Automatic generation of dynamic clamping forces for machining fixtures

Abstract

Automatic fixture configuration analysis is an essential issue in the context of computer-integrated manufacturing. In this paper, a general methodology for fixture configuration verification is presented, which is based on force closure and clamping equilibrium. The inclusion of a new clamping equilibrium criterion ensures a robust clamping layout and hence reduces the possibility of workpiece displacement within a fixture. For clamping force analysis, a new method for directly generating the minimal clamping intensity for planar fixtures is presented. Next, we develop a general friction methodology of dynamic clamping analysis and planning for arbitrary-shaped workpieces based on nonlinear programming. The objective of the presented algorithm is to determine a spectrum of minimum sustainable clamping forces for a machining process based on a proposed criterion of maximum friction. The set of variable clamping intensities is determined such that it is just enough to counterbalance the dynamic cutting forces. This approach is more realistic than other systems with static cutting conditions and frictionless contacts. The concept of maximum clamping forces is also proposed and a computation method is presented. The non-approximation representation of contacting forces presented in this algorithm guarantees the existence of an optimal clamping solution. Moreover, it makes the algorithm robust and reliable. Case studies are included to demonstrate the effectiveness and capabilities of the methodology.