To start off, I want to thank @Oddity3D for his suggestions on how to get better prints with PC filament, they’ve allowed me to continue with my test prints. I really appreciate this community.
Now however, a different question comes up. Bambu Black PC filament is extremely shiny. The product that I’m designing is for motion capture, which really tends to avoid shiny objects (as reflections from IR light tends to cause noisy data).
Is there such a thing as matte PC filament? (even if non-Bambu) Besides good old elbow grease to knock off the shine, any suggestions? (light sandblasting comes to mind)
Or alternatively, who of you out there has printed with PPA-CF? caveats? (don’t really trust what the website says about it). Looks like it has even higher tensile strength than PC, but as it is rather expensive, would like to find out from those who have used it before taking that jump.
Which mocap system do you have? I think ours is optitrack, don’t recall anyone mentioning problems in general with reflections on our gear but I’m not really a user of the system.
Paint is not ideal, as it would wear (these are head mounted camera frames for facial mocap). It might not be that big of an issue, but traditionally we try to avoid shiny objects in the volume (I’ve had situations where even my bald head would cause IR reflections, introducing ghost markers.. true story)
Prusa seems to have a matte PC filament with carbon fiber that might fit the bill, and around 70 bucks for a 800g roll, not too bad, and according to the site, AMS compatible (and they have new spools with RFID) anyone tried that?
It really depends on the rquirements you have for the part. PETG-CF is much easier to print and appears matte.
If you need a higher temp resistance, did you consider PA-CF? It is also the only material that beats PLA in z-impact strength (FDM’s weak spot). But keep the chamber warm!
Finally, PPS-CF comes to mind. But an X1 will struggle. It also has a rather unique appearance which may not be ideal.
There is a surprisingly cheap PC-CF made by IEMAI. If you want to spend the money, Prusa also sells one. But I would also suggest the spray paint route.
May I ask why you settled on PC for this application? In my view the main benefits of PC are the high temperature resistance and impact strength. It also is very fairly good at resisting creep under load. Are those properties relevant for you?
/edit: oh, sent too late, most of my points have been made already.
The main body of the HMC could be printed with PETG or any other filament, but there are thin straps that need to be really rigid but able to flex and bounce back to their printed shape (I’m not printing them flat, but curved, so that they follow the curvature I need them to)
I tried other materials but they had a tendency to break if bent too much (even with microfeatures to stiffen them up). These straps also have teeth, which need to be really hard and resist constant use.
The gears also have thin arms (think of the ratchet mechanism on the Quest VR headsets) which also need to bend and bounce back. I went through several materials and they had a tendency to lose that after a couple of uses and not spring back.
I’d avoid carbon fiber anything if it is going to be contacting skin, near eyes or can wear down in a way that the dust could get into/onto someone’s face.
It is a tad difficult to follow the requirements, but from your description, I would question the importance of choosing the material based on tensile strength. In partiular your mention of curvature and bending would point me towards bending strength and (z-)impact.
Going further, your mention of “gear” would be clear indicator for Nylon. No reinforcement if used frequently (and/or close to the skin) although you may get away with PA6-GF/CF if the gear is rarely used.
Bambu’s datasheets contain some good guidance for selection but beware that specimen print parameters may deviate significantly from those applied in your print. As a quick reference, you may find this post helpful:
You may of course also want to think a bit out-of-the-box: How about using mass and geometry to achieve the desired part stiffness and printing it in a hard TPU?
Makes sense!
But in that case, I fear that CF might actually reduce the strength that was the reason for PC in the first place. It certainly makes materials more brittle.
@EnoTheThracian Hey Eno, as always, your information is really enlightening, those graphs really put things into perspective. It almost looks like PLA will be an acceptable choice for most parts (especially those close to the skin) and it clearly illustrates why my initial tests with ASA and ABS were not very successful. I’ll have to test it for the straps (the gears will remain PC I think)
Now, in regards to mass and geometry, the whole idea is to keep both to the absolute minimum. This is a rig that goes around the head, with cameras (or smartphones) pointed towards the face to capture the actor’s performance, so reducing both is important.
I have a friend that is sending out a similar project to print via SLS with nylon, and he has reported some issues with the nylon straps (being too flexible, although tough and durable). Bambu doesn’t seem to carry any non-cf nylon (except for GF), so any recommendations based on what I’ve mentioned?
I was not aware that CF could cause issues (looked it up, and now that I know, that route is out)
Thanks again for your responses, very interesting info
I am afraid that my experience with non-reinforced Nylon is about 20 years out of date. Interestingly, that was also SLS at the time
So unfortunately, I can not recommend a brand of non-reinforced Nylon.
I have found PLA to be rather ideal for prototyping in any way. So it makes perfect sense for the initial design. However, it’ll probably not show a satisfactory durability due to embrittlement and wear.
What may also be interesting (once satisfied with the design and being aware that it is quite a bit more effort) would be to consider casting a pouring epoxy into a printed mould. Depending on size, you could even reinforce this with glass fibres.
Or to do the design prototyping in PLA and then have it milled from Al.
Both methods will give parts without the pesky layer adhesion weakness.
@EnoTheThracian You mentioned earlier GF, does that have the same caveats in regards to body contact?. There’s nothing really contacting the skin at all times. The strap for the forehead and the side pads will have additional padding.
I’m also trying to avoid sending anything out for additional manufacturing, as the one of the points of this exercise is to keep the cost down
Well, as far as I am aware GF typically has much larger diameters than CF. Nevertheless, typical GF products such as glass wool insulation mats require the use of gloves to avoid skin irritation.
We usually do not know about specific characteristics of the reinforcements (typical diameter, length, variance,…). The vast majority of particles are of course safely encapsulated in the thermoplastic matrix, but we must assume some surface particles and consider wear. So, I would definitely NOT rule out the possibility of at least skin irritation when printing GF reinforced material. Padding on the other hand will of course prevent direct contact as long as it is intact. The same goes for a thick coat of paint although it’ll probably suffer quickly from the parts flex.
Regarding cost for more durable parts, there are some online instant quote tools around. It may be worth double checking just in case FDM limitations proove to be too severe and/or frustrating.
A small aluminum part from milling should be fairly affordable when compared to an hourly rate for your efforts.
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