IMS-A integrated measuring system from Rexroth

Turning machines back on again following a power failure can result in a critical situation. The controller in many applications needs to know the position of each axis immediately. Purely incremental measuring systems need to first complete a reference run for this. This extends the ramp-up time and, in a loaded state, can result in damage to the workpieces and tools. The new integrated IMS-A measuring system from Rexroth immediately recognises the absolute position of the axis with a high degree of precision when the machine is switched on and reports them to the controller without carrying out a reference run. For this, the system does not require buffer batteries that need to be replaced regularly.

Thanks to the inductive measuring principle, the IMS-A operates without physical contact and is therefore a wear-free assembly. The measuring scale cannot be interfered with or destroyed by external magnetic fields. The IMS-A is not sensitive to vibrations up to 10G and shocks up to 50G. The sensors and evaluation electronics are located in protective housing on the end face of the runner block. Even in working spaces with coolants, dust, shavings and other contaminants, the IMS-A does not require elaborate energy-eating, high-maintenance air purge systems. Even electrical and magnetic interference fields do not affect the measurement results. This ability makes the IMS-A destined to also be combined with linear motors, for example. Here it combines precision with high dynamic performance requirements and gains the full dynamics of ball and roller rail systems from Rexroth. The permissible acceleration is up to 500m/s ² and the maximum speed is 5m/s, or even up to 10m/s upon request.

With the IMS-A, position detection takes place very close to the tool centre point, an important prerequisite for high precision, and thus surface quality in machining. The position resolution of the IMS-A is up to 0.025um. This very low value creates the conditions for excellent control loop dynamics and thus short cycle times. The system accuracy of +/- 4um/m lies within that of glass scales. This means that repeatability of +/- 0.25um is possible.

Integrated functions

The functional integration of guiding and measuring in an assembly minimises installation times. No adjustment of the measuring system is necessary. With the IMS-A, engineers can use several runner blocks on an up to 4500mm-long profile rail independently and without any accuracy limitations. All components, i.e. rail, runner block with adapter plate and scanner, are individually replaceable in the event of servicing. This reduces servicing costs. The interchangeable construction offered by Rexroth ensures even less effort. All runner blocks of the same size fit onto the profile rails of the respective size without any restrictions. The measuring system transmits the data via HIPERFACE interfaces, as well as via SSI/1Vp-p to the intelligent drives or controller. DRIVE-CLiQ and FANUC interfaces are to follow.

The integration of additional temperature and motion sensors makes this measuring system prepared for the future requirements of Industry 4.0. The additional sensors allow machine designers, for example, to read out the temperature and the actual dynamics. The sensor data also forms the basis for future approaches to predictive maintenance. The user can record and evaluate operating states online. If the accelerometers detect changes, such as increasing vibrations, then this is an indication of wear or other problems. Scheduled maintenance can then intervene before the machine needs to be shut down.

For more information about the new Rexroth IMS-A measuring system please visit www.boschrexroth.com.