Minimalistic Concrete LED Table Light

BOM

3D-printed parts

You need to print every .stl file once, except for mold_side v2 which you need to print twice. All parts need to be rotated before printing. The following parts need to be printed with support:

• connector_bottom_wideflat
• mold_center

My mold is printed from PLA+ at 0.3mm layer height. 

Screws

For the mold assembly, you need:

• 9x M3x10 screws
• 9x M3 nuts.

For the lamp assembly, you additionally need:

• 3x M3x6 screws
• 4x M3x10 screws
• 7x M3 nuts.

Aluminum extrusion & LED

The lamp is designed to house a round extrusion with 10mm diameter. The length is up to you, however I do not recommend going larger than 150cm for stability reasons.

• The aluminum extrusion + LED diffusor I used can be found here (1m length): https://www.led-konzept.de/LED-Alu-Profil-PIKO-O-schwarz-100cm-inkl-opaler-Abdeckung
• End-cap for aluminium extrusion: https://www.led-konzept.de/Endkappe-fuer-LED-Alu-Profil-PIKO-O
• The LED strip can be found here (1m length): https://www.led-konzept.de/LED-Streifen-24V-weiss-96W-m-warmweiss-2700K-5mm-breit-100cm-ohne-Anschluesse

You will also need some wires to solder to the LED-strip and a 24V power supply to power your LEDs.

Concrete

The mold takes a volume of about 470cm^3. For the concrete I was using, this meant 880g of cement powder and 160ml of water. The concrete I am using can be found here: https://www.bauhaus.info/modelliermasse-bastelbeton/ultrament-beton-giessmasse-bastel-beton/p/26502034

Consumables

• Tape
• Coating/covering material

Depending on the concrete you are using, the recommended coating material may differ. I used plastic wrapping foil that I clamped between the mold parts which worked fine.

Casting the base

1. Assemble the mold by screwing connector_bottom_wideflat and mold_side together using 8 M3x10 screws and nuts. The assembly uses drop-in nuts. 
2. Use the 3 M3x6 screws and nuts to secure the nuts at the end of the three arms of mold_center. Use some tape to cover the nut openings of those three nuts to avoid concrete leaking in (compare 3rd picture). Those nuts will later on secure connector_bottom_wideflat to the concrete base and need to be inserted before casting!
3. Secure mold_center to the center of the mold assembly by using mold_center_clamp and a M3x10 screw and nut. Note that the long “arm” hooks into mold_side. This arm will later on be used as a cable guide (compare 3rd picture).
4. Check that your mold assembly is tightly screwed together and that the inner surfaces are covered or coated, except for mold_center (this part is supposed to stay inside the final concrete part!). Ensure that the mold is standing on a secure, even surface and that there is some protective covering between the mold and the surface (in case some concrete leaks).
5. Prepare the concrete mixture and slowly pour it into the mold. Make sure no concrete gets into the center compartment or the cable channel (compare 4th picture)

Assembling the LED stick

1. Do a test-fit of the LED strip into your extrusion to make sure the length matches. It is also a good idea to power up the strip to check for defective LEDs.
2. Do a test-fit of the extrusion into connector_bottom_wideflat. 
3. There is a slit-opening at the back of the extrusion channel to allow securing the extrusion with a M3 screw. For this you need to drill a 3mm hole into the extrusion. Mark the drilling location somewhere along the slit and drill the hole.
4. Cut off 25mm of LED strips at one end. This end will sit in the base (which is 30mm high) and hence wont be visible. 
5. Solder two wires to the LED strip.
6. Remove the protective film on the bottom of the LED strip and stick it into the LED channel. Start with the end without cables soldered to it and align it with the end of the extrusion without the hole.
7. Cut off about 20mm of diffusor at one end and clip the diffusion onto the extrusion.
8. Thread the wire through the extursion channel in connector_bottom_wideflat. Insert the assembled extrusion into connector_bottom_wideflat and secure it with a M3x10 screw and nut using the hole you drilled.
9. Use 2x M3x10 screws and nuts to screw down cable_clamp and secure the cable. Do not overtighten it. The goal is to act as a stress-relieve (compare 5th picture)
10. Insert the extrusion end-cap at the top of the extrusion.

Assembling the concrete cast

1. After curing, carefully unscrew all mold screws and remove them.
2. Break off the hook end of the cable cannel.
3. Remove mold_center_clamp, mold_side and connector_bottom_wideflat. Important: Do not remove mold_center, as it is part of the final lamp!
4. Unscrew the three M3x6 screws sitting in the “arms” of mold_center. Cut off excess tape. Verify that the nuts at the other side of each arm can't escape.
5. Lift the concrete part over the LED-assembly and slide it along the extrusion down to connector_bottom_wideflat.
6. Use the three M3x6 screws to secure to secure connector_bottom_wideflat to mold_center.