ROHM DURO - Key bar chucks - Manual (Page 11)

1. Safety requirements and rules and regulations for
the use of manually operated chucks
I. Qualification of the operating staff
Persons, who have no experience in handling clamping equip-
ment, run the risk of being injured by the clamping motions and
forces occurring as a result of incorrect behaviour, especially du-
ring set--up work.
For this reason, clamping equipment may be operated, set up or
maintained by persons only who have been especially trained for
this purpose and/or have many years of experience.
II. Danger of injury
For technical reasons, this assembly may contain individual parts
with sharp edges. Always proceed with upmost caution when
working with the assembly to prevent the risk of injury.
1. Forces contained
Moving parts which are pre--tensioned by pressure springs,
tension springs, other types of spring or by other elastic ele-
ments, are a potential danger due to the forces they contain.
The misjudgement of these forces may cause severe injuries
resulting from uncontrollable flying components travelling at
the speed of projectiles. Prior to any further tasks, these for-
ces contained have to be relieved. For this reason, the respec-
tive assembly drawings always have to be inspected for such
potential hazards prior to dismantling the clamping equipment.
If a ”deactivation” of this energy is not possible without cau-
sing a hazard, the disassembly has to be carried out by autho-
rised staff members of RÖHM GmbH.
2. The maximum permissible speed
The maximum permissible speed may be run only at maxi-
mum permissible actuation force and perfectly operating clam-
ping chucks.
Non--observation of this principle may lead to a loss of the
residual chucking force, and as a consequence the work
pieces may be hurled out causing a corresponding risk of
injury.
The chuck may be operated at a high speed only, if a suitably
dimensioned protection hood has been provided.
3. Exceeding the permissible speed
This unit has been designed for rotating operation. The centri-
fugal forces caused by excessive speeds or rotational speeds
may result in individual parts becoming detached, constituting
a potential danger for persons or objects in the vicinity. In addi-
tion, unbalanced mass may occur in clamping equipment that
has been approved for lower speeds only, but is operated at
higher speeds, which may have a negative effect on the safety
and the machining results.
Operation at higher speeds than those specified for this equip-
ment shall not be permissible for the reasons mentioned
above.
The maximum speed and the operating force/pressure are
embossed on the body and may not be exceeded. Therefore,
the maximum speed of the machine used should not be higher
than that of the clamping equipment, and therefore has to be
limited.
Exceeding permissible values once may already cause da-
mage and constitutes a potential source of danger, even if this
is not immediately apparent. In such cases the manufacturer
has to be notified immediately so that the functions and opera-
tional safety of the equipment can be checked. It is only in this
case that the continuing safe operation of the clamping equip-
ment can be ensured.
4. Unbalanced mass
Residual risks may arise as a result of inadequate rotational
compensation -- please refer to section 6.2 No. e) of European
Directive EN 1550. This applies in particular at high speeds,
when machining asymmetrical work pieces or when using
different top jaws.
In order to prevent the occurrence of any damage, the chuck
and the work piece should be balanced dynamically in accor-
dance with German standard DIN ISO 1940.
Given eccentric tension and maximum speed the specific unba-
lanced mass of the unbalanced mass may not exceed the value
of 25 gmm/kg.
5. Calculation of the chucking forces required
The necessary chucking forces or the maximum speed permis-
sible for the chuck for a certain machining operation have to be
determined in compliance with the German VDI Directives 3106
-- Determination of the Permissible Speed of Rotating Chucks
(Jaw Chucks).
6. Use of other / additional clamping inserts / work pieces
The German VDI Directives 3106 -- Determination of the Permis-
sible Speed of Rotating Chucks (Jaw Chucks) -- has to be con-
sulted as a matter of principle when employing clamping inserts
or work pieces.
1. Use of other / additional clamping inserts
If clamping inserts are to be used other than those intended
for this clamping equipment, the operator has to safeguard
that the chuck cannot be run at an excessively high speed,
thus causing excessive centrifugal forces. Otherwise, there is
a risk that the work piece is inadequately clamped.
For this reason, please consult the chuck manufacturer or the
respective construction engineer, respectively, as a matter of
principle.
2. If special jaws are used, observe the following rules:
The jaws should be as light and as low as possible. The grip-
ping point should be located as near as possible to the front
of the chucking tool.
(Gripping points located at a major distance from the front of
cause higher surface pressure in the jaw ways and may sub-
stantially reduce the gripping force).
Use the following formula to determine maximum speed for a
specific machining application:
F
spo
= total gripping force of the chucking tool at standstill (N)
F
spz
= total gripping force required for a specific machining
applocation (N).
n
max
= max. speed (min --1 )
m = mass of the complete jaw unit (kg) base and top jaw
r
c
= centre of gravity radius of the complete jaw unit (m). (For
eccentric chucking, use the mean value of the centre of gra-
vity radi of the individual units).
a = number of jaws
Avoid welds as far as this is possible. If welding cannot be
avoided, be sure to check the welds for adequate resistance
to the loads applied by centrifugal and gripping forces.
The arrangement of the mounting screws should be seleczed
so as assure the greatest possible effect.
3. Danger caused by ejection
DIN EN 12415 states that a separating guard must be fitted
on the tooling machine to protect operators against ejected
components. The resistance of the guards is given in so--cal-
led resistance classes.
¯
3
F
spo
-- F
spz
30 n
max
=
m · r
c
· a
·
11
7.