Rope-climbing Robot From a Broken 3D Pen




About: I'm Mario Caicedo Langer, from Colombia, former Navy officer and BSc in Naval Sciences. Right now I'm Technical Director and Technology Lead Teacher at STEM - Engineering for Kids Azerbaijan. Also, I'm artis...

3D pens are great tools to develop the creativity of your kids. But, what can you do when your 3D Doodler Start stops working and cannot be repaired? Don't throw your 3D pen to the trash! Because in this instructable I will teach you how to transform it into a robot.

This model of 3D pen has some very interesting components: a micro-motor with gearbox, two rechargeable Lithium Polymer batteries and a mini-circuit board that can be used as a battery charger. Add some discarded 3D glasses and a few extra materials, and you can build a rope-climbing Simple Bot.

I'm participating in the "Trash to Treasure Contest" of Instructables. So if you like this project, your vote will very appreciated. Thanks for your support!

Now, grab some tools and let the fun begin!

Step 1: Inspiration, Prototype and Design

Building a rope-climbing robot was an idea I have since I was a kid, inspired by one of the favorite shows of my childhood: The Wizard. Probably you never have heard about it. You see, in a classic example of "trash to treasure", several shows that were unpopular in United States (and cancelled after only one season) became cult classics in Latin America, with complete generations having them as a reference point. So for a lot of us, "Street Hawk", "Manimal" and "Automan" were as cool as "The Fall Guy", "The A-Team" and "MacGyver".

People says that Tyrion Lannister is the first time a person with dwarfism is considered for a main character in a TV series (nothing against Peter Dinklage, he is one of the finest actors of our time), but that credit goes to Simon McKay (David Rappaport). He was awesome! A genius in robotics who used to create weapons for the government, then he quits and becomes the best toymaker, philanthropist and adventurer. Every time he and his friends were in trouble, he had some special toys in his suitcase that helped them to escape. And probably the first of his toys that impressed me was a little rope-climbing robot he has at his workshop. Several times I tried to make a toy like that one, but I failed. But after having this 3D pens problem, I decided to give another run to this idea.

First, I needed to test if the 3D pen's gearbox was powerful enough to lift the weight of the robot, so I created a prototype using the motor, a battery holder and bamboo kebab sticks, all attached using hot glue. I was surprised when I saw it worked!... for a few minutes. After that, the hot glue was not strong enough to stand the stress, and the prototype got tangled up and fell to the ground. But in its short time working, it gave me the essential information to build a better robot!

Next step (and that's something you don't see often in my instructables), I draw a design. With a pen. If I wanted to make it work, I needed to go full Engineering Design Process with it.

Step 2: Materials

So, to build the Mark II of this project, you will need the following materials. All or almost all of them are recycled, and you can use alternatives, as long as you have a motor with gearbox. You will need:

  • 1 broken rechargeable 3D pen
  • 1 3D glasses (or any kind of glasses with thick plastic frame)
  • 1 plastic bottle cap
  • 1 small switch (you can recycle it from a broken toy or even, from the 3D pen's board)
  • 1 zip tie
  • 1 Tic-Tac plastic box
  • 1 discarded ceramic continental car fuse (or any other hard plastic small piece that can be useful as a crank)
  • Wires (red and black, preferable)
  • Screws, nuts, bolts, washers
  • Superglue
  • Soldering tin

Also, you will require the following tools:

  • Dremel rotary tool
  • heat gun
  • soldering iron
  • screwdrivers
  • pliers

Step 3: Open the 3D Pen

Using the rotary tool, carefully cut the 3D pen's case through the middle (the slimiest part). But only the plastic part! If you cut too much, you can damage the board or other components that can be useful for this or future projects.

The part of the case we will use for the robot's body is where the batteries are housed. Carefully disconnect them from the rest of the circuit board.

Step 4: Mining the Necessary Components

Using a flat screwdriver and small pliers, open the black case that contains the mechanical and electronic parts. Basically, you will need the following components to create the robot:

  • Case with batteries inside: it will be the main body and power source.
  • Circuit board: it will be transformed into an independent battery charger.
  • Motor with gear box: it will move the arms of the robot.

