In case of collisions, mechanical torque limiting clutches are indispensable protective elements in dynamic servo axes, for example in machine tools. This is so even if the control unit is equipped with a monitoring function. The extremely compact and high performance density torque limiting clutches in the EAS-smartic Type series are optimally adapted to the requirements of such axes.
No machine is safe from collisions. They occur even on machines with the most intelligent control and monitoring systems. The results for the user are high costs for repairs and replacement parts, downtimes and a damaged image due to late delivery. However, quite often the consequences for the machine manufacturer are ignored. Collisions can cause hidden damage which can result in the loss of accuracy. Such quality problems with a machine and downtimes negatively influence the productivity statistics. Both cast a damning light on the machine manufacturer nd influence future buying decisions.
Some servo controls manufacturers are still of the opinion that mechanical torque limiting clutches are no longer necessary. The collision monitoring in the machine controls is intended to take over the protective function. Collision monitoring systems recognize an increase in torque and activate countermeasures. However, this only works under certain conditions and can only provide effective protection in rare cases, e.g. in applications with low dynamics and soft collision.
The technical development in the field of machine tools has always taken the opposite direction. The trend for increasing complexity, higher productivity and increased accuracy has continued. In case of collisions, reliable mechanical torque limiting clutches as protection against expensive overload damage are irreplaceable. They maintain the quality and increase the productivity of machine tools.
Machines are no longer designed to produce one and the same part during their entire service lifetime. The increased complexity with several, simultaneously moving axes multiplies the risk of collision. The increased productivity requires faster axis movements and stronger motors which possess a higher inertia. Higher speeds and larger mass moments of inertia make sure that the kinetic energy constantly increases. The demands for higher accuracy require stiffer frame and drive axis designs. In case of a collision, the torque increases so rapidly in modern machine tools that the electronic monitoring systems can no longer react effectively and in due time. Mechanical torque limiting clutches, however, separate the drive line in most cases within several milliseconds after the preset torque is reached and therefore uncouple the majority of the destructive kinetic energy.
Mechanical torque limiting clutches from mayr power transmission have always been used in the servo drives of machine tools, and have proven their worth thousands of times. Nevertheless, machine manufacturers still renounce such protective devices in many servo axes. In most cases, they are still concerned about the additional mass moments of inertia, the loss of torsional rigidity and last but not least about the higher costs. The latest generation of mayr-torque limiting clutches with the brand name EAS-smartic has confronted these concerns. They have been specially adapted to the requirements of machine tool axes.
Over 20 years of experience in the construction and production of completely backlash-free, positive-locking torque limiting clutches have influenced the development of the extremely compact and high performance density EAS-smartic. The outer diameter equals that of a standard shaft coupling, and it is only c. 10 to 15 mm longer in total length. This results in a very low mass moment of inertia which is lower than for example on a steel servo coupling. Hardened components with the tried and tested ball-detent principle and special cup springs provide extremely high torsional rigidity. All components have been dimensioned so that reliability and lifetime do not have to be compromised despite the high performance density.
Another new feature is the comfortable torque adjustment. If no specific value is required, the clutch is pre-set manufacturer-side to approximately 75 per cent of the maximum torque and delivered. A reference marking and torque indication on the clutch show the set value directly. In only a few simple steps, the torque can be changed to another required value. Comfortable handling and cost-saving were also the centre of interest when the installation mode was chosen. The clutch is mounted onto the shaft by tightening one single screw. The EAS-smartic clamping hub is dimensioned so that it transmits even the maximum torque safely and reliably.
During failure-free operation, the EAS-smartic transmits the torque from the drive shaft onto a drive element (sprocket wheel, toothed belt pulley) or - in combination with an elastic coupling - onto an output shaft. The torque is transmitted backlash-free over the entire clutch service lifetime. If the preset torque is exceeded, the clutch disengages. The torque immediately drops. A mounted limit switch registers the disengagement movement and switches off the drive. After the cause of the malfunction has been removed, the clutch reengages automatically and is ready for operation immediately.