Low cost process monitoring for CNC transfer machines
Innovative new application software enables users of high throughput, multi-process CNC machine tools to implement process monitoring without incurring any additional hardware costs. The software is likely to be of especial interest to users of high-end production systems such as transfer machines, where even relatively small operating issues can rapidly escalate into much larger, more expensive problems unless proactive remedial action is taken. Through real-time monitoring of the power/current values of the electric motors on a transfer machine throughout its milling, turning or grinding processes, it is possible to minimise system downtime and maintain production quality by guarding against faults. Typically, these would include worn or damaged tools and undersize or oversize workpiece blanks. Known as NUMmonitor, the software initially operates in ‘learn’ mode to acquire the varying loads and drive currents of motors when the CNC machine tool is running at optimal performance levels and with a sharp new tool. Up to eight motors can be monitored simultaneously throughout the machine’s operating cycle, and the software accommodates up to 11 different error detection criteria per motor. In the case of multi-NCK systems, a further 8 motors can be monitored for each additional NCK. On transfer machines, it is generally sufficient to monitor just the load (power) of the spindle motors. Both the level and duration of each load event that occurs during the ‘learn’ cycle are measured and recorded, and the process can be repeated to obtain average values. There is no limit to the number of different load events that can be accommodated during a complete machine cycle. Minimum and maximum curves are automatically generated from the ‘learn’ cycles, with the user able to define the types of error detection and the logic (for combining different error criteria, if desired). These machine cycle-time related operating parameters form ‘known […]