Photopolymerization molding with Digital Light Processing (DLP) 3D printing technology
This is a projection-based trough-type photopolymerization 3D printing technology. DLP technology is a rapid prototyping technique that primarily utilizes a projector to cure photopolymerizable liquid layer by layer, thereby constructing a 3D-printed object. This manufacturing process first employs slicing software to divide the model into thin slices; the projector then displays each slice, causing a photopolymerization reaction to occur within a very thin region of the resin layer, thereby forming a thin layer of the part. Subsequently, the build platform moves to the next layer, the projector continues to display the subsequent slice, and the curing process proceeds for the next layer. This cycle repeats until printing is complete, resulting in both high dimensional accuracy and exceptionally fast printing speeds.
Unlike traditional SLA (Stereo Lithography) technology, DLP performs a full-layer exposure in a single pass, significantly increasing printing speed.
Three-dimensional printed products fabricated using this technology with high-resolution photosensitive resin compositions exhibit high resolution (both horizontal and vertical feature sizes do not exceed 0.5 mm), high hardness (Shore hardness ≥ 80 HD, tensile strength ≥ 40 MPa), and high printing speed (exposure time: 2.5 s). These products enable the fabrication of highly detailed components, including jewelry—such as dental molds (3D-printed implant guides, casting models, dental prosthetic work models, temporary crowns, bridges, and veneers)—as well as medical and surgical guides, and even customized production of bone implants. Compared to other large-format 3D printers, DLP printing technology is incapable of producing large objects; consequently, it is predominantly employed in desktop 3D printing applications.
Application Areas Reference
Application Features
SLA Stereolithography 3D Printing Technology
Its operating principle involves using a high-power laser to cure the liquid resin within the container, enabling photopolymerization and cross-linking to progress from a point to a line, and then from a line to a plane. After completing one layer of printing, the molding stage moves vertically by one layer height to cure the next layer; this process repeats cyclically, with layers being successively stacked to ultimately form a three-dimensional object.
SLA 3D printing technology is the most traditional and widely used 3D printing technology; it imposes minimal limitations on print size, although its print speed, precision, and detail resolution are generally inferior to those of DLP/LCD 3D printing technologies. SLA 3D printers typically feature larger dimensions, making them well-suited for printing large-scale prototypes or for large-scale production scenarios.
SLA 3D Printing Technology Workflow
Step 1: Design a 3D model using CAD software. The CAD file must be converted into an STL file, which is currently the most commonly used native file format for 3D printing. The STL file is then imported into 3D printing slicer software—such as Cura—for slicing analysis; these platforms generate G-code, a machine-readable language that can be interpreted by a 3D printer. Step 2: Initiate the 3D printing process. Once this process begins, the laser projects its beam onto the photosensitive resin based on the slicing data. Under computer control, the laser projects its beam onto the liquid resin, curing the liquid to form a solidified layer. After the first layer, the print bed is raised by the layer height (typically approximately 0.1 mm), allowing additional resin to flow beneath the previously printed area. The laser then cures the next cross-sectional layer, and this process is repeated until the entire part is completed. The resin that does not come into contact with the laser remains in the print chamber and can be reused.
Step 3: Post-processing. After printing, the parts should be rinsed in isopropyl alcohol (IPA) to remove any uncured resin from the surface. Once the rinsed parts are dried, certain materials may require post-curing, a process that helps the parts achieve maximum strength and stability. Finally, remove the supports from the parts and sand off any remaining support marks to obtain a clean surface. SLA-printed parts can then be easily machined for specific applications, or finished with primer application, painting, and assembly.
Advantages and Disadvantages of SLA 3D Printing Technology
(1) Advantages: ① The photopolymerization molding process is the earliest rapid prototyping manufacturing technology; having stood the test of time, it now boasts high technical maturity. ② Prototypes can be directly fabricated from CAD digital models; the photopolymerization process is straightforward, offering rapid molding speeds, shortened product production cycles, and eliminating the need for cutting tools or molds. ③ The prototypes exhibit high precision, enabling the fabrication of prototypes and molds with complex geometries that are difficult to produce using conventional methods. ④ The surface quality is generally excellent; the top surface of the workpiece is highly smooth, although the side surfaces may exhibit steps, irregularities, or curvature variations between different planes. ⑤ This process makes CAD digital models more intuitive, thereby reducing the cost associated with error correction. ⑥ It provides physical samples for experiments, allowing for the verification and validation of computer simulation results. ⑦ The system supports online operation and remote control; once operational, the entire part fabrication process runs completely autonomously without the need for dedicated supervision, thereby facilitating production automation.
