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Extrusion International 5/2016


Millimeter wave technology

At the K-show 2016 in Düsseldorf SIKORA presents for the first time the CENTERWAVE 6000,

an innovative system based on millimeter wave technology for measuring the diameter, ovality, wall

thickness and sagging of large plastic tubes from 120mm.

The new system CENTERWAVE 6000 for measuring

the diameter, ovality, wall thicknesses and sagging based on

millimeter wave technology

SIKORA, in cooperation with the Fraunhofer Research

Institute for High-frequency Physics and Radar Technology

(FHR) and the South German Institute for Plastics (SKZ), has

developed a new technology based on millimeter wave tech-

nique. This technology measures online, on a non-contact

basis and precisely the inner and outer diameter of large pla-

stic tubes with a diameter from 120 mm and determines ova-

lity, wall thicknesses and the sagging (“sagging” of the melt

during solidification at a too high viscosity). Also the wall

thicknesses of multi-layer tubes are precisely determined by

the system, independently of material type and temperature

of the measuring object. The measuring system adapts itself

to the characteristics of the extruded plastics and does not re-

quire any calibration by the operator. This increases product

quality and ensures significant material and cost savings du-

ring extrusion.


Several static or one or two continuously rotating transcei-

ver, arranged around the circumference of a tube, continu-

ously send and receive frequency modulated millimeter

waves. A static system measures selectively the wall thickness

and the outer/inner diameter of the tube. If there is a com-

plete recording of the wall thickness around the entire cir-

cumference of the tube required, a rotating gauge head is

used. This design concept also allows to precisely measure

and represent the sagging. The measurement is based on the

runtime difference of the reflected signals that are reflected

by the boundary layers, as for example each front and back

side of a plastic. The signals that are detected and demodu-

lated by the receiver of each transceiver contain information

regarding the distance between boundary layers of different

materials. Measurements are taken from a wall thickness of

4 mm with an accuracy of a few micrometers and with a

measuring rate of 250 single measuring values per second.

After an algorithmic processing of the received signals of

each sensor, the requested measuring results are ready for vi-

sualization and control of the diverse tube dimensions in real

time. A connected processor system provides in addition to a

numerical display and graphical presentation of the measu-