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Revision to Using mesh bed compensation

Jason Znack

There is a firmware-dependent limit on the number of 441 probe points allowed. If you exceed that limit, an error message will be returned when you run the M557 command, and you should increase the mesh spacing (S parameter) to reduce the number of probe points.
+Using a small number of points (ie. 9) is akin to using the older style simple planar correction.
== Probe the bed ==
* Running G32 to auto calibrate a delta printer will clear the local height map info (but not the copy in heightmap.csv). Therefore, if you wish to use both auto calibration and mesh bed compensation, you must run G32 before you run G29, not after. You can include a G29 command at the end of your bed.g file if you wish.
* If you don't want to probe the bed every time, you can use command G29 S1 to load the height map from the last time you used G29 to probe the bed.
+== Compensation Taper ==
* You can use the M376 command to taper off bed compensation over a specified height
+* Example: M376 H10 ; Hnnn Height (mm) over which to taper off the bed compensation
+* This command specifies that bed compensation should be tapered linearly over the specified height, so that full bed compensation is applied at Z=0 and no bed compensation is applied when Z is at or above that height. If H is zero or negative then no tapering is applied, so compensation is performed throughout the entire print.
+* RepRapFirmware does not adjust the extrusion factor to account for the layer height varying when tapered bed compensation is used. Therefore it is recommended that the taper height be set to at least 20x the maximum error in the height map, so that the maximum amount of the resulting over- or under- extrusion is limited to 5%.
+* Taper is useful for cases where the bed is curved slightly and will eventually be corrected for by the extrusion as it rises.
+* You should not use taper in cases where the curvature is due to a sagging gantry, as that curvature will persist for the entire duration of the print.
== Summary of gcode commands related to mesh bed compensation ==

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