As far as desktop systems go, fused deposition modeling (FDM) may be a great technology for prototyping parts, but when high speeds and detail are required, low-cost stereolithography (SLA) and digital light processing (DLP) 3D printers may be better suited.

Fortunately, there is an increasing number of affordable SLA and DLP 3D printers hitting the market. While the material selection may not be quite as vast as those offered with FDM 3D printing, new photopolymers for desktop machines are hitting the market on a regular basis. Here are just nine 3D printing resins that may change the way desktop 3D printing is used.

How Does Photopolymerization Work?

3D printing via photopolymerization relies on hardening photoreactive liquid plastic with a light source, typically projecting ultraviolet (UV) light. The setup of most SLA and DLP 3D printers sees the light source—in the form of a laser, a lamp, a projector or light-emitting diodes—projected onto a vat of photopolymer resin.

In the case of a laser, the individual layers of a 3D model are drawn onto the resin as a printbed is raised or lowered—depending on whether the vat is above or below the light source—layer by layer until the object is complete. In the case of a lamp or projector, entire slices of the CAD model are cast onto the resin, hardening the object one whole layer at a time.

General Purpose Resins

To start, there are a number of firms producing 3D printing resins for desktop machines. Though many 3D printer manufacturers sell their proprietary materials, several generic brands have taken to making their own varieties for these systems, including MadeSolid, MakerJuice and Spot-A Materials.

A variety of 3D printing resins from SprintRay, manufacturer of the MoonRay 3D printer. (Image courtesy of SprintRay.)

At the start, desktop resins were limited in color and characteristics, leaving users with only yellowish, transparent materials. Since low-cost SLA and DLP 3D printers were introduced to the market several years ago, however, the range has grown to include oranges, greens, reds, yellows, blues, whites, grays, blacks and browns of varying opacities.

Tough Resins

Typically photopolymer resins used for 3D printing on desktop machines are somewhat fragile, leaving those delicate details susceptible to snapping and cracking. For this reason, the technology has been used more frequently for aesthetic purposes, such as artistic models and visual prototypes. To address these issues, numerous companies have begun producing tougher and more durable resins.

This 3D-printed ball joint demonstrates the durability of Formlabs' Durable Resin. (Image courtesy of Formlabs.)

Formlabs' Durable Resin, for instance, is meant to demonstrate high wear resistance for parts that bend without cracking, while the firm's Tough Resin is billed as having properties that simulate injection-molded ABS plastic.

Formlabs isn't the only one to have produced photopolymers capable of demonstrating stronger mechanical properties. Generic material makers, such as MadeSolid, MakerJuice and Spot-A Materials all manufacture tough resins as well.

Castable Resins

Casting has long been a process supported by photopolymerization technologies, with industrial manufacturers often marketing SLA and DLP machines to the dental and jewelry markets for the ability to fabricate parts that can be cast as metal. Naturally, producers of resins for desktop machines began with low-cost casting resins. In addition to some of the aforementioned firms, there are several makers of castable materials, including other printer manufacturers like SprintRay and resin producers like Fun To Do.

The key to a good castable resin is high burnout, so that when the object is cast from a 3D-printed part, all of the polymer burns away, leaving only the perfectly formed end product. Otherwise, any plastic residue will result in imperfections and deformations in the cast part.

Flexible Resins

There are a limited number of manufacturers of flexible resins, including Formlabs, FSL3D and Spot-A Materials, all of which make a material for printing rubbery parts. This is ideal for prototyping elastic products, such as water bottles, handles and grips. Careful not to stretch too much or these components might tear!

High-Temp Resins

Formlabs, however, is so far the only low-cost manufacturer to produce a resin that can withstand high temperatures. The material has a heat deflection temperature (HDT) of 289 °C (552 °F) at a loading of 0.45 MPa , which is not just good for desktop SLA, but for all 3D printing photopolymers, including industrial systems. It can therefore be used for such applications as producing injection molding tools, testing channels designed for hot air or fluids and creating tools for thermoforming and casting.

Formlabs' new High Temp resin has possibly the highest HDT on the market. (Image courtesy of Formlabs.)

Biocompatible Resins

Formlabs is also the only desktop 3D printer manufacturer to produce biocompatible resin. The firm’s Dental SG material meets EN-ISO 10993-1:2009/AC: 2010 and USP Class VI standards, deeming it safe for human contact. The translucent properties of the resin allows for the fabrication of surgical and pilot drill guides. While it is targeted towards the dental industry, this resin could also be suitable for other fields, such as the medical industry as a whole.





Ceramic Resins

Tethon3D is a materials company focused on ceramics for 3D printing, first creating its own ceramics material for 3D Systems' binder jetting 3D printers. The Nebraska-based company then launched a crowdfunding campaign for a resin called Porcelite. The material is a ceramic-photopolymer composite in which the photopolymer binds the ceramic particles. “Green” parts printed with Porcelite can be fired in a kiln, leaving a dense porcelain object that can be glazed and treated like a standard ceramic part.

A finished porcelain cup 3D printed by Nervous System on the Formlabs Form 2 3D printer using Tethon3D’s Porcelite resin. (Image courtesy of Nervous System.)

The material isn't necessarily easy to work with, according to design studio Nervous System, but once users get the hang of it, it may be possible to create some pretty stunning pieces.

Daylight Resins

Photocentric 3D is the only manufacturer of 3D printing photopolymers that react not to UV light, but they actually cure quickly in response to ordinary daylight, thus limiting the need to rely on a UV light source for 3D printing. Instead, a LCD screen can be used to cure the resin, potentially driving down the cost of DLP 3D printing. With this technology, Photocentric 3D has produced three 3D printers and a number of resins, including flexible, firm, hard and castable materials.

Open-Source Resins

It's a bit unclear how many folks are purchasing or building Autodesk's open-source Ember 3D printer, but the software company deserves props for releasing the complete designs for its DLP machine. More than that, Autodesk actually opened up the recipe for its photopolymer resin as well. The company's standard clear resin can be developed at home or in a lab or modified to produce new materials.

As with all products, it's important to do your research before buying any of these materials. 3D printing is a niche space, with low-cost SLA and DLP an even smaller niche within the niche of desktop 3D printing. Therefore, product reviews may be sparse. Some brands, like Spot-A Materials, will argue that its resins are safer than others, while 3D printer manufacturers will advocate for the use of proprietary materials on their machines. Be sure to search the forums before making any purchase!



