In addition to convenient cleaning, the top priority for food production machinery is ruggedness. Highly aggressive cleaning agents and large amounts of water are used to prevent pathogens from developing. These must not have a long-term impact on machine availability. Self-lubricating polymer plain bearings that reliably stand up to any adversity over the long-term are proving themselves in this aggressive environment.

"We are almost exclusively active in special purpose machinery building", explains Simone Singer from the sales and marketing operation of Singer & Sohn GmbH in Berching, Upper Palatinate. "And our proximity to the bratwurst metropolis Nuremberg has had the effect that our machines are frequently used in sausage and meat production. We see ourselves as problem solvers for our customers, who generally need to automate production processes with customized plants, in part to meet strict hygiene guidelines over the long term. “

Dieter Koller, Head of Design Engineering, explains: "Our machinery product range is characterized by its particularly high reliability, long service life, and ruggedness. This is particularly important in food processing applications, since these are frequently operated by unskilled workers on the one hand, while their service lives must be acceptable on the other. The market is highly competitive. Unnecessary maintenance and service downtime must be avoided at all costs. “

Hygienic cutting of sausage links

Founded in 1978 as a contract job-shop, today's focus of the family-run company with its roughly 38 highly qualified employees is on the design and fabrication of conveyor plants and special-purpose machinery that is primarily used in the food processing and beverage industry, but is occasionally also found in chemical and pharmaceutical applications. "No detail is too small for us. Ranging from a simple conveyor belt to highly complex machinery – we plan, fabricate, deliver and install cost-effective plants that have by now proven their performance capability throughout the world", explains Dieter Koller. "We are a one-stop shop, including service. " Ranging from conveyor lines for pastries and baked goods, scales, cutting plants, automatic production plants for processed meat or brush plants for salami sticks: they all involve customer specific products that are completely fabricated from stainless steel. "The material guarantees long-term and hygienic operation", explains Simone Singer. "Accordingly, all machinery elements must be compatible with this. “

The custom machinery builder has now exhibited a sausage link cutting machine, 'OptiCUT SI-1000', at Anuga FoodTec, where the machine generated considerable interest. "This design was the result of a customer inquiry, who in part wanted to significantly reduce manual labor in his production for hygiene reasons. " Whereas in the past, employees manually cut the sausage links from below with a type of razor blade, this is now accomplished with a machine. Although employees were naturally required to wear protective suits, it was unavoidable that they touched the food while performing this work, therefore risking contamination. Moreover, the manual process continuously resulted in different sausage link lengths, which caused variability in the visual impression. "And in today's world, food retailers are no longer able to communicate this effectively to their customer base", the Head of Design Engineering raises another aspect.

"The cutting operation is now accomplished fully automatically", explains Dieter Koller. A camera system optically recognizes the pinch locations and arranges the knife positioning, and therefore the accurate cutting of the sausage links. The output is currently at seven smoking trays (= triple edge aluminium rods) with 26 sausage pairs each per minute. "Our short-term objective is ten smoking trays", the Head of Design is quick to add. " The stainless steel plant can be used for a wide range of sausage types such as wieners, knockwurst in natural skins, fried or raw sausages. In connection with the material, it also meets all applicable requirements for cleaning and hygiene. "And because of the automatic cutting process, all sausages now have a uniform length for the packaging process."

Food production without external lubricants

The operating principle of the machine is straightforward. An operator removes the smoking trays with the sausage links from the boiler or smoking cart and feeds them into the sausage link cutting machine for automatic processing by the plant. The sausages are secured, spread, and respectively cut from below in the machines interior. The smoking trays exit from the opposite side of the plant and can then again be retrieved by an operator or are automatically fed to the next production process with add-on conveyor technology.

"[External] Lubricants are highly frowned upon in food production processes", Dieter Koller clarifies. "Here again, the risk of contaminating the product is much too high. " For this reason, the special purpose machinery builder has been working together with igus® GmbH, Cologne, for a number of years. The entire product range rigorously relies on self-lubricating polymer plain bearings and a host of other plastic products. They are generally available from stock and help to reduce maintenance, to cut costs, and to increase the service life.

drylin® linear guides and trapezoidal lead screws, as well as corrosion-free igubal® flange bearings also demonstrate their versatility in the sausage link cutting machine. All off-the-shelf components are designed for direct contact with foods. In addition, durable polymer energy supply systems ensure the necessary power supplies.

"Way back when, we installed needle bearings", the Head of Design Engineering reminisces. "But they did not hold up to the rough day-to-day operating and cleaning exposure." These are very sensitive: as soon as a few drops of water penetrated the seal during the cleaning process, the bearings needed to be replaced. This did not make financial sense over the long-term. By contrast, we have been very satisfied with today's solution from the get-go. The plastic machinery elements are characterized by low water absorption, and are chemically resistant. “

In-house tooling for polymer plain bearings

The wide-ranging experiences the specialist has gained during the construction of customer-specific models was reflected in the development of the 'OptiCUT SI-1000' sausage link cutting machine. A quickly assembled stainless steel drylin® W single rail guide made from iglide® J is used in the area of the spreader mechanism. In addition to the extremely durable linear guides with JUM liners, the knife edge deflectors also make use of plain bearings made from iglide® P210 materials. They are used as anti-twist protection, therefore assuring high availability. Due to their thermal stability and low moisture absorption, iglide® P bearings are among the most dimensionally stable bearings at varying ambient temperatures. Recommended for rotary movements with medium to high loads. "After many years of testing a wide range of plastics in our machinery especially in this application, we have now found the correct solution", Dieter Koller recalls.

"While our machinery is predominantly proving itself in the meat processing industry, our material handling plants can for instance also be found in industrial bakeries. The cleaning procedures vary depending on the deployment location, as do the environmental conditions. The temperatures in the immediate oven environment can be exceedingly high. Moreover, the conveyor belt rollers travel at speeds of up to 80 m/min. It took a considerable amount of time to find a material for all requirements. " By now, the plain bearing material P210 is in use so frequently that it makes financial sense to invest into our own tooling. In an effort to further improve the service life and operating performance at the customer, the standard wall thicknesses were increased from 1 to 3 mm. "As a result, we can permanently guarantee extended operating performance. “

Linear guide in the area of the spreader mechanism.

The hex guide was developed as a custom component, especially for the sausage link cutting machine.

Self-lubricating polymer plain bearings ensure malfunction-free operation. They are compatible with stainless steel as the friction partner.

energy chains from igus® are also in use.

Control panel cover with polymer plain bearing. In part, these prevent squeaking noises.

Front: Simone Singer, Dieter Koller (both: Singer & Sohn GmbH), rear: Bernhard Hofstetter (igus® GmbH).

Automatic stainless steel sausage link cutting machine.