Selecting Process Parameters and Machine Tolerances for Optimal System Performance

Machining parameter selection and tolerance specification for raw materials, machine tools and fixtures directly affect product geometric quality and system productivity. However, there currently exists no integrated method for analyzing these variables for machining systems. This paper presents a methodology for simultaneously selecting optimal machining process parameters and tolerance specifications for multistage machining systems. This methodology maximizes profit, which is formulated as a constrained optimization function in terms of product geometric quality, system productivity and cost. Product geometric quality is modeled as a set of regression functions based on a general variation propagation model and computer Design of Experiments (DOE); productivity is a function of machining process parameters and system reliability; cost is the sum of manufacturing cost and quality loss. Solving the optimization problem attains proper machining parameters and tolerances. This methodology is demonstrated using a two-stage machining system.