3D printing has made it easier than ever to turn ideas into physical objects. But one common issue that almost every 3D printing enthusiast faces is the presence of visible layer lines. Even high-quality FDM printers leave behind these tiny ridges, which can make your model look rough, unfinished, or low-quality. This is where smoothing 3D prints becomes essential.

Whether you’re working with PLA, ABS, PETG, or resin, smoothing your 3D prints can transform them from raw prototypes into polished, professional-grade products. This is especially important for 3D printed props, miniatures, figurines, prototypes, and commercial 3D products.

In this in-depth, beginner-friendly guide, you’ll learn everything you need to know about smoothing 3D prints—step-by-step methods, tools, materials, tips, mistakes to avoid, and expert techniques that will make your prints look flawless.

What Is Smoothing in 3D Printing?

Smoothing is the process of removing or reducing visible layer lines on a 3D-printed object to give it a clean, smooth, and polished surface. Depending on the method and material, smoothing can:

• Improve appearance

• Remove printing imperfections

• Prepare models for painting

• Increase durability

• Make props and miniatures look realistic

• Make models more comfortable to touch

• Create a professional, production-quality finish

Different materials require different methods—what works on ABS may not work on PLA or resin. This guide covers them all.

Why Smoothing 3D Prints Is Important

Smoothing isn’t just about looks—it improves the overall quality and usability of your print.

✔ 1. Enhances Appearance

Layer lines make prints look cheap. Smoothing gives a premium, professional finish.

✔ 2. Better for Painting

A smooth surface allows paint to stick evenly, making your model look more realistic.

✔ 3. Improves Functionality

Smooth parts may fit better and move more freely.

✔ 4. Strengthens the Surface

Some smoothing methods seal the model, improving durability.

✔ 5. Perfect for Commercial Projects

If you sell 3D printed products, smoothing helps you charge more.

Materials You Can Smooth

Different materials require different techniques. Here’s a quick overview:

Essential Tools for Smoothing 3D Prints

Before smoothing, gather the right tools:

• Sandpaper (80, 120, 220, 400, 600, 800, 1000, 1500 grit)

• Filler primer spray

• Acetone (for ABS only)

• Epoxy resin/epoxy coating (like XTC-3D)

• Hobby knife

• Putty/filler (automotive putty or wood filler)

• Heat gun

• Gloves and a mask

• Polishing compounds (for resin)

• Isopropyl alcohol

• Airbrush or spray equipment (optional)

How to Smooth PLA 3D Prints (Most Common Material)

PLA is the most common 3D printing filament, but it’s also one of the hardest to smooth because it does not dissolve easily. However, there are reliable methods:

Method 1: Sanding (Best for Beginners)

Sanding is the most accessible, safe, and affordable method.

Step-by-Step Process

1. Start With Low Grit

Begin with 80 or 120 grit to remove major layer lines.

2. Move to Medium Grit

Use 220 grit to refine the surface.

3. Move to High Grit

Use 400–600 grit for smoothing.

4. Wet Sanding

Use 800–1500 grit for a glossy finish.

Tips

• Always sand in circular motions

• Keep the model steady

• Use water during high-grit sanding

Method 2: Filler Primer (Fast + Effective)

Filler primer fills small gaps and smooths layer lines.

Steps:

1. Shake the spray can

2. Apply a thin, even coat

3. Wait 20 minutes to dry

4. Sand with 400–600 grit

5. Repeat for 2–4 layers

This creates a super smooth base for painting.

Method 3: Epoxy Coating (Glass-like Finish)

Epoxy creates a glossy, ultra-smooth surface.

Steps:

1. Mix epoxy resin

2. Brush on a thin layer

3. Rotate to avoid drips

4. Let it cure for 6–8 hours

5. Light sanding if needed

Great for props, helmets, and decorative items.

How to Smooth ABS 3D Prints (Best Material for Smoothing)

ABS is ideal for smoothing because it dissolves with acetone vapor.

