3D printing SLS

l 3D printer technology
There are already dozens of different 3D printer technologies on the market, among which are more mature methods such as UV, SLA, SLS, LOM and FDM. We will present four of the most widely used technologies below:
The principle of SLA technology 3D printer
SLA is an abbreviation for “Stereo lithography Appearance”, which is a stereo photocuring method.
Focusing on the surface of the photocurable material with a laser of a specific wavelength and intensity, from point to line, from line to surface solidification, complete a level of drawing operation, then move the lifting table vertically in the height of a layer, and then solidify Another level. This layer stacking constitutes a three-dimensional entity.
SLA is the earliest practical rapid prototyping technology, using liquid photosensitive resin raw materials, the process principle is shown in the figure. The process is to first design a three-dimensional solid model through CAD, use a discrete program to slice the model, design the scan path, and the generated data will precisely control the motion of the laser scanner and the lifting platform; the laser beam is controlled by the numerical control device. The surface of the liquid photosensitive resin is irradiated according to the designed scanning path to cure a layer of resin in a specific area of the surface. When a layer is processed, a section of the part is formed; then the lifting platform is lowered by a certain distance on the solidified layer. Covering another layer of liquid resin, and then performing a second layer scanning, the second solidified layer is firmly bonded to the previous solidified layer, so that the layers are superposed to form a three-dimensional workpiece prototype. After the prototype is taken out of the resin, the final curing is carried out, and then the desired product is obtained by polishing, electroplating, painting or coloring.
SLA technology is mainly used to manufacture a variety of molds, models, etc.; it is also possible to replace the wax molds in investment casting by using SLA prototype molds by adding other ingredients in the raw materials. SLA technology has a faster forming speed and higher precision, but it will inevitably generate stress or cause deformation due to shrinkage during curing of the resin. Therefore, the development of photosensitive materials with small shrinkage, fast curing and high strength is the development trend.
Advantages of SLA technology
1. The light curing molding method is the earliest rapid prototyping process with high maturity and time-testing.
2. Prototype made directly from CAD digital model, the processing speed is fast, the production cycle is short, and no cutting tools and molds are needed.
3. It is possible to process prototypes and molds with complex structural shapes or difficult to shape using conventional methods.
4. Visualize CAD digital models and reduce the cost of bug fixes.
5. Provide samples for the experiment, and verify and verify the results of the computer simulation calculation.
6. It can be operated online and can be controlled remotely to facilitate the automation of production.
Defects in SLA technology
1. The SLA system is expensive and the cost of use and maintenance is too high.
2. The SLA system is a precision device that operates on liquids and is demanding in the working environment.
3. Most of the molded parts are made of resin. The strength, rigidity and heat resistance are limited, which is not conducive to long-term storage.
4. The pre-processing software and the driver software have a large amount of computation and are too correlated with the processing effect.
5. The software system is complicated to operate and difficult to get started; the file format used is not familiar to the majority of designers.
6. Stereoscopic curing technology is monopolized by a single company.
Summary: The development trend and prospects of SLA
The development trend of the stereo curing method is high speed, energy saving, environmental protection and miniaturization.
Increasing processing precision has made it possible to make a difference in the fields of biology, medicine, and microelectronics.
The principle of SLS technology 3D printer
SLS (Selective Laser Sintering) selective laser sintering (hereinafter referred to as SLS) technology
Originally presented by Carlckard of the University of Texas at Austin in 1989 in his master’s thesis. After the United States DTM company in 1992 launched the process of commercial production equipment Sinter Sation. For decades, Austin and DTM have done a lot of research work in the field of SLS, and have achieved fruitful results in equipment development, process and material development. Germany’s EOS has also done a lot of research work in this field and developed a series of molding equipment.
