In 2005, Krones faced a challenge with the Variopac Pro, a fully automatic all-round packaging line: the line's output was to be increased by 20 packs per minute. There was therefore an urgent need for action on the conveyor belt deflection. Originally, metal rollers with needle bearings were used here, but these could not cope with the higher performance requirements and were cost-intensive. In the search for an alternative, Krones design engineer Jürgen Werner came across the products from Igus.

Continuous operation, sugar, heat - and no solution in sight?

The Variopac Pro packs glass or PET cans and bottles from 0.2 to 5 liters with cardboard and/or film. The parts and components have to meet stringent requirements, as the system is used in continuous operation. "This means that our systems run around the clock at the end customer's premises. Sometimes there are sugar particles in the environment due to the production process, which act like sandpaper on the moving machine components. And that at belt speeds of up to 0.9 m/s," explains Jürgen Werner in conversation. Dust, sand and moisture are also part of everyday life where the Variopac Pro is used. But that's not all. The conveyor belts are permanently exposed to temperatures of up to 100 °C directly at the shrink tunnel of the system. Despite these environmental conditions and the performance requirements, the new solution for deflecting the conveyor belts should have a service life of at least one year.

The requirements for the products needed to rework the knife edges on the conveyor belts were therefore clear. However, the problem lay elsewhere: a product that could meet these performance requirements did not exist. In its search for suitable experts, Krones came across Igus. "It was immediately clear to us that we wanted to develop a solution together with Krones. Even though our Iglidur high-performance polymers were generally developed to guarantee low wear and low friction, we were initially unsure whether they could meet the requirements of the Variopac Pro," recalls Lars Braun, Igus Industry Manager for the packaging industry.

Suitable solution developed together

Before being used in the Variopac Pro, various solutions were tested in the Igus test laboratory in order to achieve the desired result together with Krones. The first approach was to use thin-walled metal tubes into which Igloidur bearings were pressed. However, this proved to be too costly and labor-intensive, as each plain bearing had to be installed separately in the metal tubes. So Igus continued to tinker until the knife-edge roller was developed: an injection-molded solid plastic roller made from a material developed specifically for this application. "The pv values in the Krones systems were already very high back then. We therefore had to ensure that our knife edge rollers could withstand these loads and were suitable for use as a series product," explains Lars Braun.

The best test results were achieved with the material Iglidur P210. This is characterized by its high wear resistance, low friction coefficients and the resulting low drive power of the conveyor belts. In addition, like all Iglidur materials, it is suitable for maintenance-free and lubrication-free use. As it is also versatile, all requirements could be met with one material. When it became clear that the knife edge rollers made of Iglidur P210 far exceeded the required service life of one year, Krones decided to install them in the Variopac Pro. "Our systems are used all over the world and there are no breakdowns. The Iglidur knife edge rollers work simply and have hardly any noticeable wear. They are also easy to install and save our customers time-consuming maintenance work," reports Werner.

Safe transport at any belt speed

In the Variopac Pro, Krones now installs the Iglidur knife-edge rollers wherever there is a transition between two conveyor belts or plastic modular chains. As the knife-edge rollers have small diameters, the conveyor belts and modular chains can be tightly deflected and the gap between two belts is therefore very small. What sounds trivial is important in beverage production. If beverage containers tip over during transfer from one conveyor belt to the next because the gap is too large, this can lead to massive production losses and costly cleaning work. If the system is running at a low belt speed, this risk increases further.

"If, for example, sugary drinks are packaged, the cleaning effort is immense if containers tip over and burst. Even if the system is running at a low speed, we can prevent tipping with Iglidur knife-edge rollers. This means that even star-bottom bottles that are prone to tipping can be packed without any problems," explains Werner. As the belt speed increases, the risk of tipping beverage containers also decreases. However, as the Variopac Pro should be characterized by its high flexibility, it must function reliably at both 20 and 150 containers per minute. The same applies to the moving parts and components, including the Iglidur knife edge rollers.

Trends in the packaging industry

According to Werner, various future trends can be identified in the packaging industry. On the one hand, packaging sizes and environmental protection are playing an increasingly important role. Product and container sizes are increasing in order to reduce packaging waste. "We're talking about up to 45 bottles of 0.5 liters per container. This leads to high weight and higher loads for our systems and the knife edge rollers," explains Werner. The speed of the systems will also continue to increase. Currently, the running performance of a knife-edge roller in the Variopac Pro is up to 11,000 kilometers of glide path per year at a belt speed of 0.34 m/s. "Speeds of this magnitude are no problem for the Iglidur P210 knife-edge rollers. Speeds of up to 1 m/s have also been tested in our test laboratory. We are continuously working on the further development of our products and materials in order to be able to master new challenges in the future," explains Lars Braun.

The article appeared in materialfluss 11-21/21.