February 2009 - Sometimes, a single addition to a product line can have significantly positive implications for a company's customers. Siemens VAI Metals Technologies, a part of Siemens AG, Munich, Germany, noticed its line of products for aluminum cold rolling mills had room for something different, took action and recently introduced a six-high roll stand called the Siroll Alusix for a wider control range, flexible rolling scheduling and increased productivity.

"Siemens identified a gap in its product portfolio," says Peter Spencer, cold and foil mills manager, aluminum, for Siemens VAI UK. "This [six-high roll stand] technology, in particular, has become popular in China. The Alusix mill design is an extension to Siemens' existing four-high aluminum rolling mills and has been developed specifically for the high demands of processing wide and thin aluminum strip at high process speeds with a high production capability."

The Siroll Alusix is armed with long-stroke cylinders for setting intermediate rolls, which allows those rolls to easily adapt to the width of material needing to be rolled. Both the work rolls and intermediate rolls have positive and negative roll bending, creating smooth transitions between the types of bending by eliminating the need for compensation because of sudden changes.

"Most aluminum producers require a high level of control flexibility to change and dynamically adjust the roll gap profile to process numerous strip widths, gauges and alloys," says Spencer. "The Alusix mill, with its unique design features, addresses all of these aluminum-specific process requirements."

Producing results
As in any manufacturing environment in the metals industry, the amount of time steel or aluminum is in some form of processing and the amount of time that machines are active are keys to success. Idle machines, or great pauses in a processing step, must be minimized. Because of this, the Siroll Alusix is designed to increase "metal contact time," says Spencer.

"This is the time material is actually processed in the mill bite and is fundamental in maximizing mill efficiency and product throughput," he says. "Any downtime for mill setup, product change or roll change has to be considered and, where possible, minimized. Built into the design of the Siemens Alusix mill is a fast setup procedure for a given product and is simple, as all rolls of the mill stand assembly are ground parallel. Alternative designs have complex profile-shaped rollers, and thus setup knowledge and time is increased, which reduces metal contact time."

Automatic strip threading and high-speed functionality also help the Siroll Alusix increase metal contact time. Beyond this, Siemens examined what the implementation of a six-high roll stand could do for aluminum cold roll mill operators in terms of simplifying roll process scheduling and enhancing process possibilities. With the Siroll Alusix, the result is the ability to adapt to changes in material width or types of products being made without having to retool the stand.

"With all of the fully dynamic roll bend actuators from the work and intermediate rolls, the fully active intermediate roll shifting possibilities provides the operator with the maximum flexibility to adjust the roll gap profile," says Spencer. "The net aim is a mill that produces 'best quality' in the rolled product that exceeds current market requirements."

The Siroll Alusix is still new to the Siemens product portfolio, but the company hopes its presence in aluminum cold rolling mills will be felt for a long time. MM