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Idiomas disponibles
Idiomas disponibles
TROUBLE SHOOTING GUIDE FOR VNK
This is the most serious damage that can occur to the cylinder; it
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means that the rotating part of the hydraulic manifold (body) is jam-
med in the fixed part (manifold ring). This situation occurs when the
oil in the cylinder is not perfectly clean or has some metallic particles
or foreign parts inside and can be caused when:
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The oil filters are insufficient or damaged
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The circuit and the hydraulic tubes are not perfectly clean.
For other possible reasons, please see pos. 2 to 6; for possible solu-
tions, please see pos. 7 and 8.
Use of improper oil. An oil with too high a viscosity causes a located
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high heating, when working at high speed with cold oil. It can also
cause overheating in normal conditions.
The cylinder has been rotated without oil pressure.
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The fittings used have conical or too long threads, that cause defor-
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mation of the manifold ring.
The oil feeding or the oil drain tubes or the stop fork have been
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mounted 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
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assembled (bar holder, bar guide, component bearing), causing an
axial stress on the manifold ring, or, anomalous strains and shocks
have affected 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.
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lf the seizure is more serious, it becomes very difficult to dismantle
and 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
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machine that could hinder the operation of the controls. Carefully
check the electric circuit and the buttons.
Check the hydraulic circuit controlling the cylinder stroke is in good wor-
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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
E) the tubes must be properly connected.
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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
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reasons (dirty oil, overpressure, water hammering, changes in tem-
perature, wear of the internal components of the valves).
Keeping the power unit without pressure, carefully unscrew the 2
drain screws A and B (see page 29). Be careful that one of the cylin-
der chambers 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
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long or too short, causing a mechanical axial stop, hindering the
piston stroke.
The oil seal between the fìxed manifold and the rotating part of the
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cylinder is made by means of labyrinth seals, that cannot be dama-
ged. 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
B) that the drain pipe HAS THE SAME SECTION ON ALL ITS LENGTH.
C) that the drain pipe as a continous slope from the cylinder to the
power unit, WITHOUT MAKING AN ELBOW.
D) that the drain pipe into the power unit IS ALWAYS OVER the oil
level and NEVER below.
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Carefully check the area where the oil comes out: if it is from the
front part, between the body (1) and the piston rod and / or from the
rear, between washer (8) and the piston rod (all the rotating parts),
it is necessary to replace the rubber seals No. (30) and (36) , see
pag. 29.
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Let's suppose that the machine tool manufacturer dimensioned the
power unit considering the real needs of oil capacity. lf the power
unit is well dimensioned, there can be two kinds of problems:
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in the hydraulic circuit
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in the cylinder
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Problems in the hydraulic circuit:
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 delivery 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.
To be sure that the problem is in the hydraulic circuit or in the cylin-
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der, mount (using 2 suitable fittings) 2 gauges in the drain holes A
and B, (see pag. 29). Check that:
a)There is pressure alternatively in one chamber of the cylinder (e.g.
A = 30 bar
B = 0 bar and vice versa).
b)That the pressure in A or B is slightly lower than the working pres-
sur set on the unit for the cylinder itself.
A) Wear or breakage of the main seal No. (33) of the piston (see
page 29): in This case, replace the seal.
B) One of the pressure relief valves (20) is open, due to dirt or to
the unsetting of the springs. Try to pressurize and to relieve the
pressure a few times, by switching the power unit on and off. lf
the valve still remains clogged, it is necessary to dismantle the
cylinder and replace the internal components of the valves.
Usually, only a part of the cylinder stroke is used to drive a standard
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chuck. To determine the length of the connection draw tube, remem-
ber that the front limit switch is on the cylinder and the rear one on the
chuck. If the draw tube has been wrongly designed or manufactured
the cylinder will not make all the stroke requested by the chuck.
An unexined reduction in the cylinder stroke (and in the stroke of the
20
top jaws) can be due to an accidental unscrewing of the draw tube.
Screw the draw tube properly and lock it.
21
There could be some problems in the chuck: check carefully.
The increase in the oil temperature is only slightly influenced by the
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cylinder; it is mainly caused by the hydraulic circuit. A good power
unit shoul be able to keep the oil temperature between 35° and 65°
C, even in the worst working conditions. lf the temperature is higher
than 70° C, it is recommended to increase the oil volume, by adding
an auxiliary tank or by using a system of temperature conditioning.
23
Check the oil level in the power unit: a reduction in the oil volume
causes an increase in the temperature.
Insufficient lubrication of the chuck can cause noises during the
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clamping and unclamping of the component. Dismantle the chuck
and grease it with AUTOBLOK K67 grease.
Also the partial or total breakage of the draw tube or of the threads
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can cause an irregular noise: in this case, replace the damaged parts.
If there are vibrations when the cylinder is in thrust conditions (both
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when driving a chuck or a collet), this is due to the combined ben-
ding and compressive stress on the draw tube. In this case, it is
recommended to insert 1 or 2 bronze bushings, to guide the draw
tube onto the I.D. of the spindle.
27
When there is too much noise between the fixed manifold ring and
the rotating part, it is possible that the bearings are going to have a
problem, due to dirty oil or wear. Replace the bearings, check the
filters and change the oil.
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Check that the cylinder and the flange turn perfectly (see mounting
Instructions - pos. 2).
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Check that possible shocks of bars against the cylinder hole or other
vibrations have not loosen the fixing screws of the cylinder in the
front cover of the cylinder. This could knock these parts off center.
Check carefully and center again.
Check that the draw tube is not unbalanced, off center, out of
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straightness or too bent in thrust conditions.
Check carefully, removing the component, then the top jaws, the
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chuck, the draw tube, the cylinder, the flanges, unil there are no more
vibrations. Then, balance the part removed last.
32
The coolant drain pipe is clogged by chips, preventing the coolant
flowing properly and the coolant escapes from the safety hole C.
Clean the drain pipe. To avoid a similar problem in the future, it is
recommended to screw the safety drain pipe on the 3/4" GAS thread
of the plug D, to be connected to the coolant tank.
33
When the coolant pipe is clogged, the volume of the coolant coming
from the thru-hole of the cylinder is higher than the drain capacity of
the safety hole C: the coolant level increases and enters the labyrinth
seals of the cylinder. Follow the instructions of pos. 32.
Same problem as pos. 32, but in this case the safety hole C is
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obstructed: clean the hole and follow the instructions of pos. 32.
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Note: see drawing on page 29
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