JEC COMPOSITES MAGAZINE - Issue #102 - January/February 2016 - 48

control

Fig. 5: Typical curves of the thrust force as a function of cutting speed at constant advancement at 0.10mm/rev.: a) 1500 rpm; b) 8000 rpm; c) 12000 rpm

force and vibration signals and for data
storage.
The cables of the thermocouple used
have polyamide insulation for low and
medium temperatures (from -240°C
to +260°C). They are characterized
by a typical sensitivity in the order of
41μV/°C with 0 = 0.1±0.3mm.
The 9257BA Kistler dynamometer consists of four quartz piezoelectric force
sensors that, emitting voltage signals
proportional to stress, can measure the
three orthogonal components (X, Y
and Z) of a force.

An example
of signal acquirable by
a multisensor system
The system can be used for in-process
sensor-based monitoring in machining
processes for different types of materials and is easily transportable to other
machining centres. The case study
analysed in this paper is the drilling
of CFRP, as shown in Figure 3. In this
process, it is important to monitor the
temperatures and forces of the process,
and in particular the Fz component of
the cutting force.
Figure 4 shows a typical plot of the
signals acquired by the thermocouples
placed at a distance of 1 mm and 3
mm from the inner surface of the hole
executed at high speed (HSD, highspeed drilling). In particular, Figure 4a
shows the temperature trend in the case

of CFRP drilling performed using a 10
mm helical drill with a cutting speed
of 8000 rpm and a feed speed of 0.10
mm/rev. Figure 4b shows the temperature trend during the drilling of the
hole executed at 12000 rpm. These figures demonstrate that the temperature
increases appreciably with increasing
cutting speed. The maximum temperature recorded at a distance of 1 mm
from the hole surface is less than 90°C,
that is much lower than the glass transition temperature of the resin. Figure
5 shows the trend of the thrust force
(Fz) for three different cutting speeds.
As can be seen from the figure, the
maximum value of thrust force (Fz) is
approximately 300 N at 1500 rpm. The
force decreases with increasing cutting
speed and at 8000 rpm, it is about 250
N. When further increasing the cutting
speed, an increase of the thrust force
to 350 N is recorded. The thrust force
value is very important in the drilling of
CFRP since it determines the extent of
push-out delamination.
In conclusion, sensor-based monitoring
can reveal the optimum process parameters in order to improve the quality of
the hole surface. n
References
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Technol. 2002;51:611-34.
[2] Sorrentino L. and Tersigni L., A

48 jec composites magazine / No102 January - February 2016

Method for Cure Process Design of Thick
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[3] Abrao A.M., Faria P.E., Campos Rubio
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Contact:
sorrentino@unicas.it

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