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

Page 14

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:

spo

= total gripping force of the chucking tool at standstill (N)

spz

= total gripping force required for a specific machining

applocation (N).

max

= max. speed (min

--1

)

= mass of the complete jaw unit (kg) base and top jaw

= 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

14538-k001-001 23.09.2003 10:52 Uhr Seite 11

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

-- require an independently actuated holding device (e.g. cen-

tring jaws for centring and face chucks)

-- require a work piece loading mechanism (e.g. loading stock)

-- 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

-- a work piece loading mechanism (e.g. loading stock) has to

be used

-- 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

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Qual.

10.9
12.9

8,6

14,9

17,4

36,1

42,2

M10

M12

123

144

M14

195

229

M16

302

354

M18

421

492

M20

592

692

M22

807

945

M24

1017

1190