Multi-Material 3D Printing: Coasters, Project Boxes, and Sunglasses

Multi-material 3D printing opens the door to combining unique material properties in a single print including rigid plastics, flexible seals, soluble supports, and more. In this post, I’ll walk through three projects that highlight what works and doesn’t work when mixing materials on modern multi-material printers like the Bambu Lab H2-series.

https://youtu.be/fj4w5RGuKwI

Links to Projects in this Article

If you want to print any of these projects yourself, you can find them here:

• Drink Coaster (with and without logo)

• Water Resistant Project Box

• Sunglasses

Drink Coaster

I designed a coaster in PLA Matte with translucent inlaid PETG for the logo colors and TPU feet on the back.

Drink Coaster using TPU, PLA and PETG

Problems Encountered:

• PLA + PETG do not bond well. My first coaster fell apart immediately when I removed it from the print bed.

• TPU bonds slightly better to PLA, but still not strong enough to rely on adhesion alone for many applications.

PETG and PLA do not bond!

Solutions:

• I made the entire back of the coaster PLA so the PETG could only release in one direction.

• I printed the coaster face-down to create a natural mechanical interlock since the first layer mashes the filaments together.

• TPU feet were left as-is as I determined it was adequate for this application.

These fixes worked, but there’s an even better technique to get PETG and PLA to stick together: Beam Interlocking (more on that below).

Water-Resistant Project Box

This enclosure uses PLA Matte for the body and TPU 90A for the gasket and cable-pass-through sidewalls. The two circles on the bottom are for screws so you can mount the box to another structure.

Project box with seals to protect your electronics

Problems Encountered:

• TPU 68D (TPU for AMS) is too stiff for a reliable water seal. My test box leaked when using it.

The more flexible TPU 90A worked well for the lid

Solutions:

• Switching to TPU 90A created a tight, leak-free seal.

• Channels inside the model helped secure TPU in place since PLA–TPU bonding is weak. I modeled these channels into the box before I knew about beam interlocking (more on that below). If I knew about beam interlocking, I wouldn't have spent all that time modeling the channels to hold the TPU to the PLA.

Why Multi-Material Shines Here

One print produced:

• A rigid enclosure

• Flexible waterproof gaskets

• Cable-sealing TPU ports

• No assembly solution, just print and use!

Beam Interlocking: The Secret Weapon

Bambu Studio includes a feature called Beam Interlocking, which automatically creates a cross-hatch pattern between materials that typically won’t adhere.

Beam interlocking two materials

How to Enable It

1. Toggle Advanced Mode

2. Open the Others tab

3. Scroll to Use Beam Interlocking

The slicer adds mechanical cross-hatched bridges between materials, locking them together without model redesign.

Results

• Excellent for PLA/PETG inlays (coasters).

• Good for PLA/TPU integration (project box).

Limitations

You can’t yet choose which materials interlock. So when I didn't want PLA going through the screw holes, I didn't have an option to omit it.

Curved Sunglasses with Built-In Hinges

I designed 3D-printed sunglasses using PAHT-CF (nylon carbon fiber) for the frames. They require a significant amount of support because of the geometry.

3D printed sunglasses need support to print

Problems:

• PA Support: Bonds too well and left colored green support material behind.

• ABS + ABS Support: Better, but removal was still not perfect leaving some support material behind.

Dedicated PA support (green) doesn't completely remove from PAHT (black)

Dedicated ABS support (white) doesn't completely remove from the ABS (blue/red)

A notes about dedicated support material, it's really only designed to interface a layer or two. There are many reasons for this depending on what support material we are talking about. This means there is still a need for some other material to support the support material. Many folks just use the material they are printing their part with. That can be quite expensive though for some materials.

Dedicated support material generally has a limitation to only be used at the interface layer shown here

You may not want to use the same materials on your part and your support due to cost

Solutions:

• PAHT-Carbon Fiber frames with ASA supports was a winning combination. The supports came off buttery smooth. ASA prints at similar temperatures to PAHT and is significantly less expensive so it makes perfect sense for supporting PAHT.

ASA supports:

• Hold the part firmly during the print

• Peel off almost effortlessly

• Match the color well enough that any microscopic residue isn’t noticeable

• Are far cheaper than wasting PAHT-CF on support structures

This pairing worked better than dedicated nylon support materials I tested.

ASA almost cleanly removes from the PAHT after printing

Final Thoughts

Multi-material printing is powerful but material compatibility matters. Mechanical interlocks, material selection, and the right support materials make all the difference. If you’re getting into multi-material prints, Solutions like Bambu Studio’s Beam Interlocking and the PAHT-CF + ASA support combo are absolutely worth exploring. Also, as we found out, don't expect PLA to bond to much of anything.

More multi-material examples are on the way!