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⚡ Module 03 · Intermediate

Multi-part Assemblies

Ready to go beyond single prints? In this mission, we'll learn how to build BIG things by connecting smaller pieces. And we'll even discover how to make one piece act like many using physics magic! Let's go! 🧙‍♂️

⚠️ MAKER SAFETY CHECK: The 3D printer's nozzle (the 'hot end') gets REALLY hot—hot enough to cook a pizza! 🍕 Never touch it. Always print in a room with good airflow (a nearby window is great!). And remember, using tools like a soldering iron for heat-set inserts requires teamwork with a parent. Always build together!
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The Secret Ingredient: Tolerance!

Quick Quest: The Perfect Fit

You need to fit the purple peg into a hole. Which hole should you choose? Click on the best fit!

Hole A
Hole B
Hole C

You got it! If you print a 10mm peg and a 10mm hole, they won't fit. 😭 Why? Plastic shrinks a little when it cools, and the printing process isn't perfectly exact. To make them fit, we need to design a small gap. This gap is our secret ingredient: Tolerance.

Try It! The Tolerance Calibrator 📏

Drag the slider to add tolerance to the orange hole. Find the "perfect fit" for the purple 10mm peg!

✅ Perfect! Smooth fit!

[SYSTEM LOG] User Explorer has successfully calibrated a press-fit connection. ACHIEVEMENT UNLOCKED: Junior Calibrator 🏅

Two Ways to Assemble: Parts & Physics!

The coolest projects connect multiple pieces together. You can use real-world parts like screws and bearings... OR you can use physics magic to make one single piece of plastic bend and move like it's a complex machine! First, let's stock our classic workshop.

The Bot-Builder's Hardware Hub: Collect Your Parts!

Pro makers have a collection of cool parts to build with. Your mission: find the right part for the job, then collect them all for your toolbox!

⚙️ Toggle Pro-View

MISSION: To make a robot wheel spin super-fast, which part do you need to collect?

Click the "Add to My Toolbox" button on the correct part below!

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M3 SCREW

Superpower: Bolts projects together like superhero armor! The "M3" size is the most common hero in a maker's toolbox.

Common Applications: Securing PCBs to standoffs, assembling frames with T-nuts, attaching lids to project enclosures.
Pro-Spec: M3x0.5 thread pitch. Common lengths: 8mm, 12mm, 20mm.
Design Tip: In your CAD software, make the hole 3.2mm for a screw to pass through easily.
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608 BEARING

Superpower: Gives your projects super-smooth spin! This is the secret to fidget spinners, robot wheels, and more.

Common Applications: Wheels for robots and skateboards, fidget spinners, lazy susans, and spinning mechanical joints.
Pro-Spec: 8mm ID / 22mm OD / 7mm width. Also known as a "skateboard bearing."
Design Tip: A 608 bearing is 22mm wide. Design a 22.2mm hole to press-fit it snugly.
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SNAP-FITS

Superpower: Clicks parts together with no screws needed! The lid on a battery remote is a perfect example of a snap-fit.

Common Applications: Battery covers, project enclosures, toy assembly using cantilever hooks, interlocking panel parts.
Pro-Spec: Best with flexible plastics like PETG. PLA can be too brittle and snap off.
Design Tip: Add a small angled ramp (a chamfer) to your snap-fit hooks so they can slide and click into place more easily.

Level Up: Physics Magic! ✨

Now that you know how to connect separate parts, check out this mind-blowing idea: what if you could print just *one* part that has hinges and moving bits built right in? It sounds impossible, but it's real! They're called "compliant mechanisms."

📺 Maker-extraordinaire Zack Freedman shows off the "magic made out of physics" that allows single pieces of plastic to move like complex machines!

🕵️‍♂️ Video Mission: Spot the Mechanism!

Zack shows a bunch of real-world examples of compliant mechanisms. Can you spot one? Name one of the real objects he shows that uses this "impossible hinge" technology!

🤔 Think Deeper...

Zack says these hinges are awesome, but also warns that the plastic can get tired and break after lots of bending. Why do you think PLA (the most common 3D printing plastic) might not be the best choice for a hinge you need to use a hundred times?

Mission: The Goldilocks Test 🧸

Let's be Quality Control Engineers! Imagine we're building a robot and need to attach a new armor plate. We have three versions of the lid, but which one will be "just right"?

🤖 Virtual Test Lab: Try Before You Print!

Click a button to see what happens!

Now that you've seen the results, it's time for the real test! (Parents, if you have a 3D printer, this is a great chance to print these files together and let your child feel the difference in fit!) This is how real engineers test and prototype!

📦armor_too_tight.stl (0.1mm tolerance)
📦armor_just_right.stl (0.25mm tolerance)
📦armor_too_loose.stl (0.5mm tolerance)

🛠️ Intermediate Challenge: Design a Custom Snap-Fit Box

You've collected the snap-fit hardware, now put it to use! Your mission is to use a simple tool like Tinkercad to design a small two-part box that clicks together using the snap-fit principles you just learned. A perfect first project is designing a custom case for your favorite small toy, a game cartridge, or a secret treasure!

🎨 Intermediate Challenge: Sculpt a Mythical Creature

Ready to level up from blocks and shapes? Let's try digital sculpting! Tools like Womp 3D let you design "squishier," more organic models, like you're sculpting with digital goo. It's super fun and powerful!

Your challenge: Design a friendly monster or a mythical creature. Will you make a three-eyed space alien, a chubby dragon, or a grumpy garden gnome? Womp is perfect for this and will make you feel like a digital artist.

🚀 Advanced Challenge: The Print-in-Place Mechanical Iris Box

Ready for a real engineering showpiece? Your mission is to build a "print-in-place" mechanical iris box. This amazing device prints as one single piece, but thanks to perfect tolerances, its moving parts work right off the printer! It’s a project that will make your friends go "whoa."

We recommend using a browser-based tool like Onshape (it's free for students!). Why Onshape? It's a "parametric" CAD tool used by real hardware startups and robotics companies. The skills you're learning are the exact skills professional engineers use every day.

Your First Pro Move: Variables!

This is a game-changer! Instead of typing numbers over and over, you can use a variable. Watch:

  1. 1. Create a Variable: Find the 'Variable' tool (look for an 'x=' icon). Click it, name your variable #gap, and set its value to 0.3mm.
  2. 2. Use the Variable: Now, when you draw a line or a circle and the tool asks for a size, don't type a number. Type #gap instead. Boom! Onshape uses 0.3mm.
  3. 3. Magic Update: Is your test print too tight? Just change the #gap variable to 0.4mm. Your entire model updates instantly. That's parametric power!

Check out this amazing Print-in-Place Iris Box by Kagarov for inspiration and guidance!

🔥 Expert Challenge: Design a Compliant Mechanism

You saw the video, now it's your turn! Try designing your own compliant mechanism. These are incredible single-piece objects that get their motion from the plastic itself flexing, not from separate hinges or screws. It's like magic made from physics!

Your mission: Design a print-in-place box with a "living hinge," or even a pair of functional pliers that prints as one part. This is a true test of understanding materials and tolerance. Use the video we just watched for inspiration and see if you can make your own impossible-looking hinge work!

➡️ Your Next Build: The Heart of a Robot

Those skills you just mastered? They're not just for practice. They are the key to our entire Advanced Track. In `Module 4: Kinematics & Automation`, we'll show you how to import the Iris Box you designed here, attach a digital model of a servo motor, and write your first lines of Python to bring it to life.

What you built today will become the heart of a robot tomorrow. Let's go build the future. 🚀

📚 Maker Quests: Level Up Your Engineering Know-How