3D printing is great. You can create just about anything imaginable with the power of a 3D printer. New 3D printable materials are being developed daily to further advance your options when using a 3D printer. And up until now, many people limit their 3D printed creations to one material.

It would be safe to say that most people only have a single extruder 3D printer. This means that they (we) can only print with one material at a given time. That means that the final object will be all hard plastic... Or all flexible filament... Or 100% water-soluble plastic (keep away from water). But what if we want to create a multi-material print with our single extruder 3D printer? This Instructable will describe a process for doing exactly that.

Let's get started...

To learn the basics of 3D printing, read this Instructable.

Step 1: How Does It Work?

The first thing that you may be wondering is how a 3D printer can print two (or more) different materials with only one extruder. The secret is to spread the different materials across different layers. Both of the models that I showed have the materials at separate heights; on separate layers. The process basically works by printing with one material to a certain height, pausing the printer, switching materials, and continuing the print.

Step 2: Choosing a Good 3D Model

Before we 3D print anything, we need to find or design a 3D model. Use Thingiverse or design your own in a CAD program. There are a few things to keep in mind when choosing a 3D model for this process:

Choose a model that makes sense for the materials you are going to be using? I chose a toilet plunger (crude, I know) because it makes sense to use flexible filament and wood filament.
Make sure that different materials will be used at different layer heights. This is key. This process relies on the fact that your materials will be at different heights. In my example, the flexible plunger base is lower than the wooden handle.
Is your model printable with the desired materials. Remember that not all 3D printer materials will be able to print certain models.

With these guidelines in mind, let's get started.

*Toilet plunger picture used with permission from: https://pixabay.com/en/plunger-toilet-plumber-147946/

Step 3: Generate GCODE and Start Print

Use your favorite 3D printer host software and slice your 3D model into GCODE. Look up suggested speed settings for each material and use the slower of the two. Find an appropriate balance of infill, layer height, and retraction settings for your print. When you are ready, heat the printer up and load the first material into the printer. It will be possible to change temperatures later when we switch to the second material. My first material was black NinjaFlex.

When you are ready, start the print.

Step 4: Switching Materials

Monitor your printer as the first material is extruded. When you are ready to switch materials, pause the printer through the host software. Keep in mind that the printer can take a couple of seconds to pause. Now raise the printer 10 mm on the z axis. Place a piece of paper under the extruder to prevent leakage. If necessary, adjust the hot end temperature in the Manual Control tab to suit the second material. Switch to your second material and purge the extruder until the new material comes out pure. Remove your piece of paper and continue the print. Repeat this process as many times as necessary.

Step 5: Results?

Now that the basic procedure has been described, you are probably wondering how well it works. My most pressing question was how the two materials would bond together. I have tested two different materials together: PLA/NinjaFlex and wood/NinjaFlex. Surprisingly, both of these tests experienced excellent bonding between the materials. The purple and white cylinder shown above was printed with PLA and NinjaFlex. I stressed the print until it broke- two PLA layers spit apart, which means that the NinjaFlex/PLA bond is actually stronger than the PLA/PLA bond! The bonding between the wood/NinjaFlex was similarly high strength.

In sum, this Instructable proves that two different materials can be printed and bonded together successfully. I hope that the community will help me expand on this concept and create some really neat creations. Here are some other ideas of prints to try.