Measuring the thermal expansion in spindles
The SGS (Spindle Growth System) 4701 displacement measuring system is developed for high speed milling machine applications. Due to high machining speeds and the heat generated, the linear thermal expansion of the precision machine tool spindle needs to be compensated for in order to keep the tool in a defined position at all times. The SGS sensor measures the expansion of the spindle caused by thermal and centrifugal force. The measurement takes places typically on the labyrinth-ring. As well as the linear expansion, the temperature of the sensor is detected and output.These measurement values are fed into the CNC machine tool as correction values, compensating for any positioning errors.
The SGS 4701 consists of a sensor, a sensor cable and a controller, factory calibrated for ferromagnetic and non-ferromagnetic measurement objects. Two miniature sensors enable it to be installed directly in the spindle. The compact controller can be installed on the spindle housing via a flange or directly in the spindle.
The SGS 4701 operates according to the eddy current principle, which means that the measurement is non-contact and wear-free. This measuring method is also insensitive to disturbing influences such as heat, dust and oil.