before creating the height map and before loading the height map you need to have set the Z=0 Datum using a G30 at the same XY location.

You Z homing code was doing that at the end which is fine as long as you home Z to set the Z=0 Datum.

And you should turn off any "baby-stepping" as well.

Are you printing with mesh compensation enabled?

Frederick