Method 1: Acetone Vapor Smoothing

What It Does

Acetone melts the surface, removing layer lines and leaving a glossy finish.

Steps:

1. Place a paper towel inside a metal container

2. Add acetone to the towel

3. Put the 3D print inside (on a stand)

4. Close the container

5. Wait 5–15 minutes

6. Remove and let it dry

Safety

• Never heat acetone directly

• Use gloves

• Ensure proper ventilation

Method 2: Sanding + Primer

ABS sands better than PLA, so this method is very effective.

How to Smooth PETG 3D Prints

PETG is tough and flexible, but harder to sand.

Best Methods:

• Light sanding (220–600 grit)

• Filler primer

• Heat treatment (VERY carefully)

How to Smooth Resin Prints

Resin prints already have a smooth surface, but they can still have imperfections.

Best Methods:

✔ Sanding with fine grit

Start with 400 grit and go up to 2000 grit.

✔ Polishing compound

Makes resin shiny and reflective.

✔ UV curing

Hardens the surface for sanding.

Advanced Smoothing Techniques

🔥 Heat Gun Smoothing

Works for PLA, ABS, and PETG—requires control so you don’t melt the print.

🧪 Chemical Smoothing

Certain chemicals can smooth specific filaments:

• THF for PETG

• Chloroform for PLA (not recommended for beginners)

Use chemicals with caution.

Step-by-Step Guide: Full Smoothing Process

Step 1: Clean the Model

Remove dust, supports, and residue.

Step 2: Sand Rough Areas

Start with low grit, move higher.

Step 3: Apply Filler Primer

Let dry and sand again.

Step 4: Apply Final Smoothing Technique

Depending on the material:

• PLA: primer + epoxy

• ABS: acetone vapor

• Resin: polish

Step 5: Final Sanding

Use wet sanding for perfection.

Step 6: Seal or Paint

After smoothing, seal the model with a clear coat.

Tips for Professional Smoothing Results

• Always use thin coats of primer

• Don’t rush sanding

• Use dust-free environments

• Wear gloves for acetone and epoxy

• Test chemicals on scrap pieces

• Avoid overheating with heat guns

• Work slowly for delicate models

Common Mistakes to Avoid

❌ Using too much acetone
❌ Skipping sanding
❌ Applying thick primer coats
❌ Using the wrong chemical for the wrong filament
❌ Not cleaning the model before smoothing
❌ Overheating prints during heat treatment
❌ Rushing the process

Smoothing for Commercial Projects

If you’re selling 3D models, smoothing is essential.

Benefits:

• Customers prefer smooth prints

• Higher selling price

• Professional appearance

• Better paint adhesion

• Improved durability

Smoothed prints can be priced 2–5× higher than raw prints.

Conclusion

Smoothing 3D prints is a powerful technique that transforms basic prints into beautiful, professional-grade items. Whether you’re polishing resin miniatures, smoothing PLA models before painting, or giving ABS prints a glossy acetone finish, each method enhances your final result.

The key to successful smoothing is patience, proper tools, and the right method for the right material. Sanding, priming, chemical smoothing, epoxy coating, or polishing—each approach has its strengths. Once you learn these techniques, your prints will look cleaner, sharper, and far more impressive.

Whether you’re a hobbyist or a business, smoothing is the step that elevates your 3D printing game and makes your prints stand out.

FAQs

1. What is the easiest way to smooth PLA prints?

The easiest method is sanding + filler primer, which gives excellent results without chemicals.

2. Can you use acetone on PLA?

No. Acetone works only on ABS. PLA does not dissolve in acetone.

3. What is the best method for smoothing ABS prints?

Acetone vapor smoothing provides a glossy, smooth finish quickly.

4. How do I smooth 3D prints before painting?

• Sand the model

• Apply filler primer

• Sand again

• Use epoxy if needed

• Apply the final primer coat