Learning Fusion 360 by Modeling a Puzzle Box for Laser Cutting

Hey everyone! My name is Josh and I'm a Mechanical Engineering major at Washington State University. I actually created the design for this puzzle box when I was in high school, but I designed it in Solidworks. I've since lost those files but I still have the box, so I thought this recovery project would be a good opportunity to use Fusion 360 for the first time and share a fun project with all of you.

If you're just interesting in the parts and how to assemble the puzzle box I completely understand. If that's your after then skip to step 3 and go from there.

Here's what you'll need to create this:

• 5mm plywood
• Wood Glue
• 1/4" dowels
• Markers (I used Sharpies)
• Fusion 360 Software
• Access to a laser cutter (you could also 3D print this, but you'd need to change some part tolerances)

Sandpaper can also be useful, but I didn't need it.

So, before we get started I wanted to address something some of you might catch. I'm using 5mm plywood for this box but the thickness of all of my parts are 0.2 inches. I did this because 5mm is just under 0.2", which basically acts as a built-in tolerance for our parts. This combined with some material loss from the laser lets us model everything as flush with each other rather than having to worry about any tolerancing while building.

You can see in this picture that everything is perfectly flush, but once it's cut there's plenty of tolerance. I don't like to think about tolerances while designing so this is just the way I get around it. Anyways, lets get to actually building this now!

Parts

Part modeling is basically the same in fusion as in any other software. The only thing that threw me off was the location of certain tools.

Assemblies

I learned how to model in Autodesk Inventor and then in Solidworks, and these two have very similar functions and workflows. Fusion 360 does not work the same as either Solidworks or Inventor and this transition was initially really hard for me. Part mating in particular was very difficult for me to get my head around. So like any other good college student I turned to YouTube aka the best tool in the world. This is where I learned the difference between mates in Solidworks/Inventor vs. Fusion 360: mates in fusion 360 all happen at the same time and then you choose what you want to move, which was completely different from the way I was taught. However, this system has some really cool benefits including speed and easy positioning or parts in assemblies.

For example, normally to constrain the two parts in the first picture shown I would normally need to constrain the box front part in the X, Y, and Z planes. In Fusion I just use the joint tools to select the bottom corner of the tab on the front face of the box and then the corner that would be in contact with that part on the bottom of the box. This is so much faster and easier than any modeling software I've used before.

For the wheels, I got to play with how to unlock certain aspects with a joint. I centered the wheels and had them in contact with the front of the box similar to before, but then I opened the motion tab. I thought this was such a cool feature, I can unlock degrees of freedom for a part like normal, but it gives you a preview of what is unlocked. This helps with visualization of how the part is able to move after being joined.

Teamwork

I think the biggest strength of Fusion 360 is working in a team to create something. Since everything is cloud-based, everyone has access to all of the files in the project. In my junior year of college I was part of a team that was designing a 15ft long rocket, and there were a lot of problems with people not having the same parts because the updated parts weren't being shared in a timely matter. If we were to use Fusion 360 instead of Solidworks this wouldn't have been a problem. Everyone would have had access to all of the same parts at the same time, which would have saved me a lot of headaches. I was in charge of the overall model and coordinating the different rocket section's models, and it was a nightmare to get everyone to give me their updated models on time.

So here are the actual parts for this project. I saved them as STEP files so all modeling software can access them (if you don't use Autodesk programs). I'll go over how to assemble the box in Step 4.

For cutting them out on a laser, I just saved all my parts as DWG files and then took them to my laser software (Corel Draw) and fit them onto a couple of sheets of 5mm plywood. Most CO2 lasers can cut this thickness of plywood pretty easily, but if you're having problems cutting your plywood, then there are specific types of plywood made for laser cutters. If you want a laser cutting tutorial, I can make one of those later.

I made this box almost four years ago and don't have access to my laser anymore, so instead of showing you how to build it physically, I'll show you how to build the box in CAD instead. I'm not going to show the dowel steps, because honestly, I forgot to make the dowels (oops), and I think it's straightforward enough that it doesn't need a picture. If I'm wrong, then I'll add that in after I get enough people yelling at me.

I'm not going to show the locking mechanism for the other side of the box because then it gets hard to see what's happening, but the process is the same as steps 2-9

1. Start with the Box Bottom, and glue the Box Front and Box Side parts to the base and each other
2. This helps you keep everything straight and it's a little easier in the long run (for me at least).
3. Cut the 1/4" dowel into 0.75" lengths
4. This will be slightly longer than what you need in the end, but it makes it easier to glue on the wheels later
5. Glue each of the Outer Wheels onto the dowel lengths you just cut and let that dry
6. After the Outer Wheels have dried to the dowels, insert them into the holes on the Box Front part
7. Make sure that these can turn easily in the holes, if they don't then use a little bit of sandpaper on the dowels until they do turn easily
8. Now glue the Inner Wheels onto the dowels inside the box and wait for the glue to dry
9. The position of the cut on the inner wheels don't matter yet so don't worry about that
10. Take two of the Additional Struts and the one Lock Strut and glue them into the box like you see in the 5th picture
11. These act as a guide for the locking mechanism
12. Now slide the Lock into place as shown in the 6th picture
13. If it doesn't slide well use some sandpaper on the main face of the lock until it slides
14. Take two Additional Strut pieces and glue them into the lock
15. these pieces will lock the Lid of the box later
16. Glue the Handle piece into the lock
17. Make sure the glue doesn't leak onto the wall of the box and stick to it
18. Glue the Lid Lock pieces in place
19. Make sure they are flush against the side of the box, it makes everything slide easier
20. Slide the Lid into place and pull the handle up. The Additional struts should go into the holes of the lid

That's all for the base box. You technically don't need anything else to have a functional box. But, if you're like me, then you like to make people angry at you for tricking them. So let's go over some things you can do to customize this and solve it.

How to Solve it

The solution to this box isn't really a puzzle; all you do is press down on the handle while turning one wheel at a time. You'll feel the lock fall into each of the notches in the Inner Wheels as you turn, and when you line up all three notches on the inner wheels, the lock will be able to move. Easy peezy.

I would suggest practicing opening the mechanism before putting the lid on. I locked myself out of my box for about 15 minutes the first time I built this because I didn't practice.

How to Make People Angry

The real fun with this box is tricking people into thinking there's a puzzle to solve. The way I do this is to add a bunch of numbers on a grid to the lid and color each number a specific color. Then I added some numbers and colors onto the outer wheels and wrote some text on the side wall and the bottom of the box as a fake clue. I also like to put a marble inside so that they hear it roll when they move it around. Basically, the way you mess with people is to use other tropes of puzzle boxes to your advantage. Then people think they know the process and jump straight to what they know works for those boxes.

The first guy I had test this was a self-proclaimed puzzle aficionado. It took him about 1.5 hours to open it because he thought he knew the correct way to solve it based on the fake clues and red herrings I left. He was so mad when he finally opened it, but we had a good laugh about it later once he saw other people struggle as well.

Improvements

One thing that might make this box better is if you added a handle of something to the lid of the box, it would make it easier to slide the lid on and off (and you could use it as another red herring if you make it out of rope or something). Let me know if you have any suggestions, and I might try to make an updated version with some new tricks and improvements.

So that's all that I have for my puzzle box; let me know how you guys like it!