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A . HORIZONTAL AXIS HARD-BEARING BALANCING MACHINES
All the machines in the Z series have hard bearings. The basic characteristic is that the centrifugal force generated by the unbalance does not cause vibrations in the structure bearing the rotor, but is unloaded completely via the force transducer onto the frame construction of the pedestals, which is very hard. The signal obtained is proportional to the centrifugal force produced by the unbalance. The fact that the centrifugal unbalance force is independent of the rotor mass, of its inertia and its shape is at the root of the basic advantage of hard-bearing balancing machines, which consists of the possibility to calibrate its settings immediately on the basis of the rotor dimensions alone. in fact, once you have chosen the correction planes, all you have to set on the machine are the distances of these planes from their respective pedestals, the distances between the planes and the and the correction diameters. these settings, which are made with the machine at a standstill, produce excellent calibration without any test spins and without any calculations. As the elasticity of the foundations reduces the overall hardness, a hard-bearing machine has to be fixed very firmly to the ground. However, for all normal purposes, this does not require a special foundation: all you need is a normal workshop floor with a good surface and a strong cast structure.
The pedestals of hard-bearing balancing machines are practically isotropic: i.e. they are equally hard in all rections, which means that they are particularly suitable ble for balancing flexible rotors.
Z series balancing machines are all fitted with a read piezo-electric force transducer. This solution is the modern dern evolution of the semi-hard bearings system, where the force measuring transducer consisted of a sheet of metal with an electrodynamic transducer. This solution, which some balancing machine manufactures still use today, suffers the drawback of having a more limited ted range of application than the force-measuring transducer solution.In fact, in a semi-hard bearings machine, the hardness of the structure that bears the rotor must stand up two opposing conditions on the one side it must be hard enough for the critical frequency of the pedestal + rotor assembly to be much higher than the balancing speed, so as to allow for dimensional calibrations, while on the other it must be relatively soft, so that the vibrations have a large enough amplitude to be pick?ed up by the electrodynamic transducer, which is only se? sitive to the mechanical movements in the oscillating parts.
The koeng solution enables rotors with a very wide variety of weights to be balanced in a very wide range of speeds, without penalising machine performance
- MAXIMUM BALANCING MACHINE LOAD
when a balancing machine is not intended for a specific range
of parts. the maximum weight capacity of the machine should
be from two to three times he average weight of the majority of
the parts that are to be balanced on the machine.
if the majority of the parts to be balanced are not contained in
a limited range of weights, but have a tendency to accumulate
near the upp? lower limits of the machine. it is advisable to
consider using two or more different balancing machines.
Multiple machines will provide more fle? in the balancing
applications in addition to the increased accuracy.
- MINIMIM BALANCING MACHINE LOAD
A balancing machine with standard equipment can balance
rotors weighing 1/150 of the maximum weight capacity without
any problems. The flexibillity of the machine can be increased
further by using light roller carriages and perhaps an alternate
drive system.
- BALANCING MACHINE DRIVE
A balancing machine's drive motor is used to overcome the
inertia of part being balanced and to counterbalance its. passive
resistance while spinning. The power necessary to keep the
rotor spinning at speed is generally much less than that
necessary to set it in motion. Except in the case of bladed
rotors with a high windage effect. To calculate the power (N)
needed for spinning the rotor at the balancing speed (n), insert
the service speed ns and the rated power (Ns) in the following
formular
This simple calculation determines the necessary drive power
for a balancing machine.
- ROTOR DRIVE
The power necessary to turn the piece to be balanced is transmitted by various
means : a double cardan joint, belts that wrap around the rotor or stay in contact
with it, rollers, compressed air devices and electromagnetic fields. The cardan joint
is preferable for rotors with considerable inertia or ventilating effect. If the same
cardan joint is used for large rotors and smaller ones, it will produce less
accurate, sometimes completely inadequate results for the smaller rotors.
For this reason, it is advisable to keep a good store of different sizes of cardan
joints available. As the joint's size is related to the torque couple of the drive
action, balancing machines with a DC drive that can adapt the couple transmitted
to suit the rotor dimension are particularly recommended for flexible working
conditions.
Belt drive is suitable for medium and small sized pieces and can give rise to better
accuracy than the cardan joint. It has the considerable advantage of making the
piece to be balanced easier to put on the machine, which makes it particularly
suitable for working in series. In order to be able to use a belt drive, the rotor
must have at least one perfectly cylindrical worked section on which the belt can
be fitted. Belt drive becomes a necessity when the rotor has no journal to which a
cardan joint can be applied, Note that belt drive calls for the presence of axial
thrust stops to stop the rotor from making any dangerous movements, The two
types of drive can also be used together : this solution expands the machine's
range of use and makes is more practical.
END (shaft)
BELT
END+BELT
- Measuring head
ZC Measuring unit
ZE Measuring unit
ZO Measuring unit
ARV Measuring unit
ZE and ZC types of measuring instrumentation can be used on series Z balancing
machines. All these types of instrumentation are fitted with wattmeter filtering
systems, direct immediate calibration of values and positions of unbalances and
the possibility to take direct readings of the static unbalance only.
The typical features of each individual instrumentation are listed in detail in the
relative catalogues.
- CARRIAGES AVAILABLE - Rotor fitting on the balancing machine is obtained by mears of different type carriages.
Standard roller carriage.
Reverse thrust carriage for over-
hung balancing.
Flanged carriage for balancing drive shafts.(D-carriage)
V carriage with rollers forbalancing
rotors with their own bearings
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