EuroWire September 2017

Technical article

tension. Behind the levelling machine the four tension rollers, together with the recoiler, pull on the strip. By means of force superposition (tension and bending) between the groups of upper and lower levelling rollers, the internal tensions and shape deviations of the strips are reduced. To achieve a sufficient levelling effect in the case of very thin strips with material thicknesses of between 30 and 200µm, the metal strip specialist has developed a cassette with a levelling roller diameter of 8mm. For thicknesses greater than 200µm, 12mm levelling rollers are used. Deviations are automatically detected by a Vollmer shapemeter roll for continuous strip shape measurement. Strip zones with waves exert less force on the segmented roller than flat strip zones. Software calculates the mathematical formula for the strip shape with the help of the measured values and uses this to create a 3D model. Based on this, the necessary position of the levelling roller supports can be calculated and automatically adjusted. Manual readjustment is unnecessary. A special feature is the four adjusting axles at the upper levelling cassette, which ensure the ultra-precise position of the three spatial axes. “Depending on the initial flatness, evennesses down to one I-unit can be achieved. This corresponds to a 0.2mm high and 100mm long wave in the strip”, added Mr Lüdecke.

▲ ▲ A feed-in system without a manual feeder, developed by B+S, contributes to ease of operation and the economic efficiency of the line. The beginning of the strip is clamped in a clamping bar at the beginning of the line and pulled through to the outfeed. This means that no pilot strip is required, and welding or the need for guide plates is eliminated. Winding on the recoiler also takes place automatically

Highly dynamic drive for broad control spectrum In principle, all copper alloys are processed on the line without restrictions, with the strips having a wide range of cross-sections and the tensile strength of the material varying between 300 and 1,100N/mm². The thickness lies between 30 and 500µm and the width is between

100 and 450mm, which results in an aspect ratio of 1:75. If the yield strength of 200 to 1,050N/mm² is added, the ratio to be controlled for is 1:390. Due to this wide spectrum, the strip tension is measured directly at the decoiler and recoiler, as well as in front of the levelling machine, and serves as a control value for the drives. These are equipped with highly dynamic AC motors. The installed capacity here amounts to around 550kW. “Feed-in is performed with Sinamics S120 Basic Line assemblies, so that the regenerative energy can be reused via an energetic recovery system on the pull side – that is, for the motors after the levelling machine. This leads to significant energy savings,” added Mr Lüdecke, pointing out one of the main advantages of the line. Activation is performed by fully digitalised inverters, which are coupled to the PLC of the line controller via Profibus L2-DP. The actual control functions are controlled via a microprocessor that enables not only considerable ease of operation but also easy start-up and maintenance. Especially user-friendly and safe operating concept The complete line bears the CE sign and is designed in accordance with the European Machinery Directive 2006/42/EC, which provides for, among other things, a protective fence for employee safety.

▼ ▼ To still achieve a sufficient levelling effect despite strips having very small material thicknesses between 30 and 200 µm, the metal strip specialist has developed a cassette for levelling rollers with a diameter of 8mm. For thicknesses greater than 200µm, 12mm levelling rollers are used

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September 2017