ROHM KZZT / KZZT-A - Power operated pulling collet chucks - Handbuch (Seite 8)

I. Qualification of the operating staff
Persons, who have no experience in handling clamping
equipment, run the risk of being injured by the clamping
motions and forces occurring as a result of incorrect be-
haviour, especially during set--up work. For this reason,
clamping equipment may be operated, set up or repaired
by persons only who have been especially trained for this
purpose and/or have many years of experience.
After the assembly of the clamping chuck, the function of
the clamping chuck has to be checked prior to the initial
operation. Two important points are:
Chucking force: At the maximum actuation force /
pressure, the chucking force (+15 %) mentioned for
the clamping unit has to be made
Stroke control: The stroke of the clamping piston
has to have a safety area in the front and rear final
position. The machine spindle may start turning only
after the clamping piston has passed through the
safety area. Only such limit switches may be used to
monitor the clamping travel which meet the require-
ments for safety limit switches in compliance with
German standard VDE 0113/12.73, chapter 7.1.3.
II. Danger of injury
For technical reasons, this assembly may contain indivi-
dual parts with sharp edges. Always proceed with utmost
caution when working with the assembly to prevent the
risk of injury.
2.1 The maximum permissible speed
The maximum permissible speed may be run only at
maximum permissible actuation force and perfectly
operating clamping chucks.
Non--observation of this principle may lead to a loss
of the residual chucking force, and as a conse-
quence 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 provi-
ded.
2.2 Exceeding the permissible speed
This unit has been designed for rotating operation.
The centrifugal 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 addition, un-
balanced mass may occur in clamping equipment
that has been approved for lower speeds only, but is
operated at higher speeds, which may have a nega-
tive effect on the safety and the machining results.
Operation at higher speeds than those specified for
this equipment shall not be permissible for the re-
asons mentioned above.
The maximum speed and the operating force/pres-
sure are embossed on the body and may not be ex-
ceeded. Therefore, the maximum speed of the ma-
chine used should not be higher than that of the
clamping equipment, and therefore has to be limited.
Exceeding permissible values once may already
cause damage and constitutes a potential source of
danger, even if this is not immediately apparent. In
such cases the manufacturer has to be notified im-
mediately so that the functions and operational sa-
fety of the equipment can be checked. It is only in
this case that the continuing safe operation of the
clamping equipment can be ensured.
2.3 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 asymme-
trical work pieces or when using different top jaws.
In order to prevent the occurrence of any damage,
the chick and the work piece should be balanced
dynamically in accordance with German standard
DIN ISO 1940.
2.4 Calculation of the chucking forces required
The necessary chucking forces or the maximum
speed permissible for the chuck for a certain machi-
ning operation have to be determined in compliance
with the German VDI Directives 3106 -- Determination
of the Permissible Speed of Rotating Chucks (Jaw
Chucks).
If, for constructive reasons, the special clamping in-
serts required are heavier or larger than the clamping
inserts allocated to the clamping unit, the higher cen-
trifugal forces have to be taken into consideration in
the determination of the required chucking force and
the permissible speed.
2.5 Clamping force control
European Directive EN 1550, section 6.2, No. d) sti-
pulates that static force measuring devices have to
be used to check the serviced condition at regular
intervals in accordance with the maintenance instruc-
tions. Subsequently, the chucking force has to be
checked after approx. 40 operating hours -- indepen-
dent of the clamping frequency.
If and when required, the special draw--in force mea-
suring instruments have to be used. If no suitable
measuring instruments, such as pressure cells, can
be obtained, check the torque of a clamped barrel
gauge.
2.6 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 compressible 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 !
2.7 Clamping movements
On account of the clamping movements or potential
setting movements, et cetera, short travels are cove-
red at high forces, in parts, in short times.
For this reason, the drive equipment provided for the
chuck actuation shall have to be switched off expli-
citly for all mounting and setting work as a matter of
principle. If, however, the clamping movement is re-
quired during the setting operation, clamping 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. centring 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 hydrau-
lic, pneumatic and/or electric inching operation (cor-
responding control has to be possible !).
This type of auxiliary setting equipment depends ba-
sically 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 en-
tire clamping process does not endanger persons.
For this purpose, two--hand controls for clamp initia-
tion or even better corresponding safety equipment
have to be provided.
If the clamping device has been replaced, the stroke
monitoring device has to be adjusted to the new si-
tuation.
Safety instructions and guidelines for the use of
power-operated clamping equipment