Step 5: Modifications for the Circuit Board

To charge this robot, the battery must be unplugged from the motor and connected to the charger. That means we need two mini sockets compatible with the battery plug: one in the board/charger, and an extra one for the motor. You can buy a new one. Or, you can use one of the other two soldered to the board.

Using a soldering iron, remove the red mini socket, and solder a wire to each pin. We will use this one for the motor (later, I also removed the blue one, to be used in another project.)

At the end, place some heat-shrinkable tube on the socket and expose it to the heat gun, so the pins are protected.

Step 6: Building the Battery Charger

For this part you will need the modified board, the USB cable included with the 3D pen and a Tic Tac box.

Modify the Tic Tac box so you can fit the board inside. Use a Dremel rotary tool. Before inserting the board, check that the switch is in OFF (charging position.)

Step 7: Robot's Body

With the Dremel, adapt a plastic cap to cover the hole in the batteries case. This cap is very important, because the motor will be attached to it. Also, cables from the batteries and motor will pass by its side.

Step 8: Adding a Crank and Attaching the Motor

Remove the extra attachments from the shaft of the motor. Also, probably you will need to cut a section from the shaft, so it has the same length of the crank.

As a crank, we will use the fuse. Check that it fits and adapt with the Dremel or add a drop of super glue if necessary (be careful! don't jam the gearbox.)

Then, attach the motor to the bottle cap using a zip tie. Then, place the bottle cap in the body and check if the motor axle is aligned with the case's fissure.

Step 9: Electrical Circuit

This robot works with a basic electrical circuit. However, you will need to do some extra modifications to the plastic case. Using the Dremel, open a hole on the back (for the mini-socket and cables of Step 5) and on bottom (to place a switch.)

Connect the mini-socket to the batteries, and then insert it through the hole. One cable will go to one of the pins of the motor. The other one, to one of the pins of the switch. Then connect an extra cable from the center pin of the switch to the other pin of the motor, trying to keep all the cables inside the case (only exposed cables are the plug and socket of the battery.)

Use the soldering iron and soldering thin on each connection.

At the end, place the plastic cap with the motor, and fix it to the case using small screws.

Step 10: Mobile Arm

Take the 3D glasses and remove the legs. One of the legs will be the mobile arm of the robot. Drill a hole and make a groove in the points shown in the photos. Then attach it to the crank using a screw and a metal washer.

Drill a small hole in the case, being extremely careful of not piercing the batteries. Attach a metal rod from a small toy car and glue it with superglue. Then, insert a small car wheel to keep the mobile arm in position.

Step 11: Static Arm

The other arm will be fixed to the body. Drill a hole in the same position of the mobile arm, and skewer it in the other end of the motor's axle (the one without a gearbox). Attach the rest of the arm to the body, again being careful of not piercing the batteries.

Step 12: Arm Hooks

Using the heat gun, mold the arms to create a hook shape, being careful of not melting any other part of the robot. Check that, during the movement, both arms can move freely without touching each other. Also, the hooks must pass each other, so both of them can catch the rope without difficulty.

Stick some googly eyes to give extra personality to this little guy. Now, have fun with your robot, amaze your friends and give a new opportunity to a 3D pen that probably would finish in the garbage.

Happy making!

Trash to Treasure

This is an entry in the
Trash to Treasure



    • Arduino Contest 2019

      Arduino Contest 2019
    • Tape Contest

      Tape Contest
    • Trash to Treasure

      Trash to Treasure

    8 Discussions


    4 weeks ago

    This is really cool. Now it’s time to see if anyone I know has a broken 3d pen :)

    1 reply
    M.C. LangerOnionTheAnion

    Reply 4 weeks ago

    Thanks OnionTheAnion! Good luck with your hunting. Have you checked in STEM education centers?


    5 weeks ago

    That song, man ! Just in the memorabilia. Good luck ! ( Yeahh, I know you don't need that) we have a winner here

    1 reply