What G-code commands tell the printer to change nozzle on a dual extruder printer? I have been playing around with creating scripts to generate some custom G-code for a Malyan M180 and I am having trouble understand what commands to use to switch nozzles. Sometimes I can get the nozzles to switch and it doesn't recenter but sometimes it does.
I have been using:
G54
M108 T0; switch to left

and
G55
M108 T1; switch to right

Has anyone else looked into this and have any idea what commands or sequence of commands should be used to change nozzles?
No, M108 does not do that. You are looking for T#, where # is the tool position you want:

T1 ; switch to tool position 1 

T3 ; switch to tool position 3 


This tells the processor to send all heating, cooling and flow commands to this tool until another tool change is specified, and invokes the X/Y(/Z) offset for the new tool position.

See http://reprap.org/wiki/G-code#T:_Select_Tool