While 3D printing produces amazing results, your print often needs post-processing to achieve a professional, polished look. Whether you’re working with ABS or PLA, post-processing techniques like sanding, smoothing, priming, and painting can dramatically improve the visual quality of your prints. This guide will walk you through essential post-processing methods, focusing specifically on ABS and PLA, two of the most common 3D printing materials. By following these steps, you’ll transform your raw prints into professional-grade models, perfect for display, prototypes, or functional parts.
1. Why Post-Process Your 3D Prints?
3D prints often come off the printer with visible layer lines, rough edges, and minor imperfections, especially if printed at larger layer heights. Post-processing is essential if you’re looking to achieve a smooth, professional-grade surface. This is especially important for display models, prototypes, or parts that need to fit into other components. While PLA and ABS have different properties, both benefit from the right post-processing techniques.
2. Key Differences Between ABS and PLA in Post-Processing
ABS:
- More flexible than PLA, making it easier to sand without cracking.
- Can be smoothed using acetone vapor, which dissolves the surface and removes visible layer lines.
- More prone to warping during printing, which may need correction in post-processing.
PLA:
- Brittle and more prone to cracking if handled aggressively during sanding.
- Cannot be smoothed with acetone, but can achieve a high-quality finish with careful sanding and painting.
- Easier to print and often requires less post-processing compared to ABS.
3. Essential Tools for Post-Processing
- Sanding tools: Sandpaper (in different grits, from 100 to 2000), sanding sponges, and files.
- Fillers: For filling in gaps or imperfections, especially useful with PLA prints.
- Primers: Plastic-friendly primers to create a smooth surface for painting.
- Paints: Acrylic paints or spray paints that adhere well to plastic.
- Masking tape and gloves: For protection and ensuring clean lines during painting.
- Acetone (for ABS): For smoothing ABS prints.
- Airbrush (optional): For professional-grade painting with fine control.
4. Step-by-Step Guide to Post-Processing PLA
Sanding PLA
PLA prints tend to have more visible layer lines than ABS, and because of its rigidity, sanding can be challenging. Start with coarse sandpaper (100-200 grit) to remove large imperfections and gradually move to finer grits (up to 1000 or 2000 grit) to smooth the surface.
Tips for Sanding PLA:
- Sand in a circular motion to avoid creating scratches that follow the layer lines.
- Be gentle; PLA can be brittle and may crack if sanded too aggressively.
- Wet sanding with water and fine-grit sandpaper (600 and above) can help reduce heat build-up and avoid plastic deformation.
Priming PLA
Once you’ve sanded the print, apply a layer of plastic-friendly primer. Priming helps to further smooth the surface and create a uniform base for painting. For best results, use a filler primer that fills in small imperfections and sand it again with fine-grit sandpaper before painting.
Painting PLA
After priming, you can apply paint to your PLA model. Acrylic spray paints work well on PLA and offer a variety of finishes (matte, gloss, etc.). Apply thin, even coats of paint, allowing each coat to dry completely before adding the next.
Tips for Painting PLA:
- Use multiple light coats rather than one heavy coat to avoid drips and uneven coverage.
- Use masking tape to create clean edges or protect areas you don’t want to paint.
- If you’re using a brush, opt for high-quality acrylic paints and apply in thin, smooth layers.
5. Step-by-Step Guide to Post-Processing ABS
Sanding ABS
ABS is more forgiving than PLA when it comes to sanding. Like PLA, start with a coarse grit (100-200) and work your way up to finer grits (up to 2000). ABS tends to respond well to wet sanding, which helps reduce dust and smooth out the surface.
Tips for Sanding ABS:
- Wet sanding with high grit sandpaper will provide a much smoother finish.
- You can be more aggressive with ABS than with PLA because it is less brittle.
Acetone Smoothing for ABS
One of the biggest advantages of ABS over PLA is its ability to be smoothed with acetone vapor. Acetone melts the surface of the ABS, blending the layer lines together for a smooth, glossy finish.
Acetone Smoothing Process:
- Place your ABS print in a sealed container with a small amount of acetone.
- Do not submerge the print in acetone; instead, allow the vapor to gently smooth the surface.
- After 10-15 minutes, remove the print and let it dry. The result will be a shiny, smooth finish.
Tips for Acetone Smoothing:
- Do not leave the print in the acetone vapor for too long, as it can melt the details.
- Use in a well-ventilated area, as acetone fumes can be harmful if inhaled.
Priming ABS
Priming ABS is similar to priming PLA, but the acetone smoothing process may reduce the need for heavy sanding and filling. Apply a plastic primer after smoothing for best results, followed by sanding with fine-grit sandpaper before painting.
Painting ABS
ABS can be painted similarly to PLA. Use acrylic or spray paints designed for plastics and apply thin, even coats. ABS tends to hold paint well, especially if it’s been properly primed.
Tips for Painting ABS:
- Apply multiple thin coats to avoid dripping and uneven paint distribution.
- Use a matte finish for functional parts and gloss for aesthetic models.
6. Case Studies: ABS vs. PLA Post-Processing Results
Case Study 1: PLA – Decorative Vase
A user printed a decorative vase in PLA with a 0.2mm layer height. The vase was sanded using fine-grit sandpaper (starting at 200 and ending at 1000). A filler primer was applied, and after a light sanding with 2000 grit, the user applied two coats of acrylic spray paint. The result was a smooth, high-gloss finish with no visible layer lines.
Case Study 2: ABS – Action Figure
An action figure printed in ABS was post-processed using acetone vapor smoothing. The acetone eliminated most of the layer lines, and after priming and painting with an airbrush, the figure had a professional, polished look. The acetone smoothing also improved the durability of the parts, making the joints and limbs more resistant to wear.
7. Best Practices for a Professional Finish
- Work in stages: Don’t rush the sanding and painting process. Each step, from sanding to priming, contributes to the final result.
- Use wet sanding for finer surfaces: Wet sanding with high-grit paper (600 and above) helps achieve the smoothest finish, especially for PLA.
- Don’t skip priming: Priming ensures even paint adhesion and covers minor imperfections.
- Test your paints: Some paints react differently to different plastics. Test your paint on a small part of the print before applying to the entire model.
- Consider post-processing time: While acetone smoothing for ABS can save time, sanding and priming PLA often results in a superior, longer-lasting finish.
8. Conclusion
Post-processing is the key to taking your 3D prints to the next level. While PLA and ABS require different techniques—sanding and priming for PLA, and acetone smoothing for ABS—both can achieve professional-grade finishes with the right tools and methods. By following these steps and practicing your techniques, you’ll soon be producing 3D prints that are not only functional but also aesthetically impressive.
References:
- Post-Processing 3D Prints: The Essential Guide
- How to Smooth and Paint PLA 3D Prints
- Acetone Smoothing: The Secret to Shiny ABS Prints
