3D printing is an incredible tool for creating custom parts, models, and prototypes, but one common challenge is the rough surface finish that many prints have straight off the printer.
These imperfections, often caused by visible layer lines, can affect both the aesthetic appeal and functionality of a print.
(This not something you will have a problem with when your parts are printed on the high quality Multi Jet Fusion production equipment we use at BDL 3D!!).
Recent studies have highlighted that post-processing treatments, such as heat treatment, stress relieving, or surface coatings, play a pivotal role in enhancing the mechanical attributes of 3D-printed components.
These processes improve structural integrity, durability, and resistance to fatigue, addressing material-specific challenges like porosity in metal additive manufacturing.
Whether you are working with PLA, ABS, PETG, or resin, different methods can help you achieve a smooth surface.
In this guide, we will explore the best ways to remove layer lines and imperfections, from sanding and polishing to chemical treatments, heat application, and coatings.
Why Do 3D Prints Have Rough Surfaces?
Several factors contribute to rough surfaces and visible layer lines in 3D prints:
- Layer Height and Resolution – Lower layer heights (e.g., 0.1mm) produce finer details, while higher layer heights (e.g., 0.3mm) create more noticeable ridges.
- Print Speed and Cooling – Faster print speeds can cause rougher finishes, while incorrect cooling settings may lead to inconsistent textures.
- Filament Quality and Material Type – Different materials behave differently when printed. PLA, ABS, and PETG each have unique characteristics that influence surface finish.
- Printer Calibration – Proper calibration of the printer’s bed leveling, extruder temperature, and stepper motor settings can help improve smoothness.
- Support Material Removal – If support structures are used, their removal can sometimes leave uneven surfaces that require additional smoothing.
Best Methods for Smoothing 3D Prints
1. Sanding & Polishing (Best for PLA, ABS, PETG, Resin)
Sanding is one of the most effective and widely used techniques for smoothing 3D prints. It is a manual process but allows you to have full control over the finish.
How to Sand 3D Prints Properly:
- Begin with 200-400 grit sandpaper to remove rough edges and layer lines.
- Progress to 600-800 grit sandpaper for refining the surface.
- Use 1000-2000 grit sandpaper for a final smooth polish.
- For wet sanding, dip the sandpaper in water to minimize dust and improve results.
- Polish the surface with a buffing wheel or clear coat spray to enhance the final finish.
Tips for Best Sanding Results:
- Always sand in circular motions to prevent visible scratches.
- Use a sanding block to ensure even pressure across the surface.
- Wear a dust mask if dry sanding, especially with plastic materials.
If you’re new to working with different 3D printing materials, check out BDL 3D’s guide to 3D printing materials to learn which are easiest to smooth.
2. Chemical Smoothing (Best for ABS, Resin)
Some materials, such as ABS and resin, can be chemically smoothed using solvents that dissolve the outer layer, creating a glossy, seamless finish.
Acetone Vapor Smoothing (ABS Only)
Acetone is an effective solvent for ABS plastic and is commonly used for vapor smoothing.
- Place a small amount of acetone in a sealed container.
- Suspend the ABS print inside the container, ensuring it does not touch the acetone.
- Allow the vapor to soften the print’s surface over 15-30 minutes.
- Once smooth, remove the print and let it dry for a few hours.
Isopropyl Alcohol (IPA) Smoothing for Resin Prints
For resin prints, isopropyl alcohol (90% or higher) is used to remove excess resin and improve smoothness.
- Submerge the print in isopropyl alcohol for 1-3 minutes.
- Gently agitate the container to dislodge excess resin.
- Cure the print under UV light to harden and further refine the surface.
If you’re looking to achieve a uniform, professional finish on 3D printed nylon parts, BDL 3D’s PolyShot Surfacing service offers a chemical-free, automated method to smooth your prints without compromising detail.
3. Heat Gun Smoothing (Best for PLA, ABS)
Heat application can help soften and smooth out surface imperfections in PLA and ABS prints.
How to Use a Heat Gun for Smoothing:
- Set the heat gun to low-to-medium heat.
- Keep the gun moving constantly to prevent overheating.
- Apply heat in quick, sweeping motions to gradually melt the outer layer.
- Allow the print to cool down naturally before handling.
4. Filler Priming & Painting (Best for PLA, ABS, PETG)
If you want a highly polished, professional finish, filler primers and paints can be used to achieve an even surface.
Steps to Prime and Paint a 3D Print:
- Apply a thin coat of filler primer to fill in small imperfections.
- Let the primer dry, then sand with 600-1000 grit sandpaper.
- Apply a second coat if necessary for a smoother result.
- Paint with acrylic or spray paint for a polished finish.
- Seal with a clear coat or varnish to protect the surface.
Choosing the Best Smoothing Method
| Material | Best Smoothing Methods |
|---|---|
| PLA | Sanding, priming, painting |
| ABS | Acetone vapor, sanding, painting |
| PETG | Sanding, polishing, priming |
| Resin | IPA wash, UV curing, sanding |
Common Mistakes to Avoid
- Over-sanding: Can remove too much material and distort fine details.
- Excessive acetone exposure: Can weaken ABS prints if left too long.
- Skipping primer before painting: Results in an uneven paint finish.
- Holding a heat gun in one place for too long: May deform the print rather than smooth it.
When to Consider Professional Smoothing
If achieving a perfectly smooth finish is essential, professional post-processing services can offer high-quality results with specialised equipment.
How BDL 3D Can Help
BDL 3D provides PolyShot Surfacing, a process that smooths 3D prints without harsh chemicals. They also offer dyeing and painting, material advice, and design for manufacturing to support high-quality results at every stage.
Conclusion
Smoothing 3D prints enhances both aesthetics and functionality, making them more visually appealing and durable. Whether you choose sanding, chemical smoothing, heat treatment, or priming & painting, the right technique depends on the material and desired outcome.
Key Takeaways:
- Sanding is effective for most materials but requires time and patience.
- Acetone vapor smoothing works well for ABS but needs careful handling.
- Heat guns can help with PLA but require control to avoid warping.
- Priming and painting can create a flawless, professional look.