Aerospace – Drills ensure greater process reliability

The number of aircraft built per year is rising continuously. Final assembly of the aircraft, however, is still far from being a fully automated production line process. As a rule, an aircraft is fully assembled in one place. But here again, the degree of automation is increasing with more and more robots being used. Here robots with end-effectors for drilling and riveting mounted on shuttles are moved from assembly position to assembly position along the aircraft fuselage and position themselves automatically.

Conventional robots frequently do not have the optimum rigidity. This results on the one hand from the constantly changing positions of the main axes and the use of multi-stage planetary gear units, and on the other hand from the high weight of the end-effectors used that necessitate laborious control compensation before commissioning. The tool therefore has the task of carrying out the drilling process reliably and over a long tool life under these difficult boundary conditions.

In addition to this lack of rigidity, the very heterogeneous material combinations used in modern aircraft construction also represent a major challenge for the tool development. Multi-layer machining is state-of-theart with combinations of aluminium, titanium and CFRP materials often being used. MAPAL has defined various tool features especially for the aerospace industry that can be adapted optimally to the material and the boundary conditions, depending on the machining situation.

The “MicroReamer” micro-cutting stage patented by MAPAL has the ability to cut at the side and to bring the diameters of all the layers to tolerances in the IT8 range. The burr at the bore outlet that has to be less than 0.1 mm can also be reliably achieved with this micro-cutting stage.

Also of great influence is the differential tip angle, i.e. the combination of a small tip angle in the middle of the tool and a large tip angle at the outside diameter. The small tip angle in the middle ensures immediate self-centering, a good radial run-out of the tool on entering the material and hence a high diameter precision. The large tip angle at the outer diameter guarantees a small outlet burr when aluminium or titanium are on the bore exit of the component. In cases where CFRP forms the external material layer, the differential tip angle prevents delamination at the bore exit. The prevention of any burr formation and delamination is of great importance for the compact fitting of the aircraft parts and hence for optimum strength that prevents localised overloading of the structure.

In combination with innovative diamond coatings that prevent the formation of built-up edges, high-performance drills from MAPAL ensure reliable processes and cost-effective results when machining using robots.

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