FFD IM - Freudenberg Forschungsdienste SE & Co. KG

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RFID 10 RFID to be so large that the operator’s arm, for example, can also access the danger zone or the recess has to be dimensioned sufficiently small so that an emergency stop is triggered by a production item when passed through. Non-contact machine guards. Such available guards, such as light curtains, cannot distinguish between a production item and part of an operator’s body. For some applications, RFID (radio-frequency identification) technology is suitable for the installation of a machine guard. RFID uses electromagnetic waves for identification purposes. This technology is actually familiar to everyone as it is used in antitheft tagging systems in department stores. Articles of clothing are often fitted with a transponder (or radio tag). Devices which create an electrical field are positioned at the entrances to department stores. The transponder detects the electrical field on approaching it and sends a signal to an evaluation unit which generates an acoustic signal prompting the customer with an unpaid-for item to think twice before leaving the premises and to pay for the article in question. This principle can also be used on a machine guard. Function and elements of an rFID machine guard For the reasons outlined above, FFD decided in 2010 to introduce a RFID machine guard on a laboratory roller mill. This system comprises a limited number of components. The antenna is the core element of the system. It generates the electrical field (protective field) and consists of an extended conductor through which a current flows. Using a low-frequency AC current (9 kHz), a cylindrical magnetic field is generated which has a very high level of penetration through almost all materials. The antenna is positioned in parallel to the roller clearance above the rollers. To protect the operator’s hands, two transponders have to be worn on his or her wrists. Each transponder detects the field and sends a signal to the evaluation unit. In the X, Y and Z directions, the transponders are fitted with a coil which means that it is irrelevant how a transponder enters the field.
In our case, active transponders are used which draw the energy needed for signal transmission from a battery. The evaluation unit receives the signals sent by the transponders and the self-test module. These signals are redundantly processed by the control unit. The evaluation unit supplies the signal for triggering an emergency stop to the machine’s control unit. These imperative functional units are supplemented by different additional devices which are to ensure that functionality is permanently monitored. For visual display of the protective field boundary, a linear laser is used to project a mark on the roller. Since it is absolutely necessary for the machine guard to continuously check whether the protective field is available, a self-test module is used. This module is positioned in the protective field which it monitors. As soon as the protective field is no longer available, the self-test module sends a signal to the evaluation unit and the machine is emergency-stopped. This could, for example, be the case due to a broken cable or a power failure. To ensure that the transponders are applied, they have to be logged on at a log-on unit. It is only then that the system can be started. Successful log-on provides the operator with the information that the battery still has a lifetime of at least eight hours. In the case of our roller mill, log-on has to be repeated after a pre-set time in order to ensure that rolling is continuously monitored by a member of staff. The roller mill is then emergency-stopped upon expiry of this time. The objective was to achieve a finalised safety concept with a very high level of protection in the system. For this reason, traditional machine guards were also kept. FFD’s roller mill continues to be equipped with emergency stop pushbuttons, toggle triggers and a cut-off rocker. The rocker as a machine guard with an approach function has, however, been modified so that the roll of uncured rubber can be rolled and turned out and the additives dosed in an ergonomically favourable manner, providing optimum process possibilities. rFID workshop FFD invited colleagues interested in this subject to participate in the RFID workshop to present the mode of operation of an RFID machine guard to discuss the possibilities and limits of application to develop suitable decision-making aids for usage and thus to define underlying conditions for usage at Freudenberg At this workshop, RFID technology was presented by the manufacturer. During the talk given, if became clear that a wide range of different possible applications are conceivable. RFID 11
Page 1 and 2: Issue 2_2012 FFD IM DIALOG More inf
Page 3 and 4: Editorial Dear Business Partners, T
Page 5 and 6: the main causes for internal short-
Page 7 and 8: cyclical lifetime and a high curren
Page 9: As non-contact machine guards rFID
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Page 19 and 20: Figure 5: Axi-symmetrical FE model
Page 21 and 22: Location: FST Academy Building 75 F
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