Puzzle Box (Unibox) - 3D Print

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Introduction: Puzzle Box (Unibox) - 3D Print

About: I like to design and build random things.

I fielded a few questions lately about a puzzle box I made 7 years ago. Since I've learned a lot since then, I thought I would incorporate improvements into a redesign. Mainly, I hid the pivot/lock points so you can't see the solution from the outside. I also added another twist to the solution based on some of my other designs. Although 3D printed, the same puzzle could be made using wood or metal. I've included a dimensioned drawing for those interested in that route.

All 3D print (STL) files are included at the end of this instructable. Besides printing, you will also need a 5mm x 2mm magnetic and a metal rod to complete the build.

This video shows how it works.

Supplies

  • 3D Print Material (PLA used)
  • Magnet: 5mm diameter x 2mm thick
  • Metal (magnetic) Rod: diameter range 0.220" to .0250" (.240" used) by 1" long
  • Glue

Step 1: Top Level Model

The box is 4" long x 3" wide and 2 1/16" tall. The parts are color-coded for reference.

Step 2: Box

The main part is the box which covers five sides. On the right side, you will see the swivel point. This is a reverse counterbore hole to capture the rotating lid. The two notches along that hole were added to help you remove the top if needed. On the lower side, a cylinder was added to capture the metal rod. This is the first part of the locking mechanism. On the left wall (not shown in the picture), there is a hole that captures a dowel pin. This is the last part of the lock.

Step 3: Slotted Lid

This lid covers the entire opening. The slot is sized to allow the lid to slide along the rotating pin. The thru-hole is for the locking pin. The two blind holes are used as alignment features for the stationary lid.

Step 4: Fixed Lid

This part mounts to the slotted lid. The two protrusions fit into the holes on the slotted lid. The oval-shaped hole encases the locking tab.

Step 5: Rotating Lid

This part rotates along the hole in the box. I wanted it to be locking so I added an annular snap-fit joint. I was worried that it wouldn't work so I added the slots in the box. These allow you to push an object inside to deflect the cantilevers which allows the lid to be removed.

The counterbore hole is sized for the locking rod and magnet. I've used these magnets on previous projects so I had the hole size worked already.

The oval-shaped hole on the side captures the tab from the fixed lid.

Step 6: Other Parts

The Locking Pin (copper color) is glued into the base. The rounded end faces out.

The Locking Tab is glued into the Fixed Lid. Note the orientation during installation.

The Metal Rod (silver color) was cut down from a bolt in my shop. I suggest finding something in this size range and also being dense (heavy) helps. It must be able to fit through the hole and make a relatively tight fit for the rotating top. You also might want to round the edges so it slides easily through the hole. I placed mine in a drill press and used sandpaper to smooth it out.

The 5mm x 2mm Magnet was purchased. You can buy a pack of 25 pretty for very little money from Amazon or eBay.

Step 7: Ready for Build

Before assembling anything, I suggest you do a dry fit with the base and lids. Don't install the pin or tab at this point. For mine, I noticed a slight interference between the Fixed and Rotating Lids. To solve this, I used a file to remove about .001" from each mating surface.

Step 8: Assembly - Box

Make sure the Metal Rod slides easily within the hole.

Add the Locking Pin to the box with the round end on the outside. This should be an interference fit - glue if necessary.

Step 9: Assembly - Fixed / Slotted Lids

Align the holes and protrusions as shown. I used superglue for the attachment. Add the tab as shown (note orientation). This should be an interference fit - glue if necessary.

Step 10: Assembly - Rotating Lid

Add the magnet to the hole. Make sure to push it to the bottom to reduce the magnetic field for the rod. I used another bolt and hammer to press it into the PLA. It should be an interference fit but glue is another option.

