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Extruders lead to success in niche markets

26.07.2006 The Rubin Mill in Lahr in the southwestern part of Germany has successfully established itself as a maker of niche products. Last year, it expanded its range of production equipment by adding another extrusion line for making direct-expanded breakfast cereals and cornflakes. The Rubin Mill is a mid-size company with a history of over 320 years. After existing for more than 200 years as a “very small flour mill,” it added an oat mill in 1948 and a feed manufacturing facility to its operations in 1968. At the end of the seventies, the company built a new mill with a grinding capacity of 75 t/24h.

New business fields
At the end of the eighties, the market situation forced the Rubin company management to create “added value.” The oat mill benefited from the emerging “muesli” wave, which prompted the company to construct a new oat mill together with Buhler. Since then, its capacity has doubled.

In the petfood sector, the Rubin Mill set its focus on the extrusion process. In 1988, the first installation equipped with a Buhler DNDG 62mm twin-screw extruder went into service for the production of petfood and fish feed. The company was able to utilize the existing distribution channels so that the plant capacity soon had to be increased. For this purpose, a 125mm machine of type DNDH was purchased.

Two additional extruders
Since muesli sales were rising steadily, Rubin decided to produce its own additional ingredients. This required the purchase of yet another extruder. The new line comprised a second Buhler DNDG 62mm twin-screw extruder with a drying system at the end. It was designed to allow direct-expanded products to be made for processing into muesli mixes and cereal bars.

Word of Rubin Mill’s competence in food extrusion spread rapidly. Demand for additional food ingredients rose. The company management decided to continue growth in the same direction and to invest in yet another extrusion line. This system was focused on the production of ingredients for the bakery product and convenience food industries, including modified flour, starch, and breading. The heart of this line is a Buhler DNDF 93mm twin-screw extruder.

Specializing in extruded products
Today, the Rubin Mill has evolved into a leading maker of extruded products. The customer structure of the Rubin Mill is very broad. It includes makers of breakfast cereals, cereal bars, muesli, cookies, chocolate, and bakery prod ucts as well as dairy products. The Rubin Mill specializes in niche prod-ucts. “Class, not mass” is the motto. The company focuses on relatively small lot sizes of a large range of products. Last year, it offered over 80 different products made using the twin-screw extrusion proc-ess.

As a consequence of this development, the company management decided in 2005 to put another extrusion line into service. Sticking to the principle that it is “better to operate several small machines to make different products than one large high-capacity unit,” the machine selected was again a Buhler BCTG 62mm twin-screw extruder.

Less space
The requirements that the Buhler plant engineers had to meet were high. The line was to be installed in a new annex adjoining an existing hall and measuring 40 by 10 meters. Account had to be taken of the fact that the 400 square meters would also have to accommodate a raw materials storage section, a control room, and expansion areas for receiving two additional extrusion lines beside the current system. Moreover, the layout of the system had to meet the customer’s special needs. It was designed to allow reconfiguration within a very short time to enable a wide variety of products to be made.

Heart of the system
The heart of the system is the Buhler BCTG twin-screw extruder with a screw diameter of 62 millime-ters. This machine offers high torques as well as high screw speeds and pressures to cover the wide range of applications. An OTW fluid-bed dryer dries the extruded products or predries the pellets for making flakes. A modular DNTW fluid-bed dryer and toaster expands and toasts the flakes.

Another task was to ad-just the control system. Normally, the overall plant is controlled from the control room and the extru-sion process through a touchscreen attached to the machine. In response to the customer’s request, the plant control system was also integrated in the touch-screen operator terminal attached to the extruder. Thanks to the high level of modularity of the system, the plant configuration can be tailored to specific applications within a veryshort time and at low cost.

Three-shift operation
The investment sum of about 2.5 million euros for the building and the processing equipment have already paid off according to the management of the Rubin Mill. Since its start-up in the summer of 2005, over 20 new products have already been rolled out. Just like the other extrusion lines, the new system is running in three work shifts. Together with Buhler, Rubin now hopes that the two still vacant spaces in the new hall will soon be occupied.

The heart of the new plant: a BCTG 62mm twin-screw extruder The heart of the new plant: a BCTG 62mm twin-screw extruder