Mass flow control is essential for processing metals. Controlling and improving mass flow means that the width of the roll gap is controlled so that the material thickness of the end product remains as constant as possible. If the thickness before the roll stand and the velocity before and after the roll stand are known, the roll gap, which determines the thickness of the rolled product, can be adjusted in accordance with the desired conditions.
The strip thickness is measured using C-frames with an integrated, compact LSV Laser Surface Velocimeter, measuring the velocities upstream and downstream of the roll stand. Because the speed measurement is extremely accurate, you can monitor and control the roll gap more precisely using the LSV and thereby obtain better compliance with the thickness specification of the end product. The result is increased quality and, consequently, increased product output.
Laser speed sensors from Polytec measure on almost any surface, even on contaminated surfaces. The non-contact measuring technique eliminates slippage, wear and provide laser precise, reliable production control without influencing the product surface.
The skin-pass degree in cold strip skin-pass rolling is determined by the difference in strip velocity at the input and output of the roll stand, which in the past has been measured mechanically using tachometer generators. Using two Polytec LSVs prevents the occurrence of measuring errors owing to slippage and wear and the skin-pass degree measured may be used as a control parameter for adjusting the rolls. Using an LSV a major German stainless steel manufacturer confirmed an uncertainty of just ± 0.02 % of his skin-pass degree measurement.
C-Frame in rolling mill with integrated speed measurement
The metal processing industry has high standards when it comes to the dimensional accuracy and quality of steel and aluminum products. Modern rolling mills are now frequently controlled using the mass flow principle to further reduce the thickness tolerances of rolled strips. Laser surface velocimeters (LSVs) are easy to integrate and enable reliable measurement of the velocity component.
Speed synchronization in aluminum production
In the largest aluminum smelting and rolling plant in the world, the length and velocity of aluminum sheets in the manufacturing process are measured simultaneously using non-contact laser Doppler measurement technology from Polytec. Several of such optical speed encoders are integrated in the manufacturing process and provide readings for plant control.