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PA CF25 material.


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Westy119

This post is going to be a bit of a story from researching high temp/strength 3D printing filaments, to modding my Ender 3, successfully printing Carbon Fibre filled Nylon, comparing stiffness to other materials (PLA & ABS) and doing a basic heat deflection test.

 

I’m currently rebuilding my 91 SE narrow body and want to make numerous brackets, clips and spacers for under bonnet parts using my 3D printer. This way I can design and make exactly what I need.

I’ve been 3D printing for about 2 years now, so it all seemed very possible and achievable, but material choice would be critical for engine parts due to the temperature.

After disappearing down several YouTube wormholes and reading more filament data sheets than is healthy  I realised the typical filament materials like PLA, ABS, ASA and PETG were not going to cut it or be marginal at engine bay temperatures. PLA and ABS have a very sharp glass transition temperature, where it changes from a solid to a rubbery state and can deform.

I’ve printed PLA parts that have deformed when used in a car interior on a hot day.

It was from these videos that I learned about Carbon Fibre filled Nylon filament or PA CF25. This has a 25% Carbon Fibre fill distributed through the Nylon.

Nylon has a very slow glass transition that is helped by the inclusion the the Carbon Fibre. 

In my next post I’ll go though the steps to modify my Ender3 to print PA CF 25

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Westy119

Printing PA CF25 needs a higher temperature than PLA and ABS, 240 to 260 degC.

The standard hot end on an Ender 3 printer has the PTFE Bowden tube running down into the hot zone. PTFE can start to gas from 260 degC.

https://www.fabbaloo.com/blog/2020/3/18/is-your-3d-printer-killing-you-slowly

So an all metal hot end is required.


I ordered a Micro Swiss all metal hot end and some 0.6mm A2 stainless nozzles. The latter being needed due to the abrasiveness of the carbon fibre.

 

Installation took about 30 minutes and uses the original cartridge heater and thermistor and Bowden tube, after cutting it off the old hot end. In fact the Bowden tube was stuck, proving some form of degradation had occurred.


With everything reassembled the new hot end heated up and achieved the target temperature. In some videos it was suggested you need to tune the PID  temperature control coefficients. Mine seems to work just fine, with rapid heating and stable temperature. I checked accuracy with a calibrated thermocouple; no issues there.

 

Then it was a few test prints in familiar materials to make sure it’s all working.

these came out OK. Some tuning of settings required to get the top layer finishes I have had.

 

Next post is printing the first PA CF25 part and doing a comparative stiffness test.

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Westy119

The first part I printed was a simple bridge like beam to use in stiffness and heat deflection tests.

 

I use ABS for most of my other work, so there’s a draft shield around the part to help reduce warping and layer separation. But this surface demonstrates the finish you get.

This was printed with a 0.3mm layer height.

The surface is Matt with a monotone iridescence as you move the angle of view. Reminiscent of the changing surface on carbon fibre. The layer lines are partially disguised by the surface finish. I’m sure finer layer heights will produce some stunning parts.

Once removed from a glass bed, the surface is not shiny like PLA or ABS.

 

Next was the comparative stiffness test.

Not very scientific, but visually compares materials.

The samples were clamped either side of a box section until the first sample touched the surface.

Here PA CF25 wins against ABS, but is roughly equal with PLA.

 

In my next post I’ll do the heat deflection test and discuss what’s next for this material.

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maurici

Im most impressed with the idea you had to test and demonstrate the diferences between both materials. Very clever.

Cf nylon is an oustanding msterial, and pretty easy to print. However suffers of severe creep so is not a one for all solution if long term loads will be aplied to it. (Im sure you have read about it already just sharing my two cents).

 

Regarding the PID tuning, do it anyway. Is a 5 minutes operation and once extruding at different speeds will help to keep the temps even more stable. :)

 

good work and good luck with the project!

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Westy119
5 minutes ago, maurici said:

Cf nylon is an oustanding msterial, and pretty easy to print. However suffers of severe creep so is not a one for all solution if long term loads will be aplied to it.

As with most automotive plastic parts a compression limiter metal tube/insert would be needed where a bolt load could cause creep.

With careful design, I think this material has a lot to offer.

Another area of interest is using it to either skin with carbon fibre or as a prep-preg mould as it can resist the curing temperatures.

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Steve (sdh2903)

Interesting stuff :yes:

 

I've googled but no real definitive answer. What sort of temps is the cf nylon resistant to?

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Westy119
Posted (edited)
3 hours ago, Steve (sdh2903) said:

What sort of temps is the cf nylon resistant to?

I’ve done a really simple test, but it’s not conclusive.

I slowly ramped up the temperature in an oven with samples of PLA, ABS and PA CF25.

I print a beam bridge test piece in each material.
120mm long, 3mm thick, 12mm wide with a stand-off of 8mm.

Then I looked at what mass would be needed to just start deforming the weakest material at room temperature. This was approx. 100g on the ABS part.

Then into the oven at 50 degC for 20 minutes.

The oven was ramped another 5 degrees and dwelled at that temp for 20 mins.

By 60 degrees PLA had sagged fully

It was 105 degrees for ABS.

But PA CF25 went through different levels of sag from 120 to 160 degrees where it was fully sagged.

@mauricithis where the material creep may be occurring. So the time at temperature determines the creep under load.

I plan to do a long term temperature test at 120 degrees to see if it will eventually reach full sag and it was going through the glass transition slowly, unlike PLA and ABS that transition really quickly.

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Edited by Westy119
Can’t spell with fat fums
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Dave Eastwood (Gadgetman) - Club Secretary

What a great thread, thanks for all the hard work! It's really interesting to see someone actually do the leg work on this.

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maurici

Geat read this.

Mental note... buy more PAcf.

What brand are you using? My experimenting was from some leftovers from a mate... i could do with buying some.

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