Configuring Z probe Offsets for Dual Extruder Heads

Hello

I am trying to figure out how to configure the z probe parameters for a dual extruder head. I have found the z trigger height for my BL touch approximately 1.67mm and the following is a diagram of XY plane distances between the Z probe and nozzles.



I have already adjusted the Z trigger height in the config.g file which is attached and the Z probe section looks like:

; Z-Probe
M950 S0 C"io7.out" ; create servo pin 0 for BLTouch
M558 P9 C"^io7.in" H7 F120 T6000 ; set Z probe type to bltouch and the dive height + speeds
G31 P500 X0 Y0 Z1.67 ; set Z probe trigger value, offset and trigger height
M557 X50:500 Y50:500 S25 ; define mesh grid

But does anyone understand how the X and Y offsets should look like for a dual extruder set-up? Also I am not even sure my config.g file is set-up correctly for a dual extruder, but the file is attached here: config.g

Also here is an overview of what the printer looks like:

you simply ignore the second extruder. It has nothing to do with z probe. z probe is always relative to primary extruder

Edited 1 time(s). Last edit at 07/02/2021 11:37PM by Dust.

Thank you for answering this! Are the coordinates relative to the Z probe in the sense that if Z probe is +23.9mm in the X direction and +28.21mm in the Y direction from the nozzle.

Or are the coordinates from the nozzle to the BL touch which would reverse the sign.

You can choose the Head Reference Point (HRP) to be anywhere you like on the print head. Then define the offsets of the two nozzles and the Z probe relative to the HRP.

On my dual nozzle printer, I chose the HRP to be midway between the two nozzles. On an E3D tool changer it is usual to use the Z probe position as the HRP.

Your choice of HRP also affects the axis limits you set with M208, because they define the movement limits of the HRP.

HTH David

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Although I can't contribute anything which has not been covered by Dust and dc42 regarding software, perhaps this video [www.youtube.com] may have some useful ideas for measuring the X, Y and Z offsets of the extruders and touch sensor - BLTouch in your case. The Otoscope camera used is about £8.00 on eBay and the mirror I used was a front surface dental mirror - other mirrors will work equally well but don't give quite as nice a picture.

Mike

David thanks for the insight. So sounds like the default head reference point (HRP) is the primary extruder nozzle but this can be moved. So when I go to specify my Z probe it will be G31 P500 X23.9 Y28.21 Z1.67 also what does the P term mean?

I tried looking at G code dictionary to see how one would move the HRP but not sure I understand.

The G31 P value is only relevant when you set the probe type to 1, 2 or 5 in the M558 command P parameter. See [duet3d.dozuki.com] for the different types. When the value at the output of the signal conditioning filter exceeds the G31 P value then the probe is considered triggered.

Most likely you are using either P8 or P9 in your M558 command, in which case the G31 P parameter is not relevant to you.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].