1, basic principle.
Through FDM, "fused deposition" technology and heating device, the filaments such as ABS and PLA are heated and melted, then woven into the machine head, extruded like toothpaste, laminated layer by layer, and finally formed. The mechanism mainly consists of five parts: nozzle, wire conveying device, sports equipment, heating chamber and workbench. The materials used in the fusion plating process are divided into two parts. One is the molding material, and the other is the supporting material.
SLA, "Stereolithography", uses a laser beam to draw the layered shape of an object on the surface of a liquid photosensitive resin, then makes a platform, lowers a certain distance, and then immerses the solid layer in the liquid resin, and so on until it is printed. Finally, the prototype is taken out of the resin for final curing, and then the required products are obtained by illumination, electroplating, painting or coloring.
2. Form a space.
FDM3D printer is flexible and diverse in architecture, including XYZ frame structure, delta structure and mechanical arm, which can make the molding space smaller or larger. However, the mechanical structure of large FDM has the problems of poor stability and slow printing speed, which may be difficult to meet the long-term printing requirements of users. SLA is the first high-speed prototype manufacturing process to print by moving the optical axis, which can theoretically make a large size. However, SLA requires filling the molding space with resin material, because the depth of the swinging resin cylinder is the same as the height of the workpiece. In other words, the equipment must be very large. At the same time, the whole barrel should be emptied every time the material is changed.
3. Printing accuracy
FDM model is the part where molten materials are extruded through nozzles and overlapped layer by layer. The finished stair has more obvious effect (surface texture) and is not suitable for making large parts. In addition, theoretically, the smaller the diameter of FDM nozzle, the higher the accuracy, but the smaller the nozzle, the easier it is for consumables to be blocked, so the smaller the nozzle, the better. SLA industrial model adopts laser curing molding, which has the advantages that FDM model can not overcome.
4. Printing consumables
At present, FDM3D printers are common, and consumables are relatively cheap, mainly PLA, ABS, TPE, TPU and so on. Because polylactic acid is a biodegradable thermoplastic, it has no peculiar smell when printed, so it is safer to use in offices, classrooms, families and other occasions. ABS is a thermoplastic polymer material with high strength, high toughness and easy processing. Its melting point temperature is higher than PLA. When printing, the platform needs to be heated to avoid warping and shrinkage caused by poor cooling of consumables. TPE/TPU flexible materials can make objects with particularly good elasticity. But it is very difficult to print. Especially in 3D printers that provide materials remotely, it is difficult to control the advance and retreat of flexible materials. SLA consumables are liquid photosensitive resin, which has the advantages of fast curing speed, high molding accuracy, good surface effect and reprocessability, and is suitable for making handmade products such as automobiles, medical devices, electronics and building models. It should be noted that photosensitive resin is odorous and toxic, so it should be sealed. In order to prevent polymerization from happening ahead of time, it is necessary to avoid light protection.
FDM industrial equipment is mainly mechanical movement and control. Relatively speaking, the technical threshold and cost are low, the utilization efficiency of raw materials is high, and there is no pollution of toxic gases or chemicals, which greatly reduces the molding cost. The technical threshold of SLA industrial equipment is relatively high, and there are fewer equipment manufacturers, but the strength is relatively strong. There are more than 300,000 to several million kinds of industrial equipment. The price difference between the two is several times, but it is still worthwhile for enterprises that need to make high-precision models.