Biomedical Engineering Reference
In-Depth Information
2.5. Research Challenges
There are many research challenges to be considered in chatter recognition
and suppression in drilling operations. Modeling the process becomes harder
with the complexity and modifications of the chisel edge of the drill. Further,
prediction of cutting forces in this region is difficult due to the variety of
cutting speeds and rake and oblique angles along the cutting edge. As
presented in this review paper, in order to solve the problems many
researchers have simplified them by analyzing one model or one problem at a
time. The fact is that the axial, torsional and lateral vibrations can be acting at
the same time in drilling, the effect of the chisel edge, margin effect, pilot hole
size, etc., are going to be present as well and the optimal model would need to
have the option to incorporate all these effects in order for it to be successfully
used in industrial applications.
3.
I
NVESTIGATION OF
C
HATTER IN
M
ICRO
D
RILLING
In machining operations it is well known that chatter presents one of the
problems affecting the surface of the part as well as the tool used. Chatter
issues have been investigated since the 1950s in various ways, but what is
common for all the investigations is that it is necessary to have accurate
measurements of the Frequency Response Function (FRF) at the tip of the tool
when it is attached to the tool holder and spindle. For macro testing, the impact
test is sufficient for dynamic measurements, but it is impossible to apply the
same system on to micro tools due to their size and fragility. Impact hammer
forces would be detrimental to the tools used in micro machining. The
procedure is also impossible to be applied due to the mass loading necessary if
an accelerometer is to be used. Many times, tools have been modeled as
cantilever beams, incorrectly representing the actual dynamics of the tool tip.
Receptance coupling technique developed by Park et al. [40] suggests
coupling of analytical and experimental FRFs of the components with the aim
of obtaining the response of the assembly as a whole (Figure 8).
The accuracy of the receptance coupling technique depends on accurate
identification of the joint dynamics of the substructures at the assembly joint,
and the FRFs of each substructure. Any noise in the FRF and inaccuracies in
the joint dynamic parameters amplify the errors in obtaining the FRF for the
assembled tool-spindle system. This paper proposes an algorithm that allows
analytical extraction of rotational dynamics at the joints from linear
