Help G32 auto bed leveling

Hi,

I have a retractable sensor on my diy printer, which stick out 3.5mm beyond the nozzle when probing. So I wrote the Z-min endstop config:

gamma_min_endstop                            1.28^            # Pin to read min endstop, add a ! to invert if endstop is NO connected to ground
#gamma_max_endstop                           1.29^            # Pin to read max endstop, uncomment this and comment the above if using max endstops
gamma_homing_direction                       home_to_min      # Or set to home_to_max and set alpha_max and uncomment the alpha_max_endstop
gamma_min                                    3.5              # This gets loaded as the current position after homing when home_to_min is set
gamma_max                                    200              # This gets loaded as the current position after homing when home_to_max is set

And that works. When I homed Z with G28 Z0, it knows after homing it is 3.5 mm above the bed. So far so good.

Now I want to use G32 bed leveling, or however it is called. So I wrote:

# Levelling strategy
# Example for 3-point levelling strategy, see wiki documentation for other strategies
leveling-strategy.three-point-leveling.enable         true        # a leveling strategy that probes three points to define a plane and keeps the Z parallel to that plane
leveling-strategy.three-point-leveling.point1         10.0,10.0   # the first probe point (x,y) optional may be defined with M557
leveling-strategy.three-point-leveling.point2         10.0,330.0  # the second probe point (x,y)
leveling-strategy.three-point-leveling.point3         265,170.0   # the third probe point (x,y)
leveling-strategy.three-point-leveling.home_first     false       # home the XY axis before probing
leveling-strategy.three-point-leveling.tolerance      0.03        # the probe tolerance in mm, anything less that this will be ignored, default is 0.03mm
leveling-strategy.three-point-leveling.probe_offsets  0,-40,-3.5  # the probe offsets from nozzle, must be x,y,z, default is no offset
leveling-strategy.three-point-leveling.save_plane     true        # set to true to allow the bed plane to be saved with M500 default is false

But the 3.5mm distance doesn't seem to stick. I tried setting it to zero, no change. I tried setting it to 3.5 (without the minus), no change.

How can I tell it, when G32-ing, that the probe is 3.5 mm away from the bed?

Cheers,

Hugo

I even get a response when leveling:

"WARNING: probe is not within tolerance: 3.519844"

Hugo

Do not insert the probe Z offsets from nozzle, in the config
put it in start G code with G30 Z3.5 (not -3.5) before G32
It says that Nozzle is 3.5 under 0
You can find your height with the G30 Z0 and after stepping down to bed, you get the height to put in the G30 Z?
!!! Remember to activate your probe first
Here is the G code I use at the start of Simplify 3D

G28 ... Home
M280 S3.0 ... enable my probe
G30 Z1.05. ... find the bed
M280 S7 ... disable probe
G1 Z10 ... raises Nozzle 10
M280 S3.0 ... enable my probe again
G32 .. auto bed leveling
M280 S7 .. disable probe
begins to print

Thanks! I in the meantime resorted to using an M306 after the homing sequence, fooling the Z axis. I level everything and then correct the Z-value.

This is what I have now:
G00 Z10 (make room for Z-probe to be extended, regardless of where the bed really is)
M280 S12.9 (extend Z-probe)
G32 (full leveling sequence including homing X and Y, first)
G00 Z10 (move away to make room for Z-probe to be retracted)
M280 S4.5 (retract Z-probe)
M306 Z13.5 (set Z-value to it's current position relative to the nozzle)

[EDIT] The M306 does not work OK...[/EDIT]

Any specific reason you do this in the middle of your program?
M280 S7 ... disable probe
G1 Z10 ... raises Nozzle 10
M280 S3.0 ... enable my probe again

I'll look into the G30 command, might make an even cleaner set-up. And I am quietly wondering if G32 Z3.5 would work, like G30 Z3.5 does...

Cheers,

Hugo

Edited 2 time(s). Last edit at 12/03/2017 05:07AM by HugoW.

Wow, I'm nearly ruined my machine...

I ran:

M280 S12.9         ;    Extend Z-probe
G28 X0 Y0          ;    Home X and Y
G00 X150 Y150      ;    Move to middle of bed
G30 Z3.5           ;    Home and preset Z value
G00 Z10             ;    Move away from Z-trigger
G32                ;    Run auto bed leveling
G00 Z10            ;    Move away to retract Z-probe
M280 S4.5          ;    Retract Z-probe

And the nozzle crashed into the bed! I did it again step by step, checking M114 after each step, and after the G32 command the X and Y values were OK, but the Z reads 30.7! So when I gave the G00 Z10, the bed ran into the nozzle and sensor. I am happy I run the lot on very low current, nothing was damaged. But where the heck does that 30.7 mm value come from?

Hugo

Yes, if I do not send the M280 S7 (raise pin), BLTouch will fail
if I do not raise the Z hits pin the bed when I activate BLTouch (M240 S 3) again

Ah, you're running a BL Touch. I have a micro switch on an RC servo, hence the question.

I finally settled on running G32 including homing X and Y, and when done, at Z = 5 relative to the sensor, I retract the sensor and give a G92 Z8.5. I don't like using G92 as it is dangerous to mess about with values after homing, but in this case it is written in the Cura startup sequence so I cannot forget or mis-type or something like that.

Cheers,

Hugo