You might find the HAL "carousel" component helpful:
linuxcnc.org/docs/2.7/html/man/man9/carousel.9.html
To see an example of how to use it you can open the LinuxCNC config-picker and look in the sample configs. Open sim/axis/vismach.vmc_toolchange/vmc_index to see a demo config. You can run it on your actual machain controller, it won't try to access any hardware. It has an animated 3D model of VMC to demonstrate it working.
It uses a line in the INI file to re-map the M6 command:
Code:
[RS274NGC]
...
REMAP= M6 modalgroup=6 prolog=change_prolog ngc=toolchange epilog=change_epilog
This calls the "toolchange.ngc" file (the other files mentioned are standard library files). The toolchange.ngc file is a G-code routine that controls the machine movements needed or the toolchange. Note that it is quite careful to make sure that it waits for confirmation before moving on, and makes a lot of use of the (abort, ) G-code "magic comment" to deal with problems.
Code:
o<toolchange> sub
M19 R0 ;align the spindle
; only unload the tool if there is a tool in the spindle
; This assumes that the carousel is already aligned correctly.
; It is important to unload the tool before shutting down the machine.
O100 IF [#<tool_in_spindle> GT 0]
G53 G0 Z -100
M64 P2 ; move arm in
M66 P2 L3 Q5 ; wait for arm-in = true
O104 if [#5399 LT 0]
(abort, failed to move arm in)
O104 endif
M64 P3 ; release tool
M66 P3 L3 Q2 ; wait for tool-released = true
O105 if [#5399 LT 0]
(abort, failed to release tool)
O105 endif
O100 ENDIF
G53 G0 Z0
O200 IF [#<selected_tool> GT 0]
M65 P1 ; unlock carousel
M66 P1 L4 Q1 ; wait for locked=false
O106 if [#5399 LT 0]
(abort, failed to unlock carousel)
O106 endif
M68 E0 Q#<selected_pocket> ;set the carousel to move to the right pocket
M64 P0 ; start carousel
G4 P2
M66 P0 L3 Q60 ; wait for carousel finished
O107 if [#5399 LT 0]
(abort, failed to align carousel)
O107 endif
M65 P0; stop carousel
M64 P1 ; lock carousel
M66 P1 L3 Q1 ; wait for locked=true
O108 if [#5399 LT 0]
(abort, failed to lock carousel)
O108 endif
M64 P2 ; move arm in (might already be in)
M66 P2 L3 Q5 ; wait for arm-in = true
O109 if [#5399 LT 0]
(abort, failed to move arm in)
O109 endif
G53 G0 Z-100 ; pick up the tool
O200 ENDIF
M65 P3 ; clamp tool
M66 P3 L4 Q2 ; wait for tool-released = false
O110 if [#5399 LT 0]
(abort, failed to clamp tool)
O110 endif
M65 P2 ; move arm back out
M66 P4 L3 Q5 ; wait for arm-out = true
O111 if [#5399 LT 0]
(abort, failed to move arm in)
O111 endif
o<toolchange> endsub [1]
M2
You say that you have the carousel configured as a B-axis. You could keep it like that, an move it in G-code, or use the carousel component to control it.
If you keep it as a B-axis you will probably need to use the index switch as a home switch and add it to the home sequence. The B-axis will appear in the GUI, and you will be able to jog it. Which might actually be useful, though not terribly neat.
