Mesh Bed Compensation Screwy
-
Hi All, can I now confirm that I amprinting the four squares test succesfully. thanks for your help.
DC42 as a suggestion, might it be worthwhile adding the above fledged out with a little explanation to the Wiki, at least for those of us that are using Glass Beds on a Cartesian?
-
@pcsentinel. Glad you got it sorted. A couple of points. You seem to only be doing the bed compensation for 100mm x 100mm of the bed area. It's usually best to probe close to the 4 extreme corners of the axes movements so that you cover the entire printable area. Also, your Z homing example seems to indicate that you are homing Z at one corner of the bed and it's usually better to do the Z homing at the centre of the bed, because that is where the majority of your printing will take place and therefore where you need the most accuracy. HTH
Ian -
Ok, thanks I tried that, but because of my offset when I go to postion 2 on the grid with
G30 P1 X49 Y189 H0 Z-99999
the nozzle is hitting the bed and compressing the carriage before te sensor is activated therefor throwing off the reading -
Ok, thanks I tried that, but because of my offset when I go to postion 2 on the grid with
G30 P1 X49 Y189 H0 Z-99999
the nozzle is hitting the bed and compressing the carriage before te sensor is activated therefor throwing off the readingI think you must have a severely tilted bed. You can increase the Z probe dive height - it's the H parameter in the M558 command. But it's better to get the bed more level than to rely on a lot of compensation.
-
Is it possible for me to test before a firmware is released?
-
Further unknown with 4 point plane. Sorry I know this is under Mesh, but its where all the previous comments are.
I extended my four points to be wider but obviously still keep the probe over the bed.
I then thought I would check each four points without any compensation, i.e. drop nozzle to just hold paper, set z to 0, raise head by 5mm and do G30 S-1. and then check repeatability. the result are below that seem to indicate that the points all have different trigger heights but repeatability at each point is good.
Nozzle X Nozzle Y Probe X Probe Y G30 S-1 G30 S-1 G30 S-1 Average Offset from P1
Point 1 1 1 49 29 0.385 0.382 0.38 0.382333333 0
Point 2 1 161 49 189 0.298 0.298 0.303 0.299666667 -0.082666667
Point 3 131 161 179 189 0.157 0.153 0.155 0.155 -0.227333333
Point 4 131 161 179 189 0.185 0.185 0.188 0.186 -0.196333333My settings in coonfig.g are
M558 P1 X0 Y0 Z1 H5 F120 T6000 ; Set Z probe type to unmodulated, the axes for which it is used and the probe + travel speeds
G31 P500 X48 Y28 Z0.382333333 ; Set Z probe trigger value, offset and trigger heightI therefor mofidied my bed.g to
; bed.g
; called to perform automatic bed compensation via G32
;
; generated by RepRapFirmware Configuration Tool on Sun Feb 26 2017 13:25:00 GMT+0000 (GMT Standard Time)
G90
; Clear any bed transform
M561; Probe the bed at 4 points CLOCKWISE!
G28
G30 P0 X49 Y29 H0 Z-99999
G30 P1 X49 Y189 H-0.082666667 Z-99999
G30 P2 X179 Y189 H-0.227333333 Z-99999
G30 P3 X179 Y29 H-0.196333333 Z-99999 S
G1 Z5
G1 X0 Y0But after I ran the bed compensation I then went back to each probe point and dropped the Z to 0 over the piece of paper, at all points the paper was trapped until I lifted the nozzle 0.3mm. So I added:
G1 Z0.25
G92 Z0
into the bed.g before the G1 Z5 and now everything seems to be working, but I am really mystified why I have to push the the height up by 0.25 does anyone know? -
Hi, re previous post, can anyone enlighten me as really confused?
-
Hi
Would like to help but I think I asked the same or related question above… I suspect there is some thing weird in how the compensation is used...
Could be the interpolation issue now look at and hopefully corrected.
That is why I offered to test... As soon a beta is available that has the fix for interpolation I will try it... Since interpolation is probably used in the application of the correction also... My guess after 17 years in embedded software development...
-
I've just released firmware 1.18beta2 which includes fixes for mesh bed compensation when the head is outside the points actually probed. My thanks to ChristophPech for the fixes.
-
so are we saying that the same compensation routine may also be used in 4 point plane correction?
-
…
But after I ran the bed compensation I then went back to each probe point and dropped the Z to 0 over the piece of paper, at all points the paper was trapped until I lifted the nozzle 0.3mm. So I added:
G1 Z0.25
G92 Z0
into the bed.g before the G1 Z5 and now everything seems to be working, but I am really mystified why I have to push the the height up by 0.25 does anyone know?What XY coordinates to you use when you home the Z axis, in homez.g and homeall.g?
-
I've just released firmware 1.18beta2 which includes fixes for mesh bed compensation when the head is outside the points actually probed. My thanks to ChristophPech for the fixes.
And thank you for the update. Will try a new first layer ASAP. Just need to get home from work first.
-
I'm just about to flash 1.18beta2, but wanted to check where, if anywhere in particular, should homez.g and homeall.g be run?
