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How to Post-process Resin Prints

How to Post-process Resin Prints

Post-processing is important because it helps you get the most out of your (Stereolithography) SLA and resin prints. It is critical to follow the correct procedure to make sure that the quality and mechanical performance of your prints are maximized. However, stumbling blindly might make things difficult, if not impossible.

In this article, we'll go over the steps you'll need to take and the many approaches you can take for each stage as well as the safety precautions to follow and all the equipment you might need. Let's go!

Safety Precautions

Before we get started, let's make sure that you are up to date with the safety precautions that are involved with handling SLA resins. If not handled appropriately, these resins can be poisonous, and direct contact with the skin should be avoided. Spills can also create a mess, so make sure you have enough room to work.

What You’ll Need

  • Nitrile gloves
  • Safety glasses
  • A clear workspace

If resin gets in contact with bare skin, wash it off with soap and water right away. Avoid leaving resin trails on any goods you come into contact with. If there is a spill, clean it up as soon as possible before the resin hardens.

Let's get started with post-production now that that's out of the way!

Cleaning Resin Prints

  1. Rinse-Off the Part

Your part is covered in uncured resin when it comes out of the printer. Before continuing with post-processing, you'll need to rinse it out.

Method 1: Ultrasonic Bath

The ultrasonic bath used in cleaning resin prints is similar to the one used to clean jewelry, it is a professional (and a relatively expensive) method. Fill the bath with enough cleaner solution to completely cover your print and soak for a few minutes. This will remove the thin coating of uncured resin that has adhered to your model, leaving a smooth, clean surface behind.

In most circumstances, Isopropyl Alcohol (IPA) in a rather high concentration will be used, but there are other options. If isopropyl alcohol isn't available or you want something non-flammable, tri(propylene glycol) monomethyl ether (TPM) and di(propylene glycol) monomethyl ether (DPM) can be used instead of IPA. DPM is used mostly in industrial applications.

Method 2: Dunk and Rinse

If you don't have access to an ultrasonic bath, merely soaking your part in IPA will suffice. To remove the resin, move your part around and thoroughly rinse it. This procedure is simple and quick, but it won't get the job done as thoroughly as an ultrasonic bath. To remove the resin sticking to the surface, two or more rinses may be required.

  1.  Remove Supports

The next step is to detach your model from the tree-like support structures. This can be done either before or after curing, but it will be easier if done before. Always keep an eye out for stray plastic fragments that may fly.

Method 1: Break Them off by Hand

Breaking the supports off by hand is the quickest way to go if you don't mind little details. However, if your model has intricate features, it's best to be more cautious.

Method 2: Use Flush Cutters

Use flush cutters to delicately snip out the supports for more complicated components. Get as close to the model as you can without scratching it.

Small nubs will be left on your print with both procedures. This is unavoidable, but with a little sandpaper and care, it can be readily fixed.

  1. Cure the Print

UV-curing your print is the final step in post-production. This is required for most functional prints because it calibrates the model's material attributes.

Method 1: Curing Station

Curing stations are sold by many SLA printer manufacturers. These are designed specifically for their resins, allowing for precise curing durations. This is especially beneficial in professional settings and for larger prints.

Method 2: Nail Polish Curing Lamp

This is a fast and easily accessible method of curing your model at a low cost. Place it under a nail polish lamp and leave it to cure overnight. Adding a turntable can help you get a more uniform distribution of light.

Method 3: DIY Curing Chamber

Many enthusiasts will construct their own, low-cost curing chambers, which will serve as improvised counterparts of commercial curing stations. Placing a UV lamp in an aluminum foil-lined box is a simple way to accomplish this. To get uniform exposure, place the model on a solar or battery-powered turntable.

Method 4: Solar Power

Go Green! Use good old solar energy. When you put your component outside on a sunny day, you'll get a lovely, even UV light. The biggest disadvantage of this method is that it necessitates more patience. You'll have to relax and let the sun do the heavy lifting.

