How to classify rapid prototyping technology

Rapid prototyping technology can be divided into two types according to the molding method: Laser Technology based on laser and other light sources, such as: photocuring (SLA), layered solid manufacturing (LOM), and selective laser powder sintering (SLS). , Shape Deposition Molding (SDM), etc.; Jetting Technoloy, such as: fused deposition modeling (FDM), three-dimensional printing (3DP), multiphase spray deposition (MJD). The following is a brief introduction to the more mature process.

    1. SLA (Stereolithogrphy Apparatus) Process The SLA process, also known as light modeling or stereolithography, was patented by Charles Hul in 1984. In 1988, 3D System of the United States launched the commercial prototype SLA-I, which is the world's first rapid prototyping machine. SLA molding machines occupy a large share of the RP equipment market.

    SLA technology works on the principle of photopolymerization of liquid photosensitive resins. The liquid material can rapidly undergo photopolymerization under ultraviolet light of a certain wavelength and intensity, and the molecular weight sharply increases, and the material changes from a liquid state to a solid state.

    Working principle of SLA: The laser beam filled with liquid photocuring resin in the liquid tank can be scanned on the liquid surface under the action of the deflection mirror. The scanning track and the presence or absence of light are controlled by the computer, where the light is hit, the liquid It is cured. At the beginning of the forming, the working platform is at a certain depth below the liquid level. The focused spot is scanned point by point on the liquid surface according to the instructions of the computer, that is, it is solidified point by point. When a layer scan is completed. The place where it is not irradiated is still a liquid resin. Then the lifting platform drives the platform down to a height, and the formed layer is covered with a layer of resin. The squeegee scrapes the liquid surface of the resin with higher viscosity, and then scans the next layer, and the new layer is layered. Stick to the previous layer firmly, repeat this until the entire part is manufactured, and get a 3D solid model.

    The SLA method is the most studied method in the field of rapid prototyping technology. It is also the most mature method in technology. The parts formed by the SLA process have high precision, the processing precision can generally reach 0.1 mm, and the raw material utilization rate is nearly 100%. However, this method also has limitations in white body, such as the need for support, resin shrinkage leading to a decrease in precision, and photocurable resin having certain toxicity.

    2, LOM (Laminated Object Manufacturing, LOM) process LOM process is called laminated entity manufacturing or layered entity manufacturing, developed by Michael Feygin of Helisys Corporation of the United States in 1986. The LOM process uses sheet materials such as paper, plastic film, and the like. The surface of the sheet is previously coated with a layer of hot melt adhesive. During processing, the hot press rolls the sheet to bond it to the formed workpiece below. The CO2 laser cuts the part profile and the workpiece frame on the newly bonded new layer, and cuts the upper and lower aligned grids in the excess area between the profile and the frame. After the laser cutting is completed, the workbench drives the formed workpiece to descend and separate from the strip sheet. The feeding mechanism rotates the receiving shaft and the feeding shaft to move the belt to move the new layer to the processing area. The work is raised to the processing plane, the hot press roll is hot pressed, the number of layers of the workpiece is increased by one layer, and the height is increased by one material. Cut the profile on the new layer. This is repeated until all sections of the part are bonded and cut. Finally, the excess portion of the chopped portion is removed to obtain a solid part that is layered.

    The LOM process simply cuts the outline of the part's section on the sheet without scanning the entire section. Therefore, the formation of thick-walled parts is faster and it is easy to manufacture large parts. There is no material phase change during the process, so it is not easy to cause warpage. Excess material between the outer frame of the workpiece and the profile of the cross section supports the machining process, so the LOM process does not require support. The disadvantage is that the material is wasted and the surface quality is poor.

    3, SLS (Selective Laser Sintering) process SLS process is called selective laser sintering, developed by C.R. Dechard of the University of Texas at Austin in 1989. The SLS process is formed from a powdered material. The material powder is spread on the upper surface of the formed part, and flattened, and the cross section of the part is scanned on the freshly laid layer with a high-strength CO2 laser, and the material powder is sintered together under high-intensity laser irradiation to obtain The section of the part is connected to the part that has been formed below. When a section of the section is sintered, a new layer of material powder is applied to selectively sinter the lower section.

    After the sintering is completed, the excess powder is removed, and then polished, dried, and the like to obtain a part.

    The SLS process is characterized by a wide range of materials, not only for the manufacture of plastic parts, but also for the manufacture of ceramic, wax and other materials, in particular for the production of metal parts. This makes the SLS process attractive. The SLS process does not require support because no sintered powder acts as a support.

    4, 3DP (Three Dimension Printing) process 3D printing process was developed by the United States Institute of Technology E-manual Sachs and others. It has been commercialized by Soligen Corporation of the United States under the name of DSPC (Direct Shell Production Casting) to manufacture ceramic shells and cores for casting.
The 3DP process is similar to the SLS process and is formed from powder materials such as ceramic powders and metal powders. The difference is that the material powder is not joined by sintering, but the cross section of the part is "printed" on the material powder by means of a nozzle with an adhesive such as silica gel.

    Parts bonded with adhesives are less strong and require post-treatment. The binder is burned first, and then the metal is infiltrated at a high temperature to densify the parts and increase the strength.

    5. FDM (Fused Depostion Modeling) Process The fused deposition manufacturing (FDM) process was developed in 1988 by American scholar Scott Crump. The materials of FDM are generally thermoplastic materials such as wax, ABS, nylon, and the like. Feed in the form of a filament. The material is heated and melted in the spray head. The nozzle moves along the cross-sectional profile and fill path of the part while extruding the molten material, the material solidifies rapidly and condenses with the surrounding material.

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