In a previous blog I wrote a review of Proto Pasta’s Conductive PLA filament. For that review I just looked at the printing properties of the material.
I liked how Conductive PLA printed, and it had a smooth matte black finish. Texture wise it does feel silkier than normal PLA. When I discovered that the filament can be used as a pencil, I realized that the silky texture was due to the graphite in the filament.
Electrical Properties
According to the companies site it has the following electrical properties.
• Volume resistivity of molded resin (not 3D Printed): 15 ohm-cm
• Volume resistivity of 3D printed parts perpendicular to layers: 30 ohm-cm
• Volume resistivity of 3D printed parts through layers (along Z axis): 115 ohm-cm
This material has the potential for use in electrical applications. I can see variable resistors 3D printed with this conductive filament. I can also see this possibly as a low temp resistance heater for use in on 3D printer beds. For cosplayers, this would be a good way to embed wiring and LED’s into a prop.
Testing
For this I wanted to test it with a multi meter to see all of its properties. Then I remembered what happened to my last multi meter (It died a horrible electronic death, totally my fault, don’t ask).
So to test this, I decided to think outside the box and use another tool set I did have.
As a science teacher, I used Elenco Snap Circuits to show students the concepts of electronics.
I also remember that we lost a few pieces, and I am curious to see if I can 3D print them in Conductive PLA.
I made my own Snap Circuit pieces in TinkerCAD to test with. However as I test fitted them to the original Snap Circuit pieces, I hit my first issue.
The thermal expansion on this seems to be more than normal PLA. Nothing I printed fit with the dimensions of the original Snap Circuit pieces. It looks like everything Printed in the Conductive PLA had shrunk by 0.5 – 1 mm from the original dimensions.
In spite of this, I found that the graphite in Conductive PLA also makes it softer and easier to work with. I was able to press fit the pieces I wanted together.
Test 1, Light Test
For this, I wanted to see how the resistance of Conductive PLA would affect the brightness of a standard flashlight bulb.
I build the light setup shown here with the pieces in the Snap Circuit kit.
While the regular setup worked, the Conductive PLA piece that I replaced a snap with provided too much resistance to power a 2.5 V / 0.3 A bulb.
Test 2, Motor Test
In this test, I wanted to see how Conductive PLA would work in powering a small DC motor.
With the normal set up, the motor turned the fan at a good speed. With the 3D printed piece, the motor did not turn at all.
LED Test
With this test, I built a simple LED circuit. While the normal circuit worked fine,
adding the printed piece to the 10K ohm resistor did drop the brightness of the LED down.
When I changed out the Snap Circuit resistor with just the printed piece, the LED did light up with a medium brightness.
Meter Test
I wanted to see how much resistance the piece offered. With the standard Snap Circuit setup, a 10,000 ohm resistor will show as 10 mA on the meter.
With the printed piece in place, I had to switch to the 100 mA setting on the meter. I got about 50 mA with this setting.
If we use Ohms Law to find the resistance , we get R = V / I.
When you plug-in the numbers, R = 3 V / 50 mA = 60 ohms.
The piece used is 6.3 mm wide, so if we take the following value;
Volume resistivity of 3D printed parts through layers (along Z axis): 115 ohm-cm
We get that the theoretical values of this piece should be 72.45 ohms.
Now the piece was printed with only 5% infill, so it makes sense that the resistance is less than the predicted value.
Reflection
Proto Pasta’s Conductive PLA is a material for experienced 3D printers.
With the thermal expansion I experienced, you will have to design parts with a very loose tolerance to get the conductive parts to fit to your other prints. You will have to play with this filament on your printer if you want to get a super tight fit.
If you want to integrate this into your 3D print, this would be a great project for a dual extrusion head printer. I can see cosplay props with integrated LED wiring, as this filament also acts as the resistor. I can see other applications where you can save time and assembly by using this as your wire and resistor.
I know my testing in this was not super scientific, and in the future I’ll hopefully have a working multi meter to better test these pieces.
If you’re an electrical engineer, this would be an interesting material to test and develop a guide for. As more 3D printers play with this material, it would be nice to see the results of integrating Conductive PLA with other print material.
AUTHORS NOTE: Due to Copyright restrictions, I can not release the .stl files for the test pieces I copied for this test.
60 Ohms is still disappointingly high for “conductive” filament. I’d like to see what values you would get with other filaments like the iron or aluminum filled ones.
When you said it would be a great project to use with a dual extrusion head printer I couldn’t help but think about someone printing out the helmet on the movie Tron. With the electric grids in it. That would be kind of neat. You could even make a military helmet with conductive paths in it used for earphones/mic. There are all kinds of stuff that could be made. But I wish it worked better. I don’t know much about electricity so the numbers you talked about kind of flew over my head. But you mentioned the infill and the impact it had. So if you made it solid it would work better? But not to big because it would lose a lot of energy right?