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The cylinder does not rotate
The cylinder works but
not properly
SOLUTION OF THE ABOVE PROBLEMS
See also drawing at page 24.
Note:
This is the most serious damage that can occur to the cylinder; it means
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that the rotating part of the hydraulic manifold (body) is jammed in the
fixed part (manifold ring). This situation occurs when the oil in the cylin-
der is not perfectly clean or has some metallic particles or foreign parts
inside and can be caused when:
The oil filters are insufficient or damaged
-
The circuit and the hydraulic tubes are not perfectly clean.
-
For other possible reasons, please see pos. 2 to 6; for possible solutions,
please see pos. 7 and 8.
Use of improper oil. An oil with too high a viscosity causes a located high
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heating, when working at high speed with cold oil. It can also cause over-
heating in normal conditions.
The cylinder has been rotated without oil pressure.
3
4
The fittings used have conical or too long threads, that cause deforma-
tion of the manifold ring.
The oil feeding or the oil drain tubes or the stop fork have been mounted
5
in such a way to apply an axial stress on the manifold ring, damaging the
bearings.
The application requires an auxiliary device, that has been wrongly
6
assembled (bar holder, bar guide, component bearing), causing an axial
stress on the manifold ring, or, anomalous strains and shocks have affec-
ted the geometry of the cylinder.
lf there is only a slight seizure, it is recommended to disassemble the
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manifold ring, remove the seizure by an abrasive stone and replace the
bearings. Carefully clean before reassembling.
lf the seizure is more serious, it becomes very difficult to dismantle and
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repair the cylinder. In this case, it is recommended to send the cylinder to
one of the "Autoblok " Service Centers, for the repair or the replacement
of the cylinder.
Check that there is no alarm signal in the operation system of the machi-
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ne that could hinder the operation of the controls. Carefully check the
electric circuit and the buttons.
10
Check the hydraulic circuit controlling the cylinder stroke is in good wor-
king condition and gives the requested pressure; check the following:
A)
the oil level in the tank
B)
the proper working of the pump
C)
the filters must not be clogged
D)
the solenoid valves must not be jammed
the tubes must be properly connected.
E)
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Be careful not to reduce the pressure to 1/3 (or less) in one move, as
regards to the starting pressure: this would prevent the working of the
safety valves, hence, the piston stroke.
It is recommended to reduce the pressure gradually, making every time a
movement of opening / closing.
One of the two safety valves jammed into its seat, due to different rea-
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sons (dirty oil, overpressure, water hammering, changes in temperature,
wear of the internal components of the valves).
Keeping the power unit without pressure, carefully unscrew the 2 drain
6
TROUBLE SHOOTING GUIDE FOR VNK CYLINDERS
The rotating part is jammed
to the fixed manifold
The cylinder piston is jammed and
does not make the axial stroke
The cylinder leaks from the front and/or rear side of the
manifold ring (between the fixed and rotating part)
The cylinder leaks between the body and/or the
front cover and the piston rod (front or rear side)
The cylinder makes the axial stroke but moves too slowly
The cylinder does not make the whole axial stroke
The temperature in the cylinder has reached 70° C
There is a noise when the cylinder makes an axial stroke
The cylinder is noisy when rotation
Vibrations during rotation
The coolant leaks from the safety hole C
The coolant has entered the hydraulic circuit and the power unit
screws A and B (see page 24). Be careful that one of the cylinder cham-
bers is still under pressure. By loosening these screws, a certain quantity
of oil will come out from one of them, resetting the valve control.
Reassemble and tighten the screws, then operate the cylinder. lf the
piston still does not move, it is necessary to change 1 or 2 safety valves
(see instructions).
Check that the draw tube for the connection to the chuck is not too long or
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too short, causing a mechanical axial stop, hindering the piston stroke.
The oil seal between the fìxed manifold and the rotating part of the cylin-
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der is made by means of labyrinth seals, that cannot be damaged. Hence
any leak in those areas can be due ONLY TO A FAULT IN THE OIL
DRAIN
Carefully read pos. 3.4 and check:
A)
that the drain pipe is kept in VERTICAL position
that the drain pipe HAS THE SAME SECTION ON ALL ITS LENGTH.
B)
C)
that the drain pipe as a continous slope from the cylinder to the power
unit, WITHOUT MAKING AN ELBOW.
that the drain pipe into the power unit IS ALWAYS OVER the oil level
D)
and NEVER below.
Carefully check the area where the oil comes out: if it is from the front
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part, between the body (1) and the piston rod and / or from the rear, bet-
ween washer (8) and the piston rod (all the rotating parts), it is necessary
to replace the rubber seals No. (30) and (36) , see pag. 24
Let's suppose that the machine tool manufacturer dimensioned the
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power unit considering the real needs of oil capacity. lf the power unit is
well dimensioned, there can be two kinds of problem.s:
in the hydraulic circuit
-
in the cylinder
-
Problems in the hydraulic circuit:
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A)
The filters are clogged and do not allow the regular flow of the pump
capacity; in this case replace them. NOTE: Be careful that the deli-
very filter must be microfibre filter with 10µ aperture size and must
be replaced every 6 - 8 months.
B)
The pump is worn and does not guarantee the regular delivery.
Measure the delivery in l/min. and, if it is not enough, replace the
pump.
C)
The solenoid valves do not make the whole stroke and reduce the room
for the oil flow. It can be caused by wear of the valves or by the entry
of dirty oil between the pistons.
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Problem in the hydraulic cylinder:
To be sure that the problem is in the hydraulic circuit or in the cylinder,
mount (using 2 suitable fittings) 2 gauges in the drain holes A and B, (see
pag. 24). Check that:
here is pressure alternatively in one chamber of the cylinder (e.g. A =
a) T
30 bar
B = 0 bar and vice versa ) .
b) T
hat the pressure in A or B is slightly lower than the working pressure
set on the unit for the cylinder itself.
A)
Wear or breakage of the main seal No. (33) of the piston (see page 24): in
This case, replace the seal.
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