Manual part programming
The term manual part programming refers to the production of part programs directly in part program codes. It is still the most widely used technique for the production of part programs. To accomplish manual part programming successfully, specialist skills and knowledge are required by the part programmer. These include:
- The ability to read component drawings.
- A sound knowledge of trigonometry, geometry and mathematical calculations.
- An understanding of workshop practice, machine tool operation and cutting tools.
- A working knowledge of materials, feeds and speeds.
- An understanding of workpiece location, clamping and fixturing.
A knowledge of part program terminology and codes (possibly including techniques of data input).
- A thorough knowledge of the capabilities and facilities offered by the CNC machine tool.
- The ability to think clearly and logically with attention to detail.
Manual part programming is thus labour-intensive needing skilled personnel. The time involved in producing part programs is proportional to the complexity of the component. For complex three- and four-axis machining, this can involve many man hours of work. The situation is aggravated if the programmer needs to have a knowledge of more than one CNC machine tool or control system. Once the part program has been written, it must be converted into a machine-usable form, usually via MDI or punched tape. It must be verified and proven, tying up more man and machine hours.
It will be appreciated that manual programming can be very time-consuming and somewhat inefficient. The manual involvement at every stage presents the added possibility of incurring errors. The costs involved in producing the part program must be borne by the components eventually produced and can thus amount to a substantial proportion of the total cost. The time required to produce the part program can also form a significant part of the total lead time in the production of finished components. In some cases (machining in 5 or more axes), it may be impossible to produce part programs by manual programming methods.
Concept of computer aided part programming
The concept of computer aided part programming (CAPP) is to enable a computer to generate the part program code required to finish-machine the component. Advantages of achieving this include:
- Part programming procedures will be considerably simplified.
- The production of part programs will be speeded up.
- Computations of cutter path coordinates will be transferred from the programmer to the computer, thus reducing the possibility of errors.