G53-59 Coordinate System Persistence

Merlin246

Hello,

Is the G53-59 coordinate systems persistent or do they need to be referenced for every movement line?

If persistent what is the 'default' coordinate system (for instance when changing between machined coordinates [G53] and the tool coordinates [for a toolchanger there are multiple tools with different offsets]).

For example if I temporarily want to use machine coordinates when a tool is active is it:
G53
G1 Xxx Yyy Zzz
G54; (back to regular coordinates)
G1 Xxx Yyy Zzz

OR

G53 G1 Xxx Yyy Zzz
G1 Xxx Yyy Zzz; (this is in regular coordinates)

droftarts

@Merlin246 Short answer: I’m not sure, but I think G53 is non-modal, ie needs to be sent for every line that you want to move in machine coordinates. Otherwise the currently selected coordinate system is used.

RRF general conforms to NIST Gcode standard. See G53 and G54 in th Gcode dictionary: https://docs.duet3d.com/en/User_manual/Reference/Gcodes/G53 which references the NIST document. That says:

3.5.12 Move in Absolute Coordinates — G53
For linear motion to a point expressed in absolute coordinates, program G1 G53 X... Y... Z... A... B... C... (or use G0 instead of G1), where all the axis words are optional, except that at least one must be used. The G0 or G1 is optional if it is the current motion mode. G53 is not modal and must be programmed on each line on which it is intended to be active. This will produce coordinated linear motion to the programmed point. If G1 is active, the speed of motion is the current feed rate (or slower if the machine will not go that fast). If G0 is active, the speed of motion is the current traverse rate (or slower if the machine will not go that fast).
It is an error if:
• G53 is used without G0 or G1 being active,
• G53 is used while cutter radius compensation is on.
See Section 3.2.2 for an overview of coordinate systems.

So it should work like that. I’ll check with @dc42.

Ian

jay_s_uk

@droftarts that's my understanding of how it works. You need G53 on toolchangers if you want to reference the actual coordinate system

droftarts

Dc42 says:

yes G53 is an oddity, the NIST GCode standard defines it as active until the end of the line it is in.

So that’s what RRF does.

Ian

Merlin246

@droftarts awesome thanks for the clarification. This may be something useful to add into the GCode Dictionary for easy reference.

droftarts

@Merlin246 Thanks, I have updated the Gcode dictionary for clarity.

Ian