The part program is a sequence of instruction that describe the work that is to be done to a part. Typically these instructions are generated in Computer-aided manufacturing software and are then fed into the computer numerical control (CNC) software on the machines, such as drills, lathes, mills, grinders, routers, that are performing work on the part. The CNC computer then translates the set of instructions into a standardized format of G-code and M-code commands and follow the instructions in the order they are written left to right or top to bottom.
When multiple repetitive operations are needed on a large number of parts canned cycles can be used to reduce the number of operation blocks in a part program. In some cases a part might need to go between multiple machines and have multiple operations performed on it to generate the geometry that is need.
Example of the order of operations seen in a typical program [1]
- Program start
- Load selected tool
- Turn spindle on
- Turn coolant on
- G00 Rapid to starting position above part
- All machining operations to part
- Turn coolant off
- Turn spindle off
- Move to safe position
- End program
Each type CNC machine will have different name for the operation they perform to parts to achieve the desired geometry on a part such as tasks like drilling, or cutting threads, but perform these actions differently. The choice to use a mill or lathe comes down to the geometry of the part you are making and how the machine can hold onto the part and what operation you want to perform to achieve the geometry needed. If the part is very complicated it may go through multiple part programs to achieve the desired results.