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Reducing the flexspline (FS) deformation is important for decreasing the alternating stress, flare angle in the axial direction, spatial deformation of teeth, and tube length. However, it may increase the probability of insufficient engagement depth and nonexistent conjugate tooth profiles. In this study, a mathematical model of the harmonic drive (HD) with a new tooth profile is proposed to reduce the FS deformation while satisfying the engagement depth and existence of a conjugated tooth profile. First, the generation mechanism of the new tooth profile is discussed in detail and the connection method of the circular arc tooth profile and transition tooth profile in the FS were presented. Then, two key parameters of the model, the translation distance and offset distance were studied to design the ideal tooth profile. Finally, a tooth root chamfer method was proposed to achieve smooth operation of the HD. Additionally, owing to the lack of a wear assessment of the new tooth profile, a sliding coefficient calculation model was presented. To verify the feasibility of the models, a prototype with a radial deformation coefficient of 0.8 was designed, processed, and tested. The experimental results were consistent with the theoretical analyzes.

Gear involute artifact (GIA) is an object with an unbroken chain of traceable calibrations used to calibrate the instruments for measuring involute profile deviations. To machine GIA with sub-micron profile form deviations, an error analysis method for profile deviations in the involute envelope based on rolling generation was proposed. With this method, the effect on the involute profile deviations caused by the form and position errors of the core components of roller-guide involute rolling generation (roundness and eccentricity of the base circle, and straightness of the generating line) were analyzed and verified through simulations. Accordingly, methods for lapping, selecting the used segment of rollers and installing rollers were proposed. GIAs with a design base radius rb=56.3816mm were machined and measured through a double roller-guide involute rolling generation mechanism. The profile form deviations of four flanks of machined GIAs ranged from 0.34 to 0.54 μm within the evaluation range of 5 to 50 mm in roll path length (0.4 to 0.6 μm as measured by Klingenberg P40). This research provides support for high-precision GIA manufacturing in small-batch production.

Previous studies found that the peripheral cutting edge and end cutting edge in micro end milling had different cutting phenomena considering the size effect in micro cutting processes. This paper is a further study on this point considering different workpiece materials and cutting edge radii. Finite element simulations have been conducted to determine the minimum undeformed chip thickness (MUCT) by the chip morphology and the results are verified by micromilling experiments. Both the simulations and experiments show that the MUCT of the peripheral cutting edge and the end cutting edge are different even if the cutting edge radii remain unchanged. The MUCT is directly proportional to the cutting edge radius. Material properties also have some effects on the MUCT of the peripheral cutting edge. But it has limited effects on that of the end cutting edge. The results indicate that the feed engagement other than the axial depth of cut should be carefully selected in micro end milling when considering different workpiece materials.

Pumpless and directed gas transportation in aqueous environments has promising application prospects in various domains. So far, researches on gas transportation based on superaerophilic channels are limited to the transportation of fewer bubbles with low transportation velocity. How to enhance the transportation velocity and realize the transportation of a large quantity of bubbles (especially for gas jet) for practical applications remain unclear. Here, a half-open wedge-shaped channel with subaqueous superaerophilicity is fabricated, which demonstrates excellent bubble affinity and can realize the pumpless and directed bubble transportation. It is proposed that a Laplace force is the main driving force during the transportation and the magnitude of the force is influenced by both the wedge angle of the channel and geometric parameters of the bubble whereas the direction of the force is determined by the orientation of the channel. By applying a precovered air film on the subaqueous superaerophilic wedge-shaped channel, bubbles demonstrate a higher transportation velocity. Additionally, the prepared channel shows an outstanding affinity to oxygen jet at high flux, which can be utilized to transport oxygen for continuous subaqueous oxygen supplementation.

