Krones uses one of its two API trackers to make sure that the fittings and screws in its 128 individual spouts on aligned and calibrated precisely. Prior to obtaining a laser tracker, it made adjustments by hand using a slotted table. This process took an hour. Today, they can make adjustments in 20 minutes.
Anyone who has ever tried to fill a Cola bottle under a tap knows that a number of things can go wrong, particularly when you are in a hurry. That there is a machine that can fill a complete swimming pool into handy bottles in only one hour, however, thereby sound unbelievable – but is nevertheless true. It is built by Krones AG in Neutraubling, a company that relies on state-of-the-art 3D laser measurement technology.
The 30-tonne mega-filler only started on its journey to Brazil a few weeks ago; a larger system has never been built before at Krones. This machine performance was made possible by the simultaneous filling of 162 bottles through a corresponding number of filling stations arranged in a circle. The diameter of the filler alone is almost seven metres, and it is clear that systems of this size can no longer be measured with traditional measurement methods: The available space inside the systems is borderline and, as a result of the compactness of the machines, some of the measurement tasks can only be solved with a certain amount of bodily acrobatics. The optimized transport paths that can be thereby achieved in the systems promise higher efficiency and lower energy consumption. However, even the latest portable measurement machines, such as measurement arms, reach their limits here – not the least because they often have to be rearranged due to their mechanical measurement principle and the thereby limited measurement volume. Sometimes, it is also simply not possible to set them up in the system, due to their complexity.
Mobile Measurement Technology: Laser Tracker
This is where the youngest representative of mobile measurement technology comes into the picture; the laser tracker, which can measure without contact over large distances (up to 60 metres) as long as there is a direct line of sight. Krones has two of these in Neutraubling, with one tracker installed stationary in Assembly, where it sits at virtually half-height below the roof and has a complete overview from a measurement point of view. From this installation location at an airy height, which is unusual for even the most versatile mobile laser measurement systems, but is also highly efficient, the compact system from Automated Precision (API) monitors the measurements on a table with a surface area of 3.5 x 2m, on which customer upgrades for the filling system are measured. Size places a decisive role here in the selection of the measurement system. With a height of 36 cm and a weight of 8.6 kg, the API tracker is smaller than other systems.
The fittings that are to be measured include the installation of screw conveyors, inlet guide stars and guide curves that are responsible for the feed and removal of the bottles. If their positioning is not exactly matched to each other, it’s not just the filling that will go wrong. Complete fittings are sent as additional deliveries to customers, who want to be able to keep their production at the latest state-of-the-art with regard to bottle size and shape through the modifications that have been commissioned from Krones.
Johann Rappl, Group Leader of Test Equipment Organisation reports on the improvement achieved in Assembly: “Before the use of the laser measurement technology, we assembled the fittings using equipment recordings on slotted tables. The assembly time for a fitting was up to one hour at that time. With the use of a laser tracker and only electromagnetic recordings, we have been able to reduce the assembly times for the same fittings by up to 20 minutes.”
For this purpose, a slotted table was fitted with a Teflon-coated steel plate. The measurement process itself was automated by the manufacturer of the laser measurement system within the measurement software of the laser tracker, so that the actual measurements could be considerably simplified and accelerated. The measurement points are thereby run to one after the other, point for point. In addition, the measurement system from API also provides a report with the deviations from the desired state (tolerance); the measurements can be traced and repeated at any time.
Krones is the unchallenged market leader; It is said, and not incorrectly, that every 4th bottle in the world is filled on a Krones system. Whereby the actual filling of the bottles is only a part of the services that these systems provide; systems from Krones also produce the PET plastic bottles themselves on integrated stretch-blow moulding machines, and the labelling is also a component of the systems. The cleaning of returnable bottles can also take place in a separate work operation. Last but not least, the packaging of the bottles is also carried out, so that the customer obtains a complete service from a single source.
