Today we will review the basics of Resin 3D Printing, a design creation system that is gaining popularity for its great capabilities.
The technology around 3D printing has advanced rapidly in recent years, making it very affordable to the home user and small businesses. They are very interesting machines for all fans of printing detailed and complex models with millimeter precision, much better than filament 3D printers that focus on other uses. This system has its advantages and disadvantages as we will see below.
If you have any questions, leave a comment and we will try to help you.
Basic operation of resin 3D printer
The basic operation of a resin 3D printer is to project UV light on a layer of liquid resin. At the bottom we usually have an emitter of LED or laser lights and to manage the curing point we have either a system of mirrors or a shutter of UV light through LCD screens.
The liquid resin solidifies by photopolymerization, this is a chemical reaction where a liquid material changes its properties when subjected to light (UV, laser, etc.). The scientific term for this type of liquid is photopolymers or light activated resins, and in 3D printing they are simply called resins.
When the light hits the liquid resin inside the tank, the entire area becomes a solid layer. The printing base is then lifted out of the resin and a high-precision Z-axis separates the layer from the bottom of the resin tank. Gradually, the part is formed normally upside down.
Types of resin 3D printer
Resin 3D printers mainly involve several types of printing technologies such as SLA, DLP, LCD and MSLA. These share a similar working process, similar uses and can combine processes.
Stereolithography (SLA) system is a type of 3D printing technology that uses a high-power laser as a light source to solidify photosensitive liquid layer by layer in a photochemical process in which 3D models are gradually formed and created over a given area.
Digital Light Processing (DLP) technology instead of using a laser adopts a digital light projector to cure all resin areas simultaneously. Compared to SLA, DLP 3D printers can create a 3D model at a faster speed, as it takes less time to solidify each layer.
As for liquid crystal display (LCD) 3D printers, they emit light directly from a set of flat UV (Ultra Violet) LCD panels onto the build platform. The density of the LCD light is the essential factor in the quality of the prints. Higher LCD light resolution produces better quality final prints.
The most popular system today is the so-called Masked Stereolithography Apparatus (MSLA) that uses a light projector perpendicular to a high resolution 4K, 8K, 9K or 12K LCD screen (like those in cell phones) that blocks UV light. With this system it is possible to achieve impressive results in much less time.
Resin 3D printing working process
The work cycle with a resin 3D printer is somewhat laborious, unlike filament printers, we require more control in its design, cleaning, UV curing and post-processing. The results obtained at the end, on the other hand, are excellent and with a very high degree of detail.
1. Previous 3D design
To start we need a 3D model that we can download from sites like Cult3D or Myminifactory, make ourselves with any computer aided design (CAD) software or scan in 3D if we have the means. This 3D model is imported into the resin print preparation software such as ChituBOX or Lychee Slider, this software then divides the digital model into layers for printing, it will also create supports and print orientations in an automated way.
The design of parts for 3D printers in resin has several peculiarities. We can not leave internal cavities where the liquid resin is trapped, we must provide drainage holes. In addition, the part must be hung on supports that the software already places on the laminate. The position also depends on the center of gravity of the model with respect to its volume, normally they rotate about 45º on its axis to avoid deformations.
2. 3D Printing
To start 3D printing we need to level the print head if our printer does not do it automatically. We just have to place the printing base and lower it flat against the printing surface by placing a foil in the middle, then tighten the print head.
Once leveled it is necessary to load the liquid resin tank to the indicated mark, we can always recharge if we see that we run out of material. Next we need to cover the 3D printer with the casing to block the sun’s UV rays. We load the 3D model laminated and processed to the printer to start the printing process.
3. Cleaning and curing
Once the 3D printing is finished, it is necessary to remove the part from the base plate always using gloves and protections as we have indicated. It is recommended to remove the supports with your hands or small pliers, be careful not to leave marks. With the piece without support we will introduce it in a bath of isopropyl alcohol or water, depending on the resin that we are using in our impression. After cleaning the piece we dry it to try to avoid any internal liquid or on the surface.
We move on to the curing process with UV lights to improve the external surface in shape and mechanical properties. There are nowadays some good cleaning and curing combos that facilitate this process quite elegantly and do not take up much space. The curing time is relative, it will depend on the machine and size of the part.
4. Postprocessing
Once the part has been cleaned and cured, it is usually necessary to remove protrusions from the supports or to smooth the product in general. There are multiple processes available that will have a different effect.
- Dry sanding. If you need a smoother finish after the supports have been removed, you can lightly sand the part to flatten the bumps. It is recommended that at least one additional 0.1 mm layer be added to the product to allow for sanding.
- Wet sanding. Wet sanding achieves the best sanding appearance on any printed product, and can achieve better effects with each level of sanding you complete.
- Mineral oil finish. Mineral oil will even out the color of the part and help hide bleached areas from sanding. Mineral oil will help lubricate and enhance clear resins.
- Spray or acrylic paint. With them, we can paint colors or better seal the resins. Some resins do not allow spray or acrylic paints to adhere to the surface.
5. Cleaning and Recycling resin residues
After finishing the printing, cleaning and curing process we must process the resin residues and take them to a green point, never throw them to the conventional garbage or down the drain. To remove the solid elements of the resin from the printer it is advisable to make a final curing layer and take it out. In the cleaning tank it is advisable to either leave it exposed to sunlight or pass it through the curing, that way the resin particles will solidify at the bottom to be able to collect them.
- Cure extra layer of resin to solidify particles from the bottom of the tank on the FEP film.
- Remove resin from the reservoir to the bottle carefully using funnel.
- Clean transparent film from the bottom of the cuvette with alcohol or non-aggressive liquids.
Types of resins
We find in stores like Amazon a lot of 3D resins with different characteristics and colors. Depending on our needs we will need to use one type or another.
- Standard Resin: To make figures of all kinds without requiring resistance.
- Water Resin: This type of resin can be washed with water instead of alcohol.
- ABS-LIKE: It is recommended for pieces that require mechanical resistance and flexibility.
- Fast: This type of resin allows us to adjust the 3D printing with higher speeds.
- Professionals: There are also other resins for jewelry, orthodontics and all kinds of specialties.
History of the resin 3D printer
The SLA 3D printer was developed in the 1970s in Japan. Dr. Hideo Kodama was the first to attempt layered printing using a liquid polymer and ultraviolet curing. It re-emerged on the market in 1986, when it was patented by Charles W. Hull in the United States.
The resin 3D printer did not catch on very quickly due to the high cost of the equipment and materials. As patents began to expire, the UV 3D printer regained popularity. By 2011, the first desktop-sized resin 3D printer was available and this technology continues to develop to this day by optimizing its processes and lowering prices.
