RESIN PRINTING
LCD 3D printing, also called masked stereolithography or MSLA, is a common 3D printing technology that can achieve high-precision model printing and is widely used in many fields. For 3D printing enthusiasts or beginners, MSLA 3D printers are one of the most popular choices among consumer-grade 3D printers due to their ability to produce professional-grade resin prints. This technology is known for its high-speed resin 3D printing, offering rapid and accurate results.
The build plate that will hold the model upside down moves down into a resin tank filled with resin until it is a few microns from the LCD screen. Below the resin tank, there is a UV light source, usually UV LEDs. When the screen displays a layer of the model, the UV light passes through the transparent regions of the LCD and cures or hardens the liquid resin. Only the parts that are exposed to the UV light harden; the rest stays liquid. The build plate is then moved up a few millimeters to stop additional curing of the polymer and reset the layer height before flashing the next layer. Unlike FDM printing, print orientation does not change the strength of resin-printed parts. The curing process is not instantaneous, so the solidifying resin chemically bonds with its surroundings. Each new layer bonds with the layer above to create a solid piece without the gaps filament printers leave behind or varying strength depending on orientation, making it ideal for top-rated resin 3D printing.
Better resolution- The number one reason why you would want a print done with resins instead of Filaments is that resin-based 3D prints simply look better. Where the resolution of FDM printing is limited by the size of the nozzle used, resin-based printing is only limited by the size of the LED’S emitting the image (like a TV) into the liquid resin. This allows resin printing to reproduce very fine details in its models. They also come out with a much smoother finish that can only be achieved in FDM printing with a lot of post-processing.
Faster printing process- The process of printing with resin is considerably faster compared to printing with filament. In an FDM printer, the extruder needs to move around the print bed to deposit the molten filament along a specific pattern. This is a slow process due to the controlled way the filament must be extruded.
Resin printers have no such issues. In MSLA printing, a single layer is cured all at once in a single step. For this reason, fast-paced industries prefer using resin printers.
Stronger finished products- One of the major weaknesses of FDM printing is that its finished products exhibit strong anisotropy – or that their mechanical properties are not equal along all three axes. In particular, filament prints are weak against shear stresses acting along the direction of the layer lines because of the inherent weakness of the layer-to-layer boundaries.
The curing process allows for stronger layer-to-layer adhesion in resin-based printing, resulting in finished projects with mechanical properties that are much more uniform across all axes. Because of this property, prints made from resin are preferred for engineering components and functional parts.
More expensive- Printing with reason is more expensive, both in terms of the printer and the raw materials. While you can buy a desktop-scale FDM printer for about $250, the cheapest resin printer you can buy today will cost more than $500. If you want to go for one of the more popular models, you’ll have to fork over close to $2,000.
The cost of the liquid resin is also substantial. You can get a 1KG spool of PLA or ABS filaments for around $25, but some resins can be double or even triple that for the same weight. Also, with FDM printing the model is mostly hollow with infill around 15% or so, whereas a resin print is solid most of the time, consuming more material per layer.
The problem of printing with resin is that you need to fill the whole resin vat every time you start a project. Although the emission of UV radiation to the resin vat is highly controlled, it’s still not a perfect process. Inevitably, some of the unused resin would have gone through a process of premature curing. This limits the degree of recycling that can be done with unused resin.
No option for composite prints– High-end FDM printers can have multiple extruders or multi-material functionality, making it possible to create prints made with a combination of different filament materials and/or colors. This can prove really useful if you’re printing a model that requires support structures, as some materials are simply more suitable for support. For instance, PVA filament can be removed simply by soaking the finished print in water.
Resin-based printers do not have this advantage. A project must be printed in a single vat of resin, so the material will be uniform all throughout. This is quite limiting in terms of design opportunities, but also makes post-processing just a little more complicated.
Difficult and messy post-processing- In both FDM and Resin-based printing, post-processing is necessary if you want your prints to have that professional-grade finish. Support structures must be removed, imperfections sanded or polished away, and the suitable paint applied.
Removal of the support structures is much easier in FDM printing because of the option for composite printing. Although the surfaces of the prints made from filament have a lot more imperfections, the sanding and polishing process is pretty simple. There’s going to be a lot of elbow grease involved, but it’s clean and is certainly easier.
Resin post-processing is, on the other hand, quite messy and hazardous. If you’re removing support structures, you’re going to do that before the curing step. At this stage, the supports are still soft and easier to remove. You’ll also need to remove the excess resin on the surface of your finished print with isopropyl alcohol (or water for water-based resin). You need to wear gloves and a respirator while handling the print prior to washing and curing. Your workspace also needs to be covered with either plastic sheets or silicone mats. The huge mess that the process makes can prove to be very discouraging.
Three basic components are found in all photopolymer resins: monomers, oligomers and photoinitiators. The first two are the basic building blocks of what will become the printed object’s solid long-chain polymers. Photoinitiators are light-sensitive molecules that drive polymerization.
In addition to these three components, resins contain additives that affect the printed material’s physical, chemical and aesthetic properties. For example, some resins will form thermoset materials that resist high temperatures while others will form thermoplastic materials that soften and deform when heated.
I use the Anycubic Photon Mono M5s Pro resin printers with a resolution of 13312 x 5120, which is equivalent to 14K. Print capacity is 200mm X 223.78mm X 126.38mm / 7.87” X 8.81” X 4.98” (HWD)
