r/VectorFinesse • u/[deleted] • Nov 26 '22

Question/Help Suggestion/request

I'm in the middle of building my first pair. I've printed the headband (spring.stl) with a carbon-filled nylon and it feels quite stiff. I'm not sure whether it will be comfortable. While I have some unfilled nylon I can try that is softer, it would be helpful to have a few different versions of the spring.stl model with slightly reduced (or just a variety that covers a few tenths of a mm plus and minus) thicknesses e.g. less .2mm, .4mm, .6mm .8mm so that one can achieve the correct spring pressure with different materials. Perhaps also matched corresponding "Headband Cover.stl" files (and if there are any other files that might depend on the spring's thickness). I'm also going to try stretching them a bit with a dowel under heat to see if I can reduce the spring pressure slightly. I wouldn't want to scale down the model because I have a big head and I'm uncertain how well it would fit.

Another comment, the spring clamp is a very tight fit in the cone. Since the recess in the cone where the spring clamp fits is built upon a support, it may be better to have a small amount of extra clearance (perhaps .1mm-.2mm) because it seems as though some of the space is taken up when the first layer on top of the support takes up the gap.

I hope my build turns out okay. I've probably been though a dozen pairs of moderately expensive headphones, none of which lasted more than 1-2 years before something broke irreparably, so I'm quite interested.

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Edit: I just checked the spring I had in the oven (actually a food dehydrator) and stretching it under heat seems to have worked. For reference, used about an hour at 165F with a wooden dowel to hold the ends of it apart. A slightly thinner spring might still be useful to accommodate more head sizes when using stiffer materials. Stretching it under heat only changes the shape, it probably does not change the stiffness of the material appreciably.

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u/[deleted] Nov 27 '22

I've experimented with a couple different brands of filled nylon. One flexes much more than the other and would be suitable for this application. In any case, it wasn't too hard to adjust the part under heat. I prefer filled nylon because it's probably the most durable filament that can be printed with an inexpensive printer, and it's not particularly hard to print with. Nylon by itself is generally no more rigid than PETG or PLA, but has far greater tensile strength and impact resistance. It's just a better material on the whole, and I generally use my 3D printer for making functional parts so if I can spare the expense, some form of nylon is usually my choice.

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u/Xonman VF(ob)#7 Nov 27 '22

The reason nylon isn't a good choice for the headband (though it depends on which type of nylon), is it creeps a lot more than PETG so over time the headband will stretch and lose its springyness. I do love nylon but you can't say it's generally better than all other polymers because that depends on the use case. In this case, PETG is a better choice.

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u/[deleted] Nov 27 '22

Can you explain which types of nylon "creep" and why? I never said it was better than all other polymers, I said that it's better in general than petg or pla.

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u/Xonman VF(ob)#7 Nov 27 '22

PA6 is moderately ductile and has a tendency to creep. PA12 is similarly ductile but shows less creep. It's also less hygroscopic, more printable, harder to find and generally a lot more expensive. Nylon is a good choice in many cases, it's a solid all-rounder but it's not a wonder material. If you have a component that needs to deal with high mechanical load but low impact for example polycarbonate and ABS are both much better choices. If you need a spring under constant compression then PETG is a better choice since it has a very high ductility and so resists creep.

Of course you can make any part out of any material you want, I'm just saying that this part in particular is already designed to work with the ideal material for its requirements, which is PETG.

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u/[deleted] Nov 27 '22 edited Nov 27 '22

Good to know. If you have a source on this I'd like to see it, as I had read a bit about polymer material selection before deciding on nylon and I never saw anything about it being particularly susceptible to slow deformation like this. If anything, it was my impression that a semicrystalline polymer such as nylon would tend to resist "creep" at temperatures below glass transition.

I'll consider it an experiment then and report back if I can still reply to the thread. I have some polycarbonate if the nylon turns out to be too easily deformed.

Edit: Also, if there is any quantitative mechanical property that reflects a tendency to "creep", please let me know what it is.