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TROUBLE SHOOTING GUIDE FOR VNK CYLINDERS
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 chuck.
19
To determine the length of the connection draw tube, remember 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 unexplained reduction in the cylinder stroke (and in the stroke of the top
20
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 cylinder;
22
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 wor-
king 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.
Check the oil level in the power unit: a reduction in the oil volume causes an
23
increase in the temperature.
Insufficient lubrication of the chuck can cause noises during the clamping
24
and unclamping of the component.
Dismantle the chuck and grease it with AUTOBLOK KO5 grease.
Also the partial or total breakage of the draw tube or of the threads can
25
cause an irregular noise: in this case, replace the damaged parts.
26
If there are vibrations when the cylinder is in thrust conditions (both when
DISMANTLING AND REASSEMBLY OF VNK CYLINDER
Dismantling
Operations to follow before removing the cylinder from the machine.
A.
Reduce the pressure to about 10 bar (while the piston is moving).
a1.
Push the piston to about the half of its stroke.
a2.
a3.
Cut off the pressure from the circuit and remove the feeding and drain pipes.
By means of compressed air, alternatively blow into the feeding fittings
a4.
and collect the oil coming out from the other fitting.
Push the piston fully back.
a5.
Remove the rear cover
a6.
(21/1)
a7.
Remove the stroke control disc
Remove the coolant recovery housing, unscrewing the screws
a8.
lt is now possible to remove the complete unit, without influencing in any
way the adjustments of the stroke control. Be careful not to damage the
wires and the proximity switches fastened to the housing.
Remove the cylinder from the machine and put it on the bench.
a9.
B.
Dismanting of the piston
Unscrew the two drain screws "A" and "B" and the seal below (see dra-
b1.
wing of page 24).
Unscrew the fixing screws
b2.
(47)
Remove the front body
(1)
through the threaded holes
b3.
b4.
Remove the piston (3), beating with a plastic hammer on the rear side of the
piston rod. At this stage, it is possible to carry out the routine maintenance.
C.
If it is necessary to replace the pressure relief valves, follow the
instructions listed below:
c1.
lt is possible to place only the internal component of the valve 1 3/A"; the
housing is integral with the piston.
c2.
Measure with a gauge the position of the plug of the pre-loaded spring
with regard to the edge of the housing.
c3.
Unscrew the plug. (Caution: the plug is fastened with loctite).
Take out the valve and replace with new components, inserting them in
c4.
the same position as the previous ones.
Screw the plug in, as deep as before, and put some loctite to fix it pro-
c5.
perly.
The positioning of the plug is very important, because it gives the pre-
load of the spring, controlling the opening of the valve.
lf it is necessary to replace the safety valves, with the cylinder on the
D.
machine follow the instructions listed below.
Look for the 4 holes with plugs located on the outer surface of the cylin-
d1.
der: a small one and a larger one (see sect. E-E).
Remove the 4 plugs
d2.
(16) e (17) (see drawing).
Insert a rod into the smaller hole
d3.
d4
Gently push the rod unit the valve comes out from the larger hole.
Check the direction of the valve in the hole.
d5.
Place the new valve in the same position as the previous one.
d6.
d7.
Insert and screw the plugs.
E.
Dismantling of the hydraulic feeding manifold: to be made only in
the case of proved damage to the bearings.
This is a very difficult operation, which should be carried out by qualified
personnel and with special equipment. If possible, send the cylinder to a
of the coolant recovery housing.
(24)
with its ring-nut
(23).
of the front cover
(2).
.
.
driving a chuck or a collet), this is due to the combined bending and com-
pressive 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 rota-
ting 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.
28
Check that the cylinder and the flange turn perfectly (see mounting
Instructions - pos. 2).
Check that possible shocks of bars against the cylinder hole or other vibra-
29
tions 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 straightness
30
or too bent in thrust conditions.
31
Check carefully, removing the component, then the top jaws, the chuck, the
draw tube, the cylinder, the flanges, unil there are no more vibrations. Then,
balance the part removed last.
The coolant drain pipe is clogged by chips, preventing the coolant flowing
32
properly and the coolant escapes from the safety hole C.
Clean the drain pipe. To avoid a similar problem in the future, it is recom-
mended 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 cylin-
der. Follow the instructions of pos. 32.
34
Same problem as pos. 32, but in this case the safety hole C is obstruc-
ted: clean the hole and follow the instructions of pos. 32.
SMW-Autoblok service centre, if not, proceed as follows:
e1.
Remove the cover
e2. Remove support washer (8), by removing screws (43). Using an extractor
remove the oil manifold unit (5+10+11/B+12/B).
e3. Remove washer (19).
e4. Remove the front bearing (29) using a special "L" shaped tool, which has
to be put between front cover (7) and the bearing itself. There are 2 groo-
ves which should make it easier for the tool to get inside the cover.
e5. It should not be necessary to dismantle the unit 5+10+11/B+12/B.
Should it be necessary, remove screw (9) (there are 1 or 2, according to
(46).
the size) and remove ring (5) from the external housing (10) .
A.
Reassembly of the piston (3)
Insert the seals (31) – (32) – (33) and (36) in their seat, greasing them with
a1.
a suitable product.
Mount the piston rod in its seat (2), beating on the draw tube end by
a2.
means of a plastic hammer.
Caution: correctly position the pressure relief valves (Their housing acts
as antirotation pins), in order to locate them in their seats in the body.
Reassembly of the front body (1)
B.
b1.
After greasing and mounting the seal (30) in its seat, insert the body (1)
onto flange (2) and allow the assembly of the valve housings into their
seats. Slightly screw the screws (47).
Carefully center the front cover (2) as regards the body (1).
b2.
b3.
Fully tighten the screws 47) and mount the plugs A and B.
.
C.
Reassembly of the manifold ring (5 + 10)
c1. Mount the front bearing (29) and washer (19) on the adaptor (2).
c2. Put the seals (40) in their seats, mount housing (10) on ring (5) and fix it
in position with screws (9).
c3. Mount unit (5+10) on adaptor (2). This operation requires the greatest care.
c4. Mount the seal (35) and the support washer (8) without fully tightening the
screws (43)
c5. Remount cover (6).
Assembly of the cylinder onto the machine
D.
Following the assembly instructions, center the cylinder body as regards
d1.
the rotation of the spindle, then, fully tighten the fixing screws.
d2. lf the manifold ring (5) - (8) has been removed, center the stop washer
"8" and tighten the screws (43).
E.
Assembly of the coolant recovery housing and the piston stroke
control
e1
Mount the housing (21), fixing it by means of the screws (46), being care-
ful not to damage the wires or the proximity switches.
Mount the stroke control ring (24) with its ring-nut (23).
e2
e3.
Mount the cover
- Note: see drawing of page 24.
(6).
Reassembly
(21/1).
7
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