9.2 METHODS OF NC PART PROGRAMMING

The tape can be prepared for submission to the MCU using any of several different methods of NC part programming. NC programming represents one of the elements in the broader procedure called process planning. We defined process planning in Chapter 2 as a function of manufacturing engineering in which the  sequence of individual production operations for making the part are planned. We  assume here that a portion of the processing is to be done on one or more NC  machines. For those machines, the program  must be prepared.
The part programming methods include a variety of procedures ranging from highly manual  to highly automated :
1. Manual part programming
2. Computer assisted part programming
3. Manual data input
4. NC programming using CAD/CAM
5. Computer automated part programming
In manual part programming, the processing instructions are documented on a form called a part program manuscript. The manuscript is a listing of the positions of the tool relative to the workpiece that the machine must follow in order to perform the processing. The listing may also include other commands such as speeds, feeds, tooling, and so on.  A punched tape is then prepared directly from the manuscript.
In computer-assisted part programming, much of the tedious computational work required in manual programming is performed by the computer. For complex work part geometries or jobs with many processing steps, use of the computer results in significant savings in the part programmer’s time.  When computer assisted part programming is used, the programmer prepares the set of processing instructions in a high-level computer language. For complex jobs, this computer language is much easier to use than the lower-level coding required in manual part programming. The high-level language commands are interpreted by the computer, and the required calculations and data processing are accomplished to prepare the NC program for the tape reader (or other input device).
Manual data input (MDI) is a procedure in which the NC program is entered directly into the MCU at the site of the processing machine. Consequently, the use of the punched tape is avoided, and the programming procedure is simplified to permit machine operators rather than part programmers to do the programming.
NC part programming using CAD/CAM is an advanced form of computer-assisted part programming in which an interactive graphics system equipped with NC programming software is used to facilitate the part programming task. The term CAD/CAM means computer-aided design and computer-aided manufacturing. In this method the programmer works on a CAD/CAM workstation to enter the machining commands. The actions indicated by the commands are displayed on the graphics monitor, which provides visual feedback to the programmer. Also, certain portions of the programming cycle are automated by the NC programming software to reduce the total programming time required.
Computer-automated part programming extends the notion of automating certain portions of the. NC part programming procedure to its logical conclusion. It automates the complete part programming task using software that is capable of making logical and even quasi intelligent decisions about how the part should be machined.
We shall describe these various methods of part programming in the following sections of this chapter.