Keeping tabs on non-cutting time
Within a given program, there is an easy way to determine how much non-cutting time is in the program. Using this technique will help assess whether programs are running efficiently, and it’s relatively simple to do.
Simply run and time the program twice. Once with the feedrate override switch set to 100% (its normal position for running production) and once at 200% (not machining a workpiece, of course). With the two times available, calculating cutting time and non-cutting time is easy.
Cutting time = (100% feedrate run time minus 200% feedrate run time) times tw0
Non-cutting time = 100% feedrate run time minus cutting time (that you just calculated)
Note that cutting time is equivalent to the time the machine is in a feed mode, G01, G02,G03, etc. Machining efficiency will be poor if you have excessive approach and escape distances, of course.
While knowing the efficiency within a cycle is helpful, it may be a bit deceiving. With most CNC machines, for example, load/unload time is also non-cutting time. The machine cannot be cutting while workpieces are loaded (again, with many machines).
Additionally, if your people cannot keep up with the machines they run, possibly because you have them performing other tasks like cleaning and deburring, inspections, sizing adjustments, and secondary operations, the percentage of time a machine is cutting will drop even further.
The higher your production volumes,the more important it is to reduce non-cutting times. If you find them to be unacceptable, it should be taken as a signal that you must apply cycle time reduction techniques.