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The Parameterization Design and Motion Analysis for Multi-start ZA Worm Gearing Based on Virtual Processing Jianping SUN, Zhaoping TANG School of Railway Transportation East China Jiao Tong University Nanchang, Jiangxi Province 330013, China sunjianping@ Abstract Archimedes worm gear’s teeth surfaces are comply and their models were usually built approximately in CAD. This article analyses the processing character and formation principle of the Multi-start ZA worm, builds the accurate model and makes the full parametric design. In environment of Pro/E, applying the entire relevance character between virtual assembly and component, simulating reality processes, the worm gear was produced virtually, and its model was built accurately. Furthermore, the generated worm gear and worm were assembled virtually and their motions were simulated and analysed. Keywords: Computer aided design, Parameterization design, Motion analysis, Pro/E, Multi-start ZA worm gearing 1. Introduction Archimedes worm gear’s teeth surfaces are comply. At present, in the common CAD software, it is general that approximate drawing instead of worm gear’s really jugged [1] . It is very difficult to draw out its complicated and accurate tooth; in addition to, its match worm is classified for left- handed, right-handed, single-thread and multi-start. Those have increased difficulty to build its model. This paper starts mainly from the processing principle of Archimedes column worm (ZA worm), simulate its produce procedure, and make use of relations function in Pro/E, realize the accurate and parametric model of ZA worm. Furthermore, on the basis, the worm gear was produced virtually, and the generated worm gear and worm were assembled virtually and their motions were and analysed. 2. The train of thought to build model To imitate ZA worm turning process, draw cross section with the size and shape of parameterization worm gear hob’s cross section, take Archimedes spiral as trajectory, make use of the “Variable Section Sweep/Cut” function in Pro/E, cut off one slot on the worm blank, then pattern the slot, the multi- start worm gear hob is generated. It is the model difficult points to full parameterize its hands and number of threads. The key point is: firstly, to set up the parameters of hands (right-handed value is 1, the left-handed value is -1) and number of threads, to establish the Archimedes spiral by the way of equation which can change with hands and number of threads. Secondly, while pattern worm slot, it is necessary that designer select the pattern way of “Direction”, and select the worm blank’s axis as a reference to establish the first direction, enter the number of threads as number of members in the first direction and enter screw pitch as the spacing pattern members in the first direction. After finished worm gear hob parameterized model, on the basis, the worm model can generate by change parameter. The difference between worm and worm gear hob is that the worm gear hob has blade slot, and its radius is a clearance bigger than that of worm gear. The way which get worm gear model is to adopt the worm gear hob virtual processing. The basic train of thought is: in the virtual environment, to establish separately the worm gear blank and the worm hob, then place respectively them in each coordinate system which accord to the theory geometry assembles relation, make them rotate in each regulation, and do the Boole subtraction operation between them at different engagement position in the motion process, until the worm gear has been produced entire envelope surfaces [2] . 3. Build the relevance parameter From all above the train of thought, it can be known that ZA worm gearing’s parameterization design and motion analyse need to build those files such as the worm gear hob part, the worm part, the assembly between the worm gear hob and worm hob, and the assembly between the worm gear and worm. In order to realize parameterization design, these files need to parameterize their fundamental dimension. Table 1.The parametric table parameter m (modulus) q ( worm characteristic number) z1 (number of threads) xuan (hands) n (number of turns) value 5 18 3 1.0 4 parameter z2 (worm gear teeth number) hax (addendum factor) cx (bottom clearance factor) alpha (pressure angle) x2 (modification coefficient) value 53 1.0 0.2 20 -0.1 Making use of the parameters and relations function which Pro/E provides, according to the parameter relation between