How to Post-Process SLA 3D Prints – Resin

Learning how to post-process SLA resin 3D prints is something that people want to do, but haven’t found the clearest steps. This article will take you through the post-processing steps for resin models, so you can be more comfortable doing it with your own models.

Here’s how to post-process SLA 3D prints:

Wash the model
Remove supports
Sanding
Curing
Gluing and assembly of models
Priming & painting

Wash the Model

Once you take off your model from your build plate, you will need to wash it in Isopropyl Alcohol (IPA) for a few minutes. This helps to remove any uncured resin and slightly cured resin from the print.

I recommend using a Wash & Cure Station like the Elegoo Mercury Plus 2-In-One Machine. It’s a great system for resin prints that allows you to effectively wash models, as well as cure them in a later stage. This is the same one I got as my first wash and cure station, and it works great.

You can make use of a soft toothbrush to wash the surface of the resin, since some resin can be slightly cured and might not be removed from the standard washing process. Some people who don’t take this step can sometimes experience white residue on their models.

Make sure you are wearing your nitrile gloves while handling resin and the cleaning process, since resin is quite toxic to the skin over time.

There are different types of cleaning solutions that you can use such as denatured alcohol and methylated spirits.

Here’s a video demonstrating other resin cleaning solutions.

Removing Supports

After washing the model, you can now begin to remove the supports on the model once the model is dry.

It is better to remove the supports from the model before curing because the supports become much harder to separate from the main model after curing.

Also, when breaking off the supports after curing, the supports can come off with the main pieces or even cause the main model to have marks or dents.

Some people recommend even using hot water to help remove supports, by soaking it in the model and they can break away easier. In the video below by Uncle Jessy, he shows one method of using flush cutters to remove the individual supports to chip away at time.

This can take a lot longer though. When you use the hot water method, you can leave it to soak for about 30 seconds and make sure the water isn’t too hot, especially if you have models with a lot of details since it can warp.

Once you’ve done that, you can start carefully pulling the supports away from the model.

Sanding

To effectively sand your resin print, you would want to start with low coarser grit sandpaper (100-150) to dry sand the surface of the print. After the initial sanding, you can gradually progress to 220, 320, 400, and 600 grit sandpaper depending on how smooth you want the model to be.

I’d recommend going with the PAXCOO Sandpaper Assortment 120-3,000 Grit from Amazon.

While doing this, it’s a good idea to have a face mask on, with safety google to prevent the dust particles from getting into your body. You can even do wet sanding to reduce the presence of dust.

Here’s a video from 3D Printed Props that shows how to sand a resin print successfully.

Curing

The next process after you have removed supports and sanded your model is to cure it. This is done to harden the resin model fully and make it safe to handle without gloves.

The main method to cure resin models is to use a source of UV light which could either be with direct sunlight, a curing station, or UV lamp/flashlight with turntable.

I personally started out with the Comgrow UV Resin Curing Light with Turntable from Amazon. It has 6 high-powered 405nm UV LEDs that can efficiently cure resin models. The turntable is solar-powered and rotates pretty smoothly.

They do recommend to use eye protection since the lights get really bright. Many users are really happy with this as a UV curing option and say it works perfectly. You can use it to make a curing booth with some cardboard, lined with reflective aluminum sheets.

The amount of time for the model to be exposed to UV rays depends on the size of the model and the intensity of the UV rays.

It usually takes about 1-5 minutes to completely cure your resin print when curing with a UV light source. When using sunlight to cure your resin print, you would have to leave it for about 3-5 hours under sunlight.

Check out the video below to see how long to cure models.

Gluing and Assembly of Models

Some models come in pieces, so if your model is one of those, here’s where you want to start assembling them.

After curing your model, you can now begin to assemble the parts with some form of adhesive. You can simply use superglue to glue your models together. It’s a good idea to also use an accelerator to help the superglue harden quicker.

Gorilla Glue from Amazon works well for this. A good accelerator is the Starbond Instant Set Accelerator, also from Amazon. It makes superglue cure in just seconds, without the white residue that you sometimes get with other brands.

Another interesting method to glue your model together is to actually apply UV resin to the parts and cure it with a UV laser pen or UV light. I’ve done this many times successfully.

You can see it in action in the video below.

Painting

After sanding your model to your desired preference, you may want to paint it to further enhance its appearance. Before you apply paint, you want to coat the model with a primer to help serve as a base for the paint.

After priming, you can then add your desired paint to the model, either by spray-painting it, using an airbrush if you have access to one, or using a paintbrush with paint.

The simplest method is to use Rust-Oleum Primer & Spray Paint from Amazon. They have many colors that you can scroll through, until you find some that you like. If you want to paint the model a darker color, gray primer works well, but for lighter colors, use a white primer.