Hilchenbach, October 01, 2018

ALUMINIUM 2018: Anti Chatter Device reduces vibrations in cold rolling mills

The Anti Chatter Device (ACD) for cold rolling mills reduces vibrations occurring in rolling mills, especially in tandem mills. Such vibrations may lead to defects of the rolled stock and damage to the rolling equipment. By reducing the Chatter effect, it is possible to increase the rolling speed and the yield while improving the product quality. This pioneering technology is already in use in a first pilot operation and will be presented live at ALUMINIUM 2018 in Düsseldorf.

In the run-up to the trade fair, we visited Ralf Ohrndorf, Sebastian Richard and Dr. Matthias Krüger in their Hilchenbach offices and talked about the product and the trade fair appearance.

Please briefly explain your tasks at SMS group.

Ralf Ohrndorf:

My job as Head of Technical Sales Aluminum includes global key account management for aluminum as well as business development and implementation of the SMS group rolling mill portfolio in the aluminum industry.

Dr. Matthias Krüger:

As Head of the Mechatronic Systems department in R&D, I am responsible for all tasks related to mechatronics. In addition to vibration issues, this for example includes development, implementation and commissioning of technological control systems or new hydraulic/mechanical/electrical plant components in cold and hot rolling mills, both for development projects and customer projects.

Sebastian Richard:

In my job as a development engineer in the Mechatronic Systems department in Hilchenbach, I am responsible for vibration issues in cold rolling mills and the respective equipment for vibration damping. I also focus on the automated evaluation of big process data amounts from plants with regard to various quality criteria. Beyond that, I work on dynamic simulations and technical calculations in the environment of cold and hot rolling mills for flat products.

Which products will your trade fair appearance focus on?

Rald Ohrndorf:

At the ALUMINIUM 2018 trade fair, we will exhibit the entire SMS group product portfolio. This includes, among other things, casting equipment, heat treatment equipment, ingot saws, ingot scalpers, plate stretchers, strip processing lines, extrusion presses, logistics solutions, packaging lines, etc. With regard to flat rolling mills, we will not only present new plants for the hot and cold rolling of aluminum, but also modernization concepts for existing plants aiming to increase productivity, improve the quality of the rolled products and adapt the plants to new market demands. With regard to plant modernizations, we supply comprehensive, customer-oriented solutions generating a competitive advantage depending on the product and market focus of the respective customer.

At the SMS group booth, you will be welcoming visitors at the “Anti Chatter Device”. What can the customers expect there?

Sebastian Richard:

In one of our “Technology Corners”, together with our partner ERAS, we will be exhibiting a vibration simulator simulating the behavior of a mill stand. In this device – almost like in a real mill stand – two rolls are installed. Resulting from its rotation, the top roll generates vibrations, while the bottom roll is installed rigidly. By means of actuators acting on the top roll and installed both on the drive side and on the operator side, a counter-vibration can be generated which compensates chattering.

In cold rolling mills, vibrations of mechanical parts and/or the strip can affect several quality parameters such as thickness, shape, surface quality, etc. Since vibrations mainly occur at higher speeds, in most cases the rolling speed of single- or multi-stand mills for steel and aluminum has to be limited. The most critical vibration issues when running cold rolling mills are the 3rd Octave Chatter (100 Hz – 160 Hz) and the 5th Octave Chatter (> 440 Hz).

The 3rd Octave Chatter can be characterised by the following attributes: A process instability in the last or second last mill stand caused by a self-excited vibration mode, vertical vibrations of the roll stack as well as vibrations of the entry tension leading to an exit thickness oscillation right up to a strip break.

That is why SMS group developed the Anti Chatter Device (ACD) together with a partner.

The main function of the ACD is the active damping of the 3rd Octave Chatter vibration. Taking into account the transfer behavior of the piezo actuators installed, the system generates a counteracting vibration with the same frequency, an appropriate amplitude and an opposite phase relationship (180 degrees) to the undesired vibration, causing the latter to be eliminated. In this way, the active damping mechanism effectively results in an increased damping in the mill stand.

In order to identify and monitor the 3rd Octave Chatter and other vibrations in the mill stand, the use of the Genius CM Chatter plus vibration monitoring system, in addition to the installation of the ACD, is beneficial. When coupled with the Level 1 plant automation, the system is able to decelerate the mill, triggered by the early detection of chatter, within 100 ms and thereby effectively prevents chatter-related strip breaks.

What do you think is the best part of your product and what are its benefits for the customer?

Dr. Matthias Krüger:

A first pilot unit of this new, active damping technology was put into operation in 2017 on a working 4-stand aluminum tandem cold rolling mill from SMS group. Operating results from July 2017 show that the vibration amplitudes, measured in the chatter frequency range, are reduced significantly with an active Anti Chatter Control. The installation of the system in the pilot unit has therefore demonstrated the operative readyness of the piezo actuators and the Anti Chatter Control. After a few adjustments, the system enables clearly higher rolling speeds, which were previously limited by the 3rd Octave Chatter. This led to a considerable improvement in productivity of the mill.