(2) Disadvantages: ① SLA printing equipment has a relatively high manufacturing cost, and its operating and maintenance costs are also elevated. ② The photopolymer resins used in SLA printers possess specific chemical compositions; operators must therefore employ appropriate protective measures during use, and the equipment imposes stringent requirements on the working environment. ③ The printed parts are predominantly made of photopolymer resins, which exhibit limited strength, rigidity, and heat resistance; also, these materials can cause environmental pollution, making the resulting products inferior to those manufactured using conventional methods, and posing challenges for long-term storage. ④ The core technology is monopolized by a limited number of companies, meaning its full technical and market potential has not yet been fully tapped. ⑤ The preprocessing and driver software involve substantial computational loads, and their performance is highly correlated with the final machining quality. ⑥ The software systems are complex to operate, posing a significant barrier to user onboarding.
Application Fields of SLA 3D Printing Technology
It has now been widely applied across numerous fields—including automotive energy systems, electronics and electrical equipment, medical guidance devices, industrial molds, animated sculptures, architectural models, as well as academic and research institutions—meeting diverse requirements such as new product development, appearance verification, design verification, structural verification, assembly inspection, and functional testing, thereby unlocking limitless possibilities for personalized customization.
(1) Application of SLA technology in the aerospace sector: In this domain, SLA models can be directly employed in wind tunnel tests to conduct manufacturability and assemblability evaluations. By utilizing photopolymerization molding technology, a variety of missile casings can be fabricated; once sensors are installed, these casings can be directly subjected to wind tunnel testing. This approach eliminates the associated costs and time required to fabricate complex curved molds, thereby enabling the rapid identification of the optimal flow-guiding configuration among multiple design alternatives. Consequently, this strategy significantly shortens the validation cycle and reduces development costs throughout the entire product development lifecycle.
(2) Application of SLA technology in the footwear industry: In footwear manufacturing, 3D printing using stereolithography (SLA) technology enables personalized design and small-batch production of footwear products, thereby streamlining and enhancing the flexibility of the production process. In contrast, traditional footwear design and manufacturing relied on multiple complex manufacturing processes and were unable to accommodate intricate porous lattice structures.
- Applications of SLA technology in other manufacturing sectors: In addition to its significant applications in the aerospace industry, stereolithography (SLA) rapid prototyping technology also finds crucial and widespread application in other manufacturing domains, such as the automotive industry, mold manufacturing, electrical appliances, and casting. Taking automotive manufacturing as an example, a hallmark of Hyundai’s production strategy is its diverse product portfolio and short development cycles. To meet varying production requirements, continuous model iterations are necessary. For components with highly complex geometries and structures, SLA prototyping can be employed to create prototypes, enabling designers to validate their design concepts and facilitating functional and assembly inspections using these prototypes. In the automotive sector, SLA technology can also be integrated with reverse engineering and rapid mold manufacturing technologies for applications including automotive body design, prototyping of front and rear bumper assemblies, fabrication of structural and functional prototypes for interior door panels, and production of racing car components.
LCD photopolymerization-based 3D printing technology
It is a type of photopolymerization-based 3D printing technology. It has undergone three iterations: from SLA (Stereolithography) to DLP (Digital Light Processing), and then to LCD (Liquid Crystal Display).
LCD 3D printing can be categorized into two types, distinguished by the wavelength of the light source: one utilizing 405 nm ultraviolet light, and the other utilizing visible light in the range of 400–600 nm. LCD mask-based photopolymerization employs 405 nm ultraviolet light (similar to DLP) combined with an LCD panel to achieve selective light transmission; this technique is known as LCD masking, though it also has various alternative designations in the industry, such as mDLP, LCD DLP technology, and UV mask curing, among others.
