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 Discovered the 3D printer
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Balor
recumbent guru

Russia
925 Posts

Posted - 10/08/2019 :  08:59:32  Show Profile  Reply with Quote
Prusa (the printer I've got access too) recommends shore 90-ish filament, so fairly stiff.
Hmm... Bowden or direct extruder? Yours look like direct one, should handle any filament provided you turn off retract (better print in 'vase mode') and keep speeds slow and steady.
Admittedly, I think it is easier to simply buy vibration isolation mounts from amazon, they come with mounting bolts attached, and I think that their rubber has better compression set then printable TPU. On the other hand, you have much more design freedom that way, may print it hollow for instance for 'air suspension' :).
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Balor
recumbent guru

Russia
925 Posts

Posted - 10/31/2019 :  14:36:13  Show Profile  Reply with Quote
Did a test of carbon 'lug'- printed an ABS shell, vacuumed a few layers of carbon around it, than dissolved it in acetone (took awhile, process is rather stinky). Turned out pretty good, except inner diameter somehow ended up smaler than the 'mandrel' - I presume due to print lines. Good thing I've had some leeway! Should have printed it bit larger and polished it first I presume - maybe acetone-polished, by brand of ABS is pretty damn resistant to this stuff.

Next try - HIPS and lemonene (damn expencive though, not exactly mountain dew either, but at least does not stink as bad).

Edited by - Balor on 10/31/2019 14:37:10
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Balor
recumbent guru

Russia
925 Posts

Posted - 11/03/2019 :  10:14:14  Show Profile  Reply with Quote
Btw, experimenting with TPU bladders is more or less a failure: It is extremely hard to make them airtight, and even dunking into dilute glue does not seem to really work in the long run (and is stinky).
I think a better idea is to 'paint' it with a liquid latex, or two-part polyurethane/silicone. Plus, 3d printing TPU is pretty stiff by itself (shore 90Aish) so even a thin wall is rather resistant to being stretched/compressed, will only truly work for larger bladders where forces are much greater I presume.
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alevand
human power expert

USA
3696 Posts

Posted - 11/03/2019 :  11:56:57  Show Profile  Visit alevand's Homepage  Reply with Quote
You can by PVA filament that dissolves in water.


C:
Tony Levand
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Balor
recumbent guru

Russia
925 Posts

Posted - 11/03/2019 :  13:41:02  Show Profile  Reply with Quote
Yea, I know. It is pretty damn expencive though, and not stiff at all (so will need to be prined with a lot of material to avoid distorting during vacuum bagging). But it does seem like the best option if you want to avoid aggressive solvents - I've bought some lemonene, and brand of hips I have refused to be dissolved in it, only becoming kinda 'gooey'. Damn polymer chemistry...
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harv
recumbent enthusiast

429 Posts

Posted - 11/03/2019 :  16:18:29  Show Profile  Reply with Quote
If you can print polycarbonate, acetone will make it craze into tiny easy to break pieces. Even though PC is expensive it has double the modulus of HIPS so you can make the shell thinner. Also has a higher heat distortion temp than HIPS, so if there is heat from the epoxy curing the PC mandrel should distort less than HIPS.
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Balor
recumbent guru

Russia
925 Posts

Posted - 11/03/2019 :  18:45:42  Show Profile  Reply with Quote
quote:
Originally posted by harv

If you can print polycarbonate