Shaping the Edges Using Flowdrill Technology

The Flowdrill technology, also known as thermal drilling or thermoforming drilling is a chip less process of shaping rims of holes through burring and it is an alternative to conventional technology of hole rims burring, realized using presses or welded nuts to obtain threaded joints [1, 2, 3]. It is applied everywhere, where it is necessary to obtain threaded joints of high strength without application of additional connecting elements. Application of this technology allows to reduce mass of the structure and eliminates need of using the countering elements, especially when access is hindered or impossible. Making rims of holes with the Flowdrill technology consists of several stages (Figure 1): tip of the conical part of the drill comes into contact with the material surface, making it malleable and soft (Figure 1a, b), cone of the drill pushes the material in two directions: inside the shape, a bushing is formed (Figure 1c), around the upper surface (a collar occurs), the drill runs through the material, its cylindrical part finally forms the bush and the collar is cut off by the forming flange of the drill (Figure 1d, e), the tool is detracted and the rim cools down on its own (Figure 1f). An important role in the thermal drilling process is played by the temperature, which may cause damage of the material structure (e.g. burns), influence shape of the formed rims disadvantageously and change the material microstructure in the hot drill-material contact zone [4, 5]. It matters significantly in the case of materials characterized by a high temperature conductivity, as too fast decrease of temperature in the zone of drilling may cause the malleability to drop and fractures may occur [3, 5, 6].