Non-production time is any time your CNC machines are scheduled not to be running. Non-production time for each shift includes breaks and lunch (if your machines cannot run unattended). Daily non-production time includes any off shift period. If, for example, your company works two shifts, you'll have from four to eight hours of off-shift time per day. Weekly non-production time includes any time during the weekend that your people do not work. And yearly non-production time includes any shut-downs your company takes.
To improve your machine tool utilization, think of things you can do during non-production periods that will save time when you are in production. You can stagger the working hours of your setup people and production people to take advantage of daily non-production time. If, for example, you schedule your setup people to come in one hour early and work nine hour shifts, and if you stagger their lunch periods, you have the potential to utilize 1.5 hours of non-production time per shift. While you will not reap this benefit every day, the gains should far outweigh any increase incurred by the additional working hours. The same, of course, goes for making setups during weekend non-production time. Again, any overtime pay you give your setup people will be minor compared to the increase in production time.
Minor preventive maintenance tasks such as adding oil, changing filters, and simple inspections can be done during daily non-production time. Just like setup, this is easily accomplished by staggering your maintenance people's time with production. Intermediate preventive maintenance tasks like major inspections and spindle bearing replacement can be done during weekly non-production time. And major preventive maintenance like machine rebuild can be done during yearly non-production time.
Working your tool setters during non-production time can pay dividends if you can shorten on-line tool maintenance. If for example, your tool setter comes in on a Saturday to assemble and measure all cutting tools needed for your machining centers during the week, a great deal of production time can be saved.
With a little thought, you can surely think of many other things select people can do during off-shifts to keep machines running smoothly during production time. Simply watch your people to determine the bottlenecks they face. With every bottleneck, there is probably a solution that involves the use of non-production time.