There are also a number of units in China that conduct research on SLS, such as Huazhong University of Science and Technology, Nanjing University of Aeronautics and Astronautics, Northwestern Polytechnical University, North University of China, and Beijing Longyuan Automatic Molding Co., Ltd., etc., and have also achieved many major achievements, such as Nanjing Aerospace. The RAP-I laser sintering rapid prototyping system developed by the university and the commercial equipment of AFS-300 laser rapid prototyping developed by Beijing Longyuan Automatic Molding Co., Ltd.
Selective laser sintering is a method in which a laser selectively stratifies a solid powder and superimposes the solidified layer of the sintered layer to form a desired shape. The entire process includes the establishment of CAD models and data processing, powdering, sintering and post-processing.
The working principle of SLS technology 3D printer.

The whole process device consists of a powder cylinder and a molding cylinder. During operation, the powder cylinder piston (powder piston) rises, and the powder is evenly layered on the molding cylinder piston (working piston) by the powder roller, and the computer is based on the prototype slicing model. The two-dimensional scanning trajectory of the laser beam is controlled to selectively sinter the solid powder material to form a layer of the part. After the powder is completed, the working piston is lowered by one layer and the powder spreading system is coated with new powder. The laser beam is controlled to scan and sinter the new layer. This cycle reciprocates and layers are stacked until the three-dimensional part is formed. Finally, the unsintered powder is recovered into a powder cylinder and the molded part is taken out. For metal powder laser sintering, the entire table is heated to a certain temperature before sintering, which reduces thermal deformation during molding and facilitates layer-to-layer bonding.
Characteristics of SLS technology
Compared with other 3D printer technologies, the most outstanding advantage of SLS is that it uses a wide range of molding materials. Theoretically, any powder material capable of forming an interatomic bond after heating can be used as a molding material for SLS. At present, materials that can be successfully processed by SLS include paraffin, polymer, metal, ceramic powder and composite powder materials thereof. Due to the variety of SLS molding materials, material savings, extensive distribution of molded parts, suitable for a variety of applications, and SLS without the need to design and manufacture complex support systems, SLS is becoming more widely used.
Summary: SLS Technology
Among the 3D printer technologies, metal powder SLS technology is a hot spot in recent years. The realization of the use of high-melting-point metal direct-sintered molded parts is difficult to manufacture high-strength parts by conventional cutting methods, and is of particular importance for the wider application of rapid prototyping technology. Looking into the future, the research direction of SLS-shaped technology in the field of metal materials should be the sintering of metal parts of unit systems, the sintering of multi-alloy parts, the laser sintering of advanced metal materials such as metal nano-materials, amorphous metal alloys, etc. It is especially suitable for the molding of micro-components of cemented carbide materials. In addition, parts with functional gradients and structural gradients are sintered according to the specific function and economic requirements of the part. We believe that with the mastery of laser sintering metal powder forming mechanism, the acquisition of optimal sintering parameters for various metal materials, and the emergence of special rapid prototyping materials, the research and reference of SLS technology will surely enter a new realm. .
The principle of LOM technology 3D printer
LOM (Laminated Object Manufacturing), LOM is also known as lamination method. It is made of sheet material (such as paper, plastic film or composite material). Its forming principle is shown in the figure. Laser cutting system According to the cross-sectional contour data extracted by the computer, the paper coated with hot melt on the back is laser-cut out of the inner and outer contours of the workpiece. After cutting a layer, the feeding mechanism superimposes a new layer of paper, and the cut layers are bonded together by a hot-adhesive device, and then cut, so as to be layer-by-layer cut and bonded, and finally become a three-dimensional workpiece. . LOM commonly used materials are paper, metal foil, plastic film, ceramic film, etc. In addition to making molds and models, this method can also directly manufacture structural parts or functional parts.
Lom technology features
The technology is characterized by reliable work, good model support, low cost and high efficiency. The disadvantage is that the front and back processing is time consuming and laborious, and the hollow structural members cannot be manufactured.
