Balancing System; Tensions; Phase Angle; In0 - External Pick-Up Signal - Bosch WBE 4510 Instandsetzungsanleitung

Fig. 11: Menu N° 6: output
4.5.2

Balancing system

To measure the unbalance of the wheel, we use a me-
chanical system based on a 1° degree lever. The piezoe-
lectric sensors which are in the lower part of the shaft,
at its sides, detect vibrations by converting the strength
in electric tension.
Fig. 12: Position of the piezoelectric sensors
4.5.3

Tensions

the piezoelectric sensors, according to where they are,
receive a different stress and weight. In fact, the inter-
nal one, in the left side of the shaft, is excited less than
the external one. So we can say that the ratio between
them is 1.6, that is, the tension measured by the exter-
nal pick-up is 1.6 times higher than the tension meas-
ured by the internal pick-up.
Fig. 13: Stresses on the shaft
4.5.4

Phase angle

In general, we use the word phase to identify a particu-
lar moment during a periodical phenomenon (in this
case it is the electrical signal generated by the pick-up
during the launch of the wheel). When we consider two
signals (generated by the internal and the external pick-
up), we can say that there is a phase angle between
them which means that there is a difference between
the tensions. For instance, in this picture, if the black
signal represents the tension of the external pick-up
and the red signal represents the tension of the internal
pick-up, we can say that the tensions are opposite, that
is, that the difference is 180°. The crests of a signal are
lined up with the troughs of the other and vice versa.
Robert Bosch GmbH
Settings | WBE 4510 - WBE 4515 | 33
Fig. 14: Ratio between the tensions measured by the pick-ups
Fig. 15: SELFDIAGNOSIS button
Press the SETUP and then the SELFDIAGNOSIS button
to enter the self diagnosis menu; on the displays appear
in sequence both the values read by the pick-ups during
the last cycle and the phase difference in degrees.
To test the correct functioning of the pick-ups proceed
as follows:
17. mount on the machine a test wheel (14-15" of
iron) and perfectly balanced;
18. place a single test weight on the outside (e.g.
100 gr) and run a test cycle.
At the end, checking the obtained values, the tension
value of the internal pick-up must be always smaller
that the tension value of the external pick-up and the
ratio between the value of the external pick-up and the
internal one must be between 1.9 and 2.1.
Showing as example the table below, to calculate the
tension difference, we must divide the value of the ex-
ternal pick-up for the value of the internal one, getting
in this way the ratio between the two (2000/1000 = 2).
Notes for technical support
If checking the ratio between the pick-ups and the
phase difference values above tolerance limits are
found, proceed to board replacement(chap. board re-
placement) or to pick-up sensors replacement (chap.
pick-up replacement). If after replacing both the prob-
lem persists, this might be because of a too high dis-
turbance of the bearings of the measurement bench,
consider full replacement.
4.5.5

IN0 - External pick-up signal

The piezoelectric-electrical sensor reads a force varia-
tion.
when checking the machine verify that:
R
the rest value is at the half of the range scale (e.g.
8170 +/- 100);
R
pushing the shaft downwards, the value goes down
to zero;
R
lifting the shaft, the value grows up to half scale.
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1 695 655 167 2014-01-13