Introduction: D12/D20 Concrete Lamp Using a 3D Printing Mold

About: Innovation engineer. Electronic and DIY enthusiast, with personal interests in retro tech, board games and old cars.


After seeing multiple video on YouTube of people playing with concrete, it was my turn.

A lot of maker uses wood or silicon for making the mold, but I don't have the tool for wood and the money for silicon. So my main idea was to use a 3D printing mold.

With this idea in mind two options are available to me :

  • Make a reusable mold in several parts
  • Make a one piece mold and destroy it at the end of the cast

I choose the one piece mold because it's way easy to design and you can do more complex shape.

Because everyone loves numbers (me including ^^) :

Price :

  • Lamp holder + EU power socket + Power cable (2m) = 0,7 + 1,4 + 2,7 = 4,8€
  • Light bulb = 4,45€
  • Concrete (2kg) = 2€ (price according to the size of the bag)
  • 3D printing filament PLA (120g) = 2,4€
  • Spray paints (primer and gold) = 5€
    • TOTAL = 18,65€

Time :

  • Design on Fusion 360 = 2 hours
  • (Printing time = 14h12min)
  • Cast time = 15 minutes
  • Unmold = 15 minutes
  • Post process = 1 hour
    • TOTAL = 3h30min


I buy a lot of my stuff from aliexpress, but I'm sure you can find these on other websites.

Optional supplies :

Required tools :

  • A 3D printer
  • A glue gun
  • A bucket

Optional tool :

  • A hot air station

Step 1: Ideas

I love playing some board game so I choose to make a design of the lamp based on a 12-sided die (D12).

Another idea is to cast directly the lamp holder and the power cable in the concrete.

The goal of this project is to determine how many layers should the shell of a 3D print need to hold the concrete.

Step 2: Design & 3D Printing Mold

To make the 3D model of a dodecahedron on Fusion 360 I follow this tutorial made by Etienne K.

After design it, I slice the model with Cura and 3D print with my Creality CR-10.

You can find below the STL file, if you want to make the same design.

And more numbers :

  • Size : 160cm x 160cm x 160cm
  • 3D printing time : 14h12min
  • Shell with exaclty 4 walls (this represent 1.565mm on Fusion360)
  • Grams of PLA : 120 grams

In the pictures below, the mold is green and after it's red. Why ? Because the green mold is my first attempt and it was a big fail cause the mold broke. It broke cause I try with only 2 walls and it was too weak.

Step 3: Prepare & Cast the Concrete

So now you have your mold, it's time to prepare the mold following these steps :

  • Pass the cable through the mold
  • Wire the lamp holder inside the mold
  • With the glue gun fix the lamp holder on the bottom of the mold
  • Add some glue where the power cable pass
  • Make sure the lamp holder is waterproof, if not, add some glue

When the mold is ready, you can cast the concrete.

I don't have a lot of advice just follow the proportions of the concrete mixture and try to vibrate the mold to release the trapped air.

The last step is to wait a few hours/days.

Step 4: Unmold

As the mold is made of 4 walls, is pretty hard to destroy but it's possible with only a cutter.

In my case I choose to use a heat gun to melt the plastic and destroy it more easily.

As you can see in the picture the concrete have sharp edges that mean you can do more precise design.

Step 5: Additional Steps

In the list below, I give you some extra step you can make to finish the lamp :

  • Sand each faces to remove the layer mark from 3D printing (I choose to don't do it to remember the process)
  • Paint the concrete (In my case : 3 coats of white spray paint primer and 2 coats of golden spray paint)
  • Add a switch on the wire
  • Add some bumpers to protect the furniture where the lamp will be placed

As the tittle says, all the steps are additional, you can keep your lamp right out the mold.

The last step is to add the power socket :

  • Strip the 2 wires
  • If you can, tin the 2 wires
  • Pass the 2 wires and screw all parts

Step 6: Enjoy !!!

Now that the lamp is finished and the process of a one use mold is validated it's time to enjoy the lamp and think about the design of the next.

I'm pretty happy with this design, use a new technology like 3D printing to make a strong object is so cool.

If you make your own unique design, I would love to see it so don't forget to share it in comment ^^.

Have a nice day !

Step 7: EDIT : the D20 Lamp

I decide to make another lamp base on the same method.

This time the lamp has the form of a dodecahedron.

This lamp was painted silver, the color rendering is top.

The bulb I use for the D20 lamp is this one.

Lighting Challenge

Participated in the
Lighting Challenge