Design Theories And Laser Processing Methods For Miniature Coplanar Axes Line Gears

As a key component of miniature machinery,miniature gear has the characteristics of compact structure,small size,and high transmission accuracy.Miniature gears have a wide range of applications,including miniature robots,miniature pumps,precision instruments,and other mechanical systems.At present,the research on miniature gear mainly focuses on miniature involute cylindrical gear,while there are still bottlenecks in the manufacturing and application of miniature spatial gears.The traditional spatial gears have more teeth,and therefore,when their overall size is reduced,the reduction of tooth thickness makes it more difficult to achieve the machining accuracy,and the adhesion force of the tooth surface is significantly enhanced.Based on the meshing principle,the research on the miniature coplanar axes Line Gears(MLGs)with small teeth number is a direction to break through the bottleneck and has important academic value for promoting the development and application of MLGs.Based on the spatial curve meshing theory,the design theory,machining method,and measuring method of MLGs were studied.The main work can be summarized as follows:(1)Based on the spatial curve meshing theory,the meshing equations of the MLGs were derived,and the contact curves and the center curves were solved,and then the accurate geometric models of the MLGs,including the mathematical model of tooth surfaces and the3-D solid models,were established by the sweeping method.Then three pairs of MLG pairs were designed,and a pair of MLG pair was selected for kinematic experimental verification.(2)On the premise of establishing the accurate geometric model,the adhesion forces between the tooth surfaces of MLGs were studied.The D-H adhesion model was extended to accurately calculate the adhesion force between the rough peaks,and it was combined with Nayak distribution model to calculate the adhesion force between rough tooth surfaces.Then,taking the maximum contact pressure as the optimization objective,the design parameters of MLGs were optimized.(3)The nanosecond laser micro milling process and machining model of cylindrical MLGs were studied.The ablation morphology of single pulse was obtained by the simulation model,and then the morphologies of single track,micro groove,and tooth groove of MLG were obtained by superposition method,and the influences of process parameters on the machining results were studied.Moreover,in order to determine the appropriate process parameters,orthogonal experiments were carried out on the basis of the calculation model,and then the cylindrical MLGs were machined with the selected process parameters.(4)The processing technology of conical MLG by nanosecond laser micro sintering was studied.The temperature field model of the single track in the machining process was established.In the model,the heat conduction problem was solved and the heat source model was obtained by solving the laser absorptivity distribution in the powder layer.Then the conditions for forming the continuous track were obtained,and a 3-D grid microstructure was fabricated to verify the process parameters.Then,the response surface experiments were carried out,and the regression models were established.Based on the regression models,the best processing parameters of driving conical MLG and driven conical MLG were obtained,and then the conical MLGs were processed.(5)The machining accuracies of MLGs were measured and evaluated by an optical profilometer.The measuring methods of the driving MLG and the driven MLG were studied respectively.Then the nominal contact curves were extracted from the measured tooth surface data,and the corresponding deviation evaluation items were proposed on the basis of the transmission characteristics of the MLG.The items included the error of a single contact curve,the error between two adjacent contact curves,and the cumulative error of the tooth pitch.According to the deviation evaluation items,the machining accuracies of cylindrical MLGs and conical MLGs were evaluated,and the kinematic experiments of cylindrical MLG pair and conical MLG pair were carried out.