How to design and 3D print a composite model


Not everyone has the skills to design their own models for 3D printing. But editing and mixing files is quite easy and only requires a computer with a free editing program like 3D Builder.

3D Builder can perform simple edits on STL, OBJ and 3MF files. You can use it to add a name to a trophy, remove a base from a figurine, or punch holes in a print for hanging. It can also separate files and merge them, thus creating “mashups”.

Mashups are visual puns – combining two unrelated objects into something frighteningly funny. Or just terrible, depending on your sense of humor. You may have noticed that Thingiverse and Thangs, two popular free download sites, have been overrun with strange prints of Dwayne Johnson’s handsome mug plastered on everything from dinosaurs to broccoli stalks.

(Image credit: Tom’s Hardware)

Makers have been altering prints since Thingiverse began, but this latest craze is firmly TikTok’s fault. 3D printing TikTokers have gained views, followers and viral fame by posting Rock Mashups. In other words, putting Dwayne “the Rock” Johnson’s face on everything. And I mean everything.

Why wait for creators to post their mashups online when you can easily create your own? Mashups can be created with any 3D modeling software – even Tinkercad – using these basic methods. For this tutorial, we will be using 3D Builder.

What you will need

Find your files

Find the files to mix. is the oldest file sharing site and has a surprising amount of common objects to print. We’ll be using a sculpt of Dr. Smolder Bravestone (played by Dwayne Johnson) and the classic Cute Mini Octopus.

Dwayne Johnson:

Flexi Octopus:

(Image credit: Tom’s Hardware)

NOTE the Creative Commons attribution to see if you have permission from the artist to use their files. Don’t sell your mashup if it’s not allowed. Look for the “share alike” symbol, which means the artist is okay with the remixes. The Dr. Smolder STL is free to remix and share, but you may not sell this file or anything made with it.

(Image credit: Tom’s Hardware)

Open 3D constructor

3D Builder is a free app from Microsoft that comes pre-installed on Windows 10 and 11. If you don’t have it, it’s easy to To download through the Microsoft Store.

(Image credit: Tom’s Hardware)

Split files with 3D Builder

1. Open your first file by clicking on the three lines in the upper left corner and clicking “load object” to open your first file. You can also drag and drop STL files directly into 3D Builder. Let’s open the octopus first.

2. Click “import template” in the upper left corner.

(Image credit: Tom’s Hardware)

3. Click Edit in the top menu bar.

4. Click on the octopus to select it.

5. Select “separate” in the upper left corner.

A green plane appears indicating where you can split the model.

6. Move the plane up and down by entering the green plan directly with the cursor. You can also rotate the plane on the X, Y and Z axes using the blue arrows.

(Image credit: Tom’s Hardware)

seven. Move the plane under the head octopus.

(Image credit: Tom’s Hardware)

8. Click Keep at bottom from the menu bar.

9. Click Split.

(Image credit: Tom’s Hardware)

This leaves a fairly large hole in the model.

ten. Fill the hole with a sphere so the head of the Rock has a good place to sit. Click “Insert” in the top menu.

11. Now click on Sphere from the secondary menu.

(Image credit: Tom’s Hardware)

12. Left click on the sphere with your cursor and drag it to the octopus.

13. Right click with mouse to reposition the models on the screen and use the scroll wheel to zoom in and zoom out.

14. Switch from moving elements to scaling by clicking on the box with four arrows in the bottom menu.

(Image credit: Tom’s Hardware)

15. Adjust sphere size by moving the blue and green arrows.

16. Return to “move” and position the sphere to cover the hole. (I added color for clarity.)

(Image credit: Tom’s Hardware)

Add the second model

We will now do the same with Mr. Johnson.

1. Click Insert to add a second template.

2. Click on the + symbol.

3. Charge Mr. Johnson and click “import template” in the top left menu.

4. Click Edit from the top menu and divide from the secondary menu.

5. Move the green plane under his chin. tilt it with the rotation arrow to cut the model above the shirt.

(Image credit: Tom’s Hardware)

6. Make sure “Keep on Top” is selected and click “divide”.

seven. Move Mr Johnson’s head above center octopus. There is no alignment command in 3D Builder, but a handy trick is to move each model to the 0.0 X and Y coordinates using the bottom center menu.

(Image credit: Tom’s Hardware)

8. Select only the head of Mr. Johnson and scale it until it adapts to the body of the octopus. Getting the head the right size and in the right place will take some tweaking, but it’s worth it. Also consider overhangs: if you tilt his chin up a bit, you can avoid the need for supports.

9. When you are happy with the placement, select all and click on “group” in the right menu.

(Image credit: Tom’s Hardware)

ten. Save the model as STL file using the disc icon in the upper right corner.

Bring your model to your slicer of choice and print.

(Image credit: Tom’s Hardware)

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