Liquid Resin
Liquid resin is a curable photopolymer - it is used as the main material for SLA printers. The resin is hardened by applying focused light or UV light. The liquid resin helps the model have fine details and smooth finishing surfaces. Different combinations of various additives that comprise a resin in different material properties. Some main benefits of using resins are smooth, fine features, high detail, high stiffness, and a good finishing surface. However, resins also have some limitations such as being relatively brittle, not suitable for outdoors use, and susceptible to creep.
4 main groups of resins based on their properties
Standard resins: Best used for rapid prototyping, concept modeling, or art models’ applications due to there low-cost.
Engineering resins: All engineering resins require a post-curing under UV light to achieve their maximum mechanical properties. They provide many mechanism options for the parts such as durable, tough, heat resistant, rubber-like, or ceramic filled.
Dental and medical resins: Biocompatible resins are used to make customized medical equipment. The parts using dental and medical resins later can be steam-sterilized for direct use in operating rooms. These resins also have high resistance to fracture and wear make it ideal to create custom hard splints or retainers.
Castable resins: This kind of resin is ideal for parts with sharp details and smooth finish. When burned, it leaves out no ashes or residue. They are best for jewelry and other small and intricate components.
While most FDM filaments are interchangeable, 3D printing resins are for more specialized products.
Reasons for Resin over Filament
- Durability: Although objects were made by layer to layer of cured resins, they are still not exactly known for their toughness. Most resins are brittle and easy to fail by cracking or shattering. In this case, engineering resin is a solution due to it's customized to simulate the toughness of injection-molded plastics
- Flexibility: There are many resins have high flexibility that can build rubber-like products. They are known for low tensile modulus, high impact resistance, and elongation. However, being so soft can make them hard to print, these soft resins will require supportive structures during the printing process.
- Price: Printing with resins is often more expensive than printing with filaments. A liter of high-quality 3D printing resin will cost 50$ compare to an entire roll of filament of $20. Moreover, SLA often printers require enough resin in the tank that the build platform need to submerge completely.
Making resins with the Three-Roll Mill
Any kind of resin is a result of good mix from combinations of the monomers, oligomers, photoinitiators, and various other additives. Good resin requires a good dispersion of all additives, elements, and a liquid base. These requirements are achievable using the three-roll mill machines. Three-roll mill machine has three horizontal rollers that 2 rollers next to each other will rotate in the opposite direction plus at a different speed. While rotating, any material that is poured in between a tiny gap of feeder roller and the center roller will experience a large amount of shear force which will give a fine dispersion. Therefore, three roll mills are ideal for blending and dispersion of viscous materials like resin. Check out www.Threerollmill.com to learn more.
Post-process of 3D printing resins
Resin 3D printing is an optimal option to produce high details and fine feature products. However, resin 3D printing often requires supportive structures to be attached to the models, and the models need to be arranged at specific angles. These supportive structures later will leave marks and create rough surfaces. Luckily, with proper tools and cautiousness, 3D printing resins are an easy material to post-process.
Basic post processes for 3D printing resins
- Cleaning: It is important to clean all uncured resin from the print. Alcohol or water is used to clean since resin is a liquid material.
Supportive structures removal: Break off the supportive structures will leave bumpy surfaces on the model. Therefore, it is recommended adding extra thickness to the model and then sanded afterward to achieve dimensional accuracy.
- Sanding: This process is to remove any debris leftover after the printing. It can be done with dry or wet sanding tools. Wet sanding often provides a smoother surface to the print.
- Painting: Painting can be done as special requirements. Variety of colors now are available on the market.
- Polishing: This process can help bring back the transparency after sanding. With the use of various compounds, polishing can make the surface even more smooth and clear.
All these post-processes can be done manually or with special devices that are now available for all range from small to big 3D printers.
Advantages and limitations of 3D printing resins
Every technology has its advantages and limitations. Depend on the capability of the printer, the properties of resins using, resin 3D printing also has some advantages and limitations.
Advantages:
- High details: Since the model is built by loading layers of liquid, resin 3D printing will provide more complex geometries and filaments
Smooth surface: Although printing layer by layer with create some layer lines, these lines are extremely small. On some colors of resin, these lines nearly invisible.
- Various material: Nowadays, a wide range of resin materials can manage to provide all common applications and needs. Moreover, specific designs and product can be manufactured with combinations of different resins.
High speed: Resin printing is much faster than comparing to other prototyping methods. High detail features can be produced with hours and still keep the same quality.
Limitations:
- Many supportive structures: Supportive structures will help the models avoid from touching the plate. These structures after being curved, won’t be able to recycle into fresh resin. They become solid and useless.
- Necessary post-process: Post processes are required to do with resin prints before they are ready. Without post-process, model possibly can be ruined and won’t deliver the best quality.
Conclusion
As 3D printers become more affordable, 3D printing will be the fastest-growing manufacturing technology. 3D printing technology is a chance for businesses to increase their competitiveness and innovation. The uses of 3D printing for manufacture, prototype, and especially for medical is beyond astonishing. It is still new and continuously improving and adjusting. With a wide range from manufacturing processes to materials, the industry still has a lot more to achieve in the future. “If a picture is worth a thousand words, a prototype is worth a thousand pictures.”
