machinery feature | Control


PPI has now reduced scrap by 98% and start-up time by 89%. At the same time, internal defect rate has been cut to 1.3%, while the company now has an external ppm of zero. At K2016 last year, the


company exhibited its latest integrated gauging system


for in-process measurement and off-line part inspection of


plastic pipes and tubes. Its Beta LaserMike system integrates laser


diameter, ultrasonic wall thickness, fault detection, and laser length and


Sikora’s Centerwave 6000 measures pipe dimen- sions using millimetre wave technology


speed measurement technologies to automatically monitor and control pipe and tube dimensions during production. This enables manufacturers to raise product quality, increase productivity and make production savings. The new AccuScan 6000 series of four-axis gauges includes the AccuScan 6012 for measuring products up to 12mm, and AccuScan 6050 for measuring products up to 50mm. Both provide high ovality accuracy (up to 100%) and flaw detection accuracy – with a 25% improvement over three-axis measurement methods. This is done through ultra-fast diameter and ovality measurements at 9,600 scans per second, coupled with single-scan repeatability down to 1 micron (for the AccuScan 6012) and 2 microns for the AccuScan 6050.


Millimetre precision At the same time, Sikora showed a new technique for measuring pipe dimensions, based on millimetre wave technology. The concept, developed in cooperation with the


NDC’s AccuS- can 6012


four-axis gauge can measure


products up to 12mm


Fraunhofer Research Institute for High-frequency Physics and Radar Technology (FHR) and the South German Institute for Plastics (SKZ), allows precise, non-contact online measurement of inner and outer diameter, ovality, wall thickness and sagging of large plastic pipes with diameters above 120mm. The Centerwave 6000 measuring system adapts to


the characteristics of the extruded plastic and does not require calibration by the operator. The technol- ogy boosts product quality and ensures significant material and cost saving during extrusion, says Sikora.


A number of techniques exist to check the quality


of extruded plastic pipe, including optical and ultrasonic technologies, but these have limitations, says the company. Another technique is to generate terahertz impulses at the pipe: reflected echoes at the inner and


16 PIPE & PROFILE EXTRUSION | April 2017 www.pipeandprofile.com


outer boundary layers then determine the wall thicknesses.


Without any information on the properties of the


extruded materials or its temperatures, the system measures the outer contour and wall thickness simultaneously, at several positions of the circumfer- ence. Layer thicknesses of multi-layer tubes are also measured precisely. However, the technique cannot yet be used for the measuring the thickness of coatings on cylindrical products. Measurement via millimetre wave technology is based on the FMCW runtime method. Several static or rotating transceivers, arranged around the circumfer- ence of a tube, continuously send and receive frequency modulated millimetre waves. From the runtime difference, the product dimensions are defined. Because product temperature has no influence on


the result, the system is installed for hot measurement as well as at the cold end of the line for final quality control. Directly after the first cooling, the Centerwave 6000 provides precise information about inner and outer diameter, ovality, wall thickness and – in particular – sagging. The millimetre wave technology selected for the measurement covers the entire range of plastics, including PE, HDPE, PP, PA6 and PVC. If we assume that a line, where tubes are produced with an outer diameter of 400mm and a wall thickness of 27.5mm, at a line speed of 0.5m/min, the machine operator receives accurate measuring results already after around 10 to 30 minutes. Millimetre wave technology is suitable for the


measurement of any kind of plastic tube with a diameter of 120-2,500mm. It can handle either single- or multi-layer tubes. During production, there is a risk that the melt that leaves the tube tool will flow under gravity, and negatively affect tube wall thickness distribution.


This sagging is picked up by millimetre wave measuring.


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