On-line measurement system for dimension measurement of steel productsVTT Electronics has developed a real-time 3-D process measurement system for the dimension measurement of steel products. The measurement device enables automation of steel tube and beam production. The system replaces the current method of manual dimension measurement. The dimension measurement device has been integrated with the production’s control system and reduces the amount of waste in production. The measurement system is based on the 3-D measurement method, in which semiconductor lasers, advanced machine vision and dedicated 3-D calibration algorithms are applied. VTT (Technical Research Centre of Finland) is Finland’s leading R&D service provider. About 3000 employees are currently organized into six units, one of which is VTT Electronics in Oulu. The optoelectronics research area at VTT Electronics has more than 80 qualified professionals involved in optical measurement technologies, optomechanics, optical modelling and design, micromodule technologies and optical materials, as well as printable optics and electronics and biomicrosystems. VTT, Next generation optical measurement technologies for industrial applications VTT is Finland’s primary R&D service provider and research organisation in the field of optical process measurement technologies. VTT has been developing on-line measurement devices and analysers for harsh industrial processes for more than 20 years. VTT offers R&D services in the field of optical instrumentation based on visible, near infrared, mid infrared, and Raman spectroscopy and advanced machine vision technologies. VTT’s expertise covers optics, high precision mechanics, electronics and software development facilities. Consequently, VTT is able to offer one-stop shop services in optical instrumentation. VTT has broad experience of developing optical measuring systems and analyzers for the Pulp&Paper, Steel and Pharmaceutical industries in particular. VTT’s machine vision team specialises in developing advanced camera-based solutions for real-time industrial applications. VTT’s research in recent years has been focused on form, dimension, geometry, and colour measurement applications. Biometrical identification is another topic in the field of next generation machine vision systems. Recent references for advanced 3-D dimensions consist of road profile measurement system. VTT has also studied and developed fast and accurate real-time colour inspection system for industrial applications. Ruukki Production, Tubular products The tubular products manufacturer Ruukki Production is one of the biggest producers on the area of the welded tubular products in Europe. Their products cover the whole range of tubes from the smallest precision tubes, diameter 8 mm, to the biggest gas pipes, diameter 1222 mm. The tube division has five mills and Pulkkila mill is responsible for the medium-sized tubes. Pulkkila’s tube mill production is advanced with a high degree of automation. The tube mill is mainly developed together with machine suppliers, and the suppliers’ advanced technology is often ramped up first in the Pulkkila mill. Pulkkila’s product range covers a huge number of products from the circular products (from 114mm to 323mm) to the square products (from 100x100/120x80 up to 300x300/400x200). Therefore, over 1,200 product changes take place every year. The main customers are working on construction and engineering projects. Pulkkila specializes in highly demanding products with tight tolerances, high quality and short delivery times, and this has led to the need to develop a highly automated production line. Advanced 3-D measurement device for on-line production control VTT and Ruukki have developed a new advanced 3-D measurement device tailored to Ruukki’s steel production line. The development project was done in two phases. In the first phase VTT designed, realised and demonstrated the performance of the off-line measurement device. Based on the experience from this prototype instrument, the real-time production-integrated measurement system was developed in phase two. In the near future Ruukki is going to integrate this in-line dimension measurement system with their production’s control system , developed by CapriCode, in order to maximise speed and quality..
The developed 3-D measuring system is based on the optical triangulation measurement principle and employs line lasers for illuminating the target and matrix cameras. The dimension measurement is realised with a multi-camera machine vision system and accurate detection of the laser line position. The challenge in this measuring system was to construct well-stabilized high-precision optomechanics and intelligent calibration for a very demanding process application. The reflection properties of the surface of the steel tubes and pipes vary a lot and the system must be able to measure the dimensions reliably.
 The measuring system includes an integrated calibration system, which is needed for keeping the accuracy within the tight tolerances specified by Ruukki. However, the robust and well-stabilised mechanical structure has proven very good. Motorised travel between the measuring and service/calibration positions enables operators to easily remove the measuring system from the line for service and calibration purposes without interrupting production.
The calculation algorithm joins all data from four cameras and creates a cross-section profile of the steel tubes or pipes in real-time production. The accuracy of the measurement is better than 100 µm. The measuring time of the dimension profile measurement is typically 1 s.
 Results The need for a fast and reliable measurement tool mainly comes from the large product range offered by Ruukki. The short delivery times, small stocks and focus on demanding high-tolerance products has led Ruukki to renovate their production and develop state-of-the-art measuring and automation systems for their production lines. The developed measurement system will replace the manual measurement method in production, and the system offers fast feedback on tube dimensions for the automated control system. At the moment, Ruukki is developing a new fuzzy-logic automation system with CapriCode Oy, which will enable fully automated dimension adjustments in real-time production.
The 3-D dimension measurement will dramatically reduce the amount of waste because the adjustments to production can be done immediately based on reliable measuring data. The obvious benefit of the measuring system is the faster and easier product changing operation, which is essential in cost-effective production of Ruukki’s tubular steel products. For the customers, Ruukki’s tube production is able to offer better tolerances, high quality, and shorter delivery times.
 Summary VTT has developed a real-time dimensions measuring system integrated with Ruukki’s steel beam and tube production. Based on the measuring data, Ruukki has developed a state-of-the-art measuring and automation system for their control purposes. The measuring system enables continuous control and adjustment of the machine rolls and enables cost-effective, high-quality production for demanding tubular steel applications.
VTT is looking for other real-time process applications for the developed measurement technology. VTT is further developing and applying the current 3-D measuring technology to different kinds of steel applications in a joint-funded Tekes project. VTT is willing to present the possibilities of this technology for industrial partners and applications.
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