A Theoretical Method Of Automatic Assembly Design With The Adapting Accuracy For Holes-system Modular Fixture

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 .