Forming material: fiber paper coated with heat sensitive glue;
Product performance: equivalent to high-grade wood;
Main use: Rapid manufacture of new product prototypes, models or wood molds for casting.
The principle of FDM technology 3D printer
FDM (Fused Deposition Modeling) method, which uses a filamentous material (paraffin, metal, plastic, low melting point alloy wire) as a raw material, and uses electric heating to heat the wire to a temperature slightly higher than the melting temperature (about The melting point is 1 °C). Under the control of the computer, the nozzle moves in the xy plane, and the molten material is coated on the workbench. After cooling, a section of the workpiece is formed. After the layer is formed, the nozzle is moved up to a height. The next layer of coating is applied so that the three-dimensional workpiece is formed layer by layer.
Characteristics of FDM technology
The technology is less polluting and the material can be recycled for the forming of small and medium-sized workpieces. The figure below shows the FDM forming schematic.
Forming material: solid filamentous engineering plastics;
Product performance: equivalent to engineering plastics or wax molds;
Main uses: plastic parts, wax molds for casting, prototypes or models.
Ps: At present, the common personal 3D printers in China use this technology.
In addition to the above four most familiar technologies, many technologies have also been put into practical use, such as three-dimensional printing technology, light shielding process, direct shell method, direct sintering technology, holographic interference manufacturing, etc., which will not be described in detail here. (In fact, I don’t know much about it. Hey)
l Advantages of 3D printer technology
Fast manufacturing
3D printer technology is an effective means for complex prototypes or parts manufacturing in parallel engineering, enabling product design and mold production to be synchronized, thereby improving enterprise R&D efficiency, shortening product design cycle, and greatly reducing the cost and risk of new product development. For products with small outer dimensions, special-shaped products are especially suitable.
Integration of CAD/CAM technology
Design and manufacturing integration has always been a difficult point. Computer-aided technology (CAPP) is not able to seamlessly interface with CAD and CAM at this stage. This is one of the difficulties that has restricted manufacturing information technology. Rapid prototyping technology integrates CAD, CAM, laser technology, numerical control technology, chemical engineering, material engineering and many other technologies, making the concept of design and manufacturing integration perfect.
Fully reproduce 3D effects
After the rapid prototyping and manufacturing of the parts, the three-dimensional shape can be completely reproduced. Whether the curved surface of the outer surface or the shaped hole of the inner cavity can be completed accurately and accurately, it is basically no longer necessary to repair with external equipment.
a wide variety of materials
So far, there are many kinds of materials used in various types of 3D printer equipment. Resin, nylon, plastic, paraffin, paper and metal or ceramic powder basically meet the mechanical performance requirements of most products.
Create significant economic benefits
Compared with the traditional machining methods, the development cost is saved by more than 10 times. Similarly, the rapid prototyping technology shortens the product development cycle of the enterprise, and the problem of repeatedly modifying the design plan in the new product development process is greatly reduced, and the problem is basically eliminated. The economic benefits of modifying the mold are obvious.
Wide range of application industries
After years of development, 3D printer technology has basically formed a system in technology. Similarly, the applicable industries are gradually expanding, from product design to mold design and manufacturing, materials engineering, medical research, culture and art, and architectural engineering. The gradual use of 3D printer technology has made the 3D printer technology have broad prospects.
l Market application of 3D printer technology
Constantly improving the application level of 3D printing technology is the focus of promoting this technology development.
At present, 3D printing technology has been widely used in industrial modeling, mechanical manufacturing, aerospace, military, construction, film and television, home appliances, light industry, medicine, archaeology, culture and art, sculpture, jewelry and other fields. And with the development of this technology itself, its application field will continue to expand. The practical application of 3D printing technology mainly focuses on the following aspects:
Product design field
Application in the new product design process 3D printing technology has established a new product development model for industrial product design and development personnel. The use of 3D printing technology can quickly, directly and accurately transform design ideas into functional models (samples) that not only shorten the development cycle, but also reduce development costs, and also enable enterprises to occupy in the fierce market competition. First opportunity.
Architectural design field
The traditional production methods of building models are gradually unable to meet the requirements of high-end design projects. Full digital reproduction of undistorted stereoscopic display and wind tunnel and related testing standards, many large-scale facilities or venues of many design agencies now use 3D printing technology to build accurate architectural models for performance display and related testing, 3D printing technology The advantages and unparalleled realistic effects are recognized by the designer.
Mechanical manufacturing
Due to the characteristics of 3D printing technology, it has been widely used in the field of mechanical manufacturing, and is used to manufacture single-piece and small-volume metal parts. Some special and complicated parts, due to the single piece production, or less than 50 small batches, can be directly molded by 3D printing technology, with low cost and short cycle.
Mold manufacturing field
For example, in the traditional mold manufacturing field such as toy making, mold production time is long and the cost is high. Combining 3D printing technology with traditional mold manufacturing technology can greatly shorten the development cycle of mold manufacturing and increase productivity, which is an effective way to solve the weak links in mold design and manufacturing. The application of 3D printing technology in mold manufacturing can be divided into direct molding and indirect molding. Direct molding refers to the direct deposition of molds by 3D printing technology. Indirect molding is to first produce rapid prototyping parts and then parts. Copy to get the mold you need.
Medical field
In the field of medicine In recent years, people have applied more research on the application of 3D printing technology in the medical field. Based on medical image data, the use of 3D printing technology to make human organ models has great application value for surgery.
Culture and art field
In the field of culture and art, 3D printing technology is mostly used for artistic creation, cultural relics reproduction, digital sculpture and so on.
Aerospace technology
In the aerospace industry, aerodynamic ground simulation experiments (ie, wind tunnel experiments) are an essential part of designing an advanced world-class round-trip system (ie, a space shuttle). The model used in this experiment is complex in shape, high in precision, and streamlined. It uses 3D printing technology and is automatically driven by 3D printing equipment according to the CAD model.

l 3D Printer FAQ
(The problem is what I think, ask myself and answer. If you have any questions you need to answer, you can log in to my website to ask questions)
Is the 3D printer versatile?
A: At least the current 3D printer is not a panacea. Its production products are subject to the constraints of raw materials. If the material science has a breakthrough, it will be more perfect.
Will 3D printers replace traditional manufacturing?
A: It doesn’t seem to be at present. It can change some aspects of the traditional production process to make it more efficient and cost effective.
Can a 3D printer print directly print out color?
A: Many professional and production-grade 3D printers have been able to print out colored items directly. Some 3D printers I know can support 390,000 colors. Personal-grade 3D printers can also produce monochrome items by selecting colored materials.
Why are there thousands of 3D printers and hundreds of thousands?
A: The market for 3D printer products is divided into individual, professional and production grades. The structure and technology and consumption are different, so the price gap is very large.
What is an open source 3D printer?
A: Open source is a product designed by only one company. The core technology of this product is free to open to the outside world, and there is no technical patent for secondary development.
Open source 3D printers have greatly contributed to the development of this industry. Through the DIY research of open source 3D printers, the 3D printer technology can be more mature and the equipment cost is lower.
If you buy a 3D printer, you need to pay attention to those product parameters?
A: 1 printing technology: Different printing technologies directly affect the consumables you can use, which determines the quality of your products.
2 Tray size: The size of the tray that can be made depends on the size of the tray. Generally, the maximum supported item size is slightly smaller than the tray size.
3 molding speed: 3D printer production speed depends on this indicator.
4 Detail Accuracy: Whether the items made by the 3D printer are fine In addition to designing the 3D model, this indicator is also critical. (Can be referenced by the layer thickness and wall thickness indicators of 3D printers)
5 Supported consumables: Different materials directly affect the quality of the items you produce, and the prices of different consumables are also very different.


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