Experimental study and synthesis of the dynamic behaviour in high speed drilling

Abstract

This paper concerns an experimental approach of vibration phenomena in High Speed Drilling (HSD) of aluminium alloys. In order to study these phenomena, different results have been chosen to illustrate that these vibrations are generated by different deformations of the drill and the machining system. The relevant parameters at the origin of these vibrations in HSD are pointed out and their influence on the quality of drilling is analysed. The effect of the drill geometry on surface quality is reported and in particular the role of the chisel edge, the helix angle which controls the sharpness of tool corner, the thickness and the number of margins which allow the drill to be held in the hole and the rigidity of the drill materialised by its overhang. Depending on its length, the drill can deform differently. The influence of the drilling conditions on surface quality has also been evaluated: the feed rate per tooth and the cutting speed as well as the rotation frequency and the feed speed. The effect of lubrication and machine rigidity (in our case an industrial robot) has been analysed. Finally, we pointed out the apparition of vibration when two aluminium plates are drilled together. The behaviour is very variable and different steps of the drilling have to be considered: the drill entry in the aluminium part, the drilling, the drill exit from the plate and the drill backward movement. This allows for a particular value of drill diameter and drill overhang to determine the optimised feed rate and rotation frequency in order to achieve the best quality of the hole surface.