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

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Since laser interferometer systems are high accuracy, non-contact measurement and easy installation, the systems have been incorporated into such manufacturing equipment as precision cutting machines, measuring machines and lithographic systems. The unit of measure for a laser measurement system is dependent on the wavelength of the laser source. The wavelength 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, degradation in system accuracy and repeatability will occur and limit the quality of final products. We have designed and produced a new environmental chamber for precision machine tools with laser interferometer system. The chamber consists of a precise air conditioner, a negative/positive pressure controller and a closed workspace surrounded with the insulating panels. The air conditioner provides the controlled environment within temperature change of 0.2℃ P-V (peak-to-valley) and humidity change of 4% P-V. The negative/positive controller can maintain an even pressure within an accuracy of 0.4hPa 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 109nm P-V in the displacement and a form accuracy of 91nm P-V are obtained ; both the results demonstrate the highly compensated accuracy due to the new environmental chamber.