Biomedical Engineering Reference
In-Depth Information
4.2. Observations of Machined Chips
There are significant differences in the size and shape of chips when
machined at medium and high speeds. This is especially so for biological
materials such as compact bone. Figure 3 shows a collection of chips
machined from bovine femur. It is seen in Figure 3 that many of the particles
are in fact chunks of material rather than nicely formed chips. It is possible
that the chunks were formerly parts of larger chips that have since broken
down and that chip thickness values should be recalculated based on the larger
chip size.
Figure 3. Characteristic chip shapes cutting bovine femur at high speeds. Reproduced
with permission. Copyright retained by Inderscience Publishers.
It can also be seen that the chips in Figure 3 are more consistent in terms
of length, width, and depth. Their lamellar spacing is also regular in period,
which would indicate that cutting conditions at high speed are stable.
Single chip formations are shown in Figures 4 and 5. While the width
observed is similar to that for low speed cutting, the chip length of high-speed
chips is much shorter than low speed chips. This could be because at low
speed the chip has a greater time in contact with bone thereby removing more
material, which is reflected in the increased chip length. One of the major
differences observed between low and high speed micromachining of bone is
in the spacing of the lamellae. In low speed cutting, the chip spacing varies by
