Inspection station with 3D sensor and vacuum gripper for the removal of aluminium ingots

Evaluation of image acquisition for localisation with V60

Automated removal of aluminium ingots

The continuous feeding of aluminium melting furnaces with ingots weighing 5 to 25 kg is - not fully automated - not an easy job. This is remedied by a handling system that uses a vacuum gripper to convey the ingots to the crucible furnace. The control commands for the suction pad are based on the results of the VisionTools image evaluation system.

An LMS-400 time-of-flight scanner is attached to the gantry robot, which is also used to remove components from the stack. The height image determined over the light propagation time is evaluated by the V60 image processing software in combination with the reflection image (grey value image). Using two patterns - one for the top and one for the bottom of the ingot - the evaluation system searches for the rough position of the ingot. If such an ingot is found, its center point (X-/Y coordinates), the mean height around the center point (Z coordinate) and the rotation of the ingot (C coordinate) are calculated. Taking into account the scaling factors, simplified to say the conversion from pixels to millimeters, these values are converted into the coordinates of the handling. Then the evaluation system sends these results as well as the decision about "no error", "error" and "palette empty" as output signals to the control. It guides the vacuum gripper to the correct position, gives the commands to suck in the ingot and transport it to the transfer station.

The system can be adapted to linear axis systems with rotatable grippers and to robot systems. The prerequisite is a linear, uniform movement of the 3D time-of-flight scanner during image acquisition. During commissioning, a calibration run is required in which the handling system places a reference ingot at a defined position and then scans it using a camera system. The image analysis system can handle different types of ingots and can easily manage several such variants.

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