Hi there,   I build my own CNC plasma using Bobcam cad v64 and Mach 3 on my lap top with windows 10 and USB port  , driving 3 nema 34 steppers. Everything is working fine exept my cutting speed is slow but jog speed is fast. I had issues with my metric conversion that seems to be working now. I changed inches to millimeters in my post proccessor but did not insert my G21 in the beginning of my program could that be the problem. Please help as it is my first try at the CNC game.  Thanx guys

As far as Mach3 is concerned G20 and G21 are modal commands so it is good practice to always include the appropriate command at the start of every Gcode file. This is usually one of the jobs of the Post Processor.

Tweakie.

Thanx Tweakie will remove my mods and install G21 in all my files.... Luan

Hi,
on the Config/General Config page there is an area 'Initialisation String'. It is a small group of Gcodes that Mach runs when it starts. If you wish your machine to
be in inch mode as default when you start up code G20 in that string.

Your CAM program and Post Processor should put a G20 or G21 at the start of your code automatically.  Is there any documentation about your CAM program?
and have you read it?

Craig