docs: Note PROBE_CALIBRATE results invalidated on motion system update

Any hardware change to the hotend or probe, change to the kinematics,
or change to the bed tilt is likely to invalidate the results of
PROBE_CALIBRATE.  Try to warn the user of that.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

3 files changed, 40 insertions, 0 deletions

diff --git a/docs/Delta_Calibrate.md b/docs/Delta_Calibrate.md
index 7eb6ec1b..023e6865 100644
--- a/docs/Delta_Calibrate.md
+++ b/docs/Delta_Calibrate.md
@@ -30,6 +30,13 @@ automatic probe has a bias of more than 25 microns (.025mm) then use
 manual probing instead. Manual probing only takes a few minutes and it
 eliminates error introduced by the probe.
 
+If using a probe that is mounted on the side of the hotend (that is,
+it has an X or Y offset) then note that performing delta calibration
+will invalidate the results of probe calibration. These types of
+probes are rarely suitable for use on a delta (because minor effector
+tilt will result in a probe location bias). If using the probe anyway,
+then be sure to rerun probe calibration after any delta calibration.
+
 Basic delta calibration
 =======================
 
@@ -228,3 +235,15 @@ Additional notes
   errors elsewhere in the hardware. For example, small differences in
   arm length may result in a tilt to the effector and some of that
   tilt may be accounted for by adjusting the arm length parameters.
+
+Using Bed Mesh on a Delta
+=========================
+
+It is possible to use [bed mesh](Bed_Mesh.md) on a delta. However, it
+is important to obtain good delta calibration prior to enabling a bed
+mesh. Running bed mesh with poor delta calibration will result in
+confusing and poor results.
+
+Note that performing delta calibration will invalidate any previously
+obtained bed mesh. After performing a new delta calibration be sure to
+rerun BED_MESH_CALIBRATE.
diff --git a/docs/Manual_Level.md b/docs/Manual_Level.md
index 38327c97..3ae75447 100644
--- a/docs/Manual_Level.md
+++ b/docs/Manual_Level.md
@@ -185,3 +185,9 @@ This means that:
 
 Repeat the process several times until you get a good level bed -
 normally when all adjustments are below 6 minutes.
+
+If using a probe that is mounted on the side of the hotend (that is,
+it has an X or Y offset) then note that adjusting the bed tilt will
+invalidate any previous probe calibration that was performed with a
+tilted bed. Be sure to run [probe calibration](Probe_Calibrate.md)
+after the bed screws have been adjusted.
diff --git a/docs/Probe_Calibrate.md b/docs/Probe_Calibrate.md
index f7e62b4c..5ec06bda 100644
--- a/docs/Probe_Calibrate.md
+++ b/docs/Probe_Calibrate.md
@@ -70,6 +70,21 @@ results to the config file with:
 SAVE_CONFIG
 ```
 
+Note that if a change is made to the printer's motion system, hotend
+position, or probe location then it will invalidate the results of
+PROBE_CALIBRATE.
+
+If the probe has an X or Y offset and the bed tilt is changed (eg, by
+adjusting bed screws, running DELTA_CALIBRATE, running Z_TILT_ADJUST,
+running QUAD_GANTRY_LEVEL, or similar) then it will invalidate the
+results of PROBE_CALIBRATE. After making any of the above adjustments
+it will be necessary to run PROBE_CALIBRATE again.
+
+If the results of PROBE_CALIBRATE are invalidated, then any previous
+[bed mesh](Bed_Mesh.md) results that were obtained using the probe are
+also invalidated - it will be necessary to rerun BED_MESH_CALIBRATE
+after recalibrating the probe.
+
 # Repeatability check
 
 After calibrating the probe X, Y, and Z offsets it is a good idea to