What are the main types of 3D printing?

The most common 3D printing technology – Fused Deposition Technology (FDM)

The production process of fused deposition technology (FDM)

The computer-controlled heating nozzle on the machine moves in the plane according to the horizontal layering data. The wire gets heated, melted, extruded from the nozzle, and bonded to the workbench, and then it rapidly cools and solidifies. After completing one layer, the workbench lowers the height of one layer and then continues the modeling of the next layer. The process repeats until to finish the entire project. The thickness of each layer is up to the diameter of the nozzle for wire extruding.

The key to the FDM process is to keep the temperature of molten molding material just above the freezing point, usually about 1°C above. The common materials are ABS, synthetic rubber, cast wax, and polyester thermoplastics.

 The process of FDM is 3D CAD model design, CAD model approximate process, modeling at layered STL file, and post-processing.

Materials used in Fused Deposition Technology (FDM)

FDM printing materials are generally thermoplastic materials, such as wax, ABS, PC, nylon, etc., which are in reel filament with low material cost. Compared to processes using powder and liquid materials, the wire is cleaner, easier to replace, store, and has no pollution caused by liquid and powder.​​

Advantages of Fused Deposition Technology (FDM):

A wide range of materials is available for FDM. In general, thermoplastic materials like paraffin, plastic, nylon, etc., can be fused deposition manufacturing with proper modification.

the raw material is non-toxic and has no pollution during the process. The small space-occupied equipment system can be widely installed and used.

Widley for models with cavities and holes or other complicated designs.

The raw material has no chemical change during the process and has little chance for warping deformation.

The high utilization rate of raw materials and long material life.

It is easy to remove the supports to separate the model without chemical cleaning.

Disadvantages of Fused Deposition Technology (FDM):

Only for medium and small plastic parts.

It has stripes on the model surface with low precision on the surface.

The strength of the entire section direction is relatively weak.

3D Printing Technology supports Metals Printing – Selective Laser Sintering (SLS)

The specific sintering process is also different due to the materials.

The process of powder material sintering

Pre-processing

Design the 3D CAD model, convert STL data and input it into the system.

Powder layer laser sintering and superposition

The equipment sets specific manufacturing parameters according to the structural characteristics of the prototype, and the machine automatically completes the layer-by-layer powder sintering and superposition process. The finished prototype needs to be cooled to below 40°C in the molding cylinder for post-processing.

Post-processing

It needs to be reinforced with wax or resin during the post-processing because of the weak strength.

Metal parts indirect sintering process

The process includes the SLS prototype production, powder sintering, and metal infiltration post-processing.

The key to the process is how to choose a reasonable powder ratio and parameter to realize the design with high precision during the sintering process.

Direct manufacturing process of metal parts by SLS process

 CAD model – layered slicing – laser sintering (SLS) – RP prototype parts – metal parts.

 Materials for the SLS

The printing consumables currently available for SLS technology include nylon powder, PS powder, PP powder, metal powder, ceramic powder, resin sand, and coated sand.

Selective Laser Sintering (SLS) Advantages:

In theory, any powders that can form interatomic bonds after heating can be a molding material for SLS.

The process has nothing to do with the complexity of the design.

The sintered powder can be reused without waste.

 No supporting structure is required.

Compared with other molding methods, it can produce molds of high strength.

Disadvantages of Selective Laser Sintering (SLS):

The loose, porous or internal stress prototype structure model is easy for shape change in the process.

The post-processing for ceramic and metal parts is difficult.

Preheating and cooling are required.

The molding surface is rough and porous and is limited by the size of powder particles and the laser spot.

The molding process produces toxic gas and dust, which pollutes the environment.

The most mature 3D printing technology – Stereolithography (SLA)

 Stereolithography (SLA) molding process

  First, design a three-dimensional solid model through CAD, use discrete programs to slice the model, design scanning path, and the generated data will accurately control the movement of the laser scanner and the lifting platform;

  Secondly, the laser beam is irradiated to the surface of the liquid photosensitive resin according to the designed scanning path through the scanner controlled by the numerical control device, so that after a layer of resin in a specific area of ​​the surface is cured, when the layer is processed, a section of the part is generated;

 Then, the lifting table descends a certain distance, and the solidified layer is covered with another layer of liquid resin, and then the second layer of scanning is performed. ,

   Finally, after the prototype is removed from the resin, the final curing is carried out, and then the required product is obtained by polishing, electroplating, painting, or coloring.

Stereolithography (SLA) materials

Only liquid photosensitive resins can be raw material to SLA currently.

Third, the advantages and disadvantages of stereo light curing technology (SLA)

Advantages of Stereolithography (SLA):

The light-curing molding method is the most mature earliest rapid prototyping manufacturing process.

The prototype is directly made from the CAD digital model, with fast processing speed and a short production cycle, without cutting tools and molds.

 It can process prototypes and molds with complex structures or shapes that are difficult to form using traditional methods. 4. Visualize the CAD digital model and reduce the cost of error repair.

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

It can be operated online and controlled remotely and is conducive to automotive production.

Disadvantages of Stereolithography (SLA):

The SLA system is expensive, and the use and maintenance costs are too high.

The SLA system is a precision device that needs to operate with liquids and has strict requirements on the working environment.

Most of the molded parts are resin, with limited strength, rigidity, and heat resistance, which is not conducive to long-term storage.

The complicated algorithms pre-process and driving software lead to high costs in correlation with the processing effect.

The software system is complicated and hard to learn. The file format used is not familiar to most designers.

3D printing technology that can print color – three-dimensional printing (3DP)

The production process of three-dimensional printing (3DP)

The manufacturing process: model design, printing, and post-processing.

First, the designers use CAD or other production software to design the model, convert the designed model format to STL format, then slice and input the data into the printer.

Secondly, at the beginning of printing, a layer of powder material is evenly spread on the working table of the molding room. Then the nozzle selectively prints the bonding material onto the laid powder according to the shape of the prototype cross-section to form it. The powder in the solid area bond together to shape a cross-sectional profile. After printing one layer, the table falls to the height of one cross-section and then repeats the process till the whole design is finished.

 Finally, after printing the prototype, the staff takes the prototype out of the workbench and undergoes high-temperature sintering, hot isostatic pressing, and other processes for post-processing.

Materials used in three-dimensional printing (3DP)

The printing consumables that 3DP technology can currently use include gypsum powder, ceramic powder, metal powder, etc.

Adhesives are available in monochrome and color and can print full-color products like a color printer.

Third, the advantages and disadvantages of three-dimensional printing (3DP)

Three-dimensional printing (3DP) advantages:

fast molding speed, low price material is suitable for desktop rapid prototyping equipment.​​

Adding pigments to the binder can make color prototypes which is one of the most competitive features of this process.​​

The molding process does not require support, and the removal of excess powder is more convenient, especially suitable for prototypes with complex inner cavities.​​

Disadvantages of 3DP:

Low strength, can only do conceptual models, not functional tests.

WKproto is a professional rapid prototyping and low-volume production manufacture specializing in 3D printing, CNC machining, and Vacuum Casting. Our factory and parter factories enable rapid prototyping of designs from our customers and low volume production for market verification.

We have three factories. 3D printing factory meets the demands of most 3D printing services with 100 SLA machines, 10 SLS machines, 10 MJF machines, 10 SLM machines, and 20 FDM machines. CNC machining factories for processing metals, plastic and more materials with more than 200 machines for CNC milling/CNC lathes/EDM / Wire EDM and the Vacuum Casting factory is for low volume production for ABS、PC、PP、PE、PA、POM、PMMA、PVC.