ROHM DURO-T hand-operated chuck (with key bar principle) - Manual (Page 14)

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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.
7. Safety requirements and rules and regulations for
the use of manually operated chucks
GB
14538-k001-001 23.09.2003 10:52 Uhr Seite 11
7
15
If new clamping sets are to be taken into operation on the
machine, the admissibility must be previously checked. This
also includes clamping sets or clamping set components
manufactured by the user. The admissibility is influenced by
the resistance class of the guard, the masses of the possi-
bly ejected parts (determined by calculation or weighing), the
maximum possible chuck diameter (measurement), and the
maximum possible speed of the machine. In order to reduce
the impact force to the permissible level, the permissible
masses and speeds must be determined (e.g. by obtaining
information from the machine manufacturer) and if necessary
the maximum speed of the machine must be limited. Howe-
ver, the construction of all clamping set parts (e.g. top jaws,
workpiece supports, axial clamping claws etc.) must always
be as lightweight as possible.
4. Clamping of other / additional work pieces
If special clamping sets (jaws, clamping inserts, alignment
element, positioning units, points, et cetera) are provided for
this clamping equipment, only those work pieces may be
clamped in the way the clamping sets have been designed. If
this fact is not observed, persons may be injured and mate-
rial may be damaged due to insufficient chucking forces or
unfavourable clamp positioning.
For this reason, if other and/or similar work pieces are to be
clamped with the same clamping set, the written approval by
the manufacturer shall have to be obtained.
7. Clamping range
The maximum clamping and/or displacement range in case of
movable base or top jaws may not be exceeded as otherwise
no sufficient engagement can be ensured safely between the
clamping jaw and the force transmitting component part.
8. Check of chucking force
1. Check of chucking force (general aspects)
European Directive EN 1550, section 6.2, No. d) stipulates
that static force measuring devices have to be used to check
the serviced condition at regular intervals in accordance with
the maintenance instructions. Subsequently, the chucking
force has to be checked after about forty operating hours --
independent of the clamping frequency.
If and when necessary, special chucking force measuring
jaws or devices ** (pressure cells) have to be used.
9. Stability of the work piece to be clamped
In order to ensure safe clamping of the work piece to withstand
the machining forces occurring, the work piece clamped shall
have a stability suitable for the chucking force and may be com-
pressible to a minor degree only. Non-metal materials, such as
plastics, rubber, et cetera, may be clamped and machined only
after written approval by the manufacturer !
10. Mounting and setting work
On account of the clamping movements or potential setting
movements, et cetera, short travels are covered at high forces,
in parts, in short times.
Safety requirements and rules and regulations for the use of manually operated chucks
For this reason, the drive equipment provided for the chuck
actuation shall have to be switched offexplicitly for all mounting
and setting work as a matter of principle. If, however, the clam-
ping movement is required during the setting operation, clam-
ping travels of more than 4 mm
-- require the attachment of a permanent or temporary work
piece holding device
or
-- require an independently actuated holding device (e.g. cen-
tring jaws for centring and face chucks)
or
-- require a work piece loading mechanism (e.g. loading stock)
or
-- require that the setting work is carried out in hydraulic, pneu-
matic and/or electric inching operation (corresponding control
has to be possible!).
This type of auxiliary setting equipment depends basically on the
machining system used and has to be procured separately, if
and when necessary !
The machine operator has to be make sure that the movement
of the clamping equipment during the entire clamping process
does not endanger persons. For this purpose, two--hand con-
trols for clamp initiation or even better corresponding safety
equipment have to be provided.
11. Manual loading and unloading
In case of manual loading and unloading processes, a mechani-
cal hazard for the fingers caused by clamping travels larger than
4 mm has to be taken into consideration. Thus,
-- an independently actuated holding device (e.g. centring jaws
for centring and face chucks) has to be fitted
or
-- a work piece loading mechanism (e.g. loading stock) has to
be used
or
-- the clamping movements (by throttling the hydraulic supply,
for example) has to be reduced to a clamping speed ofl ess
than 4 mm s --1 .
12. Fastening and replacing screws
If screws are replaced or loosened, defective replacement or
fastening may lead to a hazard for persons and objects. For this
reason, the corresponding torque recommended by the manu-
facturer for the screw and the screw quality has to be used for
all fastening screws as a matter of principle, unless explicitly
stated otherwise.
The following torque table shall be applicable for all standard
sizes M5 to M24 of quality 10.9 and 12.9:
Tightening torques in Nm:
In case of doubt, use screw quality 12.9 to replace the original
screw. As a matter of principle, quality 12.9 shall be used for all
fastening screws on clamping inserts, top jaws, positive stops,
cylinder covers, and comparable elements.
All fastening screws, which on account of their useful purpose
have to be unscrewed and tightened again subsequently (e.g.
** Recommended clamping force measuring system EDS:
EDS 50 kpl. Id.-Nr. 161425
EDS 100 kpl. Id.-Nr. 161426
EDS 50/100 kpl. Id.-Nr. 161427
14538-k001-001 23.09.2003 10:52 Uhr Seite 12
Qual.
10.9
12.9
M5
8,6
10
M6
14,9
17,4
M8
36,1
42,2
M10
71
83
M12
123
144
M14
195
229
M16
302
354
M18
421
492
M20
592
692
M22
807
945
M24
1017
1190
Nm
Nm