  1. Sanding

Sanding resin SLA 3D printed items is very often the most effective approach for smoothing edges, removing defects, and removing any remaining support marks. Hand sanding works best on simple shapes, but complex structures with deep cracks and internal supports might be difficult or impossible to sand.

Starting with low grit sandpaper and gradually moving to finer grit levels over time is the ideal technique to sand resin prints. For example, resin SLA 3D printed items can be polished to be smooth and shiny with 3,000 grit sandpaper. Gradually raise the grit, polishing and smoothing the portion until it has the texture you want. The components should become reflective at roughly 12,000 grit. If you're having difficulties getting a smooth surface on a rough item, try sanding it under running water or with a wet piece of sandpaper.

The most common reason for sanding 3D printing parts is to remove support markings. As you gain experience with 3D printing, it may be worthwhile to put in more effort during the print preparation phase to angle your 3D prints in ways that eliminate or reduce supports from critical portions of a print. When printing a bust or model, for example, it is sometimes possible to tilt the part so that the model face does not require support. The sanding procedure will be significantly easier as a result of this.

Once you're satisfied with the sanding, a simple microfiber cloth can be used to erase any minor defects or sandpaper powder remaining on the print's surface.

It has also been discovered that rubbing the component with mineral oil after a wash might give a particularly smooth surface finish if you're doing a lot of sanding on a single part. Mineral oil, like most procedures, may or may not provide substantial improvements for your print depending on component geometry; you may need to sand numerous parts before figuring out the best finishing method.

  1. Painting

Method 1: Printing with Dyed Resin

To generate a custom color, 1Litre of Clear Resin is dyed, usually with Alcohol Ink. The updated clear resin can then be put into your 3D printed for use and the part would print in the chosen color you have created. Alcohol inks are the best coloring agents because they completely dissolve into clear resin to give you consistent color throughout your print. Make sure you separate the wash solutions for each colored part because the colored resin would dissolve in the wash. Label your wash solutions so that you don't mistakenly wash a white resin part in a container with dark dye.

Method 2: Dyeing resin parts after Printing

If you don't want to mix a complete batch of dyed material but still want to dye your parts, you can do it after they've been printed. To make multi-colored pieces, just dip sections of interest into multiple dye solutions.

Certain resins, such as Clear Resin and Elastic Resin, will be easier to color than others. We recommend making an alcohol ink solution and immersing your 3D printed parts, including the supports, in it at once.

Method 3: Painting With Acrylic

For complex sculptures with fine details, acrylic paint may be the only way to add color. Although this method is time-consuming and the outcome is dependent on your painting skills, it gives the user greater artistic freedom. To avoid contaminating other parts, dyeing resin parts after printing will necessitate a separate washing unit. Painting using acrylic avoids this problem because pieces can be washed and cured as usual before being painted.

Method 4: Spray painting

Spray painting produces smooth surfaces and strong color gradients and is particularly useful for big or flat prints. Resin 3D printed items can be spray painted swiftly in the hands of an experienced user. Spray painting is best accomplished by applying many, thin coats in a single session. Because it quickly covers a surface with an even coating, spray-on primer is the best technique to paint your printed parts.

Method 5: coating

There is one alternative step users can take in the polishing process for sections that were designed to genuinely wow. Instead of using one of the painting processes discussed above, you might coat your resin 3D printed pieces to completely polish them. To achieve a gleaming surface, a clear spray coating is usually recommended. After the component has been properly sanded, spray coatings should be applied.

It is recommended to avoid the curing phase for Clear Resin when coating  3D printing items, as it can cause yellowing. Curing to bring out the mechanical properties of the object you're coating may not be necessary if it's only going to be used for looks. After an IPA and water wash, instead of curing, the part should be allowed to air dry. Apply two to three spray applications in a dust-free atmosphere once it's entirely dry.

Conclusion

Resin post-processing is not a difficult procedure. Most users can already wash, post-cure, paint, sand, and other tasks with ease after a few prints. We have made it easier for you to bring your project to life by giving you a good understanding of how to post-process your 3D printed parts.

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