Height Map Z Values
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Hi,
The values for Z that can be displayed at each point on a height map: what are they referenced to?
I keep getting messages about too much offset even though all points have close to the same Z value.
I don't know what to do to fix this.
Thanks.
Frederick
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They are referenced to where the printer thought Z=0 was prior to running G29 to probe the mesh. That will normally be the Z=0 position set by Z homing.
To avoid getting an offset, it's best to home Z by doing a single G30 probe at the centre of the bed; or if the printer is a delta, do one cycle of auto calibration between homing and running G29 S1.
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@dc42 said in Height Map Z Values:
They are referenced to where the printer thought Z=0 was prior to running G29 to probe the mesh. That will normally be the Z=0 position set by Z homing.
To avoid getting an offset, it's best to home Z by doing a single G30 probe at the centre of the bed; or if the printer is a delta, do one cycle of auto calibration between homing and running G29 S1.
I am using G30 to probe the center of the bed as part of the macro that probes the grid using G29.
Below is the essence of what I am doing:
M307 H7 A-1 C-1 D-1
M558 P9 H5 F300 T12000 A5 S0.01 R0.2
G31 X0 Y24.5 Z1.400 P25
M280 P7 S160
G29 S2
M290 R0 S0
G90
G1 Z5 F240
G1 X0 Y-20 F6000
G30
G1 Z5 F240
M208 Y-115:100
M557 X-140:140 Y-90:90 P2:2
G29
G29 S3 P"heightmap_FAST.csv"
M208 X-150:150 Y-100:100
G29 S2
M290 R0 S0
G1 Z5 240
G1 X0 Y0 F6000There are some commands that may not be needed but I don't think they cause any problems.
Is there anyway to post formatted gcode so tabs (or spaces) are preserved?
Thanks.
Frederick
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Well after thinking about it for awhile I realized that I could do a nine point grid which will reveal what the Z value for the center of the bed was.
It appears that I have some sort of mechanical problem.
The structural member that the X axis linear guides are mounted on is a 40 x 20 extrusion. Given the hot end assembly doesn't weigh all that much I would be surprised if it was a sagging issue but maybe that is the case.
Checking with a precision straight edge doesn't reveal anything.
More thinking to be done.
Thanks.
Frederick
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@fcwilt said in Height Map Z Values:
Given the hot end assembly doesn't weigh all that much I would be surprised if it was a sagging issue but maybe that is the case.
If the X axis was sagging then you would get an apparent rise in the centre of the height map, not a dip.
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@dc42 said in Height Map Z Values:
@fcwilt said in Height Map Z Values:
Given the hot end assembly doesn't weigh all that much I would be surprised if it was a sagging issue but maybe that is the case.
If the X axis was sagging then you would get an apparent rise in the centre of the height map, not a dip.
Right, of course, typing before thinking.
Thanks.
Frederick
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@fcwilt said in Height Map Z Values:
Is there anyway to post formatted gcode so tabs (or spaces) are preserved?
Yes, use the ``` characters to denote a code block, and another set at the end to close it.
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@Phaedrux said in Height Map Z Values:
Yes, use the ``` characters to denote a code block, and another set at the end to close it.
Thanks much.
Frederick