G10 L2

Hi,

Why does linuxcnc say "Being in incremental distance mode (G91) has no effect on G10 L2". I looked though the NIST RS274NGC documentation and there is no exception for G10 L2. There is an exception for G92. G10 L2 respects G91 on the industry controls I've tested it on.

It make G10 L2 half as functional. And on top of that this behavior has filtered down into other open source machine control projects.

As a work around I have used parameters #5221-5390 linuxcnc.org/docs/2.7/html/gcode/overview.html#gcode:parameters to make an incremental shift in a work coordinate system.
Like thisto shift the G54 X+1.

That's a pretty slick workaround. Thanks for that.

Unfortunately the way I ran into this issue is trying to help someone with smoothieware. It's a 3d printer controller, and they have used EMC2/linuxcnc as a model to implement work coordinates. Their "documentation" on work coordinates is a link you linuxcnc's docs. I'm pretty sure they don't have parameters in the traditional cnc fashion, so that workaround won't work very well. GRBL also has implemented the same g10 l2 behavior.

Does anybody disagree with me that RS274NGC makes no exceptions for G10 L2 to explicitly ignore incremental mode?

Here is how I read it:

3.5.17 Set Distance Mode — G90 and G91
Interpretation of RS274/NGC code can be in one of two distance modes: absolute or incremental.
To go into absolute distance mode, program G90. In absolute distance mode, axis numbers (X, Y,
Z, A, B, C) usually represent positions in terms of the currently active coordinate system. Any
exceptions to that rule are described explicitly in this Section 3.5.
To go into incremental distance mode, program G91. In incremental distance mode, axis numbers
(X, Y, Z, A, B, C) usually represent increments from the current values of the numbers.
I and J numbers always represent increments, regardless of the distance mode setting. K numbers
represent increments in all but one usage (see Section 3.5.16.8), where the meaning changes with
distance mode.

Ok so any exceptions to this modal has to be explicitly stated somewhere in section 3.5. And in section 3.5.17 only the polar arguments are mentioned. Nothing about G10 L2.

So on to the 3.5 over view section mentions no exception to G10 L2.

Section 3.5.5, nope nothing there.

And that's all that is relevant in section 3.5.

What gives with this? As far as I can tell the linuxcnc implementation is not complaint to the standard. What's worse is embedded opensource projects are copying this gimped behavior and think they are somehow doing a good thing.

Link 1

and

Link 2

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