Deposition Layer's 3D Measurement Of Arc-based Additive Manufacturing Based On Line-structured Light

Arc-Direct Rapid Prototyping Manufacturing(ADRPM), one of the Additive Manufacturing technologies, has get much attention from researchers because of its high production efficiency, low cost and the great ability of forming component with excellent mechanical performance. But the process of ADRPM is so complicated that it's hard to predict the shape of the weld bead which deposited from liquid state. It will seriously affect the performance and precision of the metallic deposition part if the information of deposition process can't be collected. So it's very important to monitor the deposition process on time to adjust the treading track, parameters of the deposition current electricity, voltage, speed and arc length etc.To meet the requirement of measuring deposition shaping part during Arc-Direct Rapid Prototyping Manufacturing, we build a 3D measurement system based on line-structured light. Firstly, we design a set of clamping device, which on the one hand can fix the laser generator and CMOS, on the other hand can protect the measurement system. Secondly, using Matlab's tool box of camera calibration to calibrate CMOS's parameters, such as focal length in pixels, principal point, distortions and skew coefficient. Then a well-designed jagged part is used to calibrate the rotation matrix and translation matrix between camera coordinate system and world coordinate system. Thirdly, we improve the gray-gravity algorithm using adaptive threshold method, which extracts laser stripe center position at sub-pixel accuracy successfully and compute the data of measuring section. Finally, scanning the whole deposition shaping part by following the movement of CNC machine or welding robot to collect 3D size information.The results of experiments have proved that the 3D measurement system based on line-structured light we built has high precision that the measurement error in Z-direction is less than 0.4% of the range, which can fully meet the need of ADRPM. A software is developed to feedback deposition shaping part's 3D size information to path planning system, so we can generate the milling code and adjust deposition path of next layer. Practice shows that the the 3D measurement system based on line-structured light has considerable practical value.