Extrusion Asia Edition 3-2016

应用于管材挤出的外径、壁厚、偏心、熔垂 在线测量技术 Technologies for the Measurement of the Diameter, Wall Thickness, Eccentricity and Sagging during the Hose and Tube Extrusion 过去几年里，管材生产企业对测控技术和生产线控 制技术积极投入,以达到在线产品质量控制、稳定生 产工艺、降低生产成本的目的。如今，在线测量控 制仪器已经成为挤出生产线上的一个标准配置，这 些检测设备应用于挤出生产中产品内/外径、椭圆 度、偏心以及熔垂度测量（“熔垂”是指熔体在凝固过 程中温度过高而导致的材料下垂）。所使用的测量 系统基于不同应用领域也采用不同的技术。以下文 章是对传统与创新的测量技术进行概述，从而进一 步讨论它们在挤出生产线上应用的优势及局限性。 应用于管材外径测量的技术 对于管材产品外径的测量，主要有两种技术：“扫描式测量系 统”与“CCD 线阵传感器测量系统”。 32 测量 Extrusion Asia Edition 3/2016 图 1：采用旋转棱镜的扫描式测量 Image 1: Scanning method with rotating mirror (Images: Sikora) 图 2：采用CCD线阵传感技术的扫描式测量 Image 2: Scanning method without rotating mirror, with CCD-line sensor Manufacturer of hoses and tubes have been investing intensively in measuring and control technology as well as line control over the last years, aiming for an online quality control, process stability and cost reduc- tion. Nowadays, online measuring devices with a con- nected control are a standard for extrusion lines. Used test devices include, amongst others, gauge heads that measure the inner and outer diameter, the ovali- ty, eccentricity as well as ideally the sagging (“sagging” of the melt during the solidification at a too high viscosity) of the product during the extrusion process. The used measuring systems are based on varied technologies for different application areas. The following article provides an overview of conven- tional as well as innovative measuring technologies and discusses the advantages and limits of their usage in extrusion lines. Technologies for diameter measurement of hoses and tubes For the measurement of the product diameter of hoses and tu- bes, two established techniques are used: the “Scanning Sys- tem” as well as the “CCD line sensor technology”. „Scanning System“ The scanning method is based on a rotating mirror or a rotating disk, whereby a laser beam scans across the measuring field. In- between the rotating mirror and the light sensor, two lenses are arranged. The first lens diverts the laser beam almost parallel across the measuring field while the second lens directs the light beam onto a light sensitive detector. The product is arranged between these two lenses and disrupts the laser beam, while it is scanned across the measuring field. Therefore, the product dia- meter is calculated by comparing the time the laser beam needs to pass the whole measuring field with the time the laser needs to scan the complete product surface. In this case, time equals the diameter ( ). The measuring rate depends on the rota- tion speed of the mirror. An increase of the measuring rate is made possible by the use of a polygon mirror. This highlights the problem that the mirror surfaces need the exact same perfect surface finish. Often, an averaging from several measurements is necessary to achieve a reasonable accuracy. „CCD line sensor systems“ There are two measuring methods for the CCD line sensor technology prevalent. The first method is based on a laser be-