Finishing 3D prints often requires more than just removing supports or cleaning up stray material; it’s about smoothing the surface to give your object a professional and polished look. Sanding is one of the most effective ways to achieve this, and choosing the right sandpaper grit is crucial. In this article, we’ll explore the importance of sandpaper grit, how to select the correct one, and the best techniques for sanding different types of 3D prints.
What is Sandpaper Grit?
Sandpaper grit refers to the coarseness or fineness of the abrasive particles on sandpaper. It’s categorized by a number that indicates the particle size. Lower numbers (such as 60 or 100) represent coarser grits, while higher numbers (like 400 or 1000) denote finer grits.
When sanding 3D prints, the choice of grit can dramatically impact the final finish. Starting with a coarse grit will remove material quickly but leave visible scratches. Finer grits smooth the surface, gradually eliminating those scratches and giving the print a polished appearance.
Why Sand 3D Prints?
3D printing often results in visible layer lines, rough edges, and surface imperfections that can diminish the quality of the final product. Sanding helps to:
- Remove layer lines and imperfections
- Smooth over rough areas
- Prepare surfaces for painting or priming
By using the correct sandpaper grits in the right order, you can achieve a high-quality, smooth finish that improves both the appearance and feel of your print.
Understanding Sandpaper Grit for 3D Prints
The process of sanding 3D prints typically involves starting with a coarse grit to remove large imperfections, then progressively using finer grits to smooth and polish the surface. Let’s break down the types of sandpaper grit and how to use them.
1. Coarse Grit (60-100)
Coarse grits, typically between 60 and 100, are used for removing significant imperfections or excess material from a 3D print. This grit level is ideal for:
- Removing support marks
- Eliminating large layer lines
- Shaping rough edges
However, coarse grit can leave deep scratches on the print’s surface, which will need to be sanded out with finer grits later in the process. This step is best suited for rough initial work on larger or more detailed prints that require substantial smoothing.
- Recommended grit: 80 for most 3D prints when starting the sanding process.
2. Medium Grit (120-220)
Medium grit sandpaper is the next step after coarse grit. It helps to smooth out the deeper scratches left by the coarse grit and further refine the surface of the print.
- Uses: Smoothing out layer lines and scratches after coarse sanding, refining the surface.
- Recommended grit: Start with 120, then move to 180 or 220 to progressively smooth the print.
This grit range works well for both FDM and SLA prints, particularly when removing visible layer lines or achieving a smooth surface for painting.
3. Fine Grit (320-400)
Once the medium grit has smoothed the surface, fine grit sandpaper (between 320 and 400) can be used to polish the print. This step removes any remaining scratches and prepares the surface for painting, priming, or other finishing processes.
- Uses: Smoothing the print before applying paint or primer, final polish before finishing.
- Recommended grit: 320 or 400 for most final sanding stages.
Fine grit is essential for producing a high-quality finish, especially when working with materials like PLA or ABS, which tend to show layer lines more prominently.
4. Ultra-Fine Grit (600-1000+)
Ultra-fine grits are used when you need a near-polished surface. These grits are often used for finishing prints that require a smooth, glossy finish, such as decorative objects or parts that will be exposed to close scrutiny.
- Uses: Achieving a polished, glossy finish, removing minute imperfections.
- Recommended grit: 600 for a satin finish, up to 1000 or higher for a glossy polish.
Ultra-fine grit is particularly helpful for SLA prints that may need extra smoothness before being painted or finished. This grit also works well with PLA, ABS, and PETG, offering a refined look for projects that need a professional finish.
The Best Sandpaper Grit for Different 3D Printing Materials
Different 3D printing materials respond differently to sanding. Here’s a breakdown of which sandpaper grits work best for common filaments.
1. PLA
PLA is one of the most commonly used 3D printing filaments and is relatively easy to sand. It tends to melt under friction, so be careful when using coarse grits.
- Recommended starting grit: 100-120 for coarse sanding
- Final grit: 320-400 for a smooth finish
2. ABS
ABS is more durable than PLA and can be sanded more aggressively. However, it also has a higher tendency to melt due to the heat generated by sanding.
- Recommended starting grit: 120 for coarse sanding
- Final grit: 400-600 for a polished finish
3. PETG
PETG is tough but flexible, making it more resistant to sanding than PLA or ABS. However, with the right grits, it can be polished effectively.
- Recommended starting grit: 120 for initial sanding
- Final grit: 600 or higher for a smooth, glossy finish
Wet Sanding vs. Dry Sanding for 3D Prints
Sanding can be done in two ways: wet sanding or dry sanding. Both methods have their pros and cons, depending on the material and desired finish.
1. Wet Sanding
Wet sanding involves using water to lubricate the sandpaper, reducing the heat generated by friction. This method is especially useful for materials like PLA and ABS, which can melt if they become too hot during sanding.
- Advantages: Reduces heat, less dust, smoother finish.
- Recommended for: PLA, ABS, and PETG for ultra-fine sanding (600+ grit).
2. Dry Sanding
Dry sanding is faster and more convenient for quick jobs but can generate a lot of heat and dust. This method is best for coarse to medium sanding, where precision isn’t as critical.
- Advantages: Faster, no water cleanup required.
- Recommended for: Initial coarse sanding (60-220 grit).
Tips for Sanding 3D Prints Effectively
Sanding requires patience and a methodical approach to achieve the best results. Here are some tips to make the process smoother:
- Always sand in a circular motion: This ensures that the sanding is even and prevents deep scratches.
- Use a sanding block: This helps maintain flat surfaces, especially on larger prints.
- Start with coarse grit and gradually move to finer grits: Skipping grits can result in uneven surfaces.
- Apply light pressure: Avoid pressing too hard to prevent excessive heat buildup and damage to the print.
FAQs About Sandpaper Grit for 3D Prints
1. What grit should I start with for sanding 3D prints?
For most 3D prints, starting with a medium grit such as 120 is ideal. If there are significant imperfections, you may begin with an 80 grit.
2. Can I skip grits when sanding?
It’s not recommended. Skipping grits can leave scratches or uneven surfaces. Progressing through grits gradually ensures a smooth and polished finish.
3. Is wet sanding necessary for 3D prints?
Wet sanding is not necessary but is highly recommended for finer grits (400+). It reduces heat and dust, providing a better finish on materials like PLA and ABS.
Conclusion
Sanding is an essential post-processing step for many 3D printing projects, and selecting the right sandpaper grit is key to achieving the desired finish. By understanding the different grit ranges and how they affect various 3D printing materials, you can optimize your prints for both appearance and durability. Whether you’re looking for a quick surface refinement or a mirror-like finish, following a structured sanding process will elevate the quality of your 3D prints.