GCode Units question

[WarrenW]

In all the programs it allows you to setup for notmally MM or Inches. How are the gcode coordinates related to this? Say your going to cut a straight line from 10,50 to 10,100 as the X/Y coordinates. How are these related to the MM or Inches now?

Or are the lengths in gcode the same but displayed different in the cam software so you can measure the size it will come out?

I know this is probably a dumb question but I'm just trying to understand all of this better. It will all click one day!

Warren

[psychomill]

You basically answered this yourself in the thread title. CAD systems use "units" in creating geometry. When the systems are set up, you configure these "units" to mean either inches or mm. When creating the toolpaths in CAM, a post processor will use these units to translate ( not 'convert',... thats another story ) to inches or mm output. So in if you have a system configured in metric, your coordinates 10,50 to 10,100 in X/Y will place these points at : X10 mm, Y50mm and X10mm, Y100mm. If configured for inches it would be X10.000, Y50.000 inches and X10.000, Y100.000 inches.

The units that are displayed when analyzing the geometry and/or cut will depend on what the system was configured for to begin with. Which is why in many systems, its important to know that when importing geometry, was it created in inches or metric? For example: say you have a part that drawn on a metric system and you have a box that is drawn at 1mm square. If you import this geometry into an "inch" system, it will show up in the inch system as a 1" square. This is obviously a considerable difference.

Now some systems will allow you to have it converted when importing. Others you will need to scale the geometry to your system once its imported.

[ger21]

Warren, the first time you run Mach3 it ask you if you want inches or mm. You can also change it using Config>Set Native Units. Whatever this is set to is what the g-code units are. You'll see a warning mesage if you try to change it. You'll need to retune your motors if you do.

When you draw something in a CAD program, units are what you want them to be. If your drawing in inches, drawing a line 1 inch long would be exactly the same as drawing a line 1mm long using mm's. But if you wanted a 1" line using mm's, it would be 25.4mm's. Does that confusse you even more??