ROHM OVUSHH - hydraulic operated duble piston cylinders - Manual (Page 15)

Stroke control
a) The paths are mainly determined by the piston
strokes of the operated clamping devices.
b) The proximity switches relate to the operative range
of the chuck or to the indications from the machine
manufacturer.
Recommended positions for checking are for exam-
ple open position, clamping position and empty
clamping position (= clamping position without in-
serted workpiece) of the clamping fixture.
c) In case of clamping fixtures with quick change jaws,
the path check and the machine control must be
protected electrically in such a way that the spindle
may not start in ”jaw change position”.
The standard process for path check is a non-contact
process for which the stroke control disk and inductive
proximity switches are used.
Further processes are only mentioned in the following.
For more detailled information, refer to the relevant op-
erating instructions of the cylinder in question.
Processes 1 and 2 are based on defined check posi-
tions, i.e. for each workpiece or with each modification
of the clamping fixture, the clamping position needs to
be adjusted. In most cases, however, clamping position
and both end positions need to be adjusted.
Processes 3 to 6 are continuous processes. This
means that new validity ranges need to be defined for
the control only.
1. Inductive proximity switches
Path check is effected via two switching plates that
are coupled with the two clamping pistons 1 and 2.
Four to six inductive switches are located on one
limit switch panel and scan the positions of the
contorl disks. If the control disk is located in the
scanning area of the proximity switch, the switch
position is changed (i.e. a breaker opens a closed
circuit, a closer closes an open circuit).
Since the switches must suit the machine control,
they are not delivered with the cylinder.
The switch panels are not included either, since,
depending on the relevant machine, different vari-
ants exist (e.g. direct installation of the switch pan-
els at the machine housing) and different numbers
of limit switches are required.
The switch panel is attached with 2 screws (M6)
and 2 clamping sleeves Ø6 DIN 1481 or DIN 7346
to one of the three fixing surfaces of the distributor
housing.
Usually, up to 3 limit switch panels may be attached
at the distributor housing.
2. Individual limit switches
As with proximity switches, this process also regis-
ters open and empty positions. 2 switch cams and 1
limit switch are sufficient. If one ore more further
clamping positions are to be checked, additional
limit switches and, if necessary, switch cams must
be provided.
3. Analog position sensor
Like the inductive proximity switch, this system is
based on the principle of induction. However, it uses
a stroke control disk with tapered outer contour.
From its distance towards the sensor that varies
with the relevant piston position, the sensor trans-
mits an output signal that changes in a linear man-
ner (output current or output tension).
Its advantage is the continuous and thus extremely
variable supervision of the stroke.
4. Linear potentiometer
This system generates an infinitely variable electric
signal, that is related to the initial point. Such an
analog signal (variable tension) is converted into
path or stroke by means of an evaluation unit. For
advantages, see above description.
5. Angular position transmitter
With this process, the linear piston movement is
converted by means of rack and pinion into the
rotary movement of a shaft with attached code
plate. The scanning of this code plate is effected via
LEDs and photo transistors of the infrared range.
Depending on the code plate, speed changes,
slowing down, etc. may be realised. For
advantages, see above description.
6. Laser tracer
This infinitely variable measuring system is based
on diffuse laser light that the sender transmits at a
certain angle onto the object to be measured which
again reflects it to the receiver. The distance
between the object to be measured and the receiver
is determined by means of an PSD diode on basis
of the so-called triangulation process. Laser light
tracers with analog output transmit a variable
tension (0-10 V) that is proportional to the measured
distance. It can be measured directly by means of a
SPC.
As measuring object, swith plates are used again.
For functional reasons, these plates have to be
dulled.
0.10 A 0.10
A
0.050 A 0.0 050 A 0.10 A 0.10 A
A 0.010 A
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roehm_bedienung 04.08.2005 14:04 Uhr Seite 15