Also, I didn’t optimize and used the same speeds for everything (added that info). The CF layer adhesion could be improved some by slowing down the print and messing with the cooling settings some. It’s a balancing act between bridging well and good adhesion so it takes some testing.
I still love that this post is you saying hello in this forum. Like, hi, I’m Paul, I am posting for the first time, here is a dump of really interesting data that I spent a lot of time and money on.
Legend. 
Thanks a lot.
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LOL. Love that.
Everyone’s got their thing. I love testing stuff and data. I’ve been lurking a while, reading up and learning. Just thought I’d share my work as someone else might benefit. It’s enjoyable to set up an experiment and see where it goes.
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Awesome Paul! You really ran through the matrix on this one. That pile of specimens is a testament to that, and you did a good job presenting/explaining your data. For a ‘non-engineer IT guy’, you do science very well.
FWIW, I have switched to carbonX petg for most of the important parts on my primo. I haven’t had much problem with layer adhesion using the settings recommended by 3dxtech. IIRC, 245C/68C, 0.4 nozzle, .45 line width, .25 layers, 40mm/sec. I run a big-ole 3-wire PT100, which may shift the ideal hotend temp from what other machines do. You’re totally right though, that the CF only interferes with adhesion… so may tradeoffs there’s no perfect filament.
I’m also curious if you plan to add carbonx pla-cf into the mix? That stuff is a PITA to print it loves to jam, but I’m guessing it will be an edge above for non-heated parts. I had to swap my all metal e3d for a teflon lined heatbreak to use a spool of that stuff up… which is why I haven’t bought it since (lots of work for me to print it, and the all metal works with all other filaments I use).
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Thank you! It was a lot of work but not too bad. Once I got the itch to test, it needed to be scratched
One thing these tests don’t do is give a real world comparison of the MPCNC parts, under actual milling loads, and in dynamic situations. I suspect the increased strength of the CarbonX PETG in the one direction is beneficial for most MPCNC parts. There are some pieces which I wonder about like the Core and the Corner leg locks. Just because it seems like the direction of the layers and my one-thumb-in-the-air-left eye-squinting analysis at the loads there would cause the PETG-ness of the CarbonX PETG to be a liability. But it would be stiffer in the other directions…so it’s a guess what the net result would be. I think for a lot of the parts it really is a great (i.e. superior) filament. The corner top/bottom for example and perhaps the trucks look like they would benefit the most…but again just eyeballing. I don’t think many are able to print entire sets of parts and build multiple machines to test defection so we’ll have to stand on what everyone is experiencing.
While layer adhesion does seem lower with the CarbonX PETG, the standing loaded samples exacerbated that since the CF wasn’t really helping at all. It was basically just PETG at that orientation…well, PETG with lower layer adhesion than regular PETG. I don’t think it’s something that would be evident in a full MPCNC part which is dimensionally large enough you can’t just bend and snap it (most aren’t anyway). So it goes back to the question of whether it matters and does the extra stiffness in the directions the CF help enough that it’s just a moot point.
I have almost bought a roll of CF PLA a few times. I’d like to test it out. Maybe after the new year. As you can tell I’m a bit of a filament hoarder.
The CF samples are very interesting. I would expect the fibers would be oriented parallel to the extrusion which is consistent with the results.
The flat vs. edge differences could possibly be attributed to perimeters vs. infill. The edge parts are all perimeters (or anyway a much higher fraction) while the flat parts have infill at a 45 degree angle.
I would guess that a flat part with a very high number of perimeters could have the same stiffness as the edge part. If so it would confirm that the fill orientation is the reason the flat part is less stiff.
Slots in a part can force the orientation of the perimeters, which could make a significant difference for CF parts (besides the ordinary benefit of extra density in selected areas). That could make for interesting designs specific to CF.
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100% agree Jamie. If I had oriented the infill for the flat pieces along the length of the sample, the edge and flat would be much more similar.
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