Interfacial burr formation in the drilling of stacked sheets of material is a common problem in aircraft structure assembly. Eliminating or minimizing burrs at the interface of the stacked sheets may prevent the current need for destacking and deburring operations. This paper presents the results of experimental investigations into the effect of various drill geometry and process parameters on burr formation in stacks of 2024-T351 and 7075- T651 Aluminum. Analysis of the data indicates drill point angle, clamp type, and hole-to-clamp distance as being the most significant factors affecting interfacial burr formation. Further, drill feed, spindle speed (RPM) and point type, including specially ground step drills, also displayed a noticeable impact on interfacial burr formation. Comparisons of the various drill geometries under study indicate a design which performs best with regards to reducing interfacial burr formation for the workpiece materials considered in the experiments. It was found through optical comparator measurements that interfacial skin exit burrs and frame entry burrs demonstrated a similar dependence upon all the examined parameters. Averaged across all tests, frame entry burrs were approximately 15% smaller than skin exit burrs. It was found that the most significant factors in interfacial burr formation were drill point angle, clamp type and clamping distance. A combination of a 118 deg point angle with a hole location near either a hand clamp or hole clamp reduced the interfacial burr heights. Additionally, the analysis revealed that smaller feeds produced smaller skin exit burrs, while the use of a step drill reduced the frame entry burr. It is believed that these trends will hold true for both types of interfacial burrs. The post-drilling separation micrometer readings demonstrated similar trends to the optical comparator maximum burr height measurements, though with a lower magnitude. It was also found that the feed per revolution had the most dramatic impact on the drilling thrust forces. Though standard-point drills slightly outperformed split-point drills in terms of burr height, split-points required a much lower drilling thrust force. Lastly, it was found that chip entrapment in the interface occurred only in cases of a single clamp 35 mm (1.38') or greater from the hole location.


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    Title :

    An experimental study of interfacial burr formation in drilling of stacked aluminum sheets


    Additional title:

    Experimentelle Unterschung der Grenzflächengratbildung beim Bohren von gestapelten Aluminimblechen


    Contributors:


    Publication date :

    2008


    Size :

    8 Seiten, 15 Bilder, 2 Tabellen, 21 Quellen



    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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