How Do Resin Printers Work? A Complete Guide

When your 3D printed objects require high resolution and a fine level of detail, a resin printer is a much better choice compared to filament.

If you’ve never used one before, choosing between the various technologies can be confusing, especially if you don’t know how these printers work.

In a very simplified understanding and regardless of technology, a resin printer works by turning liquid resin into a solid, filament-like material. Since the material is liquid when extruded, these printers can deliver a higher resolution and greater level of detail compared to FDM printers.

The actual way resin printers work depends on the type of printer you use.

How Different Resin Printers Work

Resin 3D printers can be classified into three major categories, stereolithography, digital light processing, and liquid crystal display.

Each technology prints liquid resin in a different way.

Stereolithography (SLA)

Stereolithography, commonly called SLA, is the first invented 3D printing method and one of the most popular. 

SLA printers use a UV laser beam to cure and solidify printed resin. A pair of movable mirrors direct the beam where it’s needed, allowing for on-spot resin curing. This makes the method incredibly effective. 

In fact, SLA is one of the best 3D printing methods to use if you want accurate and smooth models. The method is often employed in the jewelry sector, engineering, and product development.

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SLA printers can work with a wide range of 3D printing resins, including biocompatible and ceramic-reinforced.

Digital Light Processing (DLP)

Less popular than FDM and SLA, digital light processing (DLP) 3D printing is one of the best choices if you need fast printing speed.

The method’s greatest advantage is that this machine uses a digital projection of UV light to expose and cure each printed layer at once.

On the downside, DLP achieves a lower resolution than SLA. This could be a drawback if you need models with a smooth surface, as DLP usually requires more post-processing. 

Similar to SLA, DLP printers use a bottom-up approach – the resin is pushed up and built upside-down onto a building surface positioned to face the light source located underneath it.

Unlike SLA, DLP uses thousands of tiny micro mirrors to direct light where needed. The quality of these digital micro mirror devices (DMD) has a direct impact on resolution.

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Liquid Crystal Display (LCD)

Often called masked stereolithography (mSLA), LCD 3D printing is more similar to DLP. This process, too, uses a light source to cure an entire layer at once.

However, instead of using mirrors and a digital projector, it uses a combination of LED and liquid crystal display to direct light where needed.

The comparison to SLA is actually given by the level of detail and resolution you can achieve with this method. As this printer relies on an LCD screen, it can control the LED light patterns and allow for customized curing of each printed layer.

On the downside, LCD printers vary from low to high resolution (more or less like LCD TVs), based on the actual number of pixels the panel has. That said, LCD and DLS printers are more common among home users compared to SLA.

The Step-by-Step Process of Resin 3D Printing

Printing with resin is fundamentally different from FDM, but the steps you should take are similar. 

1. Choose the Preferred Printing Method 

Printing 3D resin is possible with an SLA, DLP, or LCD printer. The former produces the best results, but it is the most complex and expensive. DLP and LCD are the most common 3D printers for home use. 

Prices can vary greatly based on the actual resolution, but machines like the Anycubic Photon or Elegoo Mars bring excellent value for money.

As a rule of thumb, LCD is your best choice if you want to maintain a higher resolution and achieve better results with less post-processing.

2. Choose the Resin 

Once you decide which printer type you want to use, consider the right type of resin. 

3D printing resins come in a variety of styles, from rubber-like, flexible resins suitable for wearable cases and the like to rigid and ultra-rigid variants that are majorly used for high-end prototyping and industrial applications. 

If you don’t know which resin to start with, standard or clear is probably your best bet. These resins have similar properties, but one comes in solid colors whereas the other cures to a clear, see-thru finish.

Both options are ideal for most models, especially as you’re learning resin 3D printing. 

Once you master the process, you can check out the various resin types and see which is the best suited for your purposes.

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3. Prepare Your Model 

Resin 3D printing starts in the same way as FDM 3D printing – with a CAD design. You must then save the design as an STL file and import it into a slicing software.

Preparing a 3D printing file is a relatively easy process (albeit the design part can be complicated, depending on what you wish to achieve). 

To do it: 

  • Find and install CAD software. Some programs require you to pay a one-off fee or a subscription, while others are free. 
  • Use the CAD program to design your object. 
  • Save the file as STL. This option is available in most CAD programs, but it is not the default extension. Remember to change it when saving the file, or the slicer won’t recognize it.
  • Export the file to your slicer.

4. Slice the File 

STL file prepared, it’s time to slice the file. Slicing basically refers to transforming the design into G-Code-like language that the printer can read. 

This is an important distinction compared to FDM 3D printers, because resin printers don’t actually use G-Code. Instead, they use proprietary formats, and very few slicers are compatible with all resin printer types.

Hence, you should check software compatibility before deciding which slicer to use.

For instance, Anycubic Photon uses the Photon Workshop 3D slicing software. Similar to Cura, this is an open-source program, but it might not be compatible with other printer brands. Indeed, Elegoo Mars is compatible with the Lychee Slicer 3.6

Since each software is different, the actual slicing procedure might vary. Generally, you have to import the STL file, input parameters such as layer height, etc., and hit the slice button.

5. Calibrate Printer 

Slicers typically calibrate the printing parameters during slicing, based on the type of material used. Yet, similar to FDM filaments, each resin can have slightly different requirements, based on the manufacturer. 

The reason each brand needs specific calibration is that the formula can suffer slight variations. 

Environmental conditions can also affect printing quality and calibration. These are variables that your slicer can’t account for, so you’ll have to make adjustments manually.

If this is the first time you’re printing with a specific resin type or a specific printer, leave calibration as set by your slicer. Print a small object and check for under- or over-extrusion, layer curing, and other potential issues.

Note down everything, and calibrate the machine accordingly. 

6. Post-Processing 

The last step to 3D printing with resin is post-processing.

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Resin models typically need to be washed with isopropyl alcohol or a similar solvent to remove sticky residues. Some resins are water-washable, so check before applying any treatment. 

Sanding and smoothing might also be necessary, depending on how well you calibrated the printer, resin quality, and other factors.

Advantages Of Using Resin Printers

Resin 3D printing is more expensive than FDM. Overall, it is also messier and more challenging. Yet, there are advantages to it.

Faster Printing Process 

Undoubtedly, the main advantage is the faster printing process. SLA moves a laser beam to cure liquid resin as it is deposited on the building surface. DLP and LCD are even faster, these methods curing whole layers in a single step.

Since resin is already liquid, you won’t have to wait for the material to melt either.

Higher Resolution 

Another advantage related to the physical state of resin is the resolution you can achieve. While the method and resin type can impact resolution, you won’t be bothered by clearly visible lines between one layer and the other.

Resin 3D prints are easier to post-process to a smooth, shiny finish, which makes it possible to use the casting method to 3D print jewelry, dentures, medical devices, works of art, miniatures, and other delicate items.

Another highlight is the surface which is always sealed and waterproof. 

Stronger Prints 

Lastly, resin printers create higher quality and longer-lasting prints.

Once again, the mechanical properties can vary based on the resin used (rubber-like resin has low tensile strength but is highly flexible, for instance), but generally, you can expect these parts to resist better to shear stress compared to filament prints.

Wrapping Up

Resin 3D printers use light technology to cure thin layers of resin as they are deposited onto the building surface. This method creates higher resolution and stronger parts, regardless of the resin type and actual method. DLP resin printers are some of the most popular for home use, together with LCDs. SLA printers produce exceptional results, but they are more expensive and more challenging to use.

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