Real-time automatic statistical control for the grinding process

The highly consistent axes control of current computer numerically controlled (CNC) grinding machines has ensured a high-quality output provided that the process parameters can be kept constant. However, there are many variations in the process that give rise to differences between workpieces. Typical process variations such as tool wear, materials and temperature changes are inevitable and cannot be compensated by advancements in axis servo-control. This paper addresses this problem by applying a high-level control methodology which makes use of real-time statistical process control (SPC) information to determine whether the process has deteriorated due to process variations. Adjustments to machine parameters to offset these changes can then be made. The methodology has been successfully incorporated in a control loop within the controller of the CNC grinders to achieve truly unattended grinding operations.