Z probe offset issues

[UltiFix]

No matter what I do, I can't get my printer to listen to the z probe offset parameter.

Say I set it to -0.6mm

After I run G29 it should be -0.6mm lower right? Nope.

EEPROM disabled marlin prusa i3

Look here for my configuration.h http://forums.reprap.org/read.php?406,638503

[jbrazio]

Z probe offset has nothing to do with G29.. that's auto bed leveling.

Let's imagine you have compiled Marlin with Z probe offset at -0.6 on the config file. Issue a G28 to home all your axis, when the operation finishes issue a M114 and your Z height shall be 0.6.

[UltiFix]

Click the home all button, then run M114. It says z -9.40 which is correct right? But when I print it will start printing .6mm below what the probe says is zero? Do I need to run any special gcode to get it to do that? Or is just G28 & G29 enough?

Thank you for your help! Maybe im just being dense.

[jbrazio]

No.. something is not right. Please open a serial connection to the printer and copy paste the output of the following commands in order:

M501
G28
M114

With my printer which as a Z-offset of -0.90 here is the output:

>>> M501
SENDING:M501
echo:V21 stored settings retrieved (380 bytes)
echo:Steps per unit:
echo:  M92 X160.00 Y160.00 Z8000.00 E204.15
echo:Maximum feedrates (mm/s):
echo:  M203 X200.00 Y200.00 Z3.30 E200.00
echo:Maximum Acceleration (mm/s2):
echo:  M201 X1000 Y1000 Z100 E3000
echo:Accelerations: P=printing, R=retract and T=travel
echo:  M204 P1000.00 R3000.00 T1000.00
echo:Advanced variables: S=Min feedrate (mm/s), T=Min travel feedrate (mm/s), B=minimum segment time (ms), X=maximum XY jerk (mm/s),  Z=maximum Z jerk (mm/s),  E=maximum E jerk (mm/s)
echo:  M205 S0.00 T0.00 B20000 X15.00 Z0.40 E2.00
echo:Home offset (mm):
echo:  M206 X0.00 Y0.00 Z0.00
echo:Material heatup parameters:
echo:  M145 S0 H210 B70 F0
echo:  M145 S1 H240 B110 F0
echo:PID settings:
echo:  M301 P19.18 I1.36 D67.42 C100.00 L20
echo:Filament settings: Disabled
echo:  M200 D1.75
echo:  M200 D0
echo:Z-Probe Offset (mm):
echo:  M851 Z-0.90
>>> G28
SENDING:G28
>>> M114
SENDING:M114
X:71.00 Y:133.00 Z:0.90 E:0.00 Count X: 11360 Y:21280 Z:7200

The relevant parts are:

• From M501: M851 Z-0.90 which should have the same offset and defined at compile time
• From M114: Z:0.90 which should be the inverse of the z-offset right after the G28

[UltiFix]

Here ya go... I have tried everything. Im totally stumped. http://pastebin.com/zSTZZKd5 For some reason when I ran m501 it didn't say the z offset. So I ran m851 and it spit out: echo:Z offset : -0.60

Which is correct.

While m114 is incorrect, aka not the number defined at compile time

[jbrazio]

OK you're using Marling 1.0.2 Could you please download the latest RCBugfix set it up for your printer and try again ?

[UltiFix]

I just noticed I had #define Z_MIN_POS -10 Im changing that to 0 now and re uploading, I will then test and see if that fixes it. ...waiting... Alright, know m114 spit's out the right thing. (Z:0.60)

So am I good now? Should everything be ok? After the G29 but before it start's print will it lower itself by 0.6mm? After I run G29 rep host displays a number near 6mm for the z axis and it let's me lower it down

Thanks! -Sam

[jbrazio]

If now by doing:

G28
M114

You see your Z height at Z:0.60 all is hunky-dory. G29 is automatic bed leveling.. it's another thing, what exactly are you trying to accomplish ?

[UltiFix]

I assumed that doing G29 would take the z probe offset into account, aka lowering itself lower than what the sensor thought should be zero. But thinking about it there is no reason it should.

My goal is when I print it lowers itself by .8mm (I changed my offset from -0.6 to -0.8)

Boom! G28 followed by M114 shows Z:0.80

Wahoo! Thanks!

[jbrazio]

Great ! G28 will do exactly what you want. First Marlin find the Z-zero using the inductive sensor (so this Z-zero is referenced to sensor tip) then applies the Z offset to get the Z-zero referenced to the nozzle, as the nozzle is sitting lower than the sensor tip, Z-offset is negative.

If you want to test the offset in order to fine tune try:

G28 ; Z height will be the module of z-probe offset
G1 Z0 ; move the nozzle to it's zero by apply the offset

On any print job you only have to do G28, Marlin does the rest.

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