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14 CAD/CAM technology for micro-planetary gear reducer with modular modulus <0.06mm Zhang Weiping, Chen Wenyuan, Fan Zhirong, Xu Zhengfu (National Education Committee of Film and Microfabrication, Information Engineering Research Center, Shanghai Jiaotong University, internal ring gear b Fixed, the three center wheels a, b and e simultaneously mesh with the single-ring gear planet g. There are no planetary gears and planetary bearings, which makes the structure simpler, more compact, smaller in size and easy to install, suitable for micromotors. match.
In the development process of micro planetary gear reducer with modulus less than 0.06mm, CAD/CAM technology is used to calculate various parameters of micro planetary gear reducer and graphical solid modeling, which improves the design quality and shortens the development cycle.
2 CAD technology of micro planetary gear reducer The CAD technology of micro planetary gear reducer mainly includes computer aided design calculation and graphic solid modeling of micro reducer. Through graphical solid modeling techniques, we can simulate and simulate design results and improve design parameters prior to manufacturing.
2.1 Micro-reducer computer-aided design calculation The computer-aided design calculation of the micro-reducer includes the calculation of the gears and the calculation of the gear parameters of the micro-reducer.
2.1.1 Calculation of the assembly conditions and transmission ratio conditions of the type 2 planetary gear reducer, we adopt the following formula: 2.1.2 Calculation of the gear parameters of the micro reducer 2.1.2.1 Select the appropriate actual center distance type 2 planetary gear reducer In the middle, the planetary gear g meshes with the sun gear a and the inner ring gear be respectively, and the theoretical center distances of the meshing gears are respectively: a-g outer meshing theoretical center distance Dag, b-g inner meshing theoretical center distance Dbge-g inner meshing The theoretical center is different from Deg. The number of teeth of each gear is different, and Dag, Dbg and Deg are not equal. According to the angular displacement concentric condition of micro-type 2 planetary gear reducer design, it is necessary to first determine a common center distance, that is, the actual center distance D of the meshing. Obviously, this Ds should be the minimum value Dmin and maximum of the theoretical center distance. Between the values ​​Dmax, here we take the design according to the design experience;; /= Dmin +0.76 (DmaxDmin) Then, we can carry out the meshing angle, the center-to-center variation coefficient, the sum of the displacement coefficients, the tip height variation coefficient, and the gears. Calculation of the displacement coefficient, the diameter of the tip circle, and the diameter of the root circle.
2.1.2.2 The calculation of other parameters is similar to the design of a general planetary gear reducer, and will not be repeated here.
We have compiled general software for the above calculation process. Table 1 shows the results of the parameters of the two reducers designed according to our software.
Thesis papers Computer-aided design 15 Table 1 Design examples of two reducers Number of teeth Z Actual center displacement coefficient x Root circle diameter dy. (mm) Tip circle diameter da (mm) Modulus 2.2 Micro planetary gear reducer graphics The graphical solid modeling of the solid modeling micro planetary gear reducer includes gear involute formation, single gear graphic solid formation, and assembly of the entire reducer.
Kinematics simulation is also available. Through graphical solid modeling, errors in the design can be found, avoiding interference and unreasonable tooth profile.
2.2.1 Drawing and program of the plane gear graphic After obtaining the solid model of the micro planetary gear reducer, it is transformed into the 3DS 3D animation software through the graphic interface, and the motion of the object can be simulated by the key frame technology on the computer. CAM Technology for Virtual Trial 3 Micro Reducer We have studied two methods for processing micro gear CAM technology.
One is micro-gear mask CAM technology based on semiconductor micro-machining technology; the other is CAM technology for micro-gear (EDM) processing micro-gear.
3.1 Micro-gear mask CAM manufacturing technology based on semiconductor micro-machining technology The lithography process is a key process in semiconductor micro-machining. After the photoresist pattern produced by photolithography process, electrochemical etching, electroplating and other processes can be performed. The reticle is a must in the lithography process, so the fabrication of the reticle is a critical step. Micro-gear CAM manufacturing technology based on semiconductor micro-machining technology mainly studies computer-aided manufacturing technology of micro-gear mask.
