[Firmware] Z Homing setup question

[Joco]

Background:

I'm using the Cyclone 2 Marlin_V1 firmware.

Mega 2560 with RAMPS 1.4

Question:

I understand that the intent is to use the probe g-code with suitable software to build up a z offset from a base position (presumably Z zero).  This implies we are setting a defined Z position somewhere.    Using the Marlin firmware from the repo I have X and Y homing against the endstops working fine.  I am danged if I can figure out the Z side of things.

I can see that max endstops is disabled with:

#define DISABLE_MAX_ENDSTOPS

Therefore we must be only using the MIN endstop pins on the RAMPS board. With reference to this ( http://reprap.org/wiki/File:Arduinomega1-4connectors.png ) that means pins D3 (for X), D14 (for Y) and D18 (for Z).

I also see that the direction of travel for homing is towards the min for all axis:

// ENDSTOP SETTINGS:
// Sets direction of endstops when homing; 1=MAX, -1=MIN
#define X_HOME_DIR -1
#define Y_HOME_DIR -1
#define Z_HOME_DIR -1

Interestingly the firmware is allowed to travel below the min home position with this setting:

#define min_software_endstops false // If true, axis won't move to coordinates less than HOME_POS.

Issuing a G28 Z starts the Z homing and the homing direction is down.  Not up.  What I am not clear on is where I mount the Z-axis endstop.   It can't be at the top as we are not homing in the correct direction for a max-stop type setup.

I can't see and obvious mount point on the X-carriage for the Z endstop.  Unless I am being blind again.  :-)

Anyway looking at the code config (as noted above) and thinking what is logical it would appear for Cyclone 2  we mount a Z endstop somewhere so that when Z homing it the Z carriage will head DOWN then at some safe point hit the endstop BUT somehow be able to go PAST that endstop point during probing and milling?

As you can see, totally tied myself in a knot.   Advice/guidance gratefully received.

Cheers.

[Carlos García]

Hi Joco,
The Z homing is supposed to be towards the material. This decision was made for simplicity.

I encourage you to use cncgcodecontroller: https://github.com/carlosgs/cncgcodecontroller/blob/master/CNC-GCode-Controller_libs.jar?raw=true
That version incorporates separate XY homing, a button to zero the tool, and a button to lift the tool for tool change.
It also has the dimensions for cyclone 2.

The z endstop is basically two wires that connect to the tool and to the (conductive) raw material. So when the tool touches, it will determine the Z origin.

Regards,
Carlos

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[Joco]

ahhh.   All those pictures of the Cyclone 1 with endstops above the spindle where making think I was missing something clever somewhere.

What you say makes complete sense and I had considered it but thought "I am missing something, look at these pictures".

On the controller side what about the Cyclone GUI?   Or do you consider CNC-GCode-Contoller to have superseded it?

[Carlos García]

Sorry for the late response!

The pictures on V1 are indeed misleading in regards to Z. But trust me the change makes things more intuitive! :)

I did not test Cyclone GUI so I'm afraid I can't tell whether it's better or not :-S

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