The ultra-precision master gear with high pitch accuracy has important applications in the calibration of high-precision gear measuring instruments or coordinate measuring machines and in military industries. In order to improve pitch deviations of ultra-precision gear, two gear-grinding techniques to improve pitch deviations of ultra-precision gear were proposed. First, based on the indexing plate system, the working principle of indexing plate and error transferring rules were discussed, and the technical approaches of decreasing the geometric eccentricity were proposed. Then according to the error interference principle, the offset-compensated technique and the neighbour-tooth translocation technique were proposed to improve the pitch machining accuracy of ultra-precision master gear. Finally, precision gear-grinding experiments were conducted by adopting the neighbour-tooth translocation technique based on offset-compensated technique. And the single pitch deviation fpof the test specimen is reduced from 1.06 to 0.63μm and the total cumulative pitch deviation Fpis reduced from 3.11 to 1.98μm with measurement uncertainty U95= 0.33μm, which both reach the highest class (class 1 defining in ISO 1328-1:2013). The results show the efficiency and practicability of the two gear-grinding techniques to machine ultra-precision master gear.

Higher gear-grinding accuracy can be obtained by using a flat-faced grinding wheel (FGW) and a generating method. However, the phenomenon of interfering with the adjacent tooth will happen when an unsuitable outer-edge width of the FGW is dressed. In order to optimise the shape of the FGW and further improve its rigidity and grinding accuracy, studies on the relative motion trajectory of the FGW, the correlations of the maximum outer-edge width (wmax) with the head frame setting angle (HSA, αy) and the adjustment quantity (E) in the feed direction were conducted. Finally a motion simulation and a grinding experiment verified the reasonability of the mathematical model and several improved measures to achieve interference free and rigid gear grinding were obtained. The results have important significances on formulation of scientific ultra-precision gear-grinding processes. [Received 23 February 2014; Revised 23 October 2014; Accepted 02 December 2014]

The accuracy requirement of ultra-precision involute artefacts and master gears, which are used to calibrate the gear measuring machines, is increasing as power density increases; however, the complexities and specificities in the involute processing and measuring have been the bottleneck of manufacturing technique for high-grade involute artefacts and ultra-precision master gears. In order to develop the ultra-precision involute gear profile, related researches were conducted in this study. First, the manufacturing level of high-grade involute artefacts was introduced. Then, the forming principle of the involute was discussed, and the roller–rail type and cam–baffle type of mechanical generating mechanism with little effects of driving accuracy on generating accuracy and less error sources were pointed out. Finally, the double roller–rail type of grinding and measuring devices for high-grade involute artefacts were designed according to the optimal forming principle of the involute, and a precision grinding experiment on an involute cam (a kind of high-grade involute artefacts) was conducted. The measured results show that the total profile deviation is not more than 0.6 µm and the profile form deviation is less than 0.4 µm in 105 mm generating length of the specimen. By using the refined involute cam and gear grinder with cam–baffle type of mechanical generating mechanism, a precision grinding experiment on the specimen of a master gear was conducted. The experimental results verify that the roller–rail type of mechanical generating mechanism has the processing capacity of high-grade involute artefacts with submicron-level profile accuracy and the refined gear grinder with cam–baffle type of mechanical generating mechanism has the processing capacity of ultra-precision master gear with grade-1 profile accuracy.

Harmonic-drive transmission finds many applications in industry, especially in manufacturing of industrial robots. As the key devices of an industrial robot, the harmonic drive reducers determine the robot's performance, which includes the positioning accuracy, loading capacity, life time, etc. To satisfy the need of manufacturing high performance harmonic drive devices, development of competent measurement system is of great importance. An automatic measurement system with high-precision and multifunction is under development. The system consists of the power module, loading module, torque and rotation measuring module. The measurement and operation principle were explained. The factors affecting the accuracy of the measurement system were analysed. The control system was designed to realize the automatic loading and acquisition of torque and rotation data. The principle and measurement software of the control system were also introduced. Finally, a harmonic reducer with the gear ratio 120 was measured to verify the feasibility of the measurement system.