Using conductive filaments, circuit boards and other components such as switches, touch pads, sockets, resistors, potentiometers and capacitors can be 3D printed on a standard 3D printer.
This instructable shows how to 3D print a microcontroller circuit that has a touch switch and can control LEDs.
The short video shows the microcontroller blinking some LEDs.
The first problem with 3D printing a circuit board is that the conductive ink, glue, paint, or filament used to make the traces, has a higher resistance than the copper that is commonly used. So wider and thicker traces have to be employed to compensate for this.
The second problem is that there is no conductive ink, glue, paint, or filament that will stick to the metal leads of components as well as solder. A little vibration and most component leads will loosen from the circuit board trace. The workaround is to use a combination of conventional solder, conductive PLA solder and specially designed sockets to get a solid mechanical and electrical connection to the components that will resist vibration.
Any conventional and affordable filament printer can be used to print the conductive traces.
A standard Makerbot Replicator 2 was used to print the conductive filament.
3D printing pen or standard soldering iron to solder with the conductive filament.
Acrylic sheet or PLA to make the substrate to print on.
While the conductivity of any conductive plastic is not as good as copper, conductive PLA has a low enough resistance to be quite useful. The 5 volt power wires need to be directly soldered to the microcontroller pins. The wires to the serin and serout pins can be soldered using conductive PLA.
The circuit and all components were printed on a .039 inch thick clear piece of acrylic sheet. The conductive PLA fuses extremely well to the acrylic. Alternately, they could be printed on a substrate of regular PLA printed at that thickness. There is a spacer bar that prints first and is the thickness of the acrylic sheet substrate in order to get the extruder to the proper height. If you use a thicker substrate, you will have to change the thickness of the spacer bar.
I have included an stl and a f3d file if you want to edit the circuit in Fusion 360.
Settings A Makerbot Replicator 2 was used to print the the conductive PLA. I tried printing at .2 mm layer height and it tended to clog the extruder. It also had higher resistance than printing at .3 mm.
Resistors in the 100 ohm to 100k ohm are easy to print using thin narrow traces. Step 5 pic shows a 70k ohm resistor. The second pic shows a 2k resistor between a pin4 input and ground.
This potentiometer needs design improvement, but it does work. The sliding wiper prints large and has to be filed or carved to fit snugly in the channels. The pot pictured is around 2k ohms. Adding notches to the slide channels could easily increase the resistance to higher values.
Component stl or f3d can be used to print out or modify the potentiometer, lock sockets or experimental capacitors seen in pic 3.
Conductive touch pads can be printed and wires can then be conductive plastic soldered to the traces.
I have just begun to experiment with 3D printed capacitors. While the case is easy to print, finding the right dielectric filler material will take more research. I have tried metal powders suspended in glue with only a small increase in capacitance. Next to try will be activated charcoal.
For this first circuit, I decided to use a combination of soldering and sockets to embed the components. They both ended up having about the same resistance.
To solder wire leads a 3D printing pen or a standard soldering iron can be used.
After experimenting with many kinds of sockets, the sockets shown in step 8 pic are so far the most effective to hold wire leads. Solid tinned 22 guage wire or a component lead is inserted into a hole and a knifeblade is used to push through the top slot and bend the wire through the bottom slot which provides a very good electrical and mechanical connection. These lock sockets have about the same resistance as wires soldered with conductive PLA and are quicker and easier.
Here is the simple Picaxe microcontroller schematic and program code.
At this point in time, to make the best circuits possible with conductive filament on an affordable printer, most of the components should be able to plug into sockets so that little conventional or plastic soldering would be necessary.
Ultimately, a 3D printer that prints two different materials at the same time, would be most useful. A conductive filament and a flexible material like Ninjaflex could combine to provide the springiness required to make a quick and grippy socket.