The API tracker’s flexible range can take in an entire railcar from close-up

Laser Tracker CalibrationLaser measurement technology in wagon construction

Railcar manufacturer Waggonbau Niesky evaluated several trackers. They chose API for its angular range of +/-320 degrees horizontally and +80 to -60 degrees vertically, as well as API’s attractive package of equipment, automation training and support.

As part of a new project, DB Waggonbau Niesky GmbH has purchased a laser tracker from API, because, in comparison to conventional measurement technology, the mobile measurement system offers significant advantages in time, accuracy and the preparatory work that has to be carried out. Thanks to the automation, production workers can also carry out the measurements without any problems at all.

Every now and then, it happens to all of us that we have to wait for long minutes at a closed railway barrier while an (unendlessly long) freight train passes by. In these moments of waiting, you often tend to look at the wagons a little more closely – from the “box seat” so to speak. In most cases, they all seem to have a rather simple construction: wheels, frame and a (changeable) structure. This impression will quickly change, however, if you were to visit the production facilities of DB Waggonbau Niesky GmbH: here, it can be immediately seen that a great deal of fine technology is hidden within the wagons. Above all, however, the development of each individual type of wagon always takes place individually, with an eye on the intended application in each case. The innovative solutions are thereby often to be found in the detail.

Quality assurance therefore has a particularly important role in the context of the production process. For this reason, state-of-the-art measurement systems like the API Laser Tracker 3 are used in Niesky. “We purchased the tracker as part of a new product, a 4-axle one-sided box-type tipper for Vattenfall. Compared to other wagons, there are higher requirements on accuracy here. In the welded assemblies, we are talking about overall lengths of up to 20 meters, and a millimeter is a very small magnitude in this respect. If we were to use conventional measurement instruments, we would clearly fall far behind the laser tracker with regard to accuracy, time and the preparatory work to be carried out. The mobile laser tracker, on the other hand, is ideally suited for these measurements.” explained Frank Hommel from the Quality Managementof DB Waggonbau Niesky.

The API laser tracker permits the measurement of large objects, even from small distances. The tracker head can be swiveled through +/- 320 degrees horizontally and +80 to -60 degrees vertically, so that the measurement system can be positioned close to the target location. Through the two angles and the measured distance, the 3D measurement system calculates the coordinates. Several changes of position are also no problem thanks to the low weight and the head size of 36 cm. The head of the laser tracker has been designed so that the laser beam does not have to be deflected by a mirror or by a light guide. Systemic measurement inaccuracies are thereby reduced to a minimum. In addition to the compact dimensions – and there is no laser tracker in the world that is smaller – the further highlights of the API tracker include the superior range of 120 m without having to change location. Last but not least, this feature offers the Saxons even more varied application possibilities for their mobile measurement system in the future.

Up to now, the railcar constructors have made use of the laser tracker, which was purchased in the middle of 2009, almost exclusively within the Vattenfall project. This wagon is used to take away the large quantities of (wet) ash that arise in the combustion of coal and that are cooled down with water. Due to the special requirements of the brown coal industry, the wagon also has a special inner coating to ensure a complete discharge. Furthermore, the Vattenfall wagon places high functional demands: for example, the complete skip is tilted using a pneumatic cylinder. In this movement, the rotary joints and functional elements must match each other 100%. The frame forms a functional unit with the skip, and the skip has a movable flap – and this must not only be able to be put together easily and without problems during assembly, but must also function reliably in practice.

The API laser tracker is used on a daily basis in the production of the Vattenfall wagon, sometimes in all three shifts. Measurements are carried out on the three largest assemblies – the frame, the frame, the skip and the flap. A total of five workers work with the measurement system, thereby guaranteeing that an operator is available in every shift. These are not measurement technicians, but production workers. This is absolutely no problem, however, because the measurement process is exactly described, step for step, in a software program written by API. Every measurement point to be recorded can be seen on the screen, is re-corded and is stored. The next measurement point then follows. The worker therefore sees that measurement point 1 is next, followed by number 2, and so on. Finally, the results are calculated and the values are displayed. The ‘Spatial Analyzer’ software is usually used as the measurement software. The railcar constructors are particularly impressed by this software, because any one of the measured points can be repeatedly processed, for example, to measure levels and to define separations.

The measurement plan was drawn up in a close cooperation between Waggonbau Niesky und API. The measurement points on the welded assemblies are predefined by the Design Department. “Special challenges were presented in particular by the accessibility of some of the measurement points, which, in practice, turned out to be different than shown in the drawings.

The stands that were used for the measurements also had an effect. We therefore made some changes within the measurement plans: For example, some measurements were realized in a different way, in some cases via one, two or three measurement points in order to obtain a result. The effort certainly paid off, because the automation is running perfectly,” reported Steffen Linnemann, sales engineer at API, who provides support to DB Waggonbau Niesky.

An example of one of the clever solutions that the railcar constructors found in close collaboration with API was measurement in the installation space for the traction device. The wagons have no buffers like normal wagons, but are rigidly coupled. The installation space has been designed so that you can only take measurements with the tracker, and measurements are not even possible from outside. The tracker is therefore installed under the installation space when taking measurements – and the measurement of the internal space also finally takes place from below. The Saxons show their skill by the measurement on the frame, however, because the position of the centre axis of the bearing in relation to the central axle of the frame should be determined from there. In order to do this, the ball is used with a pin nest. The pin nest is set with the pin, and can then “go around” and record the measurement points.

In the skip, frame and flap, the railcar constructors also measure many different points in many different ways. There are at least 100 measurement points that have to be checked in the skip, for example.

Up to now, the API laser tracker has run very reliably and without any problems in Niesky. This is extremely important for the Saxons, because they need the system every day. As they have only had the tracker in operation for a few months, they still regard themselves as being within a certain learning process.

In this context, the railcar constructors would still like to pick up a few more ‘tricks’ while working with the measurement system, in order to increase the efficiency of the measurements. This applies particularly to the reflector, because it is very dusty in their halls and things become dirty very quickly. Under these conditions, a certain amount of experience is required in order to avoid ‘losing’ the laser beam. With the support of API, however, the Saxons hope that they will soon find a permanent solution with regard to the reflector.

Frank Hommel draws a positive conclusion: “We invited all the providers of laser trackers to a benchmark, and we finally decided in favor of API because they presented us with the most attractive package of tracker, automation, training course and costs. The last few months have shown that we made the right decision, because the system has absolutely proved its worth for us.”


DB Waggonbau Niesky GmbH can already look back at a 175-year history. For almost two years now, the Saxon company has been a 100% subsidiary of DB Fahrzeuginstandhaltung GmbH within the DB Mobility Logistics AG. On a production area of around 36,500m², DB Waggonbau Niesky currently employs around 250 people, and has annual sales of approx. 50 million. The product range includes the development and production of goods and special goods wagons, bogies, assemblies, major components made from aluminum and body frames for locomotives, passenger carriages and trams. Customers include European railways, EVUs (railway traffic companies) and rental companies.