What is 3D printing？

3D printing technology is a machine-derived technology designed by Enrico Dini. It can not only print a complete building, but even print the shape of any desired object in a spacecraft. In fact, 3D printing technology is changing the world.

3D printer is a kind of rapid prototyping technology. It is based on digital model files, using special wax materials, powdered metals or plastics and other bondable materials to construct objects by printing layer by layer. . In the fields of mold manufacturing, industrial design, etc., it is used to manufacture models or for the direct manufacturing of some products, which also means that this technology is becoming popular.

The technical principle of 3D printing

Using a printer is like printing a letter: tap the "Print" button on the computer screen, and a digital file is sent to an inkjet printer, which sprays a layer of ink onto the surface of the paper to form a pair of two Dimensional image.

In 3D printing, the software completes a series of digital slices through computer-aided design (CAD) technology, and transmits the slice information to a 3D printer, which stacks successive thin layers until a solid object is formed. The biggest difference between a 3D printer and a traditional printer is that the "ink" it uses is a real raw material.

There are many forms of stacking thin layers. Some 3D printers use an "inkjet" method.

For example, an Israeli 3D printer company called Objet uses a printer nozzle to spray a very thin layer of liquid plastic material on a mold tray. This coating is then exposed to ultraviolet light for treatment. Then the mold tray is lowered a very small distance for the next layer to be stacked.

Another company, Stratasys, headquartered in Minneapolis, USA, uses a technology called "fusion molding". The entire process is to melt plastic in the nozzle, and then form a thin layer by depositing plastic fibers.

There are also some systems that use powder particles as the printing medium. The powder particles are sprayed on the mold tray to form a very thin powder layer, which is then cured by the sprayed liquid binder. It can also be cast into a specified shape using a technique called "laser sintering". This is exactly the technology used by the German EOS company on its stacking process manufacturing machine. The Swiss company Arcam uses a stream of electrons in a vacuum to melt powder particles.

What can 3D printing do?

Print clothing

As early as 2013, the Victoria's Secret Fashion Show had already begun to display the clothing made by 3D printing technology. At that time, the supermodel indsayEllingson was wearing a pair of wings, corset and headdress printed by a 3D printer. It is still amazing to this day. .

Printed human prostheses

3D printing technology can also print out prostheses suitable for the human body, helping amputees to treat body loss, and the human limbs made by today's 3D printing technology can almost achieve the level of fake and real.

Print anything you want

In fact, up to now, almost all common objects in life can be manufactured with 3D printing technology.

For example, automobiles can already be made using 3D printing technology. At present, major engine manufacturers even try to use 3D printing technology to make automobile engines.

Another example is our house. A construction company has already exhibited houses made with 3D printers. Although they don’t look very good-looking, the cost is extremely low. It only costs less than 50,000 yuan, and you can have your own three parties. One hall, provided that the piece of land belongs to you. In addition to houses and cars, 3D printing can also make candies, completely edible candies, without worrying about any problems, and even artworks, guns, etc. can be printed.

Types of 3D printing technology

SLA-Stereo lithography Appearance

SLA is the earliest practical rapid prototyping technology, and the raw material is liquid photosensitive resin.

The working principle is: Put the liquid photosensitive resin into the processing tank. At the beginning, the height of the worktable is different from the liquid level by the thickness of a cross-sectional layer. 

The focused laser scans the photosensitive resin surface according to the cross-sectional contour and is scanned to The photosensitive resin will gradually solidify, so that a solid resin workpiece with the same cross-sectional profile can be produced.

At this time, the workbench will drop by the height of the cross-section layer, and the cured resin workpiece will be submerged by the photosensitive resin in the liquid state that has not been irradiated by the laser around the processing tank, and the laser will start to follow the cross-section of the next layer. 

When scanning the contour of the workpiece, the newly cured resin will stick to the layer below. After such a cycle, the entire workpiece processing process is completed. Then the finished workpiece is polished, electroplated, painted or colored to obtain the required product.

advantage:

1. Light-curing molding method is the earliest rapid prototyping manufacturing process with high maturity;

2. The prototype is directly made from the CAD digital model, with fast processing speed, short product production cycle, no cutting tools and molds;

3. It can process prototypes and molds that are complex in structure or difficult to form using traditional methods;

4. Visualize the CAD digital model and reduce the cost of error repair;

5. Provide samples for the experiment, which can verify and check the results of computer simulation calculations;

6. It can be operated online and remotely controlled, which is conducive to the automation of production;

shortcoming:

1. The cost of SLA system is high, and the cost of use and maintenance is too high;

2. The SLA system is a precision equipment that needs to operate on liquids and has harsh requirements for the working environment;

3. Molded parts are mostly resin, with limited strength, rigidity and heat resistance, which is not conducive to long-term storage;

4. The software system is complicated to operate and difficult to get started; the file format used is not familiar to the majority of designers;

5. As the resin shrinks during curing, stress or deformation will inevitably occur;

SLS-Selective Laser Sintering

Selective laser sintering is the use of laser to selectively sinter solid powder in layers, and superimpose the solidified layers of sintering molding to form parts with the required shape. The whole process includes the establishment of CAD model and data processing, powder spreading, sintering and post-processing.

