1 Topic by glenenglish (edited by glenenglish 2018-05-05 09:13:01)

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Topic: extruding small diameter conductive filament with Filastruda

Hi

I have a fairly custom requirement for an extruder to produce varying conductive plastic filament, not for 3D printing, for making semi-conductive wire.

I would like to produce ~ 0.35mm to 0.75mm filament. I have a good metal-shop and CNC if I need to custom a head.

I need to produce varying conductivity filament, and this is done commercially usually by adding carbon powder to the pellets. Commercial suppliers of this - the conductivity is too low of their standard offering and I cannot seem to get them interested, and so hence do it ourselves.  This is for "poor' conductivity wire,  not for 3D printing... like 300-400 ohms per meter.

Is there any, to your knowledge , any fundamental limitation to producing the small diameter filament wit this method.  I don't know anything  about extruding plastic filament . Some nozzle mods required, maybe. It does not have to be all that uniform, either, ± 20% diameter is fine !...  have some hotend experience...on 3D printer front, I have two Deltas... :-)

Carbon , Alumina, or other powders can be used, as long as it is non magnetic. 

any suggestions or guidance  are useful and welcome.

Glen English
Canberra, Australia.
AI6UM/VK1XX

2 Reply by genesat1

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Re: extruding small diameter conductive filament with Filastruda

Targeting the higher end of that size 0.75mm would be easier than the lower end simply because of particle size.  You can buy undrilled nozzles from Filastruder and then drill them to the size you need.  You'd want the smallest particles you can find that meet your conductivity requirements - large particles in a small nozzle would probably just result in a clog the same as in a printer.  The higher the loading of the plastic the more brittle things tend to get, so PETG might work better for you than say ABS (like Eastar 6763).

What benefit is there to semiconductive wire vs normal wire and a resistor though?

3 Reply by glenenglish

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Re: extruding small diameter conductive filament with Filastruda

Hi
thanks for the info. OK on the PETG and the 6763  and 0.75mm. The working temperature requirement is no higher than 40 deg C, but the multiple repeated bending (can be controlled minimum radius) is an issue i suspect , ie choosing the right plastic.


In high RF fields, short or long lengths of wire can have currents induced, in this case 4 or 5 meters of wire , used in a high frequency field like say, 600 MHz, may be problematic from lengths of multiples of 25cm up or so, that's an over simplification, but is the reason why a long wire and a resistor at the end is incompatible. The induced currents re radiate and pertube the RF field

I am interested to work with someone that understands the  plastics.

-glen

4 Reply by carl_m1968

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Re: extruding small diameter conductive filament with Filastruda

The reason for their low conductivity I would imagine is that there is a golden ratio between pellet stock and additive at a certain percentage of additive the plastic molecules will no longer be in enough concentration to bond uniformly and would create a brittle extrusion. I doubt you reach as low as you want as the carbon would need to exceed the binder concentration resulting in a brittle to possibly no binding material that will come out in non uniform blobs.

Printing since 2009 and still love it!
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5 Reply by glenenglish

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Re: extruding small diameter conductive filament with Filastruda

Hi Carl

yeah.

and often the target of the conductive plastics is only to be dissipative , IE dissipative of static electricity buildup.

I've also tried using ultra thin copper wire- 12 micron. yes ! 0.012mm dia.... too hard to work with and put inside a jacket.   That was 150 ohms/meter. I really want around 300-800 ohms/meter.

There are also a few techniques to plate into cotton thread copper particles.

However, if I can find a plastic i can turn into conductive filament , that is my preferred route.  I guess it is back to the fundamentals.... enough conductive material load versus sufficient plastic load to bind together.