[3D Printing Knowledge] Beginner's Guide: Comparison and Principles of Five Common 3D Printing Technologies (Updated 2021/09)
Compared to mold making, in-house manufacturing in 3D printing significantly reduces costs and allows for more flexible and rapid prototyping. Currently, the three most commonly used 3D printing technologies are FDM (Fused Deposition Modeling), SLA / DLP / LCD (Photopolymerization), and SLS (Laser Powder Sintering); in addition, there are more advanced technologies such as MJF ( Multi-Jet Fusion ) and Polyjet ( Color Inkjet ), among other new types of 3D printing. Beginners, don't worry, let us guide you through a simple and easy-to-understand explanation!
First, grasp the two main principles:
I. Construction and Modeling
II. Supporting Structure
3D printing technology must consider the effects of gravity in its forming process. Imagine an object suspended in mid-air; it will fall. Therefore, when 3D printed materials encounter suspended structures, additional auxiliary materials are needed to create the suspended body to prevent the material from falling during forming. This structure is usually called a support material, and its usage and materials vary depending on the printing method. SLS (laser powder sintering) technology typically does not require this support structure, which will be explained below.
(The image shows a schematic diagram of the support structure and body of two different 3D printing technologies: hot melt stacking (left) and photopolymerization (right). The body of the object is the shell of an electric drill.)
III. Three 3D printing technologies:
(I) FDM (Fused Deposition Modeling) Technology and Applications
FDM ( Film-Derivative Manufacturing) is the most common 3D printing technology (or FFF ). Its 3D printing material is typically a thermoplastic polymer fed on a spool, commonly referred to as filament; the filament width is standardly 1.75mm or 3mm (or 2.85mm), which is then extruded through a heated nozzle. The heated nozzle is mounted on a moving rod, allowing the extruded material to be stacked layer by layer within the printing area, cooled, and solidified on a platform to complete the object. 3DM offers FDM hot melt stacking 3D printers under brands such as Ultimaker , BCN3D , Prusa , and Snapmaker .FDM is generally suitable for office environments, is easy to operate and maintain, and does not require post-processing with chemicals. The available raw materials are diverse, relatively inexpensive, easy to use, and can be stored for extended periods. While FDM technology sometimes requires a support structure, this can be effectively streamlined by considering CAD modeling and design. The market offers two main types of printheads: the earliest single-head and the latest dual-head. Using dual printheads allows the simultaneous application of two materials in a single print run; by using two different types of compatible materials (e.g., soluble water-based PVA support material), products with mechanical functions such as latches and rotations can be directly printed; or by using a peelable material, the product has a smoother surface, higher texture, and reduced post-processing.
( 
(The image shows the Ultimaker 3D printer paired with AquaSys water-soluble support filaments , providing internal support for the 3D printed object.)
(In industrial applications, FDM- type hot melt stacking 3D printers are typically used in combination to simultaneously print parts, components, or product iterations.)
.advantage:
• Easy to operate and maintain. • Relatively inexpensive compared to other 3D printing methods. • Easy to keep the environment clean, no additional chemicals required. • The device is small enough to fit on a desktop. • The entire process takes place inside the machine, requiring no additional equipment. • A variety of materials are available, and it has engineered features. • The relatively low price of the equipment helps shorten product delivery time.
(Using Ultimaker with water-soluble PVA support material, fully movable structures can also be printed. The image in the background shows the 3D printed finished product before the support material dissolves.)
.shortcoming:
The surface typically has a textured, overlapping pattern. Print quality affects the physical strength of the finished product.
(Fine layered textures from FDM 3D printing .)
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UV curing is suitable for intricate parts or jewelry designs with fine details. It almost always requires a support structure and can be used in well-ventilated small studios or technical laboratories. Post-processing is more complex than FDM , typically requiring cleaning with alcohol or, if necessary, additional UV curing to enhance the curing process. The resin raw materials are somewhat pungent, flammable, and have a short shelf life; new and old resins cannot be mixed, and the material price is relatively higher than the other two technologies. However, UV-cured products have the smoothest surface finish, making them suitable for prototyping delicate shapes or small parts.
(Finished product that has not yet been removed from the printing platform after completion using the Phrozen photopolymer 3D printer .)
.advantage:
Suitable for parts with complex shapes and fine surfaces. Finished products have smooth surfaces with minimal build-up. Provides optimal detail, making it ideal for small items. The equipment is enclosed, integrated, and easy to operate. It can print on materials with various properties.
(The armored robot, assembled using a DWS 3D printer with SLA technology , boasts numerous details and a smooth surface.)
.shortcoming:
The raw materials often have a chemically irritating or pungent odor and are flammable. Post-processing often requires the additional use of alcohol. The material is sticky, requiring careful attention to environmental cleanliness. A supporting structure is usually needed, and post-processing is time-consuming. Compared to the other two technologies, the printable volume is relatively small. The finished product is generally less robust than the other two technologies. Hollow-designed parts require small holes to allow uncured resin to flow out.
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LCD
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DLP
• High-quality Hunter photopolymer 3D printing test
SLA
3D printing of ultra-realistic machine models
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DLP
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SLA
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SanDiMa mainly offers photopolymer 3D printers under brands such as Phrozen , Anycubic , Prusa , and Flashforge .
