CNC Machining

1
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 cant 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