The designers of Rink GmbH & Co KG select all moving machine components with great care. The bearing and drive elements are subjected to heavy loads. This is because Rink manufactures machines for the fully automated uncorking or unscrewing of caps of returnable bottles that work at a speed of up to 60,000 bottles per hour. Under these conditions, iglidur plastic bearings from igus prove their worth - among others in the new carousel-type machines with increased throughput capacity.
Rink GmbH & Co KG in Kreuztal/Siegerland is a good example of the efficiency of the highly specialised German engineering industry. Founded over 50 years ago and now in its third generation of family management, the company focuses on the development and production of systems that prepare returnable bottles for reuse. This means that the machines remove crown corks from beer, water or other beverage bottles or unscrew the closures of returnable bottles, and do so at enormous speed. More than 50 percent of the plants supplied by Rink remove the corks and closures in crates with up to 12 crates per cycle and achieve typical outputs of 50,000 to 60,000 bottles per hour.
The bearing points are highly stressed at cycle rates of up to 60,000 bottles per hour. That is why the company Rink was looking for special wear-resistant linear guides and piston rings. In addition, long service life is of particular importance in this application in order to avoid interruptions during production.
With linear guides and piston rings made of the materials iglidur J and E7, the company Rink has found materials that are characterised by very low coefficients of friction. Due to the variety of materials, the right material was found for every application. Another positive specification is the freedom from maintenance and lubrication, which allows the bearings to be easily cleaned and prevents contamination of the bearing points.
In just two and a half eight-hour shifts, one machine can thus uncork one million reusable bottles in a very compact space. All moving parts reach very high cycle numbers within a very short time and are subjected to very high stress.
In addition to these systems, Rink also builds "decapper" systems for smaller outputs, which also operate in crate mode or open the bottles individually. For large capacities these machines are designed as rotary decappers. Then they use a roller-shaped tool developed by Rink, which is characterised by a continuous mode of operation during bottle opening. These machines uncork up to 4500 crates per hour with a total length of only 2.4 metres. The Rink product range also includes special machines which, for example, example, seal wine bottles or automatically empty beer and water bottles in the event of incorrect filling or labelling.
At present, rotary machines that unscrew individual bottles are in great demand. Design Manager Dipl.-Ing. (FH) Olaf Staave: "Although these machines need more space in the overall plant, the user is more flexible. " Since this requirement increasingly applies to higher throughput rates, Rink has now expanded the product range of rotary machines, first introduced eight years ago, and developed a new machine type for unscrewing up to 30,000 individual bottles per hour.
The fact that plain bearings from the product range of the motion plastics specialist were used in the design of this machine is a matter of course for the Rink engineers. The igus plain bearings offer very good sliding properties with long service life and are also ideally suited for use in the beverage industry because they are maintenance-free and do not require lubricants.
The designers at Rink use very different igus bearings in almost all machine types and also use different iglidur materials. Therefore they are well acquainted with the broad igus product range, but still would like to take advantage of the advice. Olaf Staave: "We then search together with igus for the most suitable solutions for our applications. "
Among other things, a linear bearing of the tool head was required for the new rotary machines, which moves the rotary unscrewing device up and down in a wave-like manner. In the smaller machines of this type, plain bearings made of the all-rounder material iglidur J are used at this heavily stressed bearing position. For the new models, the designers also tested alternatives such as iglidur J200 and iglidur E7 and both aluminium and stainless steel shafts to optimise the running performance.
A stainless steel shaft in combination with a bearing made of iglidur E7 proved to be the ideal material combination in this case. "The service life calculation has shown that the conversion from iglidur J to iglidur E7 triples the service life," explains Olaf Staave. "This fits perfectly with our new machine, which has a two to three times higher output than the original model. “
The company igus supplies the linear bearing drylin RJUM complete with liner JUM-01, and a precision stainless steel shaft of type AWMP. From igus' point of view, this is a very "classic" material pairing that is more than just convincing in terms of service life and availability. "The calculation also revealed a very cost-effective coefficient of friction," recalls Olaf Staave. "We can confirm that: The current consumption of the drives is indeed very low. " A linear bearing with stainless steel shaft is also used in the same assembly, for which Rink also decided to change from iglidur J to iglidur E7.
In another project, the developers at Rink also optimised the bearing point. This is a new and very compact unscrewing head that dips into boxes with small divisions for small barrels. Plain bearings made of the high-performance polymer iglidur Z are now used in the linear unit for the immersion movement, after the first unscrewing heads were still equipped with bearings made of iglidur J and iglidur W300. It was necessary to improve the performance significantly due to the higher requirements. Olaf Staave describes the result: "The headrest is extremely wear-resistant and the users are very satisfied. “
In a third application example for the optimisation of bearings, the designers dealt with a valve that is used in the systems for emptying bottles. The machine head with the valves moves into the box, the valves seal, build up pressure and press the liquid out. This prevents the formation of foam - in comparison to suctioning.
Due to the height adjustment a vertical movement of the valves with appropriate sealing is necessary. Originally, Rink used classic piston guide rings for the hydraulic cylinders for this task, which often did not provide the desired stability. Now a piston ring made of iglidur J is used – for good reason: The high-performance polymer is resistant to chemicals and is characterised by low moisture absorption. "In addition, the piston ring made of iglidur J is easy to install and is reverse compatible," explains Olaf Staave. "So we did not have to change the surrounding structure and can also retrofit existing systems. These bearings have now been our standard for two years - especially since they are available quickly and cost-effectively as catalogue parts. For a special purpose machine builder like us, factors like these are just as important as the technical aspects. " Olaf Staave concludes: "The collaboration with igus has taken us a long way. We can continuously improve our technology and optimise costs at the same time. “