When it comes to finishing 3D prints, elementary school arts and crafts ain't gonna cut it. Step up your game with this guide on the best paint for plastic.
Despite multi-material extruders and the stunning array of filament colors, you may find yourself looking to paint some of your 3D prints. The most common reason to do this is to improve how the print looks, especially if you’ve got an FDM 3D print, where the model is built using layers of filament. The technique creates a surface of characteristic lines along the Z-axis of your model.
When finishing your model, the small cavities between the layers get sanded down, filled in, or both. The result is a smoother surface. Painting can also help protect the model from the environment.
This article is divided into two parts: The first will take you through the different methods of painting your 3D print and the second will (hopefully) answer all your nitty-gritty questions about painting and how to do it best. Read on to perfect your prints with paint!
Priming a model imrpoves paint adhesion. Thus, with every painting method (except dyeing nylon), using primer is a good idea. We believe a spray primer is easiest to get good results. The process of using a primer is very straightforward:
Best for: PLA, ABS, PETG
If you paint your model with a paintbrush, it is easy to get a handmade look.
Try out a few paintbrushes first because it’s easier to get a good result with a brush that you are comfortable with. We often find ourselves using only 1 or 2 different flat brushes.
The right paintbrush can move the paint where you want it to go on the surface without dragging it around too much.
When it comes to painting with a paintbrush, you’re going to want to stick to acrylic paints.
Best for: PLA, ABS, PETG
For a more uniform look, painting with spray paint can give good results.
Searching for spray paint, you’ll find that there are many varieties available. If you’re aiming for a particular color, be wary of RAL, CMYK, and RGB numbers.
Works best with: Nylon
Instead of trying to get paint to stick on the surface of your FDM 3D printed nylon, we recommend dyeing instead. Note that this will not work at all on other materials. Although PLA is hydroscopic and will absorb some amount of water from its surroundings, it can’t be colored by dyeing. ABS and PETG don’t belong here either – this is a nylon special.
To let the dyed color show as much as possible in your nylon 3D print, you want to use a translucent or white nylon filament when 3D printing. Darker nylon filaments are also possible to dye, but the color will be much less pronounced.
The Dyeing Process
Because nylon is very hydroscopic, it absorbs water even from the open air. That’s why you should always dry your nylon filament before 3D printing. We recommend that you dye the finished model, instead of the unprinted material.
Read the manufacturer’s instructions for the dye you have chosen. In short, the method is very simple:
To make sure you get the right color, you may want to try dyeing some test prints before the actual print job.
Learn more about how to dye your nylon print from MatterHackers, who have a handy guide on the topic.
Probably the most important factor to make the paint, or liquid of your choice, stick to a solid surface is the difference in surface energy between the liquid and solid. The one with the highest surface tension always wins. (Surface tension has its own unit of measurement called dynes, or dynes per square cm.)
The rule of thumb is that the surface tension of the paint has to be at least 10 units lower than that of the solid for good adhesion. That indicates we have a liquid with a high ability to wet the solid, and wetting is what we want.
A Neat Trick
To get a hint of how well it wets the surface you want to paint, take notice of what shape a drop of liquid forms on the solid surface:
Painting FDM 3D printed models made from PLA and ABS is straightforward.
PETG, however, may be harder to paint with a durable result, but the same preparations apply as with PLA and ABS. If you really need the color to stick, we would suggest printing your PETG model in the color you want, and leave it at that.
When we’re talking about FDM 3D printed nylon, it becomes much harder to get liquids like paint to stick to the surface. It is possible to paint onto nylon, but it requires some kind of heat treating to maximize the surface tension and make it possible for the paint to wet. This is often done with an open flame or plasma – not something you want to do in a home environment. We believe dyeing, as described earlier, is far better for nylon.
Make finishing and painting a lot easier before 3D printing your model by taking these considerations in mind:
Some easy steps to enhance paint adhesion:
Feature image source: All3DP
License: The text of "Best Paint for Plastic (PLA, ABS, PETG, Nylon)" by All3DP is licensed under a Creative Commons Attribution 4.0 International License.
Subscribe to updates from All3DP
You are subscribed to updates from All3DP
You can’t subscribe to updates from All3DP. Learn more…