A New Environmental Chamber for Nano-meter Position Measurement and Control on Ultra-precision Machine Tools with Interferometry

Laser interferometer for precise positioning systems has been installed into such manufacturing equipment as precision cutting machines, measuring machines and lithographic systems. However, the wavelength of the laser in atmosphere is affected by the refractive index of surrounding air, which depends on the temperature, relative humidity and air pressure. Without proper environmental control, the form accuracy of the products is reduced due to the fluctuation in wavelength during machining. In this paper, to improve the form accuracy, a new environmental chamber for precision machine tools with laser interferometer system is proposed. The chamber consists of a precise air conditioner, a negative/positive pressure controller and a closed workspace surrounded with the insulating panels. The temperature and humidity of the environment are controlled by the air conditioner within the change of 0.2°C P-V (peak-to-valley) and 4% P-V, respectively. The negative/positive controller can maintain an even pressure within an accuracy of 0.4 hPa P-V by adjusting inside pressure to either negative or positive relative to outside. To utilize the insulating panels for making the chamber frame allows for low cost and easy construction. The fluctuation in the relative tool displacement to the workpiece and the surface profile formed by raster flycutting are measured to verify the environmental control performance for a long period. A fluctuation of 109 nm P-V in the displacement and a form accuracy of 91 nm P-V are obtained both results demonstrate the highly compensated accuracy due to the new environmental chamber.