Abstract

The need to increase quality of products, forces manufacturers to increase the level of control on finished and semi-finished parts, both qualitatively and quantitatively. The adoption of optical systems based on digital image processing is an effective instrument, not only for increasing repeatability and reliability of controls, but also for obtaining a large number of information that help the easily management of production processes. Furthermore, the use of this technology may reduce considerably the total amount of time needed for quality control, increasing at the same time the number of inspected components; when image acquisition and post-processing are feasible in real time, the whole production can be controlled. In this chapter we describe some quality control experiences carried out by means of a cheap but versatile optical system, designed and realized for non contact inspection of injection moulded parts. First, system architecture (both hardware and software) will be showed, describing components characteristics and software procedures that will be used in all the following applications, such as calibration, image alignment and parameter setting. Then, some case studies of dimensional control will be presented. The aim of this application is to identify and measure the main dimensional features of the components, such as overall size, edges length, hole diameters, and so on. Of particular interests, is the use of digital images for evaluation of complex shapes and dimension, where the distances to be measured are function of a combination of several geometric entities, making the use of standard instrument (as callipers) not possible. At the same time, methods used for image processing will be presented. Moreover, a description of system performances, related to quality product requirements will be presented. Second application examines the possibility to identify and quantify the entity of burrs. The case of a cylindrical batcher for soap, in witch its effective cross-sectional area have to be measured will be showed, together with a case study in witch burrs presence could bring to incorrect assembly or functionality of the component. Threshold and image subtraction techniques, used in this application will be illustrated together with the big number of information useful to manage production process. Third, it will be presented a possible solution to the problem of identifying general shape defects caused by lacks of filling or anomalous shrinkage. Two different approaches will be

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