CNCMill
G-Code
This may be specific to Acorn CNC at HSL.
Comments
Comments are in parentheses.
G0X0Y0 (rapid traverse to origin - the traverse will be executed, but this parenthetical comment is ignored)
Active Units
G20 (set active units to inches) G21 (set active units to millimeters)
Feeds
F sets the feed rate in the active units.
G20 (inches) F15 (15 inches per minute) G1X0Y0 (traverse to origin at 15 IPM) G21 (millimeters) F375 (375 mm per minute) G1X0Y0 (traverse to origin at 375mmPM)
Straight Line Traversal
G0 is fast traversal. Careful not to run the tool into the part. Each axis is run at full speed until reaching its destination (ie: the tool follows multiple line segments, not an interpolated straight line).
G21 (set millimeters) G0X3 (fast traverse the X axis to origin + 3 millimeters) G0X1Y-2.6Z3 (fast traverse to { 1, -2.6, 3 } millimeters)
Straight Line Cuts
G1 is an interpolated straight line from current position to the new position, moving at feed rate.
G21 (set millimeters) F350 (set feed speed to 350mm per minute) G0X0Y0Z0 (move to origin) G1X10Y20Z-5 (move in a straight line from {0,0,0} to {10,20,-5} at 350mm per minute)
Plane Selection
G17, G18, G19 select XY, ZX, or YZ as the active plane.
Arc Cuts
G2 is a clockwise cut to the destination