Liquid 3D printing, also known as rapid liquid printing or liquid additive manufacturing, is an innovative new approach to 3D printing that is gaining popularity. Instead of using solid filaments, liquid 3D printers utilize photopolymer resins that are precisely deposited layer-by-layer to create complex objects.
How Liquid 3D Printer Works
The liquid 3D printing process starts with a vat or reservoir filled with a photopolymer resin. This resin is a liquid plastic material that cures and hardens when exposed to certain wavelengths of light, typically ultraviolet (UV). At the bottom of the vat is a build platform that can move up and down. Above the vat is a light source, such as a digital light projector (DLP) or laser.
To print an object, the build platform lowers into the vat of resin until just above the bottom. The light source then projects a 2D image of the first layer, tracing and curing it onto the platform. After one layer is complete, the platform raises slightly and new liquid resin flows underneath to prepare for the next layer. This process repeats over and over, lowering the platform and projecting images of each layer, until the full 3D object is complete.
Once finished printing, the object must undergo a final curing process under UV light to fully harden the material. Any remaining liquid resin is drained or washed away. This leaves you with a solid, high-resolution 3D printed part.
Benefits of Liquid 3D Printing
Liquid 3D printing offers several advantages compared to traditional filament-based methods:
- Higher resolution: Liquid resin can produce extremely smooth surface finishes and fine details down to 25-50 microns, rivaling injection molding parts. This makes it ideal for detailed objects like jewelry, miniatures, and engineering prototypes.
- Speed: With no filament to physically push through a hot nozzle, liquid printing can achieve speeds 5-10x faster than fused deposition modeling (FDM). A bottle opener can print in under 5 minutes.
- Material properties: Photopolymers provide advanced material capabilities from rigid to flexible. Some resins even allow for dissolvable support structures.
- Part complexity: No need for support material means liquid resins can create complex geometries that would be impossible with filament. This includes crossing overhangs, interior voids, thin walls, and negative space.
- Post-processing: While washing and curing is required, there is generally less post-processing like sanding and finishing compared to FDM. The smooth resin often provides an excellent surface right off the print bed.
Applications of Liquid 3D Printing Technology
With its precision and material advantages, liquid 3D printing is revolutionizing several industries:
Dental and medical: crowns, bridges, orthodontics, hearing aids, surgical guides
Jewelry: rings, pendants, earrings, bracelets with extreme detail
Engineering: accurate prototypes, end-use parts, tooling with conformal cooling
Automotive: rapid prototyping of concept models and custom fixtures
Manufacturing: jigs, inspection gauges, assembly alignment tools Visual arts: highly detailed miniatures, sculptures, and collectibles
Both hobbyists and professionals are adopting the technology for design and manufacturing across many fields.
Types of Liquid 3D Printers
There are two main technologies used in liquid 3D printers:
Stereolithography (SLA)
- Uses a UV laser to selectively cure each layer
- More expensive, slower, but very high accuracy
- Most common in industrial printers
Digital Light Projection (DLP)
- Uses a digital light projector screen to flash cure resin layers
- Faster printing than lasers but slightly lower resolution
- Widely used for desktop liquid printers
In addition, there are a few variations on the liquid printing process:
- Nanoparticle jetting: Inkjet heads deposit liquid photopolymer droplets.
- Two-photon polymerization: Focused laser pulses initiate curing deep inside the resin vat.
- Continuous liquid interface production: Oxygen permeable window creates a “dead zone” to cure resin continuously.
Materials for Liquid 3D Printing
Photopolymer resins are specially formulated for the liquid printing process. The main components include:
- Monomers: Acrylic/epoxy base substances that cure from liquid to solid.
- Photoinitiators: Chemical compounds that facilitate curing when exposed to light.
- Additional ingredients: Agents to control properties like color, flexibility, strength, elongation, and temperature resistance.
Common photopolymer resin families include:
- Standard: Balanced performance with good detail and strength.
- Flexible: Elastomer-modified for rubbery properties with elongation and tear resistance.
- Castable: Burn or melt away to create metal casting molds.
- Dental: Biocompatible certified materials for medical use.
- Engineering: High heat and chemical resistance.
There are also advanced specialty materials like simulated wood, stone, ceramic, and biocompatible resins.
The Future of Liquid 3D Printing
Liquid 3D printing is still an emerging technology but advancing at a rapid pace. Here are some exciting developments on the horizon:
- Wider range of material capabilities, colors, and properties matching engineering thermoplastics.
- Larger build volumes over 1 liter to accommodate mass manufacturing.
- Hybrid multi-material printing with solids and liquids.
- Increased automation and software integration.
- Expansion into bioprinting cells and human tissue.
- Low-cost industrial and desktop liquid printers.
With its advantages in speed, quality, and part complexity, liquid 3D printing promises to become a major player in digital manufacturing and prototyping. Both hobbyists and industries are adopting this innovative technology to unlock new design possibilities.