I'm seeing very similar results with 1.18beta1 on a couple of points other people have raised:
Using 1.18beta1 and homing z in homez.g and homeall.g at the bed center, while printing a 50x50x1.8mm solid cube at the bed center:
-
during first layer, I needed to Baby step z to +0.3mm (i.e. one print layer height) to prevent the first layer being badly squashed, despite z-homing to be accurate to ±0.025mm (gauged with a piece of note paper, itself checked with a digital 0.001mm/0.00005" micrometer).
-
Initially I used z-taper of 3.0 mm (M376 H3.0) but didn't see any visible z motion during the entire print, so reduced it to M376 H0.6. That resulted in quite a coarse z-compensation motion in one corner, but only AFTER 0.6mm z-height:
The results above were achieved using the following 9-point height map:
RepRapFirmware height map file v1 generated at 2017-02-12 13:15, mean error -0.00, deviation 0.05 xmin,xmax,ymin,ymax,radius,spacing,xnum,ynum 25.00,165.00,15.00,155.00,-1.00,70.00,3,3 0.011, 0.013, -0.023 0.070, 0.064, -0.013 -0.051, 0.018, -0.095Just before 1.18beta2 was announced, I generated the following 25-point height map, checked a couple of times; deviation repeatability is within ±0.01mm. (I'll recheck this with 1.18beta2):
RepRapFirmware height map file v1, mean error 0.01, deviation 0.04 xmin,xmax,ymin,ymax,radius,spacing,xnum,ynum 25.00,165.00,15.00,155.00,-1.00,35.00,5,5 0.011, 0.015, -0.007, 0.010, -0.026 0.024, 0.053, 0.062, 0.041, -0.013 0.073, 0.061, 0.059, 0.040, -0.011 0.032, 0.051, 0.066, 0.040, -0.031 -0.038, -0.036, 0.019, -0.049, -0.099EDIT: pics added
-
-
If you are using mesh bed compensation and also using the Z probe to do Z homing, then you should Z home with the probe over a point that is on the grid. Otherwise the interpolated bed height at that point may not be exactly the same as the probed bed height, leading to a difference in the Z=0 position.
I guess it might help if there was a version of the G30 command that lets you specify an XY position to probe for Z homing, just like G29 does. Otherwise you will need to take account of the probe X and Y offset yourself.
-
Lets try this:
RepRapFirmware height map file v1 generated at 2017-02-13 20:49, mean error 0.15, deviation 0.08
xmin,xmax,ymin,ymax,radius,spacing,xnum,ynum
26.00,299.00,12.00,188.00,-1.00,16.00,18,12
0.017, 0.127, -0.015, 0.007, 0.127, 0.000, 0.055, 0.127, -0.010, 0.105, 0.127, -0.005, 0.092, 0.080, -0.062, 0.075, 0.010, -0.043
0.060, 0.012, 0.130, 0.037, 0.072, 0.185, 0.142, 0.127, 0.240, 0.137, 0.107, 0.235, 0.122, 0.127, 0.145, 0.057, 0.060, 0.112
0.062, 0.197, 0.100, 0.030, 0.180, 0.115, 0.137, 0.225, 0.125, 0.182, 0.240, 0.102, 0.122, 0.158, 0.117, 0.135, 0.148, 0.075
0.122, 0.182, 0.070, 0.175, 0.165, 0.110, 0.220, 0.117, 0.120, 0.275, 0.185, 0.117, 0.217, 0.150, 0.105, 0.190, 0.092, 0.060
0.182, 0.150, 0.077, 0.240, 0.178, 0.192, 0.237, 0.275, 0.180, 0.280, 0.277, 0.180, 0.342, 0.148, 0.142, 0.245, 0.137, 0.172
0.137, 0.297, 0.122, 0.172, 0.222, 0.168, 0.247, 0.270, 0.215, 0.270, 0.242, 0.212, 0.230, 0.220, 0.140, 0.232, 0.190, 0.125
0.120, 0.202, 0.205, 0.158, 0.250, 0.245, 0.165, 0.255, 0.295, 0.247, 0.287, 0.200, 0.155, 0.300, 0.320, 0.180, 0.307, 0.192
0.205, 0.115, 0.185, 0.222, 0.210, 0.267, 0.202, 0.232, 0.303, 0.332, 0.225, 0.275, 0.262, 0.160, 0.197, 0.158, 0.158, 0.180
0.135, 0.172, 0.178, 0.145, 0.265, 0.252, 0.172, 0.287, 0.188, 0.195, 0.280, 0.182, 0.230, 0.252, 0.135, 0.175, 0.257, 0.150
0.092, 0.140, 0.057, 0.145, 0.155, 0.125, 0.207, 0.142, 0.120, 0.280, 0.162, 0.140, 0.197, 0.152, 0.142, 0.200, 0.140, 0.155
0.070, 0.055, 0.037, 0.120, 0.107, 0.035, 0.142, 0.105, 0.142, 0.145, 0.097, 0.142, 0.142, 0.040, 0.148, 0.180, 0.075, 0.137
0.017, -0.003, -0.028, 0.037, 0.002, -0.053, 0.095, 0.057, -0.023, 0.110, -0.010, 0.010, 0.033, 0.012, 0.055, 0.053, 0.015, 0.050
Nope, this did not work… printed in the air... do not understand
Next try:
I do get the impression that there is some "overcompensation" done here…
I do not get the feeling when testing the bed that it is half a mm off but that is what the probe measures...But this is much better.
