The Use of Electronic Speckle Pattern Interferometry for Evaluation of Machine Tool Static Stiffness
The use of measurements performed using electronic speckle pattern interferometry (ESPI) is shown to determine the relationship between the load and field of spatial displacement of a milling machine’s frame. The results of the investigations make it possible to determine both the static stiffness of the entire machine’s structure as well as the role of individual components of the machine in its global stiffness characteristic. An ESPI interferometer has been developed and constructed for research purposes. Absolute direct stiffness, ka, of the machine ram and relative direct stiffness, kr, of a radial universal milling machine frame were determined using the results of machine quill out-of-plane displacement measurements as a function of the load applied at different positions of the machine ram and table. Measurement results show that the joints between the structural members of a machine frame play a great role in the total stiffness of the machine structure. The stiffness of joints is difficult to calculate, therefore the results of experimental research are of high significance.
Keywords: Diode pumped solid state (DPSS) laser, electronic speckle pattern interferometry (ESPI), correlation fringe pattern, out-of-plane displacement measurement, machine tool static stiffness, absolute stiffness, relative stiffness