Noise emission in milling
The third set of experiments analyzed the noise emission
depending on the Cutting speed, axial depth of cut, radial depth of
cut and feed per tooth, part stiffness ratio. The machined samples
had a ‘‘L’’ shape (Fig. 4), where the machined width defined the
radial depth of cut (ae), and together with the height (H), the
stiffness ratio. The material was a common AlSi7 die casted
aluminium alloy employed in crankcases. The reference conditions
and the range ofvariation for the experimental plan were chosen in
accordance with industry experience (see Table 2).
Fig. 5 plots the evolution of the sound pressure level measured
by the microphone outside (operator zone, lighter colours) and by
the microphone inside (cutting zone, darker colours) depending on
parameter values for milling conditions. The legal threshold of
85 dBA, over which individual protection is mandatory (only
operator microphone), is plotted as well.
It was observed that for the reference milling conditions
(vc = 1571 m/min , 4000 rpm, surface mill) a very high sound
pressure level of 92 dBA was obtained. The sound pressure level of
the same mill in rotation without milling was only 79 dBA (Fig. 4)