Feature sponsored by Test & measurement C
oordinate measuring machines (CMMs) detect the geometrical properties of workpieces in detail. For many years, measuring systems were equipped with tactile
sensors, but these are increasingly being replaced by optical sensors. Optical sensors offer numerous advantages over tactile measurement technology. Laser triangulation sensors, laser scanners and confocal chromatic sensors measure the target without making contact. This means that the sensors do not have any influence on the measuring object. The measurements are performed with micrometer accuracy and are normally faster than contact measurement methods.
In practical use, optical sensors are extremely flexible. They measure distance, dimensions, position, angles, shape, roughness and even 3D profiles. Micro-Epsilon offers a broad sensor portfolio that has proven itself in numerous measuring machines. The sensors are used in various systems for both measurement and precise positioning.
ADVANTAGES OF OPTICAL SENSORS IN COORDINATE MEASURING MACHINES
Coordinate measuring machines are used for high precision quality and parts inspection. Optical distance sensors are increasingly being used for this purpose to replace conventional mechanical gauges. There are numerous reasons for using non-contact sensors: the measurement is reactionless, fast and offers high resolution. Modern optical sensors such as laser triangulation sensors, laser scanners and confocal sensors are particularly suitable for this purpose, says Glenn Wedgbrow, business development manager at Micro-Epsilon UK...
CMMs detect the geometrical properties of workpieces. Optical sensors offer many advantages over tactile measurement
technology, as measurements are reactionless, high resolution and fast.
FINE POSITIONING WITH LASER TRIANGULATION SENSORS For positioning of the measuring head, optoNCDT 1900 laser triangulation sensors measure the distance to the target or baseplate. This type of sensor is particularly suitable for precise distance control and object detection. This allows the CMM’s geometry data acquisition systems to be aligned with maximum precision. The laser sensors are integrated into the measuring head system,
The large aperture angle and the high numerical aperture of confocal chromatic sensors enable high resolution with a small light spot size.
Curved and structured surfaces such as gears or external threads can be reliably and precisely detected using confocal chromatic sensors.
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ROUGHNESS MEASUREMENT AND GEOMETRICAL INSPECTION In terms of resolution and measuring rate, confocal chromatic sensors are among the most powerful measuring systems in optical metrology. For example, they are used for high-resolution distance measurement on various surfaces and for roughness measurement. The confocal sensor systems from Micro-Epsilon combine state-of-the- art technology and easy integration. The sensors
which is typically attached to the vertical z-axis – the quill. The laser sensor delivers maximum signal stability and due to its compact design, is easy to integrate. The lightweight, robust laser sensor makes it ideal for measurements with high accelerations. The sensor operates at measuring rates of up to 10 kHz and offers a linearity of ±1 µm and a repeatability of 0.1 µm. The measurements can be started via the encoder pulse of the CMM, thus achieving absolute time- synchronous values. Due to the sensor’s intelligent Advanced Surface Compensation feature, stable results are achieved, even on challenging surfaces. With up to 50,000 lx, the sensors are extremely resistant to ambient light and can therefore be used in highly illuminated environments. For signal optimisation, two-stage measurement averaging is available, which enables a smooth signal curve at edges and steps.
Laser scanners are used for 3D measurement of complex geometries and rotating components.
For quality assurance of rotary pistons, the piston surface is measured 360° and compared with the nominal shape within a narrow tolerance.
allow a tilt angle of up to ± 30° and offer a high numerical aperture. This enables high resolution and small light spots. Curved and structured surfaces can therefore be detected precisely and reliably. In this way, gears or external threads can also be detected. Due to the non-contact measuring principle, the sensor does not affect the target object, which enables wear-free measurements. This is why values can be detected much faster compared to tactile measuring principles. With the confocalDT controllers, measuring rates of up to 70 kHz can be achieved. For measurement in confined spaces, compact sensors, as well as sensors with a 90° beam path are available, which can be integrated in the CMM measuring head to save space.
3D MEASUREMENT OF COMPLEX GEOMETRIES AND ROTATING COMPONENTS
When measuring large, complex components, the scanCONTROL series of 3D laser scanners from Micro-Epsilon are used. These scan large
March 2023 Instrumentation Monthly
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