Nothing is more frustrating than finishing a 3D print—only to find its surface bumpy, layered, or uneven. Whether you’re making a prototype, a decorative piece, or a functional part, smoothness matters for both look and performance. The good news? Most surface issues aren’t hard to fix. This article breaks down 3 core solutions (material selection, print settings, post-treatment) to turn rough prints into smooth, professional results.
1. Choose Materials That Boost Surface Smoothness
The right filament is the foundation of a smooth print. Using materials ill-suited for your project often leads to grainy or uneven surfaces. Below is a comparison of 3 common filaments—focused on their surface quality and ease of use:
Filament Type | Surface Smoothness (1=Rough, 5=Smooth) | Best For | Key Tip for Smoothness |
PLA | 3–4 | Prototypes, toys, decorative parts | Use high-quality PLA (avoid cheap brands) to reduce stringing. |
ABS | 4–5 | Functional parts (e.g., phone cases) | Print in an enclosed printer to prevent warping (warping causes uneven surfaces). |
PETG | 4–5 | Durable parts (e.g., water bottles) | Dry the filament first—moisture causes bubbles on the surface. |
Common Question: Why does my PLA print still look rough?
PLA is easy to print, but low-quality PLA (under \(20 per kg) often has impurities. These impurities melt unevenly, leaving tiny bumps. Upgrading to mid-range PLA (\)25–$30 per kg) can instantly improve surface smoothness.
2. Optimize Print Settings to Eliminate Roughness
Even the best filament will produce a bad print if your settings are off. Two critical settings—print speed and layer height—are the main culprits behind uneven surfaces. Let’s break down how to adjust them:
2.1 Slow Down Print Speed (The #1 Fix for Bumps)
Printing too fast (over 60mm/s for most filaments) causes the printer’s nozzle to move before the plastic fully melts and adheres. This leads to:
- Layer separation (visible lines between layers)
- Stringing (thin plastic strands between parts)
- Blobby surfaces
Solution: Use this speed guide based on filament type:
Filament | Recommended Speed Range | Result of Following This Guide |
PLA | 40–50mm/s | 50% smoother surface; less stringing |
ABS | 35–45mm/s | Reduced warping; even layer adhesion |
PETG | 30–40mm/s | No bubbles; glossy finish |
2.2 Lower Layer Height for Fine Details
Layer height is the thickness of each plastic layer the printer deposits. A large layer height (over 0.2mm) makes layers visible—like stacking thin pancakes with gaps. A small layer height (0.1–0.15mm) creates a seamless surface.
Example: If you’re printing a figurine (where smoothness matters), set layer height to 0.12mm. For a simple storage bin (where function matters more), 0.2mm is okay. The tradeoff? Smaller layer heights add ~10–20% to print time—but the smoothness is worth it.
3. Post-Treatment: Turn Good Prints Into Great Ones
Even with perfect materials and settings, some prints need a final touch to be fully smooth. Below are 3 easy post-treatment methods—ranked by effort and results:
3.1 Sanding (Most Accessible Method)
Sanding is the simplest way to smooth rough surfaces. Follow these steps:
- Start with 120-grit sandpaper to remove large bumps (e.g., layer lines).
- Move to 240-grit sandpaper to refine the surface (reduces scratches from 120-grit).
- Finish with 400-grit sandpaper for a near-mirror finish (great for decorative parts).
Pro Tip: Sand in circular motions, and use water (wet sanding) for PLA/PETG—it reduces dust and makes the surface smoother.
3.2 Polishing (For a Glossy Look)
After sanding, polishing adds shine. For PLA/ABS/PETG:
- Use a plastic polish (e.g., Novus Polish) or even toothpaste (non-gel, white).
- Apply a small amount to a microfiber cloth and rub in circular motions for 2–3 minutes.
- Wipe off excess polish—you’ll see a glossy, smooth surface.
3.3 Painting (Covers Imperfections)
If sanding/polishing isn’t enough, painting hides small flaws. Use these steps:
- Clean the print with isopropyl alcohol to remove dust.
- Apply a primer (e.g., Krylon Fusion for Plastic)—primer fills tiny gaps and helps paint stick.
- Paint with acrylic or spray paint (2–3 thin coats, not 1 thick coat—thick paint drips).
Yigu Technology’s Perspective
At Yigu Technology, we often hear users say “my 3D print isn’t smooth”—and 90% of the time, the issue is a mix of material choice and speed. Our printers come with pre-set “smooth mode” profiles for PLA/ABS/PETG, which adjust speed (40–50mm/s) and layer height (0.15mm) automatically. We also recommend starting with ABS or PETG for functional parts—their higher melting points create more consistent layers than PLA. Remember: smooth printing isn’t about expensive tools—it’s about matching materials, settings, and post-treatment to your project.
FAQ
- Q: My ABS print has a smooth surface but warps—how do I fix both?
A: Warping (edges lifting) happens because ABS cools too fast. Print in an enclosed printer (traps heat) and set the bed temperature to 100–110°C. This keeps the print flat and maintains surface smoothness.
- Q: Can I get a smooth surface without sanding?
A: Yes! Use a “layer adhesion” setting in your slicer (e.g., Cura’s “Wall Line Count”)—increasing wall lines (from 2 to 4) makes the outer surface denser and smoother, no sanding needed.
- Q: Why does my PETG print have tiny bubbles on the surface?
A: PETG absorbs moisture from the air. Dry the filament in a filament dryer (40–50°C for 4–6 hours) before printing—this removes moisture and eliminates bubbles.