Laser tracker in Production and Assembly
At Krones, one of the two API laser trackers is used in the Quality Control area, and the other for mobile applications. In Quality Control, the laser measurement technology and the laser tracker have consistently proved their worth when carrying out measurement tasks on complex filling systems and their delivered parts. In the mobile application, the second laser tracker is used to carry out measurements at customers and suppliers, for example, carrying out the initial sampling of large components and product audits at suppliers.
Before this system was purchased, laser trackers from various manufacturers were subjected to various tests with regard to geometry measurements and other measurements related to the alignment and construction of machines; all the systems passed these tests. Ultimately, the decision was made in favor of the system that combined the most advantages with regard to portability and flexibility.
The measurements shown here with the tracker, with predefined tolerances in the 1/10 mm range, take place at the customer’s premises, and are used to fine-tune the machine. The zero point of the system is normally located at an inlet star, on which the measurement system would ideally be mounted. Only this type of measurement can ensure that the machine does not have to be partly dismantled again for the measurements. After the adjustment, the actual filling process is checked in a test run.
Larger Krones machines, such as aseptic fillers, are fully enclosed, and have complete encapsulation for hygienic reasons. The tracker therefore stands in front of the machine for the measurement; only in this way can the positions of the stars that cause the transportation of the bottles into the machine via semi-circles (and between which the bottles are transferred using clamps) be measured with respect to each other.
Control points are used for this, and are placed both outside the machine and on the machine itself, and allow for rearrangement and further measurement in the same coordinate system. The number of customers that resort to in-house overhauls and the replacement of complete functional assemblies also continues to grow.
Portable laser systems are also ideally suited to another measurement task in Quality Assurance at Krones; the laser tracker also comes into play whenever a number of supplied parts have to be measured at the supplier’s premises within the context of product audits. A typical component of this kind is the base plate of stretch-blow moulding machines from Krones, with which the PET bottles are manufactured. These base plates, which can be as large as 5 x 6m and are machined and welded by the suppliers on-site, are measured on the spot. The laser tracker can also use the software that Krones uses in its measurement machines. In this way, the evaluations of the different measurement systems can be brought together in the factory. As the transport of these base plates to the main plant is expensive, they want to be sure that they conform to the specification before they are sent on their way.
Mobility is everything
The high proportion of classical service and maintenance on-site demands a high degree of flexibility – not only from the workers, but also from the systems used. The rule of thumb used by Krones for a portable measurement system is that it should be able to accompany the worker on his deployments without impairing his mobility. In the case of the portable laser tracker, the problem is solved in a practical manner: a commercially available tool cart that can accommodate the complete measurement system including accessories is used for the transportation to the customer’s premises.
It was also a requirement here that the measurement system should be able to be transported in a car in as little space as possible – including the measurement stand and tripod. Nevertheless, it can happen now and again that separate travel itineraries have to be taken – for example, when, for cost saving reasons, some airlines impose such a low weight limit for the luggage that has to be transported that although the systems themselves fall below the limit, this is not the case for the necessary transport container. Laser tracker precision are measurement systems, and need to be protected from careless handling, particularly during transport – which is exactly what the transport cases do, having been specially designed for this.
Johann Rappl sums up: “The new measurement tasks at Krones, combined with higher demands on accuracy, required the use of new measurement technologies. Only in this way could we guarantee the high quality level of our products. It seemed to us that the portable 3D laser measurement technology in particular, with the help of laser trackers, was well suited to our tasks. In the meantime, laser measurement technology has proved its value so well in the Production at Krones that they are currently considering the purchase of a third tracker.”
A laser tracker is a mobile measurement system that can measure large devices or components three-dimensionally using a laser beam without any physical contact. The laser beam, which is reflected from a mirror prism mounted in a measurement ball (the “target”), is evaluated with regard to the running time of the signal and the head position of the laser tracker, and thereby makes possible the calculation of the 3D coordinates of the measurement point in space. The target itself is manually guided over the part to be measured by the measurement technician and is automatically followed (“tracked”) by the laser tracker; all structures, geometries and surfaces within the visibility range of the tracker can be measured. Modern laser trackers have an operational range of up to 120 meters.