Step 11: Assembly - Overall

This is pretty easy:

  1. Add Metal Rod into the hole in Box
  2. Place the Slotted Lid Assy on top of the Box
  3. Slide Slotted Lid Assy forward to capture the Locking Pin
  4. With the angle open, snap on the Rotating Lid
  5. Close Rotating Lid (should go into locking tab)
  6. Turn the box over to lock Metal Rod

At this point, the box should be locked and ready to be solved.

Step 12: Solution

If you have made it this far, the solution should be obvious. The key is releasing the Rotating Lid. To drop the Rod, smack the puzzle on a flat surface. This will cause the Metal Rod to release from the magnet and drop into the hole. From there, rotate the Rotating Lid. This will provide enough room to slide the Slotted Lid back. Lastly, rotate both lids to get into the box.

Step 13: Pictures

I decide to print in one color but you might want to consider printing the lids in a different color.

Step 14: Files / Drawing

I've attached the STL files for printing. Everything was printed without supports and 50% infill. You will need to supply the rod and magnet. I've also included a drawing for anyone interested in making a version from wood or metal. If you go that route, you will need to come up with a different way to lock the rotating pin into the box. A simple solution would be a cotter or equivalent pin with an opened hole.

Step 15: Final Thoughts

I'm happy with how it turned out. It did require a slight amount of sanding at the angled mating surfaces on the lid. Also, the durability might not be good enough for kids. To fix this issue, I think I would come up with a more substantial rotating pin with a tighter fit. Please let me know if you have any suggestions.

Thanks for viewing!

1 Person Made This Project!

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11 Comments

0
Art_Lieberman
Art_Lieberman

Tip 1 year ago

[I have copied this from the "I Made It" so that people will see this if they want to make the box.]
This is a Fun project! I keep playing with it over and over. Here are some hints in making it...
(1) You do not need the .stl for the rod. You're not going to print the rod. You're going to use a metal rod appx 1/4 x 1".
(2) It's important to have 100% infill for the rotating lid, otherwise the pivot stem will brake off very easily.
(3) After printing, you might find the recess for the magnet to be too small. I reamed out the hole with a 13/64" drill bit by hand (did not use the electric drill), then forced the magnet using an upside down nail and hammer. I also added glue.
(4) My magnet wasn't strong enough to hold the rod, so I simply stacked a second magnet.
(5) The print looks nicer with ironing on the slotted top, the fixed top, and the box (ironing is not needed on the rotating lid because it is printed upside down, and the top will appear ironed by the base).
(6) If the lid squeaks when pivoted, you can add some light weight oil in the slots.
(7) I added a 5mm TPU bottom so that the kids won't mar the furniture when banging the box (not shown in the photo).
(8) I discovered that if you bang the box on the left-front corner, it opens easier. I'm curious if you find that to be true, also.

Take a look at his other projects at https://www.instructables.com/member/mtairymd/instructables/. Lots of fun stuff!


0
Art_Lieberman
Art_Lieberman

1 year ago

Would a Neodymium magnet be ok, or is that too strong?

0
Art_Lieberman
Art_Lieberman

Reply 1 year ago

Thank you. That tells me the magnet is NOT Neodymium. You would not be able to release the rod being pulled by a Neodymium by simply tapping the box.

0
mtairymd
mtairymd

Reply 1 year ago

You might be able to do it if you make the gap larger. I made sure the rod was fairly heavy which helps. Also, the video might be somewhat misleading...it takes more than a light tap :).

0
wirekat
wirekat

1 year ago

Very nice design. I love puzzle boxes.

0
mtairymd
mtairymd

Reply 1 year ago

Thank you. Me too!

0
jeanniel1
jeanniel1

1 year ago

Doing this one! I have plenty of magnets - does the 1" rod have to be a magnet or can it be a steel / iron rod? So cool!

0
mtairymd
mtairymd

Reply 1 year ago

Thanks. No, the rod isn't a magnet - steel or iron is fine. Just do a quick check with your magnet and rod before starting.

0
craftisan
craftisan

1 year ago

This is very nice!

0
mtairymd
mtairymd

Reply 1 year ago

Thank you!