Juntong Xi

A model research for prototype warp deformation in the FDM process

In rapid prototyping (RP) technology, prototypes are constructed by the sequential deposition of material layers. When the deposition process involves temperature gradients, thermal stresses will develop. In this paper, the prototype deformation in fused deposition modeling (FDM) processes is studied, and the essence of the deformation and the interacting principles are analyzed. According to basic hypotheses and simplifications, the mathematical model of the prototype warp deformation is constructed, and each of the influencing factors concretely, including the deposition layers number n, the stacking section length L, the chamber temperature Te, and the material linear shrinkage rate α, is quantificationally analyzed. Based on the analysis results, some issues and phenomena in the FDM process are rationally explained. Furthermore, the improving methods for the reduction of the prototype warp deformation are proposed, and the applying effect is better.

Modeling and Calibration of a Novel One-Mirror Galvanometric Laser Scanner

A laser stripe sensor has limited application when a point cloud of geometric samples on the surface of the object needs to be collected, so a galvanometric laser scanner is designed by using a one-mirror galvanometer element as its mechanical device to drive the laser stripe to sweep along the object. A novel mathematical model is derived for the proposed galvanometer laser scanner without any position assumptions and then a model-driven calibration procedure is proposed. Compared with available model-driven approaches, the influence of machining and assembly errors is considered in the proposed model. Meanwhile, a plane-constraint-based approach is proposed to extract a large number of calibration points effectively and accurately to calibrate the galvanometric laser scanner. Repeatability and accuracy of the galvanometric laser scanner are evaluated on the automobile production line to verify the efficiency and accuracy of the proposed calibration method. Experimental results show that the proposed calibration approach yields similar measurement performance compared with a look-up table calibration method.

Accuracy improvement for 3D shape measurement system based on gray-code and phase-shift structured light projection

Accuracy is one of the most important features for a 3D shape measurement system based on gray-code and phase-shift structured light projection and it requires accurate modeling and calibration of the camera and projector that consist of the system. In this paper, a new method is proposed to reconstruct the 3D object without the inverse projector model, thus make it possible to use a more accurate projector model considering high to 4th order radial and tangential lens distortion. Moreover, we propose a new system calibration method which can calibrate the camera and projector simultaneously based on the same reference points to eliminate the disadvantage of the conventional two-step calibration methods that the accuracy of the projector calibration is always influenced by the camera calibration error. The experiments compare the performance of our proposed model and calibration method with the conventional ones and the results are presented.

Development and Verification of a Novel Robot-Integrated Fringe Projection 3D Scanning System for Large-Scale Metrology

Large-scale surfaces are prevalent in advanced manufacturing industries, and 3D profilometry of these surfaces plays a pivotal role for quality control. This paper proposes a novel and flexible large-scale 3D scanning system assembled by combining a robot, a binocular structured light scanner and a laser tracker. The measurement principle and system construction of the integrated system are introduced. A mathematical model is established for the global data fusion. Subsequently, a robust method is introduced for the establishment of the end coordinate system. As for hand-eye calibration, the calibration ball is observed by the scanner and the laser tracker simultaneously. With this data, the hand-eye relationship is solved, and then an algorithm is built to get the transformation matrix between the end coordinate system and the world coordinate system. A validation experiment is designed to verify the proposed algorithms. Firstly, a hand-eye calibration experiment is implemented and the computation of the transformation matrix is done. Then a car body rear is measured 22 times in order to verify the global data fusion algorithm. The 3D shape of the rear is reconstructed successfully. To evaluate the precision of the proposed method, a metric tool is built and the results are presented.

Integrated fringe projection 3D scanning system for large-scale metrology based on laser tracker

Large scale components exist widely in advance manufacturing industry,3D profilometry plays a pivotal role for the quality control. This paper proposes a flexible, robust large-scale 3D scanning system by integrating a robot with a binocular structured light scanner and a laser tracker. The measurement principle and system construction of the integrated system are introduced. And a mathematical model is established for the global data fusion. Subsequently, a flexible and robust method and mechanism is introduced for the establishment of the end coordination system. Based on this method, a virtual robot noumenon is constructed for hand-eye calibration. And then the transformation matrix between end coordination system and world coordination system is solved. Validation experiment is implemented for verifying the proposed algorithms. Firstly, hand-eye transformation matrix is solved. Then a car body rear is measured for 16 times for the global data fusion algorithm verification. And the 3D shape of the rear is reconstructed successfully.

An initial solution estimation method based on As‐Rigid‐As‐Possible mesh parameterization for one‐step simulation

Purpose – The purpose of this paper is to propose a universal, robust and efficient method to obtain a reliable initial guess solution for the one‐step finite element simulation.Design/methodology/approach – In one‐step simulation, getting initial guess solutions effectively is essential to ensure the success of the non‐linear resolution in the implicit static solver and to speed up the convergence of the Newton‐Raphson iterations. A newly emerging mesh parameterization approach named As‐Rigid‐As‐Possible method, which is widely used in computer graphics, is proposed as an effective initial guess estimation method in this paper. It is almost an isometric parameterization and showing excellent area‐preserving capability than other state‐of‐the‐art approaches. Several numerical examples are provided to verify the validity and efficiency of the presented method.Findings – Compared with the geometry mapping methods, the presented ARAP method shows its universality in handling types of workpieces whether they ...