In this tutorial we are going to explore different options and techniques when programming cutter movement.

Lets begin with a simple part shown in a drawing below.

Basically it is a rectangular piece 4.00x2.00
For the purpose of simplicity lets make the depth of our profile (z- dimention) 0.75"

We are going to use a 0.5" dia endmill, again because it is a very common size and is easy to do basic math with.

I took a liberty of puting locations for our part/toolpath, so it is easy to extract numbers from the drawing just by looking at it.

Notice the green rectangle. This rectangle represents the path that the center of the tool will have to take to produce the part with required dimentions.
The thing is: because endmills have certain diameter, the center of the tool must be always offset by its radius.

There are two ways of doing that.

At my day job I am starting to do more and more manual programming.

Which i do not realy like, but since am at it anyway i have decided to keep piling little articles about G-Code programming into this new category.
This way when i forget things again i will be able to quicly refresh my memory.

Program Start

O0001 (COMMENT OR PROGRAM NAME)

Starting safety blocks

(G20 IMPERIAL UNITS, G21-METRIC)
(G17 XY ARC PLANE, G18-XZ, G19-YZ)
(G40 CANCEL TOOL RADIUS COMPENSATION)
(G49 CANCEL TOOL LENGTH OFFSET)
(G80 CANCEL CANNED CyCLE)
(G90 ABSOLUTE POSITIONING MODE)

G20 G17 G40 G49 G80 G90

Tool Change Routine

(T14 - call 2.5" Face mill)
(M6 - Perform tool change)
(G0 - rapid feedrate)
(G55-G59 - Choose Work Offset)
(X, Y - Command a Position to move to)
(S - choose spindle speed)
(M03 - Turn spindle on Clockwise, M04 - Counter-clock wise)

T14 M6
G0 G54 G90 X{X} Y{Y} S{SPEED} M03;

Apply Tool length offset at retract height, Turn on Coolant

(G43 H14 Z2.0 - All codes must be in the same line Apply cutter length offset from record #14 to cuttent tool, move to 2.0 above work at the same time )
(M8 - Turn on Coolant)

G0 G43 H14 Z2.0 M8

Rapid tool to plunge height

G0 Z{Z_PLUNGE}

Plunge to cutting depth at plunge feedrate

G01 Z{Z_DEPTH} F{F_PLUNGE}

Make a straight cut in xy direction at cutting feedrate

G1 X{X_POS} Y{Y_POS} F{F_FEED}

Retract to plunge height at either rapid or retract feedrate

G1 Z{Z_PLUNGE}

Retract to rapid height, turn off colant

(M09 - Turn OFF coolant)

G0 Z{Z_RETRACT} M09

Retract to tool change height, turn off spindle

(G28 G91 Z0 - all coes must be in the same line, move Z axis to HOME POSITION through a reference point)
(G91 Z0 - Causes reference point to be the current location, thus sending axis straight up )
(M05 - Turn off spindle)

G0 G28 G91 Z0 M05

Perform Next tool change or end program

M30(end program)