Machinability estimation by drilling monitoring

Abstract

This article describes the development of a methodology to 
measure the specific cutting energy (SCE) in drilling. The 
SCE allows characterizing and the machining process, thus 
obtaining a technologic approach that allows to carry out a 
planning of the chip removal process. The main frame of this 
machine consists of a pedestal drill, instrumented with: a 
meter, a motor that controls the spindle speed, safety elements 
such as limit switches and an active power meter coupled to 
the drill motor. The mechanical power is calculated indirectly 
through the active power. To this end, it must have a previous 
calibration with a torque dynamometer to reoced theoutput 
curve and, subsequently, display the relationship between the 
mechanical power and the active electrical power. To validate 
the capability of this method, the EEC of three different 
materials is evaluated, an aluminum 7075-T6 and the steels 
C45E y 34CrNiMo6. It has been verified that the estimated 
SCE values correspond to those described by the literature. 
The influence of several parameters, like the cutting speed and 
the feed rate, on the SCE allows to estimate the sensitivity 
of this method. Finally, this works shows that the SCE in 
steel increases with the increase of the feed rate, whereas in 
aluminum the behavior is the opposite, the SCE decreases as 
the feed rate increases.