Post-processing is a vital step in SLA (Stereolithography) 3D printing. SLA produces high-resolution, accurate parts but requires further work. The raw prints are often fragile and need strengthening. Post-processing improves surface quality, durability, and functionality of SLA parts. This article outlines the key post-processing techniques for SLA prints.

Significance of Post-Processing for SLA Parts

SLA prints are not immediately ready for use. They often experience issues with excess resin, surface roughness, and trace buildup. Depending on the design and material used, post-processing helps make some final finishing to validate that the parts are clean and strong and have the desired quality finish. In addition, it’s an alternative to remove any remaining chemicals with the end products being of higher quality and performance.

Key Goals of Post-Processing

• Remove excess resin
• Improve surface quality
• Increase part strength & optimize mechanical characteristics using cross-linking.
• Remove support structures

Post-treatment process of SLA parts

The typical post-processing treatments of SLA parts include;

1. Removing Support Structures

A supporting structure is obligatory but it’s necessary to remove it after printing. These supports avoid any deformation as the structure is relatively complex and would bulge out when subjected to heat during the printing. Although, they may leave behind cuts, or are not as smooth as the original surface. Taking them out is a complicated process but must be done cautiously.

Tools for Removing Supports

• Cutters and pliers: Crucial for cutting off the supporters gently.
• Hobby knives: These are employed in removing small support remnants off their surfaces after demolition.
• Needle-nose pliers: Perfect for erasing tender or complex staking scenarios.

2. Cleaning the Part

After removing the supports, the next step is cleaning the part. There is mold material that needs to be cleared to ensure that the part is well-cured since excess resin may cause deterioration in either mechanical strength or the final part surface appearance.

Cleaning Methods

• Isopropyl Alcohol (IPA): A common solvent used for washing SLA prints.
• Ultrasonic cleaner: Is capable of cleaning small details through sound waves.
• Scrubbing: Depending on the resin type to be removed, a soft brush is used to clean embedded resin.

Place the part immediately in IPA solution and wash it in circular motions with fingers.

3. Drying the Printed Part

It’s recommended to dry the part before curing it. Moisture formation can reduce strength and cause uneven methacrylic acid curing. They must be dried properly to avoid the formation of various defects as some stage of curing or finishing is conducted. It also guarantees that there is no leftover IPA.

Drying Techniques

• Air drying: Keep parts in a dry and clean environment.
• Compressed air: Removes moisture from small and complex surfaces.
• Patting with cloth: Used after washing to get rid of surplus liquid.

The final step should begin after the surface has been thoroughly dried.

4. Curing the Part

Curing sets the resin and solidifies the casting. SLA parts require UV light for the curing of the exposed parts. It increases the mechanical strength and stability of the part. Curing time differs based on the resin type in use and the part size to be laminated.

Methods for Curing

• UV lightbox: Irradiates parts with up to uniform doses of UV light.
• UV resin curing station: A specialized machine for curing SLA parts.
• Curing time: Depending on the role typically for some small roles it can be as short as 5-15 minutes.

The UV light exposure can be used in moderation to prevent over-curing.

5. Sanding the Part

After curing a part, you may have rough areas present and require some cutting work. Sanding also tends to make the surface more flat and erases irregularities on that surface. 

Sanding Process

• Coarse grit sandpaper: Use a low grit for rough sanding and then gradually increase the grit number to get finer sanding.
• Finer grits: Moves on to finer grits to polish the surface.
• Wet sanding: This product will eliminate dust and at the same time avoid leaving scratches.

When starting this process, the metal is first ground using 100 – 200 grit then gradually increasing to even finer grains.

6. Polishing the Part

Polishing acts to give the required attractive shiny and smooth surface. It is usually followed by polishing to improve the parts’ physical appearance. Polishing pulled out small dents and rough surfaces. It may be done manually or by the use of automated machines.

Polishing Methods

• Polishing compounds: Wipe with a soft material to polish the surface.
• Buffing wheel: A mechanical tool for polishing.
• Polishing paste: Ideal for final-stage smoothing.

7. Coloring and Coating the Part

Certain assemblies in SLA require further coloration or plating to complete the build. Painting of SLA prints gives the prints some level of sophistication and protects them from environmental degradation. Coatings also enhance the wear, moisture, and overall UV resistance of the part. There are several methods of coloring and coating, which are to be discussed in this work.

Painting SLA Parts

• Primer: This assists paint to stick better to the resin.; This aid helps paint to stick well to the resin.
• Spray paint: A rapid and also layer for large products.
• Airbrush: Suitable for fine or colored applications.

Make sure you are using paint that works well with the resin materials that are to be used.

Protective Coatings

• Clear coats: Serve as a shield from scratches.
• Epoxy resin coatings: Add extra strength and come with improved durability.
• Varnishes: Offer protection against the impacts of sunlight and water.
• Coating added its duration and appearance to the part.

Best Practices for Post-Processing SLA Parts

Here are the best tactics to post-process SLA printed parts;

Handle with Care

During post-processing, SLA parts remain rather delicate. Take extra care during the washing and sanding phase and be very gentle in part handling. Soft tools must be used to avoid damaging very fine features that may crack or bend when using other tools.

Follow the Resin Manufacturer’s Recommendations

The post-processing of each resin must comply with instructions given out by the resin manufacturer. It guarantees your part gets the right properties as well as the right quality.

Experiment on New Methods of Scrap Parts

Any new post-processing techniques introduced should first be enacted on scraps. This way, you can give attention to the techniques you use, without the cost of expensive parts.

Regularly Clean Post-Processing Equipment

Keep your cleaning, curing, and sanding tools in top condition. Stains or soiling are prominent issues that may cause a machine to be unclean – which in turn results in an uneven spread of ink or toner, or even worse, ink or toner spilling over the paper. The gain of resource utility due to maintenance covenants prolonged tools durability, and reliability.

Conclusion

Post-processing is essential for turning SLA parts into functional, high-quality objects. Removing supports, cleaning, curing, sanding, polishing, and painting all contribute to the final product’s success. By following the proper techniques and using the right tools, SLA parts can achieve optimal strength, surface finish, and durability. Post-processing transforms raw prints into professional-grade parts ready for use.