Realising high accuracy machining by applying optimal clamping forces

Abstract

In this research, appropriate magnitudes of clamping forces and their applying methods are studied to improve machining accuracy. The objective of this study is to find a minimum-clamping load that must be applied to keep a workpiece in static equilibrium and to assure that the total workpiece deformation is minimised in a machining process. In particular, a machining feature-based clamping force optimisation model is presented for this purpose. Through cutting experiments, it is observed that the maximum cutting forces occur in different directions for each machining feature. These maximum cutting forces are measured and integrated into a machining feature-based cutting force database. The deformation of a workpiece is then estimated using finite element analysis, when clamping force and cutting force along tool path are loaded. By combining the results of the above two steps, a mathematical optimisation model is formulated. This model not only makes it possible to minimise the workpiece's deformation under several cutting operations in one machining process, but also finds optimum clamping forces exerted at the contact regions. The results of the case study demonstrate the effectiveness and validity of the methodology, which shows promise of improving the quality of machined products based on the optimised fixture design and set-up.