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Project of the Week: How to Smooth PLA Prints Without Using Sandpaper

Picture of Tyler Koslow
by Tyler Koslow
Jun 14, 2018

Maker and YouTuber 3DSage shares an informative tutorial on how to create incredibly smooth 3D prints out of PLA without needing to use sandpaper or other post-processing techniques! 

If you happen to own a FDM 3D printer, you know that the sky’s the limit when it comes to what you can create. However, in order to achieve a smooth surface, there are only a handful of post-processing techniques that will eliminate those pesky layers and procure a glossy look. Unlike ABS, which can be smoothed out by Acetone, there’s no easily accessible chemical that works with PLA, the most popular and easy-to-use filament.

One constant that is commonly found in most surface smoothing methods for PLA is sandpaper. You can gradually move through a variety of different grit sizes to obtain a smoother surface. It works, but repeatedly grinding down your print with sandpaper can be a timely and exhausting exercise.

Thankfully, a YouTuber who goes by the name of 3DSage has recently shared a way to smooth your PLA prints without using any sandpaper at all. The results of his methodology are extremely impressive, even more so when you find out how little was needed to make it happen. This post-processing technique is especially useful for prints with sharped curves or rounded surfaces, creating a stair-stepping effect.

Let’s dive into 3DSage’s unique method to smoothing out your PLA prints.

Smoothing PLA Prints Without Sandpaper: What You Need & How to Do It

All you need to perform this technique is a can of spray paint that bonds well with plastic (such as Rust-Oleum) and a bottle of Fast Drying Polyurethane – Clear Satin. You’ll also want to print a model that has clear layer lines, that way you can really get a sense of how this process works. On his Instructables post detailing the project, 3DSage shares the Skeleton model that he uses in his own example.

The step-by-step process is simple and non-labor intensive. First, you’ll want to check for any dust or dirt on your 3D printed model, making sure there’s nothing unwanted that will get trapped in the smoothed out model. Taking the spray paint of your choice, coat the 3D print with a layer of paint, quickly followed by a layer of the Polyurethane.

Next, carefully place the coated 3D print under a fan to make it dry faster and prevent dripping. During this time, you’ll start to notice that the combination of paint and Polyurethane will mix into the layers, along with any holes or unexpected flaws. The process works best with thin layers and patience. According to 3DSage, he waited a total of 20 minutes between layers and an entire day before adding the final coat of spray paint, which is used to get rid of discoloration and other flaws.

When talking about the benefits of his process, the maker says that it has enabled him to print faster with a larger layer thickness. The process will cover up any potential for lessened quality. Another advantage is that you can use any color of paint you want, and of course, that it doesn’t require and sanding or other trying post-processing techniques!

License: The text of "Project of the Week: How to Smooth PLA Prints Without Using Sandpaper" by All3DP is licensed under a Creative Commons Attribution 4.0 International License.

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