Concept of a stored program
systems operate by carrying out sets of instructions in a strict and ordered
manner. A collection of such instructions is known as a program and the
task of providing such instructions is known as programming. In the
case of a CNC machine took such a program is often designed to perform the
complete machining of a component or a part. A program of instructions for a
CNC machine tool is thus termed a part program.
A part program is a set of instructions formulated to describe the actions required of the machine took These instructions must be presented to the machine tool control unit (MCU) in the order in which the programmer requires them to be performed. This is because the control program within the MCU is designed to start interpreting the part program from the first line of instructions, in strict sequence, to the last line of instructions. It cannot be stressed enough that that MCU will merely carry out the instructions as presented to it, not what the programmer thinks has been presented.
safety grounds it is important that all instructions, and the sequence of all
instructions be checked, and double checked, prior to their execution at the
machine. At best, any errors may only result in damage to tooling, the
workpiece or the machine tool itself. At worst, the operator could sustain
serious injury as a result of a tool/ workpiece collision. It is strongly
suggested that one, or more, of the methods of proving a part program,
presented in section 7.5, be adopted prior to execution at the machine.