D12/D20 Concrete Lamp Using a 3D Printing Mold

Hi,

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

Supplies

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

Lamp holder E27
EU power socket
Vintage power wire cable
Different decorative light bulbs are available :
- Firework light bulb (like in the picture) (I choose the G80)
- Retro light bulb
- Filament light bulb
Some concrete or plaster (This design required approximately 2kg of concrete)

Optional supplies :

Primer spray paint
Color spray paint
Power switch
Some chair bumper

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.

Lamp_Mold_4Layer_Shell.stl
Download View in 3D

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 :