In metalworking, the accuracy and reliability of tool and work piece retention has a direct influence on the quality of the machining process. This is why sensors on the spindles of machining centres that detect the retention of tools play an important role.
The spindle is exposed to a very harsh environment, with high vibrations during cutting, coolant and chips flying around. For this reason, inductive proximity sensors are often used, which can withstand such harsh environments and work reliably due to their non-contact principle of operation.
However, the downsizing of the equipment and the variety of tool detection due to complex machining and the production of many different products have led to the following challenges.
■ Difficult to mount on a small spindle by proximity sensors due to restrictions on adjacent installation
■ Long downtime due to proximity sensor position adjustment during process changes
Balluff inductive positioning system BIP is a sensor that detects the position of metal in a horizontal position. By continuously monitoring the position of the drawbar on the spindle using this sensor alone, it is possible to determine whether the tool is clamped/released/empty. If the hydraulic pressure used to power the spindle is also monitored at the same time, a more reliable and safer tool clamping system can be established.
The sensor contains eight coils that generate a magnetic field, similar to a proximity sensor, which emits and scans the magnetic field at high speed so that there is no interference between adjacent coils. Each coil detects the magnetic field attenuated by the metal and calculates the position information using a unique algorithm.
Using this sensor with intelligent IO-Link offers additional benefits (depending on product type):
■ Configure switching points where each clamp state can be monitored in bits
■ Clamping frequency counting function as an indicator of spindle maintenance
■ Self-diagnostic information, such as start-up count, operating time, internal temperature, etc.
This information will contribute to efficient control and predictive maintenance of machine tools.
More detail of inductive positioning system is here