Duet setup for a e3d Chimera

[RGN01]

I'm converting a cartesian printer to the Duet from RAMPS and am having trouble figuring out how to configure the firmware for the e3d Chimera.

On the RAMPS, when switching nozzles the whole print head would move 18mm on the X-axis to position the active nozzle in the same place. I can't figure out how to do that with Gcodes.

I presume that the tools configuration and the tpre1.g, tpost1.g and tfree1.g files are where this is done but I'm struggling to find the correct combination to achieve this.

What I'm trying to do is:
For tool change from 0 to 1:

• move the print head 18mm left

• select the standby temperature on nozzle 0

• wait for the temperature on nozzle 1 to reach operating temperature

For tool change 1 to 0:

• move the print head 18mm right

• select the standby temperature on nozzle 1

• wait for the temperature on nozzle 0 to reach operating temperature

My Tools section in config.g is:

; Tools
M563 P0 D0 H1                                                   ; Define tool 0
G10 P0 X0 Y0 Z0                                                 ; Set tool 0 axis offsets
G10 P0 R150 S210                                                ; Set initial tool 0 active (S) and standby (R) temperatures
M563 P1 D1 H2                                                   ; Define tool 1
G10 P1 X18 Y0 Z0                                                ; Set tool 1 axis offsets
G10 P1 R150 S210                                                ; Set initial tool 1 active and standby temperatures
 

tpre0.g is:

G91				; Set to relative positioning
G1 X18
G90				; Set to absolute positioning
 

tpre1.g is:

G91				; Set to relative positioning
G1 X-18
G90				; Set to absolute positioning
 

I have got the temperature control part sorted so not listing that here.

The tpost?.g and tfree?.g files do not contain any movement codes, just a wait for temperature to be reached.

Sending T1 moves the head 18mm left so the active nozzle (on the right) is in the correct position.
Sending T0 moves the head 36mm right (this should be 18mm)
Sending T1 again moves it 18mm left so the head moves progressively to the right as the sequence above is repeated.

Setting the offset in the config.g Tools section to 0 for both tools has no effect on this behaviour.

It's probably simple but I can't see what I am doing wrong.

Can anyone point me to any documentation on how to do this correctly, please?

Richard

[RGN01]

Update: commenting out all entries in tpre0.g gives no head movement when selecting T0 but the T1 command still moves the head 18mm left so repeating the T0 T1 cycle moves the head left 18mm each time.

[dc42]

Don't move the head in the tool change files, just declare the nozzle XYZ offsets from the print head reference point in the G10 command for each tool. The movement will be done automatically. Instead of taking place immediately it is deferred until the next move takes place, because changing the tool position immediately is unsafe if the tool has a Z offset.

[RGN01]

Thanks, David. When you say "…declare the nozzle XYZ offsets from the print head reference point in the G10 command for each tool." , I interpret that to mean set the left hand nozzle with an X offset of -9mm and the right one as +9mm as they are 18mm apart with no Y or Z offset. The reference point is thus between them. Am I understanding correctly?

Richard

[dc42]

You can define the head reference point wherever you like. On my dual nozzle build I define it to be midway between the two nozzles, but you can define it to be at one of the nozzles instead as you appear to have done. Don't forget that the Z probe offsets in the G31 command and the axis limits in M208 are also relative to your chosen head reference point.

[RGN01]

Thanks, David. That makes sense and your comments about axis limits etc. have probably saved me asking another question on here!

Richard