Digital Inspection Of Mechanical Parts Based On Positioning Process Features

In recent years,the three-dimensional digital inspection technology is gaining more and more attention with the rapid development of the acquisition technology of point cloud.The key steps of this technology are pre-processing of point cloud,registration between CAD model and point cloud,error analysis and visualization and so on.Mechanical parts possess positioning process features with high precision in the practical manufacture processing.This paper introduces aforementioned features as constraint reference for the registration between point cloud and CAD model,followed by developing the 3D digital inspection system based on these features,which improves the accuracy of 3D digital measurement of mechanical parts.In this paper,developing positioning process features-based three-dimensional digital inspection system is studied,including pre-processing and registration of point cloud.By adopting octree to establish geometry topology between points,the speed of neighboring points searching significantly increases.Sampling strategies are then applied on huge amount of point cloud to reduce redundancy and improve efficiency.The enhanced Z-score statistic model is employed to denoise the point cloud,which further guarantees the reliability of the measuring data.As the foundation of the following feature construction and constrained registration,a CAD-based point cloud segmentation algorithm that segments point cloud according to CAD surface is designed.This paper proposes six fitting algorithms corresponding to six features in machinery manufacturing.Accurate features can be constructed through fitting algorithms.Based on the property of fitted features,a constrained registration algorithm is proposed to get accurate registration result.At last the method of measuring and visualizing the inspection error is researched and the positioning process features-based 3D digital inspection system is developed.The positioning process features-based three-dimensional digital inspection system makes full use of the positioning process features with high precision and improves the accuracy of 3D digital inspection,which is of great significance to analyze the actual industrial deformation.