RESEARCH FOR

Kristiāns Štekelis
Noise and vibration are present in all woodworking
and woodworks manufacturing processes. Practice
shows that working with bed-type milling machines
noise exceeds the maximum allowed level 87 dB(A)
by 15...20 dB(A). Noise is also influenced by the
vibration of a machine. Especially it is observed in
cases when equipment is not sufficiently amortized,
contains statically and dynamically unbalanced
components, has insufficient amount of grease, and
technical maintenance of equipment is not performed
in time. Vibration can originate also in case the correct
constructive solution of cutting tools is not selected
or the way of cutting material is incorrect (Eglīte et
al., 2004). In the wood cutting process the level of
noise at the bed-type milling machines is increased;
it gradually increases in the work process because
the cutting tools become less sharp. Thus, the control
and supervision of the workplace and noise level are
needed to protect workers and avoid idle standing,
which could appear if a worker becomes incapable.
It would be ideally to follow simultaneously the
dynamics of noise increase and surface quality during
processing to judge about the compliance of surface
quality to the required changing interval of the cutting
tool under equal conditions of woodwork mechanical
processing.
In order to measure noise, various measuring
equipment can be used. Several measuring
instruments, a computer and software are needed to
register the noise level qualitatively. First, a device
to register the noise level is needed. Often these
devices are equipped with a display where one can
ReseaRch foR RuRal Development 2012
QUALITY CONTROL MANAGEMENT
PROBLEMS OF WOODEN PRODUCT SURFACES
Figure 3. A set of devices for registering and keeping the noise level:
1– a device for registration of the noise level; 2– a module for reading and accumulating
the noise pressure level; 3– a computer with software.
follow the noise level during measuring. The devices
are battery-operated or accumulator-operated and are
small and portable. Using such devices, it is easy to
measure noise at the workplace, but if data processing
is needed, a module for reading and accumulating the
noise pressure level ‘HOBO’ is needed in addition. It
is a small device connected to the noise registration
device. Its main task is to register changes of the
noise level. It is needed to accumulate data and
later on analyze them with a computer. The changes
in the noise level are recorded by an interval of 0.5
seconds, which is very fast and gives a lot of data to
be analyzed. Noone could write data by hand so fast.
In order to install and start the module for reading and
accumulating the noise pressure level, a computer
with software is needed in a set with the device. The
components are depicted in Figure 3.
First, the module is connected to the registration
device, afterwards – to the computer by a special cord.
When the module is connected to the computer and
all necessary settings are completed, it is started by
the help of special software. Measurements are taken
at least in the distance of one metre from the surfaces
and walls reflecting sound. The measuring tool is
placed on a stand 1.5 – 1.7 m above the ground level.
The microphone is turned into the direction of the
largest source of noise. After taking measurements,
the module and the device for data registration are
repeatedly connected to the computer to save the
obtained data. It has be noted that the measuring
devices must be verified and calibrated.
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