Additive Manufacturing with Resin - An Introduction

This blog post is not intended to be an all-encompassing collection of knowledge for Additive Manufacturing with resin, but rather a brief compendium of the most important features and functionality of this technology.

3D printing with resin, more precisely epoxy resin, is one of the four major sub-technologies within Additive Manufacturing. The technology, which is particularly popular in the dental industry, comes with its own advantages and disadvantages, as does each of the sub-technologies.

Before we get to those, though, I'd like to explain the different methods available for Additive Manufacturing with resin, how they work, and list some of the manufacturers of resin 3D printers.

How resin 3D printing works

Without first going into more detail about the individual methods: 3D printing with resin produces components from liquid epoxy resin, which is cured with the aid of UV light and thus transformed into plastic.

 One layer after the other is applied to the build plate, similar to filament printers. These layers are then cured individually with the help of the irradiation of UV light, after which the next layer is applied to the previously cured layer.

After printing, the components are removed from the printer and briefly washed in a solvent, which removes excess resin from the component. The component must then be post-cured to achieve the necessary strength and stability. Last but not least, the support structures, which are always necessary for components produced with resin 3D printing, must be removed from the components.

There are many different methods within resin 3D printing. I will focus on the four most important of these and briefly describe their processes.

Stereolithography

Stereolithography, often abbreviated as SLA or SL, is the oldest patented Additive Manufacturing process. As early as 1984, this patent was registered by the US physicist Chuck Hull, who later founded the company 3D Systems®, of which he is now vice president.

In this manufacturing process, a design platform is lowered onto the bottom of a resin tank. There, the first layer is cured using a UV laser beam that moves from point to point and "traces" the geometry of the component. Once the first layer is fully cured, the build platform is raised by the height of one layer.

In most cases, the strength of the laser beam cannot be adjusted on SLA printers. Therefore, print jobs with different plastic effects are only possible with SLA technology after a complete change of the laser beam.

Digital Light Processing

Digital Light Processing, or DLP, is relatively similar to the SLA process, but has one major difference - the light source. Whereas in SLA printers this moves from place to place to cure the layers, DLP printers use a projector to cast UV light onto the entire build platform, thus curing the entire layer at once.

In contrast to the SLA process, the DLP also allows the intensity of the UV beam to be controlled individually, making different plastic effects possible.

Lubricant Sublayer Photo-curing

Lubricant Sublayer Photo-curing, or LSPc® for short, was developed by Nexa3D® and is used solely in their 3D printers.

In this process, too, first and foremost the light source changes. The LSPc® process uses a 4K monitor, which projects the UV light in the form of pixels in combination with a high-contrast mask to the right places.

With this method, too, the intensity of the light source can be controlled individually.

Vision-Controlled Jetting

Vision-Controlled Jetting, or VCJ, was developed by Inkbit and can be found exclusively on the Inkbit Vista™.

VCJ works with the jetting process. This means that the build plate is not dipped into the resin so that it can be selectively cured, but rather the build plate is "sprayed" with resin in the right places and this resin is cured directly with the aid of a UV lamp.

Another difference to the other processes is the high level of automation. In the VCJ process, the print is automatically scanned by a camera after every second layer to detect possible errors. If an error is detected, no interaction is necessary - the integrated artificial intelligence ensures automatic error correction.

Who makes resin 3D printers

Many different manufacturers of resin 3D printers exist. Due to the abundance of the offer of printers of this type, I will focus on the largest manufacturers for professional and industrial resin 3D printers.

3D Systems®

The US company 3D Systems® mentioned earlier is still active in the production of SLA 3D printers today.

The 3D Systems® portfolio includes, for example, the industrial SLA 750, the ProX and the ProJet series.

Inkbit

Inkbit is a young, US-based company best known for developing VCJ technology.

To date, Inkbit has only one printer in its portfolio, the industrial Vista™, which uses VCJ technology and is specifically designed for volume production.

SoonSer

Chinese company SoonSer has been producing resin 3D printers for an international buyer base since 2013.

These resin 3D printers include the industrial Mars Pro series and the professional Smart series.

Nexa3D®

Nexa3D® is a US company with a large portfolio of resin 3D printers and the patent on LSPc® technology.

Nexa3D®'s portfolio includes the industrial NXE 400Pro, NXE 200Pro and the NXD 200Pro designed specifically for the dental industry, as well as the professional XiP 3D printer.

EnvisionTEC

The US company EnvisionTEC, mostly abbreviated as ETEC, is the pioneer for the use of DLP technology within 3D printing.

ETEC sells several resin 3D printers, including the industrial Xtreme 8K and the professional Envision One and D4K printing systems.

Stratasys®

Stratasys® is a US-Israeli company known for its Neo® Stereolithography series.

This series consists of the industrial Neo®800, Neo®450s and Neo®450e manufacturing systems. The Stratasys® portfolio also includes the UV800 post-curing station.

The advantages of resin 3D printing

The greatest advantage of Additive Manufacturing with resin is the surface quality of the components. Provided that the necessary post-processing steps are adhered to, the surface quality will be of highest quality.

3D printing with resin also achieves absolute top performance in terms of detail and resolution.
Other positive aspects include the very high printing speeds and the general user-friendliness of resin 3D printers.

Another massive advantage of this printing technology is the ability to print completely transparent components without visible layers. This is particularly essential for medical indications, e.g. in dentistry, to ensure patient satisfaction.

Highly complex components are no problem for Additive Manufacturing with resin. Whether snake-shaped tubes or components with the smallest cavities inside, resin 3D printing offers the possibility for very high design freedom.

Last but not least, the high manufacturing accuracy should be highlighted. 3D printing with resin enables very precise dimensional tolerances, so that the digital model can be fully realized.

The disadvantages of resin 3D printing

Like everything in life, resin 3D printing has some disadvantages as well as all its advantages.

On one hand, Additive Manufacturing with resin requires a comparatively large number of process steps before a finished and usable component is produced. Washing, post-curing and support removal are necessary for each component and represent a large time expenditure in the long run.

Furthermore, resin components are usually relatively brittle and therefore not suitable for applications in which the parts are exposed to very strong forces.

Caution should also be exercised when exposed to UV light. The resin still reacts to UV light even after post-curing and can be weakened by prolonged exposure to sunlight.

Nowadays however, there are special resins that can eliminate this weak point, at least for the most part.

The last disadvantage to be mentioned is the toxicity of the material. Working with resin requires a safe environment and occupational safety measures such as gloves, protective goggles, etc. to ensure the safety of the users.

Which areas of application resin 3D printing has

Additive Manufacturing with resin has one of its largest applications within dentistry. Whether dental models, surgical guides, splints of any kind, or temporary dentures, resin 3D printing offers dental laboratories a cost-effective and high-quality way to produce dental indications.

But 3D printing with resin is also used in general medicine. Models of organs, casts and splints are just a few of the options that manufacturing with resin offers.

Thanks to its high stability, low weight and the wide range of resins available for a wide variety of component properties, Additive Manufacturing with resin is also excellently suited for tool production.

Resin components have also found a place in the automotive and aerospace industries because of these properties.

Conclusion

3D printing with resin is, with stereolithography, the oldest patented Additive Manufacturing process. However, this does not mean that this technology has had its day - on the contrary!

In the field of Additive Manufacturing with resin, research is constantly being carried out and groundbreaking progress is being made time and again. The development of new technologies such as LSPc® or VCJ technology are impressive proof of this.

I hope this brief overview of resin 3D printing was able to help you gain a little more understanding of the technology and what it can do!