404 CHAPTER 22 Chapter Outline 22.1 Developing CNC Programs 22.2 Programming Methods 22.2.1 Manual Programming 22.2.2 Conversational Language Programming 22.2.3 CAM Programming 22.3 CAD and CAM Software 22.3.1 CAD Software 22.3.2 CAM Software 22.4 CNC Programming Codes 22.4.1 G-Codes 22.4.2 M-Codes 22.4.3 Assigned and Unassigned Codes 22.4.4 Other Letter Codes 22.5 CNC Modal Commands 22.5.1 G00—Rapid Travel 22.5.2 G01—Linear Interpolation 22.5.3 G02 and G03— Circular Interpolation 22.5.4 G20 and G21— Units 22.5.5 G90 and G91—Absolute and Incremental Positioning 22.5.6 Setting the Modal Commands Learning Objectives After studying this chapter, you will be able to: • Explain the process of planning and developing a CNC program. • Describe three methods of generating CNC code. • Summarize the use of CAD and CAM software in CNC programming. • Classify the types of codes used in the ANSI/EIA 274D code format. • Identify commonly used CNC modal commands. Technical Terms absolute positioning assigned code block circular interpolation G-codes incremental positioning linear interpolation machine control unit (MCU) manual data input (MDI) M-codes modal command offline programming post-processing unassigned code word word address format CNC Programming Basics