3D production data acquisition for railway wheels
To assign the production data for railway wheels to each individual wheel, they are marked with a series of numbers. These numbers embossed on the side when red hot. The production data has to be read in an untreated, slightly oxidised condition before subsequent machining begins. The reading station must be designed in such a way that it is suitable for the harsh environment with dripping cooling agent and falling fragments of rust and scale. Because the production sites are located in various countries, the operator interface needs to be in multiple languages.
The lack of contrast between the text and background means that conventional 2D camera systems cannot be used. In these cases, the CV-600 system with a three-dimensional camera is used. The system works on the triangulation principle with a laser line and, with each image captured, detects a height profile at the laser position. Moving the optical sensor with a rotary axis results in a relief (3D image) of the wheel blank. Depending on the wheel radius, up to 40,000 images are recorded and evaluated for a complete blank. To do this, a special image pre-processing function extracts the text from the 3D image and the integrated reading software then identifies and reads the important series of numbers.
A linear axis is fitted on the rotary axis to allow the system to be adjusted for the different wheel diameters. The drives for both of these are controlled using the intuitive operator interface, along with the machine vision parameters.
Recording the wheel number enables the production machine data for each wheel to be stored for documentation and traceability purposes. Customers require this as the railway wheels need to meet important safety criteria.