SIKORA develops key technology for quality assurance during the extrusion of big tubes

Stagnation is a foreign word to the 200 SIKORA employees worldwide. Regarding this background, a new product of groundbreaking innovation was created, the CENTERWAVE 6000. The core: Several transceivers, arranged around the circumference of a tube, sending and receiving continuous frequency modulated millimeter waves for a non-contact and µm-precise online measurement of diameter, ovality and wall thickness for larger plastic tubes during the extrusion.

During the last years, enormous successes regarding measuring accuracy were achieved by researching metrological applications with frequencies in the millimeter waves range. Nevertheless, the results could not yet be used for the coating thickness measurement of cylindrical products. With the novel, innovative measuring system, the CENTERWAVE 6000, SIKORA creates completely new preconditions for the reliable measurement of the nominal size as well as the outer diameter, ovality and wall thickness of all kinds of extruded DIN-tubes.

Advantages of the new millimeter waves technology

Even without any knowledge of the properties of the extruded materials and its temperatures, the CENTERWAVE 6000 measures the outer and inner contour as well as the wall thicknesses simultaneously at several places of the circumference, providing a precision to a previously unknown degree. Layer thicknesses of multi-layer tubes can also be measured precisely.

Several sensors, so-called transceivers, arranged around the circumference of a tube, continuously send and receive frequency modulated millimeter waves. Boundary layers, as for example each front and back site of a plastic, reflect these waves, which are detected and demodulated by the receive unit of the regarding transceiver. These receive signals contain information regarding the distance between boundary layers of different materials. After an algorithmic processing of the receive signals of each sensor, the requested measuring values are ready for visualization within only a few milliseconds. The values can as well be used for the control of the different dimensions of a tube in the extrusion line.

Replacement of conventional technologies

For the development of the technology on the basis of a CW-millimeter wave chip, the goal of creating a non-contact measuring device at the extrusion of tubes that is maintenance-free and durable, was decisive. By independently identifying the characteristic values of the material, the CENTERWAVE 6000 generates the measuring values with highest precision, without the need for specifications regarding the material parameters.

The CENTERWAVE 6000 is going to provide highly precise measuring values at different positions of the production line (even in the hot area) as there are no coupling mediums needed, temperatures are not decisive and no calibrations are necessary

Product spectrum

Two stand-alone gauge heads for different tube diameters from 120 to 400 mm and a version with a rotating measuring gauge head for diameter ranges from 250 to 1.000 mm were created. The industrial PC ECOCONTROL 6000 offers, besides a numeric presentation of the measuring values, also a graphic visualization as well as extensive trend and statistic data features. The calculation of virtual measuring values at the position of the extruder allows the line manager to react quickly to changes. Even with larger delay times between the position of extrusion and the measurement an effective and fast control of the wall thickness and especially the elimination of excessive consumed material is guaranteed.