Investigation of methods for identifying of location of part hidden in powder

The aim of the study is to develop and compare the methods for visualization and localization of sintered parts inside of a powder material with subsequent automation of the process of their extraction in batch production conditions. Seven classes of methods applicable to detecting the position of a part manufactured by selective laser sintering (SLS) completely immersed in powder were considered. The first approach is based on working with streaming X-ray images and three-dimensional tomograms. It provides a high level of image detail. The analysis showed that CT systems are effective for both preliminary detection and subsequent defect detection, but their use is hampered by the high cost of equipment and long scanning time. The second class of methods is thermography in three modes: pulse, lock in and continuous active. These methods demonstrate the efficiency of heat map processing, but require a significant temperature gradient between the part layer and the powder. In turn, ultrasonic visualization and optical coherence tomography are characterized by a limited wave penetration depth and high sensitivity to the inhomogeneity of the powder materials. This makes them advantageous for monitoring the sintering process and inspecting surface layers, but inapplicable for detecting parts immersed in powder. Terahertz spectroscopy is capable of providing wave penetration to a depth of 10 cm and allows identifying geometric outlines of the part without contact, but the image quality is quite low, and technological features complicate integration into standard assembly lines. Automated cleaning of the upper powder layer with video analytics is considered in contact and contactless versions. The advantages of both methods are minimal capital costs, the absence of expensive equipment and the ability to work with a single gripping tool, while the main risks are the possibility of damaging the part during contact cleaning and contamination of the optics during contactless cleaning. The considered archaeological methods of searching for hidden objects turned out to be inapplicable to the problem of identifying the part located in powder, since they are based on a significant difference in physical quantities that is absent in the problem under consideration. In conclusion, it is substantiated that the combination of automated cleaning with adaptive video analysis and neural network monitoring is the simplest, most economically viable and technologically promising solution for automating the extraction of sintered parts from powder. The use of computed tomography and terahertz spectroscopy to determine the location of the part is highlighted as a promising technologies, which also allows one to perform the sintering control and defectoscopy of the part. The practical significance of the study lies in identifying a number of methods that allow one to have an automatic monitoringl of the orientation of the part in the powder mass, and to conduct their comparative analysis within the framework of applicability to the practical problem under consideration. Identifying the most suitable methods opens up prospects for automating post-processes in selective laser sintering and developing the technology as a whole.