-
Hi DC42in answer to your question, re four point plane above, I use the first probe point for HomeZ and HomeAll
-
In the override-config.g there is three G31 lines.
T1 had a z compensation number but not the X an Y. Why? I have this in my config.g file… But I do not have the T1 set in that file...
This is from my setup:
M558 P1 X0 Y0 Z1 H3 F200 T4000 ; Smart IR Z probe, used for homing Z axis, dive height 3mm, probe speed 200mm/min, travel speed 5000mm/min
G31 X-25.19 Y7 Z2.3 P500I trigger the override-config.g later in the config.g file thus overriding my previous setup...
This could be the root cause to my "overcompensation" problem.
Now the main problem is the fact that this override-config.g is automatically generated.
Will test to do what is not recommended and that is to update the file.
I have the Z probe that came with my E3D Bigbox. Is that a type T1 probe then?
Why can't I set the probe placement relative to each tool separately?
Why do I have a T3 and T4 G31 in my automatically generated file?
I got hopeful that is was Tool 1 probe offsets in each G31...
The more I read the less I seem to understand how this work...
-
Why can't I set the probe placement relative to each tool separately?
Because it has nothing to do with the tool offsets. Think of the IR-sensor as if it it's own tool.Also your measured bed-matrix looks very inconsistent. I had the same problem on my BigBox in the past, the reason was that the angle of the IR-sensor was not parallel to the bed. I couldn't even change the angle because the screws of the sensor mount have made some groves.
The "correct" bed-matrix on the BigBox should look mostly flat with a slight bulge upwards in the center (this is due to the sag of the smooth rods)
-
In the override-config.g there is three G31 lines.
T1 had a z compensation number but not the X an Y. Why? I have this in my config.g file… But I do not have the T1 set in that file...
This is from my setup:
M558 P1 X0 Y0 Z1 H3 F200 T4000 ; Smart IR Z probe, used for homing Z axis, dive height 3mm, probe speed 200mm/min, travel speed 5000mm/min
G31 X-25.19 Y7 Z2.3 P500I trigger the override-config.g later in the config.g file thus overriding my previous setup...
This could be the root cause to my "overcompensation" problem.
Now the main problem is the fact that this override-config.g is automatically generated.
Will test to do what is not recommended and that is to update the file.
I have the Z probe that came with my E3D Bigbox. Is that a type T1 probe then?
Why can't I set the probe placement relative to each tool separately?
Why do I have a T3 and T4 G31 in my automatically generated file?
I got hopeful that is was Tool 1 probe offsets in each G31...
The more I read the less I seem to understand how this work...
Yes the IR sensor that came with the BigBox is a type 1.
Probe X and Y offset in the G31 command is relative to the head reference point, just like the G10 tool offsets. So you don't need a different probe offset for each tool. You can choose the head reference point wherever you like. If you have just one nozzle, then you would normally use the nozzle position as the head reference point. On my dual nozzle printer, I chose the head reference point to be mod way between the two nozzles.
RRF records separate G31 parameters for probe types 0 or 1 or 5, 3 and, 4 so that you can use more than one Z probe. Running M500 saves all of them. That's why you get G31 commands for probe types that you have not actually configured.
I just tried changing the probe offset by sending a G31 command with X and Y parameters, then I ran M500. The new offsets were correctly shown in the G31 command in config-override.g. Perhaps you last ran M500 when before you included X and Y offsets in your G31 command?
-
@CHP:
Why can't I set the probe placement relative to each tool separately?
Because it has nothing to do with the tool offsets. Think of the IR-sensor as if it it's own tool.Also your measured bed-matrix looks very inconsistent. I had the same problem on my BigBox in the past, the reason was that the angle of the IR-sensor was not parallel to the bed. I couldn't even change the angle because the screws of the sensor mount have made some groves.
The "correct" bed-matrix on the BigBox should look mostly flat with a slight bulge upwards in the center (this is due to the sag of the smooth rods)
How did you fix it?
That is the way it looks when making a five point bed level… And one other thing that is weird: the five point bed level shows the corners approximately at the same height... But not the mesh level.
I have not the borosilicate glass but the PEI aluminum bed from Clever3D. So it MIGHT be less flat... But then again does not look that way when checking with a straightedge.
So test for tonight : somehow get the sensor more level... Is the one that is sold on duet3D better (although not more square) ?
I will try to set the bed height relative the nozzle with the bed level screws then somehow get the sensor more square to that...Then I'll change my offset to the middle point of the print heads... (and verify that the new offset is recorded in the file after m500.)
