Metal Casting Technologies : MCT-2NDQRT-2017
22 www.metals.rala.com.au METAL Casting Technologies 2nd Quarter 2017 23 Overview he ability to automatically scan the entire surface of forgings and castings for tiny cracks, pores or other glitches in forgings or castings, is of great benefit to the foundry industry. Fluorescent penetrant testing is well-established inspection technique in the foundry industry and is widely used for examining both ferrous and nonferrous materials but usually requires darkened rooms, or the use of tents and awnings as the effectiveness of of this technique requires that the ambient lighting conditions are very low. This limits certain NDT inspection operations and makes others impossible altogether. Furthermore, for inline inspection in a continuous production environment, the extra time and resources necessary for operating under low light conditions can cause serious production bottlenecks and is expensive in terms of the manpower. “Mixed Light” inspection is the term given to a new industrial technique which enables the detection of the very small levels of light emitted from fluorescent penetrant dyes against a background of strong daylight or other brightly-lit environments. A UK company, Inspection Technologies Ltd, has developed a Mixed Light system that eliminates these production bottlenecks and significantly increases throughput rates at inline inspection points. Furthermore, the system comes with software that completely automates the inspection process, hence removing the need for expensive highly-qualified inspectors. After the automated inspection process is complete, visual photographic records of all inspections, either pass or fail, are permanently stored for compliance and 100% Quality Audit purposes. The System The ML-2000TM Mixed Light system (Patent Application #GB1610988.6) is shown in Fig. 1 below and comprises of a specialised camera, patented driver electronics and a self-contained UV light source. Not only suitable for inline inspection of forgings (or castings) on a conveyor belt for example, the ML-2000TM also makes it possible to inspect forgings, castings, tools and patterns which are too big or too heavy to be moved into a darkened inspection room in the foundry or in the workshop. Moreover, for both By Dr Geoff Diamond A new and improved way for inline inspection of castings and forgings Mixed light inspection Mixed light inspection FEATURE FEATURE inline inspection of parts on a conveyor belt, and inspection of fixed plant in-situ, the system’s software can be adapted to automatically detect and report any class of surface or process defect, that fall both inside and outside of the range of user- defined acceptance criteria. The system also employs digital signal processing (DSP)-assisted noise reduction, filtering and contrast enhancement methods to provide a more contrast and a sharper, more clear image in which any detected fluorescence can be more easily seen. The final image, which eliminates all background light and shows only the part, is shown in real-time, thus allowing the user to visually identify an area in which only the fluorescent material is present as a continuous streaming video-feed. Such an arrangement is advantageous in an NDT setting where the fluorescence corresponding to a crack or other defect can de detected as part of a dynamic or moving inspection process such as in-line inspection of objects on a moving conveyor belt in a production setting. The system’s detection software also makes it possible to represent surface defects, deviations and imperfections with overlain colour graphics on top of regular-looking photographic images of the inspected part. Optionally, if desired, the software can provide streaming real-time visual overlays of these regions of fluorescence and identified defects, on top of ordinary visual images of the object under inspection. Moreover, all captured images, regardless of whether they contain detected defects or other regions of interest, are permanently stored. This has several advantages in terms of compliance and insurance issues in that it effectively provides a truly 100% Quality Audit. Apart from the cost savings reducing production bottlenecks by speeding up inspection and increasing overall production throughput, other advantages are: z No limitations on metal composition or heat-treated condition. z No limitations that are imposed on the size or shape of forgings which can be inspected. z Liquid penetrant inspection can now be performed at any stage of manufacture, irrespective of background light conditions. The ML-2000TM system also overcomes the ever-increasing problem of the industry wide shortage of qualified inspectors emerging from the training system. As the ML-2000TM is an expert system in its own right, this means that technician grade staff could be used in lieu of more fully trained inspector, and/ or or that the productivity of a qualified inspector could be increased dramatically if they were able to inspect remotely via telemetry by supervising or reviewing the work of technicians on the ground in multiple geographically separated sites. System Performance If an inspected part falls within the acceptable limits as defined by the user, the part is accepted, and proceeds to packing and shipping. However, if the inspected part is defective in any way, the part is either rejected and/or appropriate alerts are delivered to operators and management. The entire test cycle takes just seconds. Dependant on size of part and, if necessary, the availability of appropriate mechanical handling equipment such as robot arms etc., the throughput is typically hundreds of parts per hour dependent upon complexity of shape and size and and the relative defect size. FIGURE 1. Scanner head of inline inspection system T FIGURE 2. (Left) Standard MPI test piece. (Right) Simultaneous view of same scene with the Mixed Light apparatus.