Learning Mach 3

[BobF]

I am learning mach 3. Been reading and watching the videos. If I load the roadrunner on a machine setup with inches (not a real machine yet) I see that units in G-code appear to have no units.
Am I right in assuming that G-code has no units associated and there is therefore no translation in Mach?

[tauntdesigns]

I'm new to mach too,

All the programs that I've run or programed have the units selected in the program using G20 or G21. That said, I noticed that the roadrunner didn't have the units selected in the program (and other g-items) but, I did noticed and kinda remember something in Mach about start up items (active mode).

Look next to the diagnostics tap at the top of the program run mach screen:
(mill-> G90 G17 G49 G20...... etc) active stuff

Hopefully someone will pipe in on the subject for ya

[ger21]

You can use G20 or G21 for inches or mm's, but it's not recommended. When you first run Mach3, you set it up for either inches or mm's. While using G20 or G21 to switch to different units may work, Art has always recommended to set up two configurations, one for inches and one for mm's. Then just start Mach3 with the profile for the units you plan on using. The reason for this in the past is that there are many, many places in Mach3 where numbers needed to be converted, and I don't think there was any guarantee that you wouldn't have problems somewhere, although I think it worked well for most.

Most likely you won't be switching units from part to part, but if you do, it's pretty easy to just make two profiles and use the proper one for the job at hand.

[BobF]

I realize from watching some of the videos that the roadrunner file is mm. Is there any indication in a g-code file that it is metric or inches?
Looks like I have a lot to learn.
Thanks

[ger21]

Originally Posted by BobF Is there any indication in a g-code file that it is metric or inches?

You can usually tell by the numbers. 1 inch = 25.4mm's, so mm files have much larger numbers in them.