Thermal error mode analysis and robust modeling for error compensation on a CNC turning center

In this paper a novel concept of thermal error mode analysis is proposed in order to develop a better understanding of the thermal deformation on a tu rning center. The thermal error of the machine can be treated as the superp osition of a series of thermal error modes with corresponding mode shapes a nd time constants. The selection of sensor location can then be improved ba sed on the thermal error mode analysis. A robust modeling approach is also proposed to minimize the errors due to temperature measuring noise and the adverse effect of environmental changes. Through the use of thermal error m ode analysis and the robust modeling approach, the number of thermal sensor s has been reduced from 16 to four. The thermal error compensation system h as been applied to a turning center in daily production for more than two y ears and it has kept year-round accuracy. The thermal drift in workpiece di ameter on the turning center has been reduced from 35 mu m to 6 mu m from i ts center of tolerance. (C) 1999 Elsevier Science Ltd. All rights reserved.