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Safety precautions and directives for the use of force
I. Qualifications of operating personnel
Personnel lacking any experience in the handling of clamping
devices are at particular risk of sustaining injury due to
incorrect handling and usage, such injuries emanating in
particular from the clamping movements and forces involved
during setup work.
Clamping devices should therefore only be used, set up or
repaired by personnel
specially trained or instructed for this purpose and/or who have
long years of experience.
Chuck functionality should be tested after mounting prior to
commissioning.
Two important points are:
Clamping force: The clamping force specified for the
clamping medium (+15%) should be achieved at max.
actuation force/pressure.
Stroke monitoring: The clamping piston stroke should have a
safety range in the front and rear end position. The machine
spindle should only start if the clamping piston has passed
through the safety range.
Only limit sensors should be used for monitoring the clamping
distance, and these should meet the requirements for safety
limit sensors specified in VDE 0113 /12.73 Section 7.1.3.
II. Injury risks
This module can, for technical reasons, consist in part of
individual components with sharp edges and corners. Any
tasks involving this module should be carried out with extreme
care to prevent risks of injury!
1. Maximum permissible speed
The max. permissible speed may only be set with applied
max. actuation force and clamping chucks which are
functioning perfectly.
Failure to observe this basic principle can lead to a loss of
residual clamping force and, consequently, workpieces being
thrown out of the chuck and the risk of injury associated with
this.
The clamping device should only be used at high speeds
under an adequately--dimensioned safety guard.
2. Exceeding the permissible speed
This equipment is intended for revolving operation.
Centrifugal forces created by excessive speed and/or peri
pheral speed can result in individual parts loosening and
becoming potential sources of danger for personnel or
objects in the near vicinity. In addition to this, clamping media
which are only designed for use at lower speeds but are
operated at high speeds can result in unbalance which
adversely affects safety and the machining results achieved.
Operation at speeds higher than those permitted for these
units is prohibited for the above--mentioned reasons.
The max. speed and actuation force/pressure are engraved
on the body and should not be exceeded. This means that
the max. speed of the machine being used should not ex
ceed that of the clamping device (i.e. it should be limited
accordingly).
Even a singular incident where the permitted values are
exceeded can lead to damage or injury and represent a
hidden source of risk, even if not immediately detected.
The manufacturer should be informed immediately in such
cases so that an inspection of functional and operational
safety can be conducted. Further safe operation of the
clamping device can only be guaranteed in this manner.
actuated collet chucks
3. Unbalance
Residual risks can emanate from insufficient rotary
compensation, see § 6.2 No. e) EN 1550. This applies in
particular where high speeds are involved, when machining
asymmetrical workpieces or when using different collets.
The chuck should be dynamically balanced with the
workpiece mounted in accordance with DIN ISO 1940 to
prevent any resulting damage.
4. Calculating the required clamping forces
The required clamping forces and/or permissible maximum
speed for the chuck should be determined for a specific task
in accordance with VDI Guideline 3106 (governing the
determination of permissible speeds for rotary chucks (jawed
chucks)). High centrifugal forces associated with special
collets which, due to their design, are heavier or larger than
the collets allocated to the clamping medium should be taken
into consideration when determining the required clamping
force and permissible speed.
5.Use of other collet chucks
VDI Guideline 3106 governing the determination of permissi-
ble speeds for rotary chucks (jawed chucks) should always
be consulted when using special collets/workpieces. The
operator must rule out use of the clamping device at an ino-
dinately excessive speed and, consequently, the generation
of excessive centrifugal force if collets other than those inten-
ded for this clamping device are used. A risk exists otherwise
that the workpiece will not be adequately clamped.
The clamping point must be within the clamping cone area.
(Clamping points outside this area lead to collet and clamping
device damage, thus posing a risk caused by workpieces
being spun out).
The clamping device manufacturer and/or designer should
therefore be consulted in all such cases.
6. Clamping force inspection
Static clamping force measurement fixtures must be used in
accordance with Guideline EN 1550 § 6.2 No. d) to check the
service condition at regular intervals in accordance with the
servicing instructions. Clamping force should therefore be in-
spected after approx. 40 operating hours (i.e. regardless of
clamping frequency).
If necessary, special clamping force measuring collet chucks
must be used. In the event that no suitable measuring
devices such as, for instance, pressure measuring cell can
be obtained, a torque check must be carried out using a
clamped plug gauge.
7.Danger due to ejection
So as to protect the operator against ejected parts and in line
with DIN EN 12415 a separating protective equipment must
be fitted to the machine tool, the resistance capability of
which is specified in so--called resistance classes. Should
new clamping sets be used on the machine, their approved
suitability must first be checked. This also includes clamping
sets and/or parts thereof manufactured by the user himself.
This approved suitability is influenced by the resistance class
of the protective equipment, the mass of the possible ejected
parts (determined by calculation or weighing), the max. possi-
ble chuck diameter (measure) as well as the max. possible
speed of the machine. In order to reduce the possible impact
force to the permissible value, the permissible mass and
RPM must be determined (e.g. enquiry at the machine manu
facturer) and then the max. RPM of the machine restricted (if
required). However, the parts of the clamp set (e.g. collets,
workpiece supports etc.) should be designed to be as light as
possible.
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