Research Topics
Coaxial laser cladding and rapid prototyping(RP)
Coaxial laser cladding is one of the new processes applied to the rapid prototyping industry for its excellent flexibility in generating the metallic components directly from CAD drawings.
Coaxial laser cladding is one of the new processes applied to the rapid prototyping industry for its excellent flexibility in generating the metallic components directly from CAD drawings. However, due to the inefficient usage of the powder in the process, many attempts have been made to improve the nozzle design. There are many industrial processes similar to coaxial laser cladding, which involve jets impinging on a solid surface.
Hybrid pulsed laser and resistance spot welding
Hybrid pulsed laser and resistance spot welding uses laser welding of the base material and part of the pole handle, combined with resistance welding from the other side to weld the remaining multi-layer pole handle, thereby reducing the welding power and reducing the possibility of shrinkage cavities.
Auto-focusing system
Focal position is an important parameter affecting the laser processing. The auto-focus system uses red light as the reference light source. It can keep the defocusing distance while processing on the board with height difference, thereby optimizing the laser processing.In laser micromachining, alignment is difficult due to the small working area. If there is a slight position deviation, the laser heat source may damage the surrounding materials, so it is very important to process alignment. Through machine vision, capturing the processing position with the lens has become a key technology, which can not only solve the problem of alignment in small areas, but also achieve the purpose of automation.
Through seven edge detection methods to do the global search focusing experiment, and see the peak changes of the seven methods, to find the most suitable method. From the following figure, it can be found that from a quantitative point of view, Gradient and Roberts each have one Larger wrong area peaks, so think of this as a less accurate way of the focus function
The figure below shows the experimental results. The depth of the melting pool before and after focusing is observed with a lateral microscope, which is represented by contours. The depth and width of the molten pool were observed from the side, and it was found that there were obvious changes in the depth, and the coordinate position of the side profile was marked with several points by ImageJ software to form an xy line graph The following figure (a) is the side profile of the unfocused side. Figure (b) is the side profile of the focus, and the unfocused groove shape can be sorted out through the chart, the top width is 0.16mm, the total depth is 0.24mm, and the groove shape after auto-focusing, the top width is 0.15mm, and the total depth is 0.15mm. 0.7mm.It can be found that the depth difference between autofocus and non-autofocus is 3 times
Laser Assistant Nano-Fabrication Processing
Using a 25W CO2 laser to process two different powders with dual powder feeding laser coating, a dual powder mixer was designed in this study to improve the single powder feeding shortcomings of traditional laser coating
The picture below shows the powder mixer developed in the laboratory. In the past, only one powder material was used in traditional laser coating. In order to explore the influence of two different powder materials on the actual coating, the properties are also different. The internal design of this powder mixer is based on a cyclone separator, and the powder to be coated is transported by shielding gas from the inlets on both sides. The two sides of the quick connector pipelines can respectively feed powders of different properties at different mass flow rates, which are mixed by the mixer and then sent to the coaxial laser nozzle for processing through the lower outlet connecting pipeline.
Through the mesh analysis in Ansys software, in order to increase the accuracy of the simulation values, the Inflation function in the mesh is also used to refine the surface of the cylinder and the cylindrical part of the model, which can increase the accuracy of the boundary layer. However, this simulation analysis mainly discusses the influence on the distribution of the powder mixed by the mixer in the outlet pipeline under different powder feeding conditions.
Cladding completion results
SLS(Selective laser sintering)
Laser scanning experiment configuration diagram
Selective Laser Sintering (SLS) is an additive manufacturing technique that uses a laser as a power source to sinter powder materials, automatically aiming the laser at a point in space defined by a 3D model, and bonding the materials together to form a solid structure.
Selective Laser Sintering (SLS) is an additive manufacturing technique that uses a laser as a power source to sinter powder materials, automatically aiming the laser at a point in space defined by a 3D model, and bonding the materials together to form a solid structure.
Selective laser sintering has the advantages of being able to quickly produce products and objects with complex shapes. However, problems such as surface roughness and porosity need to be improved. The higher the porosity, the lower the strength of the test piece. That is, the strength of the finished product after sintering is lower than that of the original metal material, so the problem of reducing porosity is very important, and the parameters affecting the sintering quality are sintering time, sintering temperature and sintering environment (whether it is in a vacuum state) and so on.
There are many methods for measuring porosity, such as floating weight method, paste coating method, and image analysis method. The method is to put the captured metallographic microscopic pictures into the image software (Image j), and use the analysis function of the image software. The proportion of the total area is obtained to obtain the percentage of the block, and then the porosity of the test piece is analyzed.
