Measure spindle extension on high speed machine tools. With milling and grinding machines, loss of accuracy can be a real problem, especially if high accuracy is required for machining of very precise components. Unwanted thermal expansion of the spindle can occur if the CNC system does not actively compensate for these temperature increases. If the spindle expands by even a small amount, the machine tool head can cut too deep. By working closely with machine builders and spindle manufacturers, Micro-Epsilon has developed a special sensor system, the SGS (Spindle Growth System), for solving this issue, which also enables machine tool operators to change the spindle without having to re-calibrate the sensor and electronics. The sensor, Micro-Epsilon's eddy current eddyNCDT sensor, is accurately measures any Z-axis expansion of the spindle. The system enables the active compensation of the axial spindle extension via a CNC machine tool. The result is a much more accurate milling or grinding machine. The SGS sensor system was originally developed for Steptec, a Swiss manufacturer of machine tool spindles. The sensor is based on Micro-Epsilon's standard eddyNCDT sensor but has a special aluminium, more compact housing and is rectangular in shape rather than cylindrical. The SGS measuring system uses the eddy current measurement principle. The sensor is controlled by electronics with a digital signal processor (DSP). All sensor-specific data is stored on the sensor itself, using an embedded EEPROM chip. After changing the spindle, the system is ready to run The sensor has very high temperature stability of ±0.01% FSO/°C. Resolution is less than 0.5µm and the sensor controller measures just 175mm x 110mm x 45mm. The controller housing is made from a heavy duty cast aluminium, which gives it excellent protection against electromagnetic noise and dirty environments (IP67). Micro-Epsilon normally supplies its SGS system to spindle manufacturers, for integration, but can also supply direct to the machine builder if required. _________________________________________________________ September2005

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