Know-how for you as the user
EMG strip guiding systems: Strip guiding on the uncoiler
In this and in the following articles of this series, we summarize know-how on the use of EMG strip guiding systems and try to give you the necessary basics for the planning of the applicable components and for the design of the systems.
Strip guiding on the uncoiler - area of application
A strip guiding control on the uncoiler is used to feed the decoiled strip into from into a production line or machine with edge or centre guiding. It is necessary when individual windings protrude from the delivered material coils, when the winding condition is generally unsatisfactory and to compensate the strip camber. A further reason for an automatic strip position guiding is given when the coils are not exactly centered on the coiler mandrel.
Normally a continuous electro-hydraulic control circuit is used for strip guiding control. Alternativcely an ESZ electric servo cylinder can also be used for low masses to be moved. The deviation of the strip position from the nominal position is determined by an optical HF alternating light measuring device - either so called EVK(sensor positioner edge)) or EVM (sensor positioner centre). Due to the large distance to the strip, inductive or capacitive solutions are ruled out in an arrangement as shown in the large picture above. The electronic strip guiding controller EMG iCON® reads in the edge values of the strip position measurement. The power amplifier of the strip guiding controller then continuously steers the servo valve in the hydraulic control circuit so that the unwound strip is held in the preselected position. Depending on the line process, the unwinding can be carried out either as strip center or strip edge control.
Important to know!
For control reasons, the measuring device must be mounted as close as possible to the coil. The HF alternating light measuring system, which is immune to extraneous light, allows a distance of up to 4 m between the receiver and the light source.
In systems with trimming shears directly behind the deflectior roll, we recommend a mechanical or electro-hydraulic coupling of the uncoiler and the deflectior roll in order to achieve the highest possible accuracy.
In continuously operating production lines, the installation of the measuring device is often only possible behind the stationary deflector roll, i.e. far away from the actual "control location" (see picture above left). However, the use of EMG's patented "dead time compensation" circuit with metrological consideration of the strip speed ensures stable control. Only in these cases also an inductive strip position measurement from the SMI sensor family can be used.
In summary - Which EMG components do I need?
The essential components are:
- EVK - sensor positioner edge or
- EVM - sensor positioner centre or
- SMI - inductive strip measuring sensor (only for installations behind the deflector roll and centre control),
- EMG iCON® as intelligent digital control system,
- EMG servo valves (single-stage or two-stage) as part of a hydraulic system, or
- Electric servo cylinder ESZ and
of course, know-how in design, construction and installation. You will find all this at EMG!
What happens next?
Our sales and service staff, our international sales organization or our product manager Mr. Martin Wied (email@example.com) can offer you concrete advice on the design of your control system at any time.