Ensuring stable quality of ground parts by monitoring the process system parameters

Abstract

Abstract. The paper proposes a system for monitoring surface wheel-grinding by analyzing the dynamic alterations in output variables and the process system state parameters. It analyzes the intervals of the process system state parameter interrupts. State space analysis was employed to describe the behavior of the grinding process system. The dependencies obtained enable a complete description of how the system behaves at any interval of the main interrupt period. The analysis of such behavior is reduced to sequential calculation of its parameters at times t1, t2, ..., ti at interrupt intervals T1, T2, ..., TN. The proposed state space analysis method enables an independent evaluation of output perturbations. Besides, by analyzing the dependencies we had obtained, we concluded that for such evaluation, one would have to calculate not only the absolute values of output variables, but also their first and sometimes even second derivatives. Problem statementOne current trend in mechanical engineering is that assembling joints are becoming considerable more accurate. This necessitates better quality and performance of finishing machining. Metal machines and complexes are equipped with highly efficient controllable drives, special information systems and other functional devices with improved performance. More and more automated equipment comes in use with every year. Analysis of the existing production facilities shows that automated equipment is only used to 70 or 80 percent of its capacity when it comes to cutting and grinding operations.Let us analyze the reasons why automated equipment is used under-efficiently. When operating conventional machines, operators rely on their observation and operation experience to adjust the cutting parameters. One can machine a shaft in 30 or 40 seconds using a conventional machine, while it takes 100 to 120 seconds when using a CNC machine. This is due to the considerable alterations in the process system state that occur in machining. To ensure the specified quality as well as the stability of output variables, operations are configured for the worst system state.As a rule, automated systems are coupled with the existing process engineering and control principles without reconsidering and improving the latter. The process is designed once and for all and is usually subject to no alterations over the entire production of a product whereas alterations occurring in the process system are ignored. Operations result in considerable alterations in the accuracy and stiffness properties of machines; the physical and chemical properties of the cooling lubricant may also considerable alter between replacements, and so do the environmental temperatures, the diameter of the grinding wheels, and the condition of their applied surface. Each workpiece has specific properties.A relevant problem of material cutting theory consists in studying the improvements in performance achieved by monitoring the machining process, i.e. by analyzing the dynamic alterations in the output variables and the pr...

Determining deviations of output variables from forecast values in system for monitoring external round grinding process

“…In the paper [13] the authors simulated the state space with the consideration of the possibility to restore system parameters for the grinding process. As a result, we obtained the following equations:…”