PETG Post-Processing Techniques — Sanding, Polishing & Bonding Guide

PETG has become one of the most popular 3D printing materials, combining the ease of printing of PLA with the durability of ABS. But getting a professional finish requires proper post-processing. In this guide, we’ll cover everything from basic sanding to advanced chemical smoothing.

Why Post-Process PETG?

Raw PETG prints have visible layer lines and may not meet aesthetic or functional requirements for final products. Post-processing can:

• Improve surface smoothness for visual appeal
• Increase strength through better layer bonding
• Create waterproof seals for functional parts
• Enable painting and finishing

If you’re still deciding between materials, post-processing capabilities might influence your choice.

Sanding PETG

Starting Point

PETG sands well but is softer than PLA. Begin with:

1. 200-400 grit — Initial layer line removal
2. 600-800 grit — Smoothing transition
3. 1000-1500 grit — Final polish preparation

Technique Matters

Always sand in circular motions rather than back-and-forth. This prevents directional scratches that become visible after finishing. Wet sanding reduces heat and clogging.

Progression Example

Chemical Smoothing

Unlike ABS, PETG doesn’t respond to acetone vapor. However, alternative methods work well:

Heat Gun Smoothing

A carefully controlled heat gun can smooth PETG surfaces:

1. Set heat gun to 200-250°C
2. Hold 15-20cm from surface
3. Move continuously in sweeping motions
4. Stop when surface glosses but before deformation

ABS users with acetone experience will find this technique different but manageable.

Epoxy Coating

A thin epoxy coating creates a smooth, glossy finish:

1. Sand to 400 grit minimum
2. Clean surface with isopropyl alcohol
3. Apply thin epoxy layer
4. Allow full cure (24 hours)
5. Sand lightly with 2000 grit if needed

Bonding PETG Parts

Large prints often require multi-part assembly. Here are proven bonding methods:

Super Glue (Cyanoacrylate)

Works well for small, non-stress parts:

• Clean surfaces with alcohol
• Apply thin, even layer
• Hold parts in position for 60 seconds
• Full cure in 24 hours

Epoxy Bonding

Best for structural applications:

• Rough surfaces with 120 grit
• Mix epoxy per instructions
• Apply to both surfaces
• Clamp during cure
• 24-hour full cure

Plastic Welding

Creates strongest bonds by melting material together:

• Use PETG welding rod or cut filament
• Heat gun or dedicated plastic welder
• Practice on scrap first
• Fill gaps completely

Production-scale projects benefit most from welding.

Filling and Painting

Priming

After sanding:
1. Apply plastic primer spray
2. Light, even coats
3. Allow flash time between coats
4. Sand with 600 grit before color

Malerei

PETG accepts most paints well:

• Acrylic paints brush-on easily
• Spray paint provides smoothest finish
• Clear coat protects finish
• Avoid solvent-heavy paints

Troubleshooting

Sanding discolors my print

This indicates excessive heat. Wet sand to cool the surface, or use lower grit more gently.

Chemical smoothing doesn’t work

PETG requires different chemicals than ABS. Heat-based methods work better.

Bond fails under stress

Use epoxy or welding for structural bonds. Super glue isn’t suitable for stress applications.