G32 doesnt save after True Bed Leveling

[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

[johny]

@fcwilt Thanks frederick.
Yes, i am printing with compensation enabled, dunno why it doesn't compensate :S The bed is awful, I don't know how can a thick AL plate have these waves, it's strange. Anyway the bed compensation should compensate for all of this no?
This is my starting gcode:
G31 P25 X31 Y4 Z0.50
G28
;M572 D0 S0.6 ;pressure advance
M190 S75
M375 P"heightmap.csv"
M109 S250 T0
G92 E0
;G1 E75 F100 extrude filament line
G0 X100 Y0 F9000 ; Go to front
G0 Z0.15 ; Drop to bed
G92 E0 ; zero the extruded length
G1 X40 E25 F500 ; Extrude 25mm of filament in a 4cm line
G92 E0 ; zero the extruded length
G1 E-1 F500 ; Retract a little
G1 X80 F4000 ; Quickly wipe away from the filament line
G1 Z0.3 ; Raise and begin printing.
G92 E0

Note: it won't solve the problem but if i get a new bed... maybe its the PEI or the magnet stick below the PEI.

[fcwilt]

@johny

Just FYI you can load the height map with G29 S1 if you are using the default name as created by G29 S0.

Is your bed made from CAST ALUMINUM TOOL PLATE (CATP) ? Plain old aluminum sheet/plate is likely not going to provide the flatness you need. CATP is specified to have a certain flatness.

Example of CATP with specs

This start code you posted - where is it located? Did you enter it into the slicer somewhere?

Frederick

[droftarts]

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

Anyway the bed compensation should compensate for all of this no?

With the probe homing in the middle, and setting Z0 at that point, the Z axis can't go below zero, because your Z limit is set by M208 to be

M208 X-10 Y0 Z0 S1                               ; set axis minima

Set it to Z-1.

Ian

[johny]

@fcwilt The bed is from AL plates cut in laser maybe i need to get it from another supplier, aliexpress?
The Gcode is the start Gcode on the slicer.

@droftarts I understand what you are suggesting and i will add the line to let the Z go bellow zero 1mm but it wont affect this behaviour because as you can see in the 1 layer print the nozzle its already too close to the bed; i want to figure out why and how to solve it

[fcwilt]

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

The bed is from AL plates cut in laser maybe i need to get it from another supplier, aliexpress?

Being cut with a laser doesn't mean it will be flat.

Did you read about the CATP that I provided a link to? You can order a piece of CATP of the desired thickness and size from them. It takes a while but that have always proven to be reliable.

And there are other vendors that can do the same, such as these folks: cut2sizemetals

The Gcode is the start Gcode on the slicer.

Thanks.

the nozzle its already too close to the bed; i want to figure out why and how to solve it

That is likely caused by the Z trigger height parameter in G31 being a bit too large.

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Frederick