Control of Vertical Spindle Surface Grinding from a multi-axis Numerically Controlled Machine

Abstract

Due to the increasing need for components comprised of hard and brittle materials such as glasses, steel alloys, and sophisticated ceramics, standard grinding and polishing techniques are no longer able to meet the expectations of today's precision manufacturing community. Grinding machines' functional capabilities, control systems, and peripheral process monitoring equipment have all improved during the last 20 years. Process enhancement technologies such as touch detection, wheel balancing, and in-process gauging may be incorporated into higher-end grinding machines based on specific customer requirements; however, due to the differing features and functionality of equipment from different suppliers, this requires significant customization work by the manufacturer. Moreover, the execution of long-proposed optimization strategies such as adaptive and intelligent control has not progressed significantly beyond specific research programs tied to a specific machine and controller, frequently using non-industrial equipment for key process data monitoring. However, it is vital and absolutely necessary to carry out such activities using a scientific approach, i.e., the process should be quantitatively controlled and optimized rather than done by trial and error. There is also a need to produce innovative and modern control system for controlled vertical spindle surface grinding multi-axis Computer Numerical Control (CNC) machine. Theoretical modelling and instrumentation for controlled vertical spindle surface grinding multi-axis Computer Numerical Control (CNC) machine are provided and addressed in depth in this study. During the grinding process, a method in which controlling of surface parallelism by changing the depth of cut is done, is applied. The achievable single pass tolerances in vertical spindle surface grinding are frequently restricted by machine compliance and also, the grinding wheel. The approach presented here involves precisely altering the depth of cut during grinding to maximize dimensional precision without the need for additional spark out passes. In this stage, the projected deflection from the simulated compliance and the measured vertical force are utilized to perform the correction. Two distinct methodologies are compared to determine the system's compliance. A controller of multi-axis commercial Computer Numerical Control (CNC) is altered to process the measurement of dynamometer in real-time, calculate controlling commands, and actuate servo loops. Because the system's deflection fluctuates with force of grinding, using depth of cut manipulation, a tracking controller tracks the expected deflection of the wheel, cancelling out part form defects. The results from experiments are shown for a variety of process settings, demonstrating the efficiency in terms of ground part parallelism, of the compensation system. It also resulted in significant improvement in quality of surface grinding.