For all additive manufacturing processes, choosing a suitable raw material is a basic step in the printing process. This is especially important in resin 3D printing, in which photosensitive materials are cured layer by layer until a highly detailed part is finally formed. In addition, the choice of resin also depends on the photopolymerization process used. One is stereolithography, or SLA, which uses lasers to cure materials, and the other is DLP and LCD methods, which use light display. In order to better understand the currently available material options, this article summarizes the types of resins used in the light-curing 3D printing process on the market and their different characteristics.
It should be noted that the performance of the resin is determined by the optimal polymerization for light-induced curing, and the curing light can be single-wave or multi-wave. This is where the concept of resin wavelength comes into play. The lower the wavelength rating of the resin, the higher the light output power required for curing. It is for this reason that manufacturers specify a wavelength that their resin is compatible with. Therefore, the wavelength of DLP/LCD resins is generally larger than that of SLA resins.
△Photo source: Ackuretta
Standard 3D printing resins
Standard types of 3D printing resins are the most versatile and common resin materials on the market. Almost all manufacturers have developed standard resins, so you can buy them everywhere, at an affordable price, and in a variety of colors. They are a very versatile choice, as parts printed with them have smooth and detailed properties, as well as a fairly high hardness, requiring only simple post-processing processes such as painting and sanding. However, care must be taken when printing parts with standard resins, as they are brittle and prone to breaking and cracking. Its accessibility and ease of use make it ideal for getting started in the world of resin 3D printing and for making decorative items, prototypes, figurines, etc.
Transparent resin
Transparent resin is very similar to standard resin, this resin is useful for making small objects with a high degree of precision, but it has the additional property of being translucent and colorless. In addition to facilitating the sanding and subsequent painting process, it also allows you to create glass-like effects for various decorations, all with the same smooth and soft texture as standard resin. It should be noted that although transparent resin is not recommended for use in the food sector, these parts can be applied in waterproofing applications.
△3D printed chess pieces made of transparent resin
Washable resin
Generally speaking, resin 3D printed parts require some post-processing to remove supports and excess resin. These cleaning steps are usually performed with isopropyl alcohol (IPA). However, there is a type of 3D printing resin that is water-washable, so no chemical treatment is required. By washing the parts with water, a smoother and more pleasant touch can be achieved. In this way, the stickiness that is characteristic of other resins is gone, and the odor associated with standard resins is reduced. The only downside to these water-washable resins is that accuracy may be affected.
Flexible 3D printing resin
These types of 3D printing resins have rubber-like qualities, with a Shore hardness of around 80A. They are characterized by the ability to create objects with high strength, as they are able to bend and compress without losing their shape. Parts 3D printed with flexible resins will have rubber-like properties, being able to return to their original shape after being compressed. Due to their long lifespan and ability to withstand continuous use without breaking, flexible resins are ideal materials for creating prototypes of shock absorbers, handles, or moving parts.
△3D printed parts made with BASF's Ultracur3D EL 4000 flexible resin (Image source: zortrax)
Industrial 3D Printing Resins
Industrial photopolymers, also known as hard resins, are materials with high mechanical properties, ideal for demanding applications. They are characterized by their ability to withstand pressure, as well as withstand shocks and impacts, all without breaking or cracking. These capabilities allow them to be used not only as prototypes, but also for tasks that require strength and durability. In this large category of resins are included heat-resistant and flammable resins, as well as dental resins, due to their interesting properties that are compatible with the dental field.
Heat resistant resin
Want to create parts that can withstand high temperatures? Then these 3D printing resins are ideal for you. Heat-resistant resins can be considered industrial resins. They are characterized by excellent heat resistance, i.e. the parts created can be exposed to temperatures of up to 230°C without affecting their shape and performance. Therefore, they are ideal for making casting tools, tools that will be exposed to hot liquids, and equipment exposed to intense heat.
Combustible resin
Like heat-resistant resins, combustible resins can also be classified as industrial resins. The application of these parts starts with the design and printing of the model to a high level of detail. Later, metal casting is carried out, in which the combustible resin evaporates without leaving ash or residue. In this way, the surface of the final object remains clean and has a smooth surface. This type of resin is used in the field of jewelry and dental restorations, for example, where it is necessary to have a part with an appearance free of roughness and defects.
Dental resin
Unlike other resins, dental resins are composed of organic elements that do not contain toxins. This allows it to be used in dental applications without risking the health of the patient. Dental resins are advantageous for creating parts with a smooth texture and a fairly high level of detail. This option is ideal for the manufacture of retainers, crowns, bridges, surgical models, dentures or anatomical models, among other dental applications. In addition, they significantly reduce the production costs of traditional dental restorations.
△An example of dental resin application
in conclusion
Although resin 3D printing itself is very versatile, there are some disadvantages of the resin material itself that should be taken into account before printing. It is especially important to understand any necessary precautions before using any kind of resin. With the exception of dental and other biocompatible resins, most resins are toxic. It is recommended to wear gloves and a mask when handling them, at least until the final piece is fully cured. In addition, it is recommended to keep the production space well ventilated to avoid the accumulation of toxic vapors.
Another point is that they are susceptible to UV rays, so it is not recommended to leave the work in the sun for a long time. Long-term exposure to light can cause the polymer to lose cohesion and cause the print to deform. Finally, these materials are not suitable for contact with food, especially liquid beverages. Related to the first point, resin is a toxic material, so contact with liquids will cause the work to dissolve over time.
Still, the versatility of different types of 3D printing resins makes them ideal tools for a variety of applications. From creating prototypes and figures to designing dentures, jewelry, or industrial tools. What you need to do is determine which type of resin is best for your application, and which resin 3D printer is best suited.
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