Ok, that's not the classic 3*3*3 one-color-LED cube but a 4*4*4 RGB cube, but at least in a kind of classic design ^^.
I used all mayor tools in our fablab for these object: pcb mill, laser cutter and 3D printer - the latter at the end of it's resolution (which means winning a better one for the lab/me/science would be of course great :-)
It uses 64 WS2812B bare LEDs, an ATTiny85 as controller, and a bunch of capacitors and some other bird food as electronics (connected with silver wire or/and the pcb). The LEDs are inserted in clear, 2mm acrylic housings (which is also used for the outer boxing). 5mm*5mm laser cutted squares out of diffuse, special LED acrylic (0M200) (3mm thick) are used as a enlighted box on top of each LED.
The wood frame consists of 2, 1 and 3mm lime wood sheets (maximal 10 cm wide) and 4 1cm diameter, 9cm long pieces of lime round wood.
4 reachargeble batteries (mignon, 1,2V) are used in 2* double housings as a 4.8V power source.
Since the 3D printer was at the end of the resolution by printing the capitels of the columns, i decided not to print some statues but instead bought a box of Spartans (1:72 scale).
Spartans, column capitels are painted silver with Revell model paint, the wood is finished with wood stain (Aqua clou, cherry tree).
More details in the next steps.
Step 1: PCB Milling and Soldering
The PCB mill makes life easier: Just load the Box1.brd file in eagle, export it for the LPKF mill, load it there and let the mill do the magic stuff.
Then solder the Attiny, capacitors etc. on the PCB. One jumoer wire has to be on the other side - to keep it still flat i decided to mill a small channel in the PCB (and removing the rest of the pinheader on the bottom - see fourth picture) and inserted the silver wire in the channel.
Bonus: You can also add e.g. four buttons on each side of the PCB, pinheaders for them are already included, but yet unused.
The program is just the classic strand test example from the adafruit neopixel library, uploaded to the attiny as described by High-Low Tech. Just change number of leds of the strip to 64 and the PIN to 0. The six-pin header is for programming (MISO,MOSI,SCK,RST,VCC and Ground), just used the .brd file and the HIGH-LOW tech description of the wiring with an Arduino for programming. No magic here.
Step 2: Laser Cutting
Again, for the cutting(and engraving) the machine did the job. Just cut the different layouts out of the corresponding material (you will need 5 parts the "filling" material for the inside - use cheaper material, nobody will see it :-)
You might need to install two fonts for the decoration on the sides: Soft Ornaments Three and Bodoni Ornaments.
The building process is rather simple: Just staple the bigger parts, the round wood will align them. Insert the small walls in the corresponding slots (smaller tenon upwards). Glue it together with wood glue -apart from the bottommost layer of wood, which will serve as a kind of hatch for changing the batteries. I added small holes in each layer for small screws, but until now the tenons from the sides are strong enough to hold the bottom part by friction.
Some rings will be used as lower parts of the columns, and the small rectangles are used as a socket for the statue at the end of a column. But stain the latter along with the built (after the glue dried) socket.
Step 3: 3D printed stuff, painting...
The silver parts of the decoration: Along with four 3D printed column capitels (found in the internet a long time ago, so no file for it - just search for corinth capitel resize it and substract a 1 cm hole for the column)
After the 3D-printer did his work (i totally like automatic tools), i opend my newly bought Spartan box, took 4 of them (Still have an army for future builds :-) and painted them along with the column capitels and laser-cutted rings silver.
Step 4: Adding LEDs
No machine for that... Now i had to work myself. That's sad :-)
Anyways - In each laser cutted acrylic holder (the ones with the 4 rectangles inside, the side with the smallest distance from rectangle to outside is the bottom) four WS2812B are inserted: The should be all in the same direction (look out for the small triangle on one pin), and the two pins of one side should be on opposite sides of the acrylic- which should fixate them. A small 5*5mm square made of 3mm diffuse acrylic is mounted on top of each LED, and they are fixated with a second piece of acrylic (both pieces form a cross when looking from above).
Fixate them with a very, very small drop of glue on end of the such made acrylic column.
For soldering: First connect the ground (triangle) and VCC (diagonal opposite) pads with silver wire, adding some space on the bottom for inserting in the PVb and soldering there.
Now it becomes complex: Connect each VOUT data pin with the VIN data pin of the next WS2812B (see datasheet :-), that means i started with one column by addin a wire on the VIN pin (which will go straight to the bttom to the PCB). Then i soldered a wire to the VOUT of the lowest LED and wrap them halfway around the column on the way to the VIN pin of the next led. Continued the same way to the top LED, where a wire is soldered on the VOUT pin which is used to connect with the topmost LED on the next column - where the whire went downwards from DOUT of an LED to the DIN pin of the next (lower) LED.
The next neighbour now starts again frm the bottom. So only two different types of colums are used. That would be boring. So: The wiring on the PCB changes direction form one row to the next (which means the data line, VCC and Gnd are on a different position). Not that hard, it only kind of mirrors the insertion process for each row, but of course i just mounted them first straight symmetric. Only after soldering but luckily before cutting the rest of the wires on the bottom i recognized that someting looked strange :-)
Step 5: First testing...
Not really the first one: In best practise it would be better to check not only the first column as i did but each. But then i would have seen my error with the changing direction after one column and hadn't have to removed eight of them, that would have been too easy.
Step 6: Add the decoration, Have Fun!
The rest was easy: Just add the rings on the lower parts of the colums, the acrylic sides and top (using a twezzer to arrnge the LED columns). Then fixate the sides with the top with glue. Add the capitels on top of each column and the small wood rectangel on top of them, which a statue on top to guard your Led cube. (And glue everything together)