Many people’s gripe with finishing 3D printed parts is sanding. Understandably so, as it can be the most time consuming part (and can be physically laborious at times). Aside from the paint job, sanding tends to be what makes the difference between a mediocre project and professional-grade. It’s all about that polish!
Before diving in I would like to add that this guide is specifically geared towards sanding 3D printed parts, although the materials and techniques in this guide can be applied towards other stuff too. There are also some resources like XTC 3D and filler primer that make sanding much easier. However, I will not be discussing these in that much in this particular guide. For a more comprehensive guide, I wrote an introduction to finishing 3D printed parts that you can read here
Sandpaper comes in many forms and varies greatly in grit number, you’ll rarely ever only use one type. I use 80-220 the most. Some hobbies require fine grit all the way up to 10,000 grit. Unless you’re a pro propmaker like VolpinProps looking to make it big, finishing prints at 800-ish is good enough.
Don’t hesitate to reach out with questions or share your own techniques by emailing me at FjoriMakes@gmail.com
i. Sandpaper Types and Tools
- Sanding Sheets
- Sanding Sticks
- Elastic Backing
- Sanding Block
ii. How to Sand
- Get Rid of Layer Lines
- Detailed Prints
Chapter i Types of Sandpaper
Sanding sheets come in a variety of grit numbers, but I find that I mostly use these for 60-100. They can be cut into exact sizes for various tools and purposes, like the sanding block. I personally like cutting them into strips.
Sanding sticks are great for getting details or hard to reach areas. They can be found in any hobby store or on Amazon.
This is 3M brand 220 grit sandpaper with ultra flexible backing. I find this works well with prints that have a lot of detail and/or lots of nooks and crannies. The flexibility allows for contouring on organic shapes as well.
Combined with a sanding sheet, sanding blocks can be used to sand large, broad areas as well as corners.
Shown here from left to right is 60, 80, 400, 800, and 220.
Chapter ii How To Sand
This section might seem a bit silly or unncessary to some, but not everyone has experience in this area. The idea is simple in theory: repeated back and forth motions with sandpaper until it’s smooth. Easy enough, right? Well, sometimes it’s complicated.
Getting Rid of Layer Lines and Seams
60-100 grit sandpaper is great for getting rid of seams, tough layer lines, and uneven edges between assembled parts. Just keep sanding until it’s flush, then move up in grit number. Do this step outside though as it can get pretty messy!
TIP: With or without XTC 3D, Filler Primer is an absolute must in the 3D printing world. Not only does it prep your print for painting, but it helps fill in some gaps between layer lines. I usually do some preliminary sanding before spraying with filler primer.
Sanding Detailed Prints
TIP: For sanding detailed parts: Sandpaper+filler primer will usually be enough for a print. However, it’s a good idea to print small/detailed parts at .1-.15 layer height.
Sanding sticks can get weird angles and areas too small for sanding sheets.
Sandpaper with elastic backing excels at getting hard to reach corners and hard edges. I generally fold it upwards a bit and push against what I’m sanding.
Here is an incredibly exciting gif of sanding in action. This print has been sprayed with filler primer after some initial sanding. Here I’m trying to use it to fill in between layer lines. Honestly, it’s just a bunch of this repeated over and over with different grits.
After some practice and elbow grease, your print will be nice and polished. Now you’re ready to paint!
Good luck and happy sanding!