Schaeffler reckons that its new SpindleSense spindle monitoring system can make a significant contribution to machine tool uptime and performance.
In most machine tools the main spindle is at the heart of the machine and largely defines the achievable cutting capacity, surface quality, and precision. In turn, the spindle bearing support is one of the most heavily loaded components because it must transmit machining forces precisely at very high speeds for long periods of time, and the risk of collisions can never be ruled out.
It therefore comes as no surprise that the majority of machine tool downtimes can be traced back to defective spindles, particularly as a result of collisions and continuous, undetected overloads.
In milling operations, for example, the combination of high radial loads, long tool protrusions, and high speeds leads to particularly high loads and unfavourable kinematic conditions on the spindle bearing in the vicinity of the tool.
One reason why these loads occur is because to date operators have not had a suitable tool for measuring borderline loads on spindle bearings. Schaeffler reckons that the SpindleSense monitoring system is just the tool required.
The system provides electronic protection against continuous overload and collision damage. The sensor ring monitors any displacement of the spindle bearing with micrometre precision, and this data, in combination with Schaeffler’s expertise in rolling bearings, enables assessment of operating conditions.
All the software and the required algorithms are integrated into the 16mm-wide sensor ring. No further components are required for the system. The system is locally functional and transmits an individual warning signal to the machine’s control system.
The sensor technology is capable of signalling an overload at a digital output within 2ms. This allows serious subsequent damage to be minimised or even prevented through fast deactivation of the drive.
It also provides long-term protection for machine tool spindles. Because SpindleSense immediately triggers a warning signal when an overload is detected, operators can adjust the machining program right after the first manufactured part and reduce the spindle load by using a new tool or modified cutting values, or by employing a more suitable tool type.
The operator thus achieves lower and less frequent peak loads, and benefits from a longer spindle operating life with less machine tool downtime, which ultimately means more production time and reduced repair costs.
Two options are available for outputting the measured values. Variant C-A0 transmits alarm signals as soon as the individually defined limit values for the bearing load and kinematics are reached. Variant C-A1 outputs the measured radial and axial displacements including tilting via CANbus.
Machine tool and spindle manufacturers can use these displacement values to develop analysis tools for optimising the utilisation of spindle capacity, for example by visualising the deflection collective measured by the sensor ring as a load collective.
For the first time ever, the machine operator will have accurate data on how the spindle capacity in each machining process is being utilised and thus be able to adjust the machining process to optimise capacity utilisation and operating life for each machine: This means that harmful overloads are prevented despite maximum spindle loads.
Safe operation in the limit range allows operators to increase their productivity and also to benefit from longer spindle operating life and less frequent machine downtimes.
The measured displacements that are output via CANbus can also be used for zero point compensation. This makes it possible to produce the same quality with larger cutting values or higher quality with unmodified cutting values. The monitoring of the maximum displacement can also be used for quality assurance.
The first production-ready SRS sensor ring units – including radial and axial measuring ring with an inside diameter of 70mm – will be available to coincide with the major Hannover metalworking expo, EMO 2019 in September.
Additional sizes with 80 and 100mm inside diameter will be available at the end of 2019. All units have a standard width of 16mm. The system includes an SST setup service tool, with which SpindleSense can be parameterised and put into operation.
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