Page 39 - June

METALWORKING EQUIPMENT AND TOOLS

intense self-oscillation, the power consumption can be reduced by up to 50%, but operation in
this mode affects the surface finish and durability of the tool that operates under shock loads
[16, 17]. Figure 5b shows a "rose of vibrations" when turning hardened steel, the contours
of which characterize an attractor of type 2. Cutting with attractor 1 also represents a self-
oscillating mode, but with significantly smaller deviations from the tangential direction, without
shock loads, with an acceptable quality surface.
Figure 6 shows examples of surface areas obtained by turning with intense self-oscillation
at a frequency of about 130 Hz, which corresponded to the natural frequency of a fixed workpiece
with a non-rigid rear center. In Fig. 6a, self-oscillation cycles are clearly visible, and it can be
seen that when passing from cycle to cycle, the cut from the cutter undergoes axial shifts and
distortions in width. This is due to the complex the spatial trajectory of the tool tip movement
during intense self-oscillations. At the bottom of the figure is a photo of variable-width chips,
which were obtained by turning with self-oscillations. From the shape of the chip edge, it can be
concluded that the increase in the depth of penetration of the cutting edge occurred with cyclic
impacts.

a b

Fig. 6. Examples of surface relief distortion when turning with intensive self-oscillations: a - distortion of the helical groove
from cycle to cycle (c - self-oscillation cycle); b - horizontal traces from the shifts of the shavings (s is the step of the shift of
the elements of the shavings).

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