Three-dimensional printing (3DP) is a technology that generates three-dimensional solids by adding material layer by layer through the superposition of successive physical layers. It is different from the traditional processing technology of rapid prototyping and additive manufacturingremoving materials, so it is also known as additive manufacturing (AdditiveManufacturing) or additive manufacturing (AM) technology, formerly known as rapid prototyping (RP) technology.
Principle of DLP process
Digital Light Processing (DLP) is a 3D printing information technology that has developed and emerged in recent years, and has a similarity to SLA's molding process technology enterprise, which is a variant form of SLA. In the processing of production products, the use of these digital micromirror elements The product structure cross-sectional design graphic data projected into the liquid can be bright resin material surface, so that the irradiated resin layer by layer for the use of light curing. DLP 3D printing process due to the network of each layer cured by learning slide-like sheet curing, speed than the same type of SLA speed can be faster. This research technology is very well suited for high resolution already molding, represented by Envisiontec of Germany.
The SLA process focuses a laser of specific intensity onto the surface of a 3D printed material to cure and shape it. SLA molding is primarily a step-by-step process of point-to-point and line-to-surface molding. Unlike SLA, DLP technology primarily utilizes DLP projection, in which the entire surface of the laser is focused on the surface of the 3D printed material. As a result, DLP technology allows for faster printing speed models.
Pros and cons of DLP process
1) Product performance is similar to SLA process with faster molding.
2) Limited by the resolution of the digital light mirror, only by printing the size of the impact of smaller business products.
DLP wax mold printing technology has a long history in the jewelry field, and the application is more mature. With the increase of digital optics mirror resolution, its application in the field of industry, literature and innovation will rapidly spread.
Layered solid manufacturing (Lom) was one of the first 3D printing technologies, developed by Helisys (now Cubic Technologies).
The LOM method uses a thin sheet (e.g. paper, plastic film or composite material) as the raw material and uses a CO2 laser cutting system based on computer-extracted cross-sectional profile data. The paper sheet coated with hot melt adhesive on the back is cut with the laser to cut out the inner and outer contours of the workpiece, while the non-part areas are cross-cut to facilitate scrap removal. After cutting one layer, the feeding mechanism stacks a new layer of paper sheets and the table drives the formed workpiece down (usually with a material thickness of 0.1-0.2 mm), rapid injection mouldingseparating it from the strip sheet (material belt); the feeding mechanism rotates the receiving and feeding axes, driving the belt movement and moving the new layer to the processing area; the table rises to the processing plane; the workpiece layers are increased by one layer and the height by one material thickness by hot pressing with paper rolls. The cross-sectional profile is then cut on the new layer, and the part is finally finished.
The LOM process is carried out at relatively low cost due to the ease of access to raw materials for companies students. The processing and production process does not involve chemical reactions and is suitable for making large-sized design products by themselves. However, due to the high cost of the traditional Chinese LOM molding technology process CO2 laser, too few types of raw materials, the strength of the paper is weak and susceptible to moisture, and other reasons, has now begun to gradually withdraw from the historical and cultural stage of 3D printing.
The principle of SLM process
SLM is a technology that uses metal powder that is completely melted and cooled and cured under the heating of a laser beam. The SLM and SLS part processes are very similar and will not be repeated here. However, the SLM process usually requires the addition of a support structure. The main functions of the support structure are: 1. To receive the next unformed powder layer and prevent the collapse caused by the laser scanning to too thick a metal powder layer; During the molding process, after the powder is heated, melted and cooled, there are internal shrinkage stresses that cause the part to warp. The support structure connects the molded part to the unformed part and can effectively suppress shrinkage, and the molded part Stress balance can be maintained.
Pros and cons of SLM process
1)1) SLM process processes standard metal density of more than 99%, its good mechanical properties are comparable to the traditional process.
2) Different types of machinable materials for SLM increase, and the machined parts can be welded later.
3) High price and low speed.
4) Limited precision and surface quality, which can be improved by post-treatment.
SLM process application range
1) Machining the appearance, assembly and functional prototypes of standard metals.
2) Support a part, such as fixture, fixed working device, etc.
3) Small batch part production.
4) Injection mold.
Principle of SLS process
The principle of selective laser sintering molding method is shown as follows: 1. In the printing process, powder particles are stored in the supply bin on the left side, and the lift platform of the supply bin is raised upward; the powder above the printing plane is pushed onto the printing plate in the printing chamber through the powder spreading roller to form a thin and flat powder layer; in the laser beam scanning system, the powder layer is scanned selectively according to the sliced 2D CAD path, and due to the laser focal point of high temperature, the scanned powder particles sinter together but produce a solid sheet with a certain thickness, and the unscanned area remains as loose powder. After completing the sintering of one layer, the printing platform is lowered according to the slice height, the horizontal rollers flatten the powder again, and then the sintering of a new layer begins, at which point the layers are also sintered together at the same time; this is repeated until all layers have been sintered. The un-sintered powder is removed and recycled to remove the printed solid model.
Advantages and disadvantages of the SLS process
Compared to other 3D printing methods, the advantages of the SLS process are obvious:
1) The molding technology material has a very wide range. In a theoretical sense, any powder material rapid prototyping typesthat can be heated to form interatomic bonds can be used as a molding material for SLS;
Can print any complex structure, including hollow structure, hollow structure, etc. process independent of the complexity of the part and the high strength of the part.
3) High material utilization, un-sintered powder can be reused, less material waste;
4) no support structure is needed, and the loose powder plays a supporting role, reducing the difficulty of model processing in the pre-printing stage
5) SLS process can be processed with a good mechanical system performance of the standard for plastic ;
6) can process an increasing variety of materials, small batch production price advantage is obvious.
Compared with the corresponding injection molded parts, SLS process products are not exactly the same performance, especially the product surface is more rough. SLS process can be used in almost all industries, not only in the R & D design phase of proof of concept, the same applies to the production of functional manual panels, terminal parts production, and can be used directly or indirectly for a variety of rapid casting. The process is currently used in a wide range of applications in aerospace, home appliances, automotive manufacturing, medical AIDS, applied arts and lighting.