Octagon: Non-contact thickness profile measurement system

At K 2004, Octagon Process Technology GmbH, Würzburg, has presented its new VenPad capacitive thickness profile measuring system which permits non-contact measurement on the outside of the film bubble. In contrast with other non-contact sensors, the VenPad sensor maintains a constant and extremely small distance between
itself and film bubble, ensuring exact and reproducible measuring
conditions. The sensor measures within the range of 6 to 500 µm with a
resolution of 0.1 µm. VenPad is equally suitable for single-layer blown
films and for co-extruded films with any number of layers; in the latter
case, the system indicates the overall thickness.
Through the special design of the VenPad system, air flows at high speed
tangentially between the film and sensor, creating a Venturi effect (partial
vacuum between the film and the VenPad sensor) which generates an air
cushion of constant thickness. Thus the system operates ‘automatically’
and without any need for adjustment at a constant distance from the surface
of the film – an important prerequisite for comparative measurement.
VenPad is highly suitable for reliable, trouble-free thickness profile measurement,
especially in the case of films with tacky or delicate surfaces.
Used in conjunction with Octagon’s SmartLip thickness profile control,
VenPad permits the efficient cross profile control of the most sensitive of
film products. Moreover, VenPad can be integrated into an existing
extruder control system, for which purpose the sensor is equipped with a
Profibus interface.

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