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This paper presents a miniature three-degree-of-freedom laser measurement (3DOFLM) system for displacement feedback and error compensation of a nanopositioning stage. The 3DOFLM system is composed of a miniature Michelson interferometer (MMI) kit, a wavelength corrector kit, and a miniature autocollimator kit. A low-cost laser diode is employed as the laser source. The motion of the stage can cause an optical path difference in the MMI kit so as to produce interference fringes. The interference signals with a phase interval of 90° due to the phase control are detected by four photodetectors. The wavelength corrector kit, based on the grating diffraction principle and the autocollimation principle, provides real-time correction of the laser diode wavelength, which is the length unit of the MMI kit. The miniature autocollimator kit based on the autocollimation principle is employed to measure angular errors and compensate induced Abbe error of the moving table. The developed 3DOFLM system was constructed with dimensions of 80 mm (x) × 90 mm (y) × 20 mm (z) so that it could be embedded into the nanopositioning stage. A series of calibration and comparison experiments were carried out to test the performance of this system.

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Interference fit is widely used in many industrial fields for its high ability to transmit an axial force or torque between a shaft and hub. But the performance of interference fits during their life in service is limited by stress concentrations and surface wear. Nowadays, theoretical methods based on thick-walled cylinder theory become increasingly abundant. However, the prediction results of stress distribution in press-fit process are not accurate for ignoring the stress concentrations. Since the stress distribution is significant for analysis of surface wear and assembly quality, especially for precision assembly of small parts, the purpose of this study is to build a new theoretical model to predict the stress distribution. The stress distribution equation was deduced based on a simplified model that a nonuniform linear load acts on a portion of semi-infinite plane. Finally, the stress distribution in the press-fit process was analyzed by the theoretical model, as well as the stress distribution of different material pairs (Ni36CrTiAl–50Ni-50Fe, AISI 1045–AISI 1045) under full contact condition. The comparison between theoretical and numerical results shows that the new theoretical model has high accuracy in predicting stress distribution and maximum stress, and the relative error is less than 17%. Therefore, the new theoretical model can give more reasonable results and provide a more reliable approach for design of interference fits. Furthermore, the model provides a method for the optimization of interference analysis under different structures and working conditions, and gives a theoretical basis for real-time estimation of assembly quality.

UV-LIGA technique is used to fabricate hot embossing mold of PMMA microfluidic chip. Pre-polished Ni plate serves as electroforming substrate and the micro channel is the only structure to be electroformed in the fabricated mold. The precision of the micro channel strongly depends on the process parameters. Experiments show that the width of micro channel varies with the electroforming time. With the electroforming time of 108, 140 and 160 min, the width of micro channel reduces to 89, 86 and 82% of patterned SU-8 mold respectively, which is caused by swelling of SU-8 in acidic, high temperature electroforming solution. This swelling is the key answer to the slope of the sidewalls of the electroformed structure. This study is beneficial to optimizing microfluidic chip mold design.