Reliance on scanning inspection of the body shape of the white film of the accuracy of the inspection

The basic inspection flow marks the surface of the object to be inspected. According to the basic requirements for photogrammetry, non-encoded mark points and coded mark points need to be attached to the surface of the object to be inspected. The non-coded mark is a black-white dot high-contrast special material printed with a thickness of 0.2 mm. The back surface is glue, which can be easily attached to the surface of the object to be inspected. The coded reference point is designed in binary digits and can be used by the image recognition system to identify its unique identification code. The material uses magnetic rubber, which can be easily adsorbed on the surface of some steel parts and can be reused. The thickness of coded mark points is generally between 12mm. As shown.

The mutual distance of non-coded markers is generally about 200 mm, and they are randomly distributed as much as possible. Because the material is a thin print, it is easy to deform, so it should be attached to the surface of the workpiece in the flat ZXY image space space, and the surface of the workpiece is clean and free from oil and dust. If the coordinates of the non-coded marker points are used as detection data in the later period, then the thickness of the marker points must be reduced in the detection items with higher accuracy requirements.

The global ruler of the system global ruler system is the basis for the final calculation of the three-dimensional coordinates of the system. Therefore, the accuracy of the ruler and the placement position thereof have certain requirements.

The current scale is made of invar alloys with a very small coefficient of thermal expansion and undergoes rigorous testing. The place of the ruler should be placed according to the shape characteristics of the object to be inspected and the accuracy requirements of each part. Generally, it follows: 1) The area controlled by the ruler is the maximum effective area of ​​the object to be inspected, and it is placed close to the object to be inspected; 2) Accuracy requirements The high position must have a ruler, and the end of the scale must have enough coded mark points.

The XJT UDP system uses global digital cameras to take pictures. Based on the requirements of the photogrammetry system, the subject is photographed from different locations to obtain photos containing coded mark points, non-coded mark points, and global ruler information, and imported into XJTUDP. The system performs calculations to obtain the global three-dimensional coordinates of the non-coded points and coded landmarks on the surface of the object to be inspected.

Perform comparative analysis of key points under UG or Qualify. Import the global 3D coordinate points calculated by the XJT UDP system into UG or Geomagic Qualify software. Set the different tolerance limits according to the process and design requirements. Analyze the objects to be inspected. The distribution of error is used as the basis for detection and determination of the object to be inspected.

Perform full-scale analysis with the XJTUOM system To further determine the accuracy of the entire profile, global 3D coordinate points can be imported into the XJ-TUOM 3D point cloud measurement system to scan the mold profile and key positions of concern for process design. Automatic identification marks and splicing, and finally get the surface of the detected mold dense point cloud. In general, only the key points need to be detected. It is not necessary to use the XJTUOM system for surface scanning to meet the rapid detection requirements at the production site.

The foam model was tested in the XJTUDP system and the global coordinate points were collected and calculated. The foam model of the A-TP5-141-003_new-scale mold was spotted. Photographs of different positions were taken after the mark was marked, and 93 photos were taken. The calculations were performed under the XJTUDP system as shown.

The global coordinate point of the bubble model's global coordinate point is calculated and the global coordinate point is output. The surface global coordinate point file paomo_NOID_UnCode.txt of the bubble model is obtained. This file contains the three-dimensional coordinate information of all the points. After changing the general format with the suffix “.asc” directly, , can be read by UG, CATIA and other three-dimensional processing design software.

The selection of the coordinate system can not determine the selection of the reference plane because the number of bubbles before the measurement is not obtained. Therefore, the coordinate conversion of the global coordinate point cannot be completed in the XJTUDP system at a time. Therefore, the global coordinate point and the foam number model are not included under UG. Matching and alignment are performed. Corresponding to the design of the coordinate system of the digital model, the detection requirements under different design margins are satisfied. The file name after the corresponding coordinate system adjustment is named points.igs.

The 3-2-1 alignment function has been designed for coordinate conversion in the XJTUDP system. The coordinate conversion between measurement data and digital-to-analogue can be easily performed in the case of known coordinate reference, without the need of third-party software. Under the conversion alignment, as shown.

Conclusion The experimental results show that the application of XJTUDP digital close-range industrial photogrammetry system can meet the requirements of industrial field rapid detection, high measurement accuracy, speed detection block, portable, fluid characteristics, strong adaptability to the environment, can be large castings, Forgings, stampings, molds, etc., can also be measured deformation, reverse engineering, etc., with good versatility.