A key limitation of LCD technology is its lower optical efficiency compared to DLP. Whether by increasing the brightness of a 405 nm lamp to achieve higher luminous flux, or by employing visible-light LCDs with high-sensitivity resins for comparable luminous flux, the curing speed achievable cannot rival that of DLP. A practical benchmark indicates that for a 100 μm thick layer, DLP curing takes from fractions of a second to several seconds, whereas 405 nm UV-LCD or visible-light LCD curing requires tens of seconds.
modelling
Model slice
Printed model
reprocessing
Advantages of LCD photopolymerization 3D printing:
I. High Precision and High Resolution: LCD photopolymerization 3D printers typically employ transparent printing beds with 4K or even 8K resolution, enabling them to easily achieve a precision of 100 μm. This performance surpasses that of earlier SLA technologies and is on par with desktop-grade DLP technology. Smooth Surface Finish: As the photopolymerizable resin forms an exceptionally fine surface during curing, LCD photopolymerization 3D printers produce models with smooth surfaces and richly detailed features.
II. Rapid Printing: Surface Formation Technology: LCD photopolymerization 3D printers employ surface formation technology, in which the light source projects layer-by-layer light onto the surface of liquid photopolymer resin, enabling layer-by-layer curing and shaping. This technology allows LCD photopolymerization 3D printers to print multiple models simultaneously, with each layer requiring only a very short printing time, thereby significantly enhancing printing efficiency. Printing Speed: Compared to SLA dot formation technology, LCD photopolymerization 3D printers offer faster printing speeds, enabling the completion of printing tasks within a short period of time.
III. Ease of Operation and Maintenance Simple Operation: The operation of an LCD photopolymerization 3D printer is relatively straightforward; users only need to upload the model file to the printer, configure the parameters, and then initiate the printing process. Simple Maintenance: The architecture of an LCD photopolymerization 3D printer is relatively simple, lacking complex components such as the laser galvanometer found in SLA printers or the projection module found in DLP printers; consequently, its maintenance is also more straightforward.
IV. General Consumables: Strong Compatibility: The primary materials used in LCD photopolymerizable 3D printers are photosensitive resins, most of which are theoretically compatible with the resins used in DLP technology. Also, certain resins specifically designed for SLA printing may also exhibit good compatibility when used in LCD photopolymerizable 3D printers.
V. Broad Application Scope and Diverse Use Cases: LCD photopolymerization 3D printers can print models of various shapes, making them suitable for producing small-batch components, prototypes, toys, and more. Also, owing to their high precision and rapid printing capabilities, these printers find extensive applications in areas such as prototype fabrication, customized dental device production, and jewelry modeling.
VI. Cost-Effectiveness: High cost-performance ratio: LCD photopolymerizable 3D printers have relatively low manufacturing costs, and owing to their high efficiency and user-friendliness, they can save users significant amounts of time and money. Also, for specific application scenarios—such as prototype fabrication and customized dental equipment—LCD photopolymerizable 3D printers can provide more cost-effective solutions.
Disadvantages of LCD photopolymerization-based 3D printing:
Disadvantage 1: Limited selection of suitable LCD light sources for replacement: The critical light source projection screen for this technology must exhibit excellent light transmittance at 405 nm, withstand hours of high-intensity thermal cycling under 405 nm LED beads rated at tens of watts, and meet stringent requirements for heat dissipation and temperature resistance. Consequently, not every LCD panel is suitable for this application. Disadvantage 2: Susceptibility to aging: The LCD panel is a consumable component that tends to degrade during operation; therefore, users are advised to plan for regular panel replacements. Disadvantage 3: Limited printable size range: While larger industrial-grade equipment can naturally print relatively large objects, for standard desktop-grade systems, the printable size remains relatively limited, and there are no available accessories to expand this capability.
Additional comments from netizens: The following responses were provided regarding the shortcomings: 1. In the early stages, LCD technology was primarily used in laptops, televisions, and mobile phone screens, offering limited application options. Currently, LCD panels are predominantly manufactured using molds designed for the 3D printing industry. 2. For custom-made black-and-white LCD displays, the typical service life now exceeds 2,000 hours. 3. The largest industrial LCD printer currently available measures approximately 32 inches; for consumer applications, the common size is around 16 inches—roughly equivalent to the screen size of a laptop.
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