Customised bearings for hygiene-sensitive multihead applications

Profile

• What was needed: iglidur plain bearing, drylin linear bearing
• Requirements: High precision, lubricant-free, low wear, corrosion resistance, resistance to cleaning processes under hot steam and high pressure as well as when using aggressive media.
• Sector: Food industry
• Success for the customer: Whereas previously the right material was selected for the specific area of application, today a single iglidur material is used that covers all properties in terms of temperature spectrum, electrical conductivity and hygiene. Newly developed linear housings made entirely of stainless steel have also been launched. Multipond thus achieves improved corrosion resistance.

Numerous food manufacturers rely on the highly automated multihead weighing systems from Atoma GmbH, which markets its systems under the brand name Multipond.
The weighing systems work very accurately thanks to the high-precision load cells with transducers. The most powerful Multipond scales with 36 heads achieve more than 500 weighings per minute. They are usually integrated directly into the fully automated production line. In addition to weighing, the newer models are also capable of dosing and counting.
In addition to ever higher performance and accuracy, more and more "hygienic design" should also be taken into account. The weighing systems come into direct contact with the product and must therefore be lubricant-free. Depending on the area of application, it is also necessary to fulfil properties relating to the temperature spectrum, electrical conductivity, hygiene and FDA requirements.
Rotary and linear bearing technology is used at various points here and must fulfil these and other requirements:
For example, in the ejection mechanism of the containers after weighing. This requires bearings that can withstand the thorough cleaning processes in food production under hot steam and high pressure as well as aggressive media.
However, Multipond is also increasingly supplying conveyor technology plus peripherals for integrating the weighing technology into the entire production system. For a 36-head weigher for cereals, for example, the transfer system was planned. The lower part of this system, the so-called lowering panel, raises and lowers in a fast cycle and with a stroke of 40 millimetres above the packaging machine and ensures that each individual packaging unit is filled quickly and precisely. As the lowering panel is only attached on one side, high forces, including tilting moments, act on the linear bearing required for this.

The Multipond designers decided in favour of iglidur and drylin bearing technology for the bearing components within the various system parts:

Discharge mechanism
Thus, iglidur bearings are used in the discharge mechanism of the containers: The lubricant incorporated in the lubricious high-performance polymer is not released into the environment. In addition, the plastic plain bearings are insensitive to the very thorough cleaning processes. While the multipond engineers used to select the right material for the specific area of application, a single special  iglidur material is used today. This covers all three properties - temperature spectrum, electrical conductivity and hygiene - and can therefore be used universally. This enables Multipond to reduce the variety of bearing types to a third.

Filling the packaging unit
Linear bearings from the drylin R programme are used for the lower part of the Multipond system, the so-called lowering panel. This raises and lowers in a fast cycle and with a stroke of 40 millimetres above the packaging machine and ensures that each individual packaging unit is filled quickly and precisely. The RGAS type housings allow precise and wear-free shaft guidance via the proven iglidur sliding foils.
There is also a current development project here: A special design of the RGAS linear housing was created for Multipond, which - apart from the sliding elements, of course - is made entirely of stainless steel. The end pieces of the shafts are also made of stainless steel. This enables Multipond to achieve improved corrosion resistance during the frequent and thorough cleaning processes to which such machines are subjected.