Automatic Shaft Measurement

| Information and Communication Technology

Measuring station moves along the shaft and uses the four offset optical micrometers

Triangulation sensors and optical micrometers put a new spin on measuring axles and shafts

Autonetics, a specialist in custom measurement systems that are used in a wide range of industries, has chosen to use non-contact laser micrometers and non-contact laser triangulation sensors from Micro-Epsilon on its Vertical Gauging Unit (VGU), a measuring tool for the precise measurement of shafts and axes.

The VGU is equipped with a tailstock and servo drive, linear drives with rack and a precision turntable. In addition, four optoCONTROL 2600 laser micrometers and an optoNCDT 2300 laser triangulation distance sensor from Micro-Epsilon are integrated into the VGU. All components together measure axial lengths, diameters, concentricity and splines, achieving cycle times and accuracies that cannot be achieved using manual measurement techniques. Not only do the sensors enable fast, non-contact measurement of shafts and splines, they also ensure stable measurements to sub-micrometer accuracy, even on metal surfaces. Comprehensive software enables evaluation of measurement data, recording of key values and data output to a PLC. The measurement data is automatically sent to the CNC controller so that tool adjustments can be made automatically in real time to compensate for tool wear.

Measuring tractor axle shafts

The VGU is used, for example, in an automated machining centre for tractor axle shafts. The shafts are guided into the VGU by a robot and clamped into position. The measuring station moves along the shaft and uses the four integrated optoCONTROL 2600 optical micrometers to determine the diameters. The four micrometers individually have a 40 mm measurement range but are arranged in pairs and offset in order to detect a range of shaft diameters from 58 mm up to 178 mm. In addition, the optoNCDT 2300 laser triangulation sensor, in combination with the rotary stage, is used to measure the splines of the shaft.

The optoCONTROL 2600 is an optical measuring system (sensor unit and controller) with integrated high resolution CCD camera. The sensor has been developed with solid state (non-rotating) optics and so the measurement accuracy does not drift over time. Using a special lens arrangement, an LED light source produces a parallel light curtain (visible red light), which is imaged on the CCD camera via a telecentric lens. If an object to be measured is placed in the light curtain, the shadow it creates is detected by the CCD array – even transparent targets can be measured. The measured data is output via analogue and digital interfaces, enabling easy integration for both OEMs and end users. The system is insensitive to high external light conditions, as well as dirt and moisture. The optoCONTROL 2600 has a measuring range of 40mm, a resolution of 0.1µm and a measuring rate of 2.3 kHz.

The optoNCDT 2300 is the high performance model out of the range of Micro-Epsilon’s laser triangulation sensors. It has an adjustable measuring rate of up to 49.14 kHz and a resolution of 0.03µm. The entire electronics are integrated in a compact sensor housing. The laser sensor is particularly suitable for high speed applications such as measurements on challenging surfaces, including diffuse reflective surfaces, glass and transparent plastics. The A-RTSC (Advanced Real Time Surface Compensation) feature enables more precise real time surface compensation during the measurement process. A range of interfaces is available including analogue, RS422, Ethernet, EtherCAT, Profinet and Ethernet/IP.

Jonathan Newell
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