FDM (Fused Deposition Modeling)
The FDM melt layer forming technology heats and melts the filamentous hot-melt material, and the three-dimensional nozzle is selectively coated on the table according to the sectional profile information under the control of the computer, and rapidly cooled to form a layer. After one layer has been formed, the machine table is lowered to a height (please check the picture) and the next layer is formed until the entire solid shape is formed.
Advantages of FDM technology:
1) The operating environment is clean and safe, and the materials are non-toxic. It can be carried out in the office and home environment without the danger of poisonous gas and chemical pollution.
2) No expensive components such as lasers are required, so the price is cheap.
3) The raw material is in the form of a reel wire, which saves space and is easy to handle and replace.
4) The material utilization rate is high, there are many alternative materials, and the price is relatively cheap.
Disadvantages of FDM technology:
1) After forming, the surface is rough and needs to be polished later. The highest precision is only 0.1mm.
2) The speed is slow because the nozzle makes mechanical movement.
3) Materials are required as support structures.
SLS (Selective Laser Sintering)
The technique uses a powder layer to lay a layer of powder material on the upper surface of the formed part and heats it to a temperature just below the sintering point of the powder, and the control system controls the laser beam to follow the cross-sectional profile of the layer on the powder layer. Scanning, the temperature of the powder is raised to the melting point, sintered and bonded to the underlying formed portion. After the completion of one layer, the workbench is lowered by a layer thickness, and the paving roll is covered with a uniform dense powder to perform a new section of sintering until the entire model is completed.
Advantages of SLS technology:
1) A variety of materials are available. The usable materials include various powder materials such as polymer, metal, ceramic, gypsum, and nylon. In particular, metal powder materials are one of the most popular development directions in current 3D printing technology.
2) The manufacturing process is simple. Due to the large amount of materials available, the process can directly produce prototypes of complex shapes, three-dimensional construction of cavity molds or components and tools, depending on the material.
3) High precision. Generally, tolerances of (0.05-2.5) mm over the entire range of the workpiece can be achieved.
4) No support structure is required. The suspended layer that occurs during the lamination process can be supported directly by the unsintered powder.
5) High material utilization rate. Since there is no need for support, there is no need to add a base, and the material utilization rate is the highest among several common 3D printing technologies, and the price is relatively cheap.
Disadvantages of SLS technology:
1) The surface is rough. Since the raw material is powdery, the prototype is constructed by layer-by-layer bonding of the material powder layer by heating and melting. Therefore, the surface of the prototype is strictly granular and the surface quality is not high.
2) There is an odor in the sintering process. In the SLS process, the powder layer needs a laser to heat it to a molten state, and the polymer material or the powder particles volatilize the odor gas during laser sintering.
3) High-performance metal box ceramic parts cannot be directly formed, and warpage deformation is likely to occur when forming large-sized parts.
4) Long processing time. Before processing, there must be 2 hours of warm-up time; after the parts are built, it takes 5 to 10 hours to cool before they can be taken out of the powder cylinder.
5) Due to the use of high-power lasers, in addition to the cost of the equipment itself, many auxiliary protection processes are required, the overall technology is difficult, and the manufacturing and maintenance costs are very high.
SLA printing technology
SLA (Stereo Lithography Apparatus, selective curing of photosensitive resin).
The liquid tank is filled with liquid photosensitive resin, which is rapidly solidified under the irradiation of the ultraviolet laser beam emitted by the laser (SLA is different from the laser used for SLS, SLA uses ultraviolet laser, and SLS uses infrared laser). At the beginning of the forming, the lifting table is below the liquid level, just one layer thick. The laser beam focused by the lens is used to scan the cross-sectional profile along the liquid surface in accordance with machine instructions. The resin in the scanning area is rapidly solidified to complete a one-layer process to obtain a layer of plastic sheet. Then, the workbench is lowered by a layer thickness of the section layer, and the other layer section is solidified. Such layer stacking constitutes a constructed three-dimensional entity.
Advantages of SLA technology:
- SLA is the most mature technology and the most widely used. Among the rapid prototyping machines installed worldwide, photocuring systems account for about 60%.
2) The forming speed is faster and the system works stably.
3) Highly flexible.
4) High precision, can achieve micron level, such as 0.025mm.
5) The surface quality is good and smooth: suitable for fine parts.
Disadvantages of SLA technology:
1) Need to design the support structure. The support structure needs to be removed when not fully cured, and the molded part is easily broken.
2) The 3Dprinting equipment is expensive and the cost of use and maintenance is expensive. SLA systems require precision equipment that operates on liquids and is demanding in the work environment.
3) Photosensitive resin is slightly toxic, pollutes the environment, and has an allergic reaction to some human skin.
4) Resin materials are expensive, but the strength, rigidity and heat resistance after molding are limited, which is not conducive to long-term preservation.
5) Since the material is a resin, the temperature will be too high to melt and the working temperature should not exceed 100 °C. It is brittle after curing, easy to break, and has poor process-ability. The molded parts are easy to absorb moisture and have poor corrosion resistance.