Multi-part Assemblies
✨ PAN'S RULE: If it's not chaotic, it's not magic! ✨
Ready to go beyond single prints? Let's build big things by printing smaller pieces and putting them together with screws, snaps, and hinges!
The Secret Ingredient: Tolerance!
Here's a maker secret: if you design a 10mm peg and a 10mm hole, they will never fit together. It’s like trying to put on jeans right after they come out of a hot dryer—they shrink! Plastic does the same thing when it cools. To make parts fit perfectly, you need to add a tiny bit of extra gap space. This secret ingredient is called 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!
PAN'S MISSION: The Escape Button! 🕵️
You're building a top-secret escape pod! The big red launch button is exactly 12mm wide. To make sure the button slides into its hole smoothly without getting stuck, how big should you design the hole?
Level Up: Adding Real Hardware
The coolest projects use real-world parts like screws and bearings to add strength and motion. Let's see how the pros do it.
The Hardware Hub
Click to open your new virtual tool drawers!
🔩 Screws: Click me to learn how we bolt things together!
Most makers use 'M-series' metric screws. M3 (3mm diameter) is the most common size for projects. You design a hole slightly larger than 3mm, and the screw threads bite into the plastic for a strong connection.
[+] Pro-Specs: Choosing the Right Screw
Screws are measured by diameter and length (e.g., M3x8mm is 3mm wide and 8mm long). You also need to model a space for the 'head' of the screw so it can sit flush. For a super-strong connection, look up heat-set inserts—they are little brass threads you can melt directly into your parts with a soldering iron (with parent supervision!).
⚙️ Bearings: Click me to see how we make things spin!
Want smooth spinning action for fidget spinners or wheels? You need bearings! The classic '608' skateboard bearing is a hero in the 3D printing world. It's exactly 22mm in diameter. And guess what? That perfectly-sized hole needs our secret ingredient again—tolerance! You might design the hole to be 22.2mm to press-fit a 22mm bearing.
👨👩👧 Parent Corner: Sourcing Parts Safely
Ready to build? You can find "M3 screw assortment kits" and "608 bearings" easily on sites like Amazon. They are a great, inexpensive addition to your maker toolkit. This is a fantastic opportunity to teach your child about real-world hardware!
🛡️ Safety Check: Always supervise the use of small screws, nuts, and bearings, as they can be a choking hazard for younger children.
Mission: The Goldilocks Test 🧸
Let's become Quality Control Engineers! The best way to find the perfect fit is to test it. We have a simple project box that needs a lid.
Your mission is to print three different test lids to find the one that's "just right":
lid_too_tight.stl(designed with 0.1mm tolerance)lid_just_right.stl(designed with 0.25mm tolerance)lid_too_loose.stl(designed with 0.5mm tolerance)
Print all three and test them on the box. Which one has the perfect 'snap'? This is how real engineers test and prototype their designs!
💡 Pro Move: Designing with 'DFM' in Mind
In the real world, this is called 'Design for Manufacturing' (DFM). You're not just designing a cool shape; you're thinking about how it will be made—how it shrinks, what hardware it needs, and how it will be assembled. You're already thinking like a real product designer!
🚀 Advanced Challenge: Design a Parametric Hinge
Ready for a real engineering task? Your mission is to use a parametric CAD tool like Onshape (it's free for students!) to design a box with a fully functional, M3-screw-based hinge.
What makes this a pro-level skill? In a parametric tool like Onshape, you can link the size of your screw hole to a variable called tolerance. If your first print is too tight, you don't have to redesign the whole model. You just change the tolerance variable from 0.2 to 0.3, and the entire model updates automatically. It's like magic for engineers.
➡️ Your Next Build
Once you master creating your own joints and hinges, you're ready for the next level: Kinematics & Automation. In the upcoming Advanced track, we'll use these exact skills to build a multi-part robotic claw that you can control with code. The hinge you design today is the first step. You'll even learn to design parts for multi-color printing to make your creations pop! 🎨
📚 Learn More
- TinkerCAD Hinge Tutorial - Learn how to design hinges and joints right in your browser.
- The Engineer's Guide to Snap-Fit Joints - A pro-level guide to designing parts that click together.