The analysis of factors influencing defect detection in PVC materials using thermal imaging

In traditional PVC pipe production, product inspection primarily relies on visual examination to detect surface defects such as protrusions or indentations, which indicate potential issues. However, this method is ineffective for identifying internal defects or voids formed during the extrusion process. This study simulates the cooling process of PVC pipes after extrusion, using a cold-water bath and thermal imaging to assess the consistency of temperature changes during cooling, thereby identifying potential internal defect locations. The experiment involved creating a three-layered pipe structure by nesting smaller diameter PVC pipes, with various sizes of defects intentionally designed within the interlayer to simulate hidden internal flaws. After heating the pipes to 60°C and rapidly cooling them in a 25°C cold water bath, infrared thermal imaging was used to observe the pipes, clearly revealing the defect locations. To minimize the cost of experimental materials and avoid equipment limitations, CAE simulation software was employed to model different extrusion temperatures, cooling water temperatures, defect sizes, and pipe wall thicknesses. Using a 2n factorial experimental design method, the study identified the most significant factors influencing defect imaging (temperature difference). The simulation results indicated that pipe wall thickness and extrusion temperature are the primary factors affecting the visibility of defects in thermal imaging.