Automatic Modification of Local Drilling Holes via Double Pre-Assembly Holes

Qiubai Yan,Wenliang Chen

doi:10.4236/wjet.2015.33c028

Abstract

Manufacturing accuracy, especially position accuracy of fastener holes, directly affects service life and security of aircraft. The traditional modification has poor robustness, while the modification based on laser tracker costs too much. To improve the relative position accuracy of aircraft assembly drilling, and ensure the hole-edge distance requirement, a method was presented to modify the coordinates of drilling holes. Based on online inspecting two positions of pre-assembly holes and their theoretical coordinates, the spatial coordinate transformation matrix of modification could be calculated. Thus the straight drilling holes could be modified. The method improves relative position accuracy of drilling on simple structure effectively. And it reduces the requirement of absolute position accuracy and the cost of position modification. And the process technician also can use this method to decide the position accuracy of different pre-assembly holes based on the accuracy requirement of assembly holes.

Highlights

Almost seventy percent of fatigue related aircraft crashes result from fastener structures, while eighty percent of those fatigue cracks occurred at fastener holes
An online modification method is proposed for drilling holes based on double pre-assembly holes
The main conclusions are as follows: 1) Compared to traditional revisions, it is more robust in that it can guarantee the drilling accuracy along the line determined by the pre-assembly holes

Summary

Introduction

Almost seventy percent of fatigue related aircraft crashes result from fastener structures, while eighty percent of those fatigue cracks occurred at fastener holes. The manual drilling process can no longer guarantee the quality of them [3] [4] Under such circumstances, automatic assembly has been widely investigated and used in practice to increase. During the process of automatic drilling, model parameters like hole’s position and normal direction could be obtained from CAD modules of structures. A great amount of airplane components is simple structural elements They do not need high standard of position accuracy but as long as a fair position of intersecting point and reasonable hole margin. Given the limits of current measurements and assembly structures, we often measure the offset between positions of pre-assembly holes and their theoretical values The average of those offsets is used to modify the assembly. The locations of holes along the line where two pre-assembly holes lie on could be obtained

Modification of Straight Drilling on Single Degree Skin

Modifications of Translations

Validation

Conclusions