DESIGN AND EVALUATION OF AN ELEVATED TEMPERATURE CUTTING FORCE DYNAMOMETER FOR HYBRID MANUFACTURING

Cutting force coefficients, workpiece dynamics, and uncut chip area all change as a function of temperature during machining processes at elevated temperatures. In a traditional milling process, these parameters are nearly constant. The bulk workpiece temperature remains well below the working limit of the material, generally near room temperature. However, workpiece temperatures in hybrid manufacturing, where additive deposition precedes machining, are spatially and temporally variable. A milling force model that does not incorporate temperature effects will generally overestimate the cutting force and workpiece dynamic stiffness and underestimate the chip area. Milling parameters that are stable at room temperature may be unstable at higher temperatures, leading to unexpected chatter and poor part quality. A cutting force dynamometer was designed, constructed, and tested to measure cutting force during milling with the workpiece heated to a constant bulk temperature of up to 500°C. The measured cutting forces were used to determine temperature dependent cutting force coefficients. These coefficients and workpiece dynamics were integrated into a time domain milling simulation to predict cutting force and stability under elevated temperature conditions. The outcome is improved modeling capabilities for hybrid manufacturing processes.