The demand for packaged beverages is increasing. In order to make the handling of the different sized glass and PET bottles quickly and reliably, the so-called clamping star wheels play an essential role in the complex beverages bottling lines. They are exposed to very high loads especially in the high output range. Since they have been equipped with double-component plastic rollers, their life has almost doubled.
"Brew house, filtration, bottling, logistics - we inplement not only complete breweries, but are a familiar name worldwide in the beverages industry," says Jürgen Steimmer, group leader labelling equipment, container sets and special star wheels of the Krones AG, Neutraubling, a global leader in beverage filling and packaging technology. "The demand for complete solutions is increasing. We serve the entire value-added chain of our customers from beverages production to goods distribution. " Krones plans, develops and manufactures machines and complete plants for the fields of process, filling and packaging technology and intralogistics. Every day, millions of bottles, cans and moulded containers are "processed" on Krones plants; primarily in breweries, the soft-drink sector, and for wine, sparkling wine and spirits producers, as well as in the food and beverage industry and the chemical, pharmaceutical and cosmetics sectors.
The clamping star wheels of Krones AG, Neutraubling, can easily grab glass and PET bottles up to a size difference of 20 mm. On a carousel, the bottles are transferred to subsequent machines at high speed.
For a beverage filling machine, Krones AG was looking for plastic rollers that would work permanently in the application. Due to the high number of cycles and use in three-shift operation, the rollers must be suitable for continuous use.
The material iglidur J with an outer jacket of TPU is used in this application. The iglidur material is characterised above all by its wear resistance. The outer jacket provides good grip on the outer component so that the bearing is always carried along. Accordingly, only the inner roller made of iglidur J wears out. The service life could almost be doubled with the iglidur rollers.
Since it was founded in 1951, Krones has developed far beyond the classical machine and plant engineering. The company has become an "all-round partner" for its customers. Mechanical engineering, plant know-how, process engineering, microbiology and information technology were harmoniously combined and optimised. Today, Krones is synonymous with "systems engineering".
Krones is a global player in this field. "Our machines and equipment offer customers added economic value worldwide," says Jürgen Steimmer. "We strive to find the right solution for every requirement. " Example: Inspection, filling and labelling of glass and PET bottles. Here the so-called clamping star wheels prove their capability. Their field of application is mainly the inspection equipment. On a carousel, the bottles are led past cameras at a high speed. They check not only the condition and type of single bottles, but also detect whether there is still debris or contaminents inside it. The bottles are then passed via a clamping star wheel to other areas, for example to the labelling. Such clamping star wheels are available in four different star wheel pitch circle diameters.
In each clamping unit - here for the inspection equipment - eight lubrication-free and maintenance-free iglidur rollers are installed.
They are interesting, for example, in systems for large breweries or mineral water bottlers, which have to handle many different bottle sizes. Since a clamping star wheel compensates a diameter tolerance of 20 mm, it can grab various bottle sizes. It therefore saves time for machine changeovers.. "The star wheels are permanently in use in the machine. Its service life was however limited earlier," Jürgen Steimmer looks back. "So we had to urgently remedy the situation. “
A solution for the clamping star wheel was developed together to extend its service life significantly. Double-component rollers are used in the spring clips for this purpose for the past two years. For the inside roller, the polymer material "iglidur J" was selected, which has proven itself for years in all industrial sectors of the packaging and bottling equipment. This new double-component option turned out to be an ideal solution for the requirements on site. It minimises wear and provides even longer machine running times.
A clamping star wheel can consist of, depending on diameter, four, eight, twelve, eighteen, up to 24 parts. A PEEK cam passes through between the clamping units, which provides for the opening and closing of the clamp, actuated via a control bolt. "Earlier the rollers in particular wore out too quickly, so that the customer had to overhaul the clamping star wheel relatively frequently," reports Jürgen Steimmer. Their bottling plants were at a standstill then and the number of complaints were increasing Customers often kept a second star wheel in stock so that it can be replaced quickly in an emergency. Of course that was associated with additional costs which they did not want to accept. "Here there was an urgent need for action. We have now eliminated this weakness. “
The new double-component roller developed for Krones is an option made of iglidur plastic roller and TPU outer jacket. It ensures smooth and wear-free movements on the expensive PEEK rotation axis.
The clamping star wheel is highly stressed in the everyday operation of breweries. In the upper output range, up to 66,000 bottles are guided through per hour in large breweries, which equates to 66,000 opening and closing cycles per hour. In order to increase the life of the roller, therefore, numerous attempts have been carried out with a variety of materials. "At first we contacted different plastic suppliers," Jürgen Steimmer looks back. "However, the results were not satisfactory. Either rollers or the rotation axis wore out even more. Only when we brought igus on board did we gradually come closer to solving the problem. " Bernhard Hofstetter, the technical sales consultant at igus elaborates: "Till that time we were known at Krones as a specialist in plastic bearings, not as a roller specialist. The present application was a great opportunity to bring other areas of our portfolio into focus. “
Following extensive tests, Krones was presented with a variant comprising a plastic roller and TPU outer jacket. Initial trials with rollers made of iglidur J material first found that the coefficient of friction from the inside outwards was not big enough to permanently provide for wear-free movements on the expensive PEEK cam. Only the new double-component model with a good coefficient of friction inside and a poor friction coefficient outside led to success. The iglidur J roller with TPE outer jacket today rotates smoothly and wear-free primarily on the axis and ensures a smooth operation. "Now we have no more complaints," says Jürgen Steimmer, "the service life is significantly longer. “
The roller is made of the tribo-optimised polymer material iglidur J, the outer jacket is made of TPU.
The double-component roller was tested almost for a year before it was incorporated into the first plants of Krones. While orange colour was selected for the TPE outer jacket initially, this is now delivered in the corporate colour blue. "We were able to get two birds with one stone," says Jürgen Steimmer. "First, blue matches our machines better and second, the blue colour has the RoHS certification, so these rollers were installed since summer of 2009. " The tribo-optimised plastic rollers are supplied in six different installation sizes. It has something to do with the size of the bottles and thus the opening angle of the clamps. The rollers are available for bottle diameters from 50 mm to 110 mm. "The opening angle for a 3-litre Coke bottle, which is customary in the American market, has to be correspondingly large for effective handling," explains Steimmer. Due to the size and heaviness of the bottle "only" 20,000 bottles can be channeled per hour via the multifunction star wheel in these bottling plants.