The technology mainly includes micro-gear mask pattern segmentation, processing data generation, and processing data simulation.
3.1.1 Micro-Gear Mask Pattern Pattern The mask pattern is formed by successive exposure of the exposed rectangular window on the mask sheet. The first step of the micro-gear template CAM technology is to divide the gear into rectangles, and the division should cover all the areas only allow overlap, no leakage is allowed, and the rectangular window is between 0.1Mm ~ 150rtn (depending on the mask exposure machine technical parameters) And) Otherwise, the exposed area will not form a complete picture, and the production of the gear can only end in failure. The sun gear, the planetary gear, the fixed internal gear, and the rotating internal gear are respectively divided into 1095, 803, 1548, and 1443 exposure rectangular windows. The gear teeth of the external gear and the overall segmentation result are as follows, for example, the gear teeth of the internal gear and the overall segmentation result are respectively.
3.1.2 Data Generation Module After the gear pattern is segmented, the rectangular window will be exposed with 5 parameters (X, Y, WHA), X and Y represent the center coordinates of the rectangle, W and H represent the length of the two sides of the rectangle, and A represents An acute angle between the edge (W5 16 Computer Aided Design Thesis or H) and the positive direction of the horizontal axis X. That is, a processing data stream file that can be recognized by the X-ray mask exposure machine is generated. The X-ray mask exposure machine can be exposed to generate a micro-gear pattern mask as long as it is read.
3.1.3 Data simulation module After the graphics segmentation and data generation, the gear processing data file is formed. These files are directly written to the file after being judged and calculated by the program. In order to ensure the success rate of micro gear processing, we have added a data simulation module. The purpose is to convert each group of data (X, Y, W, H, A) into rectangular four-vertex coordinates according to the generated data file, and then display the micro-gear graphic on the screen to verify the data file and data file. Generate the correctness of the program.
3.2 CAM technology using special precision machining method for micro-EDM processing of micro-gears) The micro-tool is used for micro-machining between the electrode and the workpiece. The electrode and the workpiece are filled with liquid (oil or water), and the electrode is in the liquid. Discharge, the workpiece is partially melted and evaporated, and one side of the chip is driven by the numerical control platform.
On the basis of the previous CAD, the coordinates on the gear contour line are converted into the NC code that can be used to operate the CNC platform. The EDM CNC machine tool reads the code to machine the gear product.
4 Examples Using the CAD/CAM technology discussed above, we designed and fabricated two types of micro-gear reducers with parameters as shown in Table 1. The micro-gears with a modulus of 0.06 mm were processed using micro-EDM technology with a modulus of 0.03 mm. After the graphic mask is fabricated, it is fabricated by photolithography and electroplating. Micro-planetary gear reducer with modulus of 0.06mm, its performance index: reduction ratio is 44. 2, outer diameter is 4mm. Modulus is 0.03 micro-planetary gear reducer, its performance index is reduction ratio: 44.2, outer diameter It is 2mm. At present, both of these reducers are installed on the mm electromagnetic micromotor developed by Shanghai Jiaotong University, and the operation is in good condition.
The electron microscopy and physical photos of the micro planetary gear reducer processed by the two methods are as follows: 0. Rao Zhengang. Planetary Transmission Design (Second Edition). Beijing: National Defense Industry Publishing. Micro processing technology. Changsha: Lu Chuanxian, a magazine on microfabrication technology. Practical computer graphics.峨嵋: Southwest Jiaotong University Press, Hu Wenji. 3D graphics and applications. Chengdu University of Electronic Technology Press, Lu Cunwei. EDM technology. Beijing: National Defense Industry Press, 1988. Peak. numerical technology. Beijing: China Railway Publishing House, 1983. Zhang Jiliang. MEMS and related technologies. Shanghai: Shanghai Jiaotong University Publishing 12