Design modelling and control of an experimental cylindrical grinder

Abstract

Nowadays machining in manufacturing industry has become more competitive and demanding than ever before. Grinding as one of the last stages in the manufacturing process has been the focus of the research studies in the field of manufacturing for quite some time. Grinding process compared to the other machining operations involves in low rates of material removal. The thermal, metallurgical, and mechanical phenomena coupled with the grinding process, make the contact dynamics unpredictable and complicated; hence the grinding wheel life and cycle times cannot be determined from any available standard tables and charts. This is due to the fact that, a large number of parameters are influencing each other in a grinding process. During a grinding process there are undesirable experiences that can be included as thermal effects, chatter vibration, rapid grinding wheel wear, etc. In order to overcome these problems associated with the grinding process a correct understanding of the involving factors in the process is of great significance. This thesis work is focused on design and implementation of a bench scale plain type cylindrical grinding machine for grinding of the rolls in plunge and traverse cut in the laboratory environment. The servo controlled feed-drives and slide-way motions, which allow an efficient operation, are presented for each axis of the machine. Nonlinear friction effect as one of the major disturbances affecting the motion control systems is identified for the in-feed axis of the machine tool based on LuGre model. A novel method for grinding force estimation by monitoring of the thrust force in the infeed axis is presented based on the identified friction. The implementation of such an approach benefits the low cost compared to the common methods which use the dynamometer sensors for condition monitoring of the grinding process. A traverse grinding cut model is presented in succeeding chapter to show how this type of vibration can give rise to the grinding force value and make it unstable. The stability analysis for demonstration of the stability boundaries is presented, and the time domain cutting force in tangential and normal directions are presented numerically. Further investigations need to be conducted to validate the stability results.