(III) SLS (Laser Sintering) Technology and Applications
SLS technology uses powdered polymers as the raw material for 3D printing . The powder is poured into the machine, where a thin layer of powder is spread back and forth over the printing area. Then, laser light is used to fuse the material, and the printing is completed by slight height adjustments. Because the powder printing material fills the entire internal space, there is no need for supporting structures to assist in the molding process (since the entire structure is a dense powder before printing, there is no problem of hollow material falling off). Unused powder can be sieved through specialized equipment and then mixed with new powder for reuse.
SLS technology is suitable for designs with complex structures, high mobility, and numerous suspended details. The finished product has a matte finish and is less prone to texture stacking. In terms of initial setup and maintenance, SLS is the most expensive of the three 3D printing technologies, and the equipment used is relatively more difficult and complex than the aforementioned FFF and LCD technologies. It is recommended to use the entire internal printing volume of the machine each time a 3D print is performed to avoid wasting powder.
(Staff are processing excess powder after Sinterit printing.)
.advantage
The finished product has a matte, finely textured finish with minimal graining. The parts offer high articulation and mechanical strength .
No supporting structure or materials are required during printing. Some materials have high temperature resistance and chemical resistance. Finished products are generally more robust than those produced using the other two techniques.
No supporting structure or materials are required during printing. Some materials have high temperature resistance and chemical resistance. Finished products are generally more robust than those produced using the other two techniques.
( SLS technology is suitable for creating complex mechanical structures and can be formed in one piece in a single 3D print.)
.shortcoming
The equipment is relatively large. Masks must be worn during post-processing to prevent dust inhalation. There are limited choices in material types and colors. The equipment and materials are relatively expensive, and initial training is required for operation and maintenance. Post-processing and powder recycling are necessary.
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IV. Key Points Summary
SLA ( Silicon Lamination) technology is ideal for printing small objects, figurines, shaped objects, jewelry, etc. with intricate details; the finished product has a smooth surface and can display complex textures, with less physical and mechanical stress compared to the other two technologies.
SLS laser powder sintering offers the best mechanical and functional properties, emphasizing industrial prototyping applications. It produces a matte finish, requires no support, and the finished product is relatively robust and durable. However, it is relatively difficult to operate and requires wearing a mask to remove the powder.
Each of the three technologies has its own strengths, and there is no inherent good or bad among them. As long as they are designed properly, they can all 3D print movable structures and flexible materials. These desktop 3D printing machines are the right size to be used for rapid prototyping within the company, effectively reducing development time and costs.
V. Advanced Techniques
With the basic concepts above, you should now understand the operating principles of photopolymerization and SLS powder sintering. In recent years, these two technologies have also given rise to new 3D printing capabilities, namely PolyJet (color inkjet) and MJF (multi-jet melting):
PolyJet (color inkjet)
PolyJet uses resin directly as inkjet and employs a photocuring molding principle to cure the inkjet immediately after it is sprayed by rapid light exposure, completing 3D printing through layer-by-layer hardening. Because inkjet printing can mix multiple colors, it can achieve full-color 3D printing , material simulation, and even combine the original transparency of resin to represent the appearance and texture of glass, acrylic, etc.
(The new Stratasys 3D printer features a high-speed rotary printing platform with PolyJet technology for inkjet printing followed by photopolymerization, achieving fast-curing full-color results.)
With further technological advancements, PolyJet can not only create up to 500,000 color combinations based on Pantone color swatches, but also print on up to five different resins simultaneously and adjust the hardness of the printed product. This makes PolyJet technology a new option for design, development, and product replacement, with full-color effects achieved directly in a single print!
(From circuit board internals to touchscreen simulation, from mesh casing to plastic base, everything can be completed using Stratasys PolyJet full-color 3D printing technology, allowing samples to instantly leap off the page and into your hand.)
PolyJet technology is primarily developed by Stratasys , a major 3D printing manufacturer, and is currently used in industrial machines with a price tag of over one million units. However, we also provide 3D printing OEM services , allowing you to spend less and do better!
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MJF (Multi-Jet Melting)
The one-piece movable structure and support-free nature of SLS powder printing are amazing features, but there is more than one way to do powder 3D printing . HP's MJF (Multi Jet Fusion) technology is another form of powder printing: after the powder is laid flat on the printing platform, a solvent is sprayed on the forming area and a fine agent is sprayed on the non-forming area to prevent sintering; then infrared light is used to irradiate the area, and the part sprayed with solvent absorbs heat and melts to form a shape, and the 3D printing is completed by continuously repeating layer by layer.
The fine solvent used in non-molded areas of MJF helps to enhance the features and sharp edges of 3D printing , making it suitable for creating intricate structures, such as the sharp, protruding edges of gears, which can also be accurately rendered. MJF finished products are typically black because dark solvents can more effectively absorb heat. Compared to other technologies, it currently offers fewer options for softer solvents, or a deeper understanding of the differences between SLS and MJF is needed .
Three key factors determine the outcome: Laser sintering vs. Multi-jet melting.
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