Measurement of concentricity of wires and cables, hoses, tubes and other round products

Highest quality, process optimization and cost reduction are the crucial factors on which manufacturers of round extruded products, like wires and cables as well as hoses and tubes, are assessed against global competition today and in the future. These requirements demand for innovative measuring technology – from SIKORA.

An important parameter during the production of round extruded products is the compliance with specifications like the concentricity of the conductor in the insulation, or the even wall thickness distribution of multilayer composite hoses and tubes. SIKORA lays the foundation with its diverse systems for precise eccentricity measurement for an optimal production.

When the conductor of a cable does not run exactly concentrically in the guide during production, the material will be applied unevenly over the cross-section of the cable.

If the total wall thickness will be now reduced to the required nominal dimension, the single wall thicknesses at the different measuring points show strong fluctuations. In places, the insulation will be applied to thickly or even too thinly onto the cable – with foreseeable impact concerning the quality and safety of the end product.

Combined eccentricity measurement of a conductor in the insulation via laser and induction

The CENTERVIEW 8000 from SIKORA is based on an optical and inductive measuring procedure. With the inductive measuring circuit which is set between two optical measuring planes, the exact position of the conductor will be determined. With the optical system. the outer position of the cable will be measured. An eccentricity value derives when both positions differ from each other. Simultaneously, the optical system detects precisely the diameter and the ovality, exceptionally, also the “roundness” of the cable.

All necessary calculations and analyses are done in the measuring system. The measuring values are ready to be transmitted via different interfaces to a display and control system or to a plant computer.

Eccentricity measurement via X-ray technology

X-RAY 6120 PRO Exzentrizitätsmessung während der Kabelextrusion

SIKORA’s X-ray measuring systems X-RAY 6000 PRO for the application in extrusion plants for the manufacturing of data, automobile and installation cables as well as hoses and tubes detect reliably the eccentricity of the products.

The technical basis of the X-RAY 6000 PRO is an image processing method. Two X-ray tubes that are at right angle to each other light the product diagonally to its axis. A line sensor each is positioned across the two X-ray tubes. The line sensors are equipped with a scintillator that converts the received X-rays into light from which an image of the product is generated within milliseconds.

During the running production process, accurate measuring values are continuously recorded online. The evaluation is done directly from the X-ray image. The detection of materials with different attenuation ultimately leads, due to a specific analysis and mathematical algorithms, to a visible contrast of each layer and to a micrometer precise measurement of the product dimension.

When using X-ray technology, an adaptation to the materials is not required, nor is any coupling media – as is necessary, for example, for ultrasonic technology. Furthermore, the technology is independent from the temperature of the extruded material.

X-RAY 8000 NXT Exzentrizitätsmessung für Höchstsspannungskabel

During the production of medium, high and extra-high voltage cables in CV-lines, the measurement of the eccentricity is done by the X-ray measuring device X-RAY 8000 ADVANCED/NXT. Two high-speed scanners scan the product contactless with X-rays. The calculation of the measuring values of all cable dimensions as well as the eccentricity is done directly from the X-ray image. At the layer transitions, the radiation absorption changes. The transition points between the individual insulation layers are clearly visible and the eccentricity is determined precisely.

Benefits of the non-contact inline eccentricity measurement with SIKORA

A continuous control of the product data and single values generally helps to avoid any excess of the wall thickness. However, only when a concentric layer distribution can be ensured, the wall thickness can be completely reducedto the smallest permitted value under consideration of the statistical variation. The production requires less material and achieves a more efficient material usage. Each micrometer of production material that can be saved by applying measuring and control technology, makes the production more economical and also preserves short resources.

  • Assurance of a concentric material distribution
  • Reduction of the total wall thickness to nominal value
  • Avoidance of faulty products
  • Maximum savings on material