Strip Guidance on the uncoiler
If a strip centre or strip edge guiding system is provided on the uncoiler, the coiler moves the coil, from which the strip is being uncoiled, transversally to the system axis and thus acts against central and/or lateral deviation of the strip. The deviation of the strip position from the set position is determined by the measuring system and transferred to the electronic control amplifier. The output of the amplifier continuously activates a servo valve, which moves the hydraulic cylinder of the uncoiler accordingly so that the uncoiled strip is returned to the position preselected on the measuring system. For control reasons, the measuring system must be mounted as close to the coil as possible. The HF alternating light measuring system, which is protected against ambient light, permits a distance between the receiver and the light source here of up to 4 m.
For systems with an edge trimming shear installed immediately downstream of the deflector roll, we recommend coupling the uncoiler and the deflector roll mechanically or electro-hydraulically. When using an accurate measuring system – such as the SMI-HE inductive strip centre measuring system – this model is able to ensure a very high guidance accuracy immediately upstream of the shears.
In systems with a greater distance to the trimming or slitting shear, an additional steering roll is installed upstream of the shears and connected to the control system on the coiler (HQT).
Strip Guidance on the Uncoiler with Remote Measuring Equipment
In the case of fully automatic systems, the measuring equipment must often be installed downstream of the stationary deflector roll because of the presence of various auxiliary devices installed in the uncoiling area. As a result, a delay occurs between the adjustment of the uncoiler and detection of the effect by the measuring equipment, which leads to instability of the control circuit, especially in the case of low strip speeds.
Using EMG's patented "phase-lag compensation" circuit, which takes account of the strip speed and the adjustment of the uncoiler as a position control loop, however, ensures stable control. A certain inertia in the control circuit cannot be avoided though, as it is not possible to fully correct dynamic faults of short duration.
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