1. An Introduction to Process Planning and G-Code
CNC Machining
An Introduction to
Process Planning and G-Code

2. Process Planning
Determines appropriate procedures for transforming raw materials into a final product given an engineering design
Engineering designs convey information such as dimensions, tolerances and material
CNC machining is used to transform engineering design to product

3. Machine Instruction
When the designed product is produced using CNC machine tools, the machine tool controller needs explicit instructions describing the type and order of individual steps required to perform a given task. We use an instruction language called G-Code to deliver these instructions to the machine.

4. Advantages Does what manual machines can’t do Repeatability
Reduce time and warehousing costs
Reduced lead time and tooling costs
Lower operator skill requirements

5. Disadvantages Requires large investment
Machines do not program themselves
Must invest in software and computers
High maintenance costs
Not cost effective at low production levels

6. G-Code An alphanumeric code delivering instructions to CNC machine
Revolution Mill uses a standard Cartesian coordinate system for tool paths
Code is evaluated one line segment at a time called a block

7. Common G-Code G00 Rapid linear motion
G01 Linear motion at preset feedrate
G02 Circular feed motion – CW
G03 Circular feed motion – CCW
G04 Dwell can be timed or untimed
G40 Deactivates cutter compensation
G80 Deactivates canned cycles

8. Common M-Code M00 Program stop M03 Spindle on (CW)
M04 Spindle on (CCW)
M05 Spindle off
M07/9 Turn coolant (mist) on/off
M06 Change tool
M30 End program

9. Other Codes S Spindle speed F Feed rate T Tool number
X,Y,Z coordinate axis motion
R arc / corner radius
I X-axis center offset
J Y-axis center offset