| Aircraft assembly technology shows its competitiveness of a nation’s aviation manufacturing industry. Assembly process effects wear life of aircraft seriously. Amount work of assembly is about half of making a whole aircraft, or more. A large number of holes want to be made during plane assembly process, such as rivet hole and bolt hole. Hole quality and efficiency made by manually do not meet the high demand of modern aircraft, which impedes the development of airplane. Hole making automatically is an inevitable trend, including automatic fastening system, flex-track and robot. Hole wall roughness and countersink depth are two important items that used to check hole machining quality. Under the support of a national defense project, the effect of pressure-foot which was assembled on robot hole making end-effecter was studied deeply through theory analysis and experiment. The effect of pressure foot on hole quality was got.The important of bolt holes and the necessity of automatic machining hole were analyzed. State of the automatic machining hole was described, mainly focus on automatic fastening system and industry robot. Straits and applicable situation of every technology was compared, and existing problems of robot drilling system were shown. Based on above analysis, content and study frame of this paper were presentedPressure-foot is an important element during robot drilling hole. It is necessary to understand the key technologies of robot drilling before analyzing the function of pressure-foot and its effect on hole precision. Construction of robot drilling experiment system and straits of industry robot were introduced firstly in the second chapter. Construction of end-effecter, including its mechanical parts and controlling method of pressure-foot, was described in detail. Then the key technologies of robot drilling were introduced.The first function of the pressure foot is to improve rigidity of the robot, which can increase the steady of drilling process. The structure of industry robot is cantilever, and it is prone to deform when pressure foot force are applied to it. To decrease the negative effect of robot deformation, and attain precision of bolt hole, the following works were done. Law of the robot deformation with pressure foot force, applied interval and persistent, was analyzed. An optimized drilling posture was got. The second function of pressure is to control depth of countersink. But pressure foot can cause error of countersink. Effects of such elements as geometry of workpiece and deformation of workpiece on countersink were studied, with theory analysis and experiment. As a result, a conclusion of how to control countersink depth precisely was got.On the base of analyzing the effect of pressure foot on robot deformation and countersink depth, experiments were done to study the effect of pressure foot on hole quality. Cutting forces and pressing force were compared when drilling Al alloy and Ti alloy, it shown that the ratio of cutting force and pressing force is o.3that machining quality can be guaranteed. |
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