The entire process device consists of a powder cylinder and a forming cylinder. The powder cylinder piston (powder feeding piston) rises during operation, and a layer of powder is evenly spread on the forming cylinder piston (working piston) by the powder spreading roller. The computer slices the model according to the prototype. Control the two-dimensional scanning trajectory of the laser beam to selectively sinter the solid powder material to form a layer of the part.

After a layer of powder is completed, the working piston is lowered by one layer thickness, and the powder spreading system is spread with new powder. Control the laser beam to scan the sintered new layer. This cycle repeats, layer by layer, until the three-dimensional part is formed. Finally, the unsintered powder is recycled into the powder tank, and the molded part is taken out. For metal powder laser sintering, before sintering, the entire worktable is heated to a certain temperature, which can reduce thermal deformation during molding and facilitate the bonding between layers.

advantage:

1. SLS uses a wide range of molding materials. At present, the materials that can be processed by SLS are paraffin, polymer, metal, ceramic powder and their composite powder materials. The performance distribution of the molded parts is widely suitable for a variety of purposes.

2. SLS does not need to design and manufacture complex support systems.

shortcoming:

The surface of the workpiece after the SLS process is rough, and the post-treatment process to enhance the mechanical properties is also more complicated. (Roughness depends on the diameter of the powder)

LOM-Laminated Object Manufacturing

Using sheet materials (such as paper, plastic film or composite materials) as raw materials, the laser cutting system uses a laser to cut the inner and outer contours of the workpiece on the paper with hot melt glue on the back according to the cross-sectional contour data extracted by the computer.

After cutting a layer, the feeding mechanism superimposes a new layer of paper, and uses a hot-adhesive device to bond the cut layers together, and then cuts, so that layer by layer is cut and bonded, and finally becomes a three-dimensional workpiece . Commonly used materials for LOM are paper, metal foil, plastic film, ceramic film, etc. In addition to making molds and models, this method can also directly manufacture structural or functional parts.

advantage:

1. Reliable work, good model support, low cost and high efficiency. The disadvantage is that the pre- and post-processing is time-consuming and laborious, and hollow structural parts cannot be manufactured.

2. Forming material: fiber paper coated with thermal adhesive;

3. Parts performance: equivalent to high-grade wood;

4. Main purpose: rapid production of new product samples, models or wooden molds for casting.

FDM-Fused Deposition Modeling

This method uses filamentous materials (paraffin, metal, plastic, low melting point alloy wire) as raw materials, and uses electric heating to heat the wire to slightly higher than the melting temperature (about 1°C higher than the melting point). Under the control of the computer, The nozzle moves in the xy plane to coat the molten material on the worktable. After cooling, a layer of the workpiece is formed. After one layer is formed, the nozzle moves up to a height to coat the next layer (also written in the literature) The worktable is lowered by the height of a cross-section layer, and then the nozzle prints the next cross-section), so that the thermoplastic filamentous material will be sprayed and printed on the worktable layer by layer to complete the required cross-sectional profile. Until the final completion.

The FDM process can choose a variety of materials for processing, including polycarbonate, engineering plastics, and mixed materials of the two.

This process does not require lasers, is simple to use and maintain, and has low cost. Prototypes made of ABS are widely used in product design, testing and evaluation because of their high strength.

In recent years, PC, PC/ABS, PPSF and other higher-strength forming materials have been developed, making it possible to directly manufacture functional parts with this process. Because this process has some significant advantages, the process is developing extremely rapidly, and the FDM system currently has the largest share of the installed rapid prototyping systems in the world.

advantage:

1. The technology has low pollution, and the material can be recycled, and it is used for the forming of small and medium-sized workpieces;

2. Forming material: solid filament engineering plastic;

3. The processing of bottle-shaped or other hollow-shaped workpieces can be achieved by using water-soluble support materials to separate from the workpiece;

4. Part performance: equivalent to engineering plastic or wax mold;

5. Main uses: plastic parts, wax patterns for casting, samples or models.

shortcoming:

1. The processing accuracy is lower than that of the SLA process;

2. The surface of the workpiece is relatively rough;

3. The processing time is longer.

3D printing

3D printing, a 3D printer using 3DP technology uses standard inkjet printing technology. By laying a liquid connector on a thin layer of powder, each part is created layer by layer by printing cross-sectional data to create a three-dimensional solid model. The sample model formed by technical printing has the same color as the actual product, and the color analysis result can be directly depicted on the model. The model sample conveys a large amount of information and is currently the most mature color 3D printing technology.