BS 869:2006 pdf download – Safety of machinery — Safety requirements for pressure metal diecasting units
5.2.3 Guards for the die closing mechanism area
Access to the die closing mechanism area shall be prevented by interlocking movable guards. The movableguards shall either
a)be interlocked with the power supply for the dangerous movements (e.g., switch off the hydraulic pump and release the pressure of the accumulators).The relevant part of the control system shall have a safetycategory of not less than 1 in accordance with EN 954-1.Restarting the machine shall only be possible ifthe guard for the closing mechanism area is closed;
b) be interlocked with the control system.Opening of the guards shall stop all dangerous movements. The relevant part of the control system shall have a safety category of not less than 3 in accordance withEN 954-1.Restarting the dangerous movement shall only be possible if the guard for the closingmechanism area is closed.Movements of the ejector system with guard open are allowed, if,
1) for machines with a clear vertical distance between the tie bars up to 1 200 mm, the dangerousmovements are restricted as stated in 5.9.2;
2) for machines with a clear vertical distance between the tie bars greater than 1 200 mm,the
conditions of 1) shall be fulfilled and additionally the speed of the ejector shall be reduced to 30 mm/s.The parts of the control system related to the speed reduction shall be at least category B inaccordance with EN 954-1.
Fixed guards can be used for the die closing mechanism area if no frequent access is required (e.g, accessless than once a shift, according to EN 953:1997;
5.2.4 Additional requirements for movable guards and access doors General
Movable guards and access doors,see 5.2.5, shall be interlocked with the control system in such a mannerthat movements of the die and positioning movements of core pullers can only be initiated ifthe movable guards for the die area and for the die closing mechanism area and the access doors are closed.
The opening movement of the platen with the die area guard open shall only be possible if it is impossible toreach in these conditions the crushing and shearing points behind the moving platen. Ejector movement shall only be possible with the guards for the die area closed. Deviations from the requirements of and (see also 5.10 of EN 954-1:1996) areallowed and the ejectors and core pullers may be operated with guards for the die area open provided that:a)the ejectors and core pullers have no shearing or crushing areas
or, if there are shearing or crushing areas,
b) a lockable mode selector switch (or equivalent access code in case of numerical control) is provided sothat operation with the guard open can be selected.
Any opening of the guard protecting the die shall immediately stop the die closing movement. The casting process shall only take place when the movable guards of the die area, or the accessdoors are closed and the die is closed and locked.
NOTE In case of machines with toggle actuation the die closing movement is completed when the die is closed andlocked by the toggle in stretch position.
ln the case of machines with hydraulic closing actuation the die closing movement may not be completed when the closingcylinder is applying fulocking force. Additional measures are necessary to ensure that the die is adequately closed. the next cycle after guards have been opened in automatic mode.
Starting the next cycle shall be initiated by an intentional start command (see also
lf, for machines with a tie-bar distance up to 1 200 mm, because of technological requirements, the guard isclosed automatically, e. g.,on a time basis (see the next cycle shall be initiated by an intentionalcommand within a time limit of 10 s. After exceeding this time limit the guard shall open. Additionally, if theclear distance between the tie bars does not exceed 650 mm, the next cycle can be started automatically byclosing the interlocking guard for the die area. Whenever the guards close automatically on a time base because of technological requirements,e. g., material properties like cooling rate, stability of die temperature, the re-closing time of the guards shallbe defined taking into account the ergonomic aspects (stress of the operator).The re-closing time shall be setby a system whereas the access to this system is restricted to certain categories of persons (e.g. with apassword restricted to persons in charge of machine setting). The devices for intentional starting the cycle shall be positioned in such a way,that the operatorusing them has a good view of the die-area and the area between the die-area and the guard.
5.2.5Diecasting units
When the interaction between the diecasting machine and the ancillary equipment (e. g., a robot take-off-unit)prevents the use of a movable guard as defined in, a distance guard shall be provided (see Figure A.9).
NOTE This requirement does neither define the safety requirements of ancillary equipment nor the requirements for theinterlocking of enclosures for these devices. Higher levels may be required in some circumstances.
Within the distance guards emergency stop devices (according to EN 418) shall be installed at suitable places.The emergency stop devices shall be adapted to the local conditions, e. g., permanently connected movableor fixed devices.
Accesses (doors) in distance guards shall be designed so that they do not open inwards. Doors shall beconnected with the control system of the diecasting machine and its ancillary equipment by two mechanicallimit switches. Instead of mechanical limit switches safety devices operating on different principles are allowedif they at least fulfil the same level of safety (according to 6.3.1 of EN 1088:1995).
In case of two mechanical limit switches when the door is closed, one limit switch shall be actuated positivelyby the door and the other limit switch shall be released.The coupling of the limit switches shall be in such amanner that it shall only be possible to start the diecasting machine and its ancillary equipment after the dooris closed and a reset command has been given. The reset device shall be installed near to the door outsidethe danger area in such a manner that it can only be actuated from outside the distance guards.