The rapid development of 3D printing technology is changing our traditional production methods and lifestyles. As a typical representative of the emerging manufacturing technology, the early application of metal 3D printing technology in the aerospace field has turned to the industrial, automotive, medical, mold, education, and jewelry markets. How much do you know about metal 3D printing technology? Today, Dr. Trunnano Leo will introduce to you the current mainstream metal 3D printing technology.
The RMIT University team in Australia has researched a new type of 3D printing technology called "Directed Energy Deposition (DED)," which uses ultrasound to enhance the strength of 3D metal parts by changing the microstructure of materials.
It is understood that RMIT researchers printed samples using two different common alloys: Ti-6Al-4V is a titanium alloy commonly used in aircraft parts and biomechanical implants; Inconel 625 is a nickel-based high-temperature Alloys, widely used in the marine and petroleum industries.
Regardless of the alloy used, the deposition surface is a sonic detector, a tool that generates ultrasonic vibrations. During the solidification of the metal, fluctuations can cause micro-crystallization to form a more compact structure. It was found that these materials had a 12% increase in tensile strength and yield stress compared to the same samples without the use of ultrasound.
Also, you can create individual projects with different microstructures in different areas by turning the ultrasound generator on and off during printing. This is a quality called "functional grading," which is very useful in objects that consider factors such as low weight or reduced material use.
Researchers believe that once ultrasound-enhanced 3D printing technology is further developed, it is difficult to use it for other metals such as stainless steel, aluminum alloys, and cobalt alloys.
Many types of hydraulic components have been 3D printed with metal. For example, Android uses stainless steel printed hydraulic valve blocks to control single-acting cylinders (Figure 1). The company can save space and optimize its internal channels, with higher flow rates and lower pressure losses compared to traditional components. Since no auxiliary drilling is required, the possibility of external leakage is also eliminated.
Besides, a 3D printed design and improvement produced a stackable hydraulic valve (Figure 2). Directly operated pressure reducing valves are made of steel and galvanized to prevent corrosion. When Aidro's customers have a small amount of valve demand, CNC machining is uncontrollable for delivery time and cost. Instead, the valve was redesigned and manufactured using 3D stainless steel, which reduced weight by 60%. The structural wall is as strong as before, and the new design results are comparable under the 250bar pressure test.
Methods of metal 3D printing technology:
There are five mainstream metal 3D printing technologies: laser selective sintering (SLS), nanoparticle spray metal forming (NPJ), laser selective melting (SLM), laser near-net molding (LENS), an electron beam selective melting (EBSM) technology.
Laser Selective Sintering (SLS)
The entire SLS process device consists of a powder cylinder and a molding cylinder. The powder cylinder piston rises, and the powder is spread evenly on the molding cylinder by a powder coating vehicle. The computer controls the two-dimensional scanning trajectory of the laser beam according to the prototype slice model. There are options. The solid powder material is sintered to form a layer of the part. After one layer is completed, the working piston is lowered by one layer thickness, the powder coating system is coated with new powder, and the laser beam is controlled to scan and sinter the new layer. Repeat this cycle, layer by layer, until the three-dimensional part is formed.
Nanoparticle spray metal forming (NPJ)
As we all know, ordinary metal 3D printing technology uses laser melting or laser sintering of metal powder particles, and nanoparticle spray metal forming (NPJ) technology uses not a powdery form, but a liquid state. These metals are wrapped in a tube in a liquid form and inserted into a 3D printer, which is spray-molded with metal iron particles containing "hot metal" during 3D printing. The benefit is that the metal is printed with hot metal, the whole model will be more rounded, and ordinary inkjet print heads can be used as tools. When printing is complete, the build chamber will heat the excess liquid by evaporation, leaving only the metal parts.
Laser Selective Melting (SLM)
The basic principle of SLM technology is to first design a robust three-dimensional model of the part on a computer using three-dimensional modeling software such as Pro / e, UG, CATIA, and then slice and layer the three-dimensional model through the slicing software to obtain the outline of each section. The data, the filling scan path, is generated from the contour data, and the device will control the laser beam selection to melt the metal powder materials in each layer according to these filling scan lines and gradually stack them into three-dimensional metal parts. Before the laser beam starts to scan, the powder spreading device first pushes the metal powder onto the substrate of the forming cylinder. The laser beam then fills the scanning line of the current layer, selects the area to melt the dust on the substrate, processes the current layer, and then the forming cylinder descends by one. The distance of the layer thickness, the length of the powder cylinder rising by a certain depth, the powder coating device then spreads the metal powder on the processed current layer, and the device transfers the data of the contour of the next layer for processing. The part is processed.
Laser near-net forming (LENS)
Laser near-net molding (LENS) technology uses the principle of simultaneous laser and powder delivery. The computer sliced the 3D CAD model of the part layer by layer to obtain the 2D planar contour data of the part, which was then converted into the motion trajectory of the NC table. At the same time, the metal powder is fed into the laser focusing area at a certain powder supply speed and is rapidly melted and solidified. Through the layer, point, line, and surface layer superposition, a near-net-shaped part substantial is finally obtained. Be usable. LENS can achieve the moldless manufacturing of metal parts, saving a lot of costs.
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