10 months ago



Ready to take on

Ready to take on challenges of Industry 4.0 New modules from Mayr power transmission enable quick and easy monitoring of safety brakes and facilitate uniform deceleration of machines and devices. These intelligent modules create the pre-requisites for predictive maintenance and fault recognition, and thus increase the productivity of machines and systems. When driving a car, drivers use the footbrake to decelerate the vehicle in a targeted manner. Nobody would come upon the idea to pull the handbrake or parking brake when a car is driving at speed. The same principle applies for devices and machine applications which features dynamic braking procedures; where controlled, uniform deceleration is often desired. However, unlike automotive brakes, electromagnetic safety brakes only have two design-dependent operating conditions, the braking torque present and the braking torque cancelled, and therefore each braking procedure is implemented with the maximumavailable braking torque, determined through the spring pressure. On devices such as material handling truck, on which the loads vary, the brakes were designed with maximum load in consideration. However, it is not always practical to operate with full braking torque. As a result, in case of a partial load, a more severe deceleration can lead to damage of the transportation goods or even to blocking or skidding of the wheels. In applications such as film wrapping machines, in which the torque changes as the wrapping radius increases and decreases, limitation of the tensile forces through a correspondingly-adjusted braking torque is often significant for the protection of the material, but also for the machine design. For this reason, the braking expert, Mayr power transmission has now developed the Roba-torqcontrol module, an intelligent and economically-attractive solution, using which adjustable braking reactions are possible and machines can be brought to a defined standstill. value the fact that the Roba-torqcontrol module can be extremely easily integrated into superordinate control and regulation systems, and that no undesired feedback occurs on the control and regulation systems”. This module can either be operated with 24 or 48 V DC voltage, and controls brakes with a nominal coil current of 10 or 5 A. With two digital inputs, the resulting contact force on the brake linings can be specified to 30, 50, 75 or 100 % of the nominal spring force. Alternatively, a stepless analogue specification signal of 0 to 10 V (30 to 100 %) is possible. MOTION AND DRIVES Gentle and well-aligned braking 01 With the Roba-torqcontrol module, the company has developed an intelligent solution, with which machines can be decelerated uniformly and brought to a defined standstill The pre-requisite for this electronic braking torque control is that the system measures the operating conditions such as loading, speed or acceleration, and converts these measurements into a specific signal for the Roba-torqcontrol module. Frank Timmler from electronics development team at Mayr power transmission explains “If the module is used in a closed control loop system, then it is possible to run defined deceleration ramps, i.e. bringing the machine to a standstill gently and in accordance with the requirements. Using this module, it is possible for us to continuously change the contact force on the brake linings, and therefore the braking torque, during operation. In addition, in the case of applications which require a constant braking torque within narrow tolerance limits, negative influences on the braking torque consistency can be compensated through such braking torque control. Our customers particularly 01 02 02 Besides the switching condition, the brake-checker module monitors the tensile path reserve and detects safetycritical changes in voltage, air gap and temperature without sensors 28 WORLD OF INDUSTRIES 7/2018

03 Measuring current vs. torque, with 2 digital inputs, the resulting contact force on the brake linings can be specified to 30, 50, 75 or 100 % of the nominal spring force 04 Measuring current vs. torque, alternatively, a stepless analogue specification signal from 0 to 10 V (30 to 100 %) is also possible Electronic braking torque control In order to control the brakes, the Roba-torqcontrol module specifically influences the current and voltage, and therefore the internal physical values. Besides the parameters of friction radius, coefficient of friction and the number of active friction surfaces, the braking torque of a safety brake is also calculated from the sum of the spring force and magnetic force. “The maximum torque of the closed brake is achieved when the magnetic force is equal to zero, and only the springs are taking effect”, explains Frank Timmler. “If the magnetic force is then specifically applied against the spring force, then direct influencing of the effective spring force and therefore the braking torque is possible. We can already specify the desired braking torque with the module prior to application of the brake”. Permanent brake monitoring and predictive maintenance Besides the Roba-torqcontrol module, the company has developed an intelligent solution for monitoring the brakes with the Roba-brake-checker module. Both modules are based on the same functional principle. The brake-checker module exclusively serves to monitor the brakes; the torqcontrol module shares this monitoring function, and can also control the brakes. Users can select the appropriate solution depending on the application case. Both modules operate without sensors; instead they use the brake itself, i.e. the electromagnetic actuator, as the sensor. In this way, the modules analyses the physical conversion processes in the brake, i.e. the conversion from electrical to magnetic and then to mechanical energy. These processes generate reactions, and can be identified through the assessment of current and voltage. Through current and voltage analysis, the modules recognise the movement of the armature disk, and thus get to know the condition of the brake. In addition to the switching condition, the modules can also determine the temperature, wear and tension path or tensile force reserve, i.e. whether the magnet is still able to attract the armature disk. With the new modules, a significantly larger number of processes can be depicted by the monitoring than was hitherto the case, for example using Hall sensors, which monitor the energization of the magnetic field. On reaching the tensile force reserve, both the modules emit a warning signal, early enough so that a defined operating time of the brake is still possible. Within this time, the machine operator can undertake specific maintenance in coordination with their work process. The brake-checker module is now available in a design for AC voltage. In addition, the future version of the module will also take on the supply of the brake, and as a result, replace the rectifier. Thus combining switching condition monitoring and brake control in one unit. Condition monitoring without switches Due to the fact that both the modules operate without sensors, i.e. no micro switches or proximity sensors have to be attached to the exterior of the brake for switching condition monitoring. Thus all possible weaknesses of today’s micro switches, such as incorrect adjustment, limited service life etc., are eliminated. Additional wiring is rendered obsolete and depending on the protection, so is the sealing of the switches and sensors. The modules therefore ensure complete design freedom. This is very different to the solutions with switches and sensors, which are exposed to impacts and vibrations due to the installation position on the brake. The modules monitor or control from the control cabinet, i.e. from a protected environment. They operate without mechanical contacts and with high reliability, and remain wear-free, independent of the cycle frequency. Photographs: Chr. Mayr GmbH + Co.KG WORLD OF INDUSTRIES 7/2018 29


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