3D printing (3DP) technology, also known as additive manufacturing or additive manufacturing (AM) technology. It refers to the technology of generating 3D solid by adding materials layer by layer through continuous physical layer superposition, which is different from the traditional material removal processing technology.

1、 SLA light curing 3D printer

SLA technology is the first generation of light curing mainstream technology. It has many translation terms in China, such as stereo lithography, stereo printing, light modeling, and so on. SLA forming technology is not only the earliest and commercialized rapid prototyping technology in the world, but also one of the most in-depth and widely used rapid prototyping technologies.

The basic principle of SLA forming technology is to use ultraviolet laser (355 nm or 405 nm) as the light source, and use the galvanometer system to control the laser spot scanning. The laser beam draws the first layer shape of the object on the surface of the liquid resin, and then the production platform drops a certain distance (between 0.05 and 0.025 mm), and then immerses the curing layer in the liquid resin. After repeated, the solid printing is finally completed.

2、 DLP light curing 3D printer

Digital Light Processing (DLP) came into being more than ten years after SLA technology appeared. It is also the second generation of light curing molding technology recognized by the industry, and has a development history of more than 20 years. DLP technology is a rapid prototyping technology that uses a projector to cure photosensitive polymer liquid layer by layer, thus creating 3D printing objects.

This molding technology first uses slicing software to slice the model, and the projector plays slides. Each layer of image will produce photopolymerization reaction and solidify in the area where the resin layer is very thin, forming a thin layer of the part. Then the molding table moves one layer, and the projector continues to play the next phantom film, and continues to process the next layer. This cycle, until the end of printing, so not only the molding accuracy is high, but also the printing speed is very fast.

3、 LCD light curing 3D printer

In fact, LCD light curing molding technology has just emerged in 2013. The characteristic is that the core components of open source technology are relatively cheap, but the core components are consumables.

Let's talk about his forming principle first. In fact, compared with DLP molding technology, the simplest understanding is that the light source of DLP technology is replaced by LCD, and the others are basically the same. The imaging principle of LCD panel is to use optical projection to pass through the red, green and blue primaries filter to filter out infrared and ultraviolet rays (infrared and ultraviolet rays have a certain damage effect on the LCD panel), and then project the three primaries through the three LCD panels to synthesize projection imaging.

Because the molding technology requires the use of high-power ultraviolet light irradiation, and the use of a very small amount of ultraviolet light for curing and molding. The LCD screen itself is afraid of ultraviolet radiation, and it will rapidly age after being exposed. At the same time, the core component should not only withstand the test of heat resistance and high temperature heat dissipation, but also withstand several hours of high-strength baking of dozens of watts of 405 LED lamp beads, so its service life is very short. If it is used frequently, its core component LCD screen will often be damaged within one to two months. If it is not used properly, it may need to be replaced within a few hours.

4、 FDM (molten deposition) 3D printer

Fused Deposition Modeling (FDM) is a 3D printing technology developed after LOM process and SLA process. This technology was invented by Scott Crump in 1988, and then Scott Crump founded Stratasys. In 1992, Stratasys launched the world's first 3D printer based on FDM technology - "3D Modeler", which also marks the commercial stage of FDM technology.

Principle: heat and melt the filamentous hot-melt material, and extrude the material through the extruder with micro-nozzle. The nozzle can move in the direction of the X axis, while the workbench moves in the direction of the Y axis and the Z axis (of course, the mechanical structure design of different equipment may be different). The molten wire will be bonded with the previous layer of material immediately after being extruded. After a layer of material is deposited, the workbench will drop a thickness by a predetermined increment, and then repeat the above steps until the workpiece is fully formed.

Advantages and disadvantages of FDM

Advantages: the whole system is simple in construction principle and operation, low in maintenance cost and safe in operation. The non-toxic raw materials can be used, and the equipment system can be installed and used in the office environment. The process is clean, simple, easy to operate and does not produce garbage. The unique water-soluble support technology makes it easy to remove the support structure, and can quickly build bottle-shaped or hollow parts and one-time assembly structural parts. Raw materials are provided in the form of material rolls, which are easy to handle and replace quickly. A variety of materials can be selected, such as engineering plastics ABS, PC, PPSF and medical ABS in various colors.

Disadvantages: the forming accuracy is relatively low compared with SLA process, with an accuracy of 0.178mm. The forming surface finish is not as good as SLA process. The forming speed is relatively slow.

5、 Difference between SLA and DLP

The consumables used by SLA and DLP are photocurable resins, and the principles of the two molding technologies are very similar. Therefore, the industry often likes to treat these two technologies as similar technologies when studying the 3D printing molding technology, but there are still differences between them in many aspects.

1. Mechanical structure. DLP uses digital light source of projector, while SLA uses ultraviolet laser light source.

2. Forming speed. Because the working principle of DLP is to use digital micro-mirror elements to project the product cross-section onto the surface of liquid photosensitive resin, so that the irradiated resin will be light-cured layer by layer, so the printing speed is very fast; SLA, on the other hand, uses a laser beam to draw objects on the surface of liquid resin, from point to line, and then from line to surface to form a solid model, so its work efficiency is far lower than that of the former.

3. Printing accuracy. Theoretically, the accuracy of both can reach the print accuracy of micron level. The minimum spot size that DLP can achieve is ± 50 microns, while the minimum spot size that SLA can achieve is ± 100 microns. Due to the high power of SLA laser, it is easy to lead to large forming spot error. In addition, the requirements of micron precision for the main components of SLA laser and galvanometer are very high. Generally, it is difficult for domestic oscillators to meet the requirements, and the cost will increase significantly to reach the micron level. In contrast, DLP is easier to reach the micron level. To sum up, the printing accuracy of DLP is higher than that of SLA.

4. Print size. DLP is limited by the resolution of digital optical mirror, and can only print products with smaller size compared with SLA.

In general, these two technologies have their own advantages and disadvantages, but in actual use, DLP 3D printer is obviously more advantageous.