A versatile approach, considering tool wear, to simulate undercut error when turning thin-walled workpieces

Abstract

In-process workpiece elastic deflection is the major source of geometrical error when machining low-stiffness workpieces. It creates an undercut error which needs to be corrected by time-consuming and labour-intensive operations. For this reason, cutting process simulation is growing in interest. To do so, a model representing the workpiece flexibility is coupled with a model to predict the applied cutting forces. For a given tool-material set, these cutting forces depend on the cut section, which therefore depends on current deflection of the part during machining, but also on the level of tool wear. This research work focuses on developing a general coupling approach to tackle this challenge. The case study is the finish turning on thin Inconel 718 discs. The cutting forces are predicted by a mechanistic model taking tool wear into account. The wear effect is expressed using the cumulative removed volume. The workpiece stiffness is determined with a reduced model using a modal basis. When dealing with large workpieces, it results in a remarkable computing time reduction during the time domain simulation. Cutting tests with varying engagements are simulated in a dexel-based versatile framework and undercut errors are compared to experimental observations.