摘要
夹具设计自动化可以极大地提高生产效率,其研究具有重要意义。本文在分析国内外夹具设计研究的基础上,针对当前研究的不足,提出了一种精度自适应的夹具自动组装理论方法。
所谓精度自适应的夹具自动组装理论方法是一种先对所有夹具元件进行编码并记录尺寸及精度数据,然后自动选用已编码的元件进行定位方案设计,再调用定位方案所选元件的精度数据和工件的定位基准误差数据自动进行定位误差分析,优选定位方案,最终输出最优夹具组装方案的夹具设计方法。精度自适应的夹具自动组装方法主要由夹具定位方案自动设计方法和定位误差自动分析方法组成。该方法可以自动进行夹具定位方案设计及定位误差分析,实现了夹具的自动组装。此外,由于充分考虑了夹具元件的误差对定位误差的影响,该方法还具有精度适应能力。
孔系组合夹具由于具有元件种类和数量较少、可重复利用、组装方便等优点,适合于夹具设计自动化研究。本文以孔系组合夹具为研究对象,对精度自适应的夹具自动组装方法进行了以下几个方面的研究:
(1)开发了孔系组合夹具定位方案自动设计原型软件,输入夹具元件信息、工件信息和定位信息,输出定位元件方案(定位元件的位置和定位元件编码)、工件在夹具坐标系中的位置,实现了定位方案的自动设计。
(2)研究了定位误差自动分析方法,建立了一面两孔定位方案的机构学定位误差分析模型,并使用概率分析法进行了定位误差分析。
(3)设计了夹具元件测量系统,可通过处理由三维扫描仪获取的夹具元件的图形数据,提取出夹具元件的准确尺寸数据,以供定位方案设计和定位误差分析使用。
另外,本文设计了一种新型的孔系组合夹具——圆锥孔系组合夹具。该夹具系统使用圆锥孔/销进行定位/夹紧,不仅使得元件拆卸方便,而且使得定位件、紧固件等元件与基础件的配合间隙可调,减小了元件之间的配合误差及由此引起的定位误差,也可减小因元件磨损而产生的误差。
本文在最后对相关研究进行了总结和展望。
The automation of fixture design can raise the production efficiency in mechanical manufacturing industry , so its research is very important and indispensible . After analyzing the research situation and the shortcoming of the application of fixture design in recent years , a method of accuracy self-adaptive and automatic assembly of fixture system has been advanced .
The method of fixture design firstly codes all the fixture elements and records their sizes , then designs location plans and fixture assembly plans using the coded elements , analyzes and calculates the location errors according to the data of elements error and workpiece’s location datum error , outputs the final fixture design schemes sorted by the location error . This method consists of the automatic plan of location and the analysis method of location error . The method can design fixture location plan and calculate their error automatically , so the assembly of fixtureis easy to be achieved . The accuracy of the fixture scheme , based on the method , adapts to that of workpiece as fully considering the fixture elements error .
As the assembly of holes-system modular fixture is easy and the fixture elements can be reused , the paper makes some studies into the holes-system modular fixture based on the methodabove mentioned .
(1) An antitype software has been developed that can design the locating plans of holes-system modular fixture automatically . The software inputs the information of workpiece size , fixture structure parameters and location datum , then outputs the location plans automatically including the position of the elements and workpiece .
(2) The approach of automatic analysis of fixture location error has been presented . Using this approach , the paper establishes a link mechanism model to analyze the workpiece location error in fixing the part with one surface and two bores .
(3) A measurement system of fixture elements has been designed to acquire raw data of elements for reducing the location error caused by their manufacturing error . Lastly , an taperholes-system modular fixture has also been designed with the taper hole structure . On the one hand , the taper hole structure of the fixture elements makes fixture elements easily assembled and adjusted , which reduces the location error of fixture . On the other hand , the base plate of this fixture system can be specifically designed to be low-fidelity that cuts down the cost of production .
Based on the paper’s research , some useful conclusions , effective ideas and methods for further research are put forward .
引文
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