Real-time Detection And Closed-loop Control Of The Deposition Height In The Process Of CO₂ Laser Addictive Manufacturing

Addictive manufacturing with laser heat has many advantages compared with other heat method. Laser addictive manufacturing（LAM） method has high degree of flexibility and roughness as well as low-environment requirements, which results more attention and study. LAM method has widely used in many fields like aerospace and medicine.LAM process primarily focuses on the forming technology and the microstructure and properties about the forming parts. There are few researches on the test and control process in laser addictive manufacturing. This article’s intent is to study the stability of the CO₂ laser addictive manufacturing process, adding detect and control system on the process.The paper focuses on the detection and control with CCD（Charge-coupled Device） sensor. A software system consisting of detecting software and control software is developed. The system accomplishes the function about real-time height detection, real-time display, saving date and replay function. The system can also communicate with the original equipment.A good algorithm of image process is the key factor to get satisfactory result. Considering the interference of plasma, the article selected a reasonable detecting area and a series of image process algorithm, managed to get the extraction character about the laser cladding. A series of experiments is accomplished, and the result shows the error of the height is less than 0.1mm. Study finds that powder feed rate and deposition speed are the main factors of the deposition height of one layer.Considering the fact that deposition height of each layer becomes lower along with the more layers, a model about deposition average height of each layer and deposition speed is developed. What’s more, a fuzzy controller is developed and the simulation based on MATLAB toolbox is carried out, the result shows that the controller can quickly adjust the deposition speed, and the average height of the layer returns to the former height.Based on the image process and fuzzy control method, an experiment is conducted with the help of CO₂ laser addictive manufacturing equipment. An open-loop control experiment results in a bad deposition morphology because of the heat accumulation. While a close-loop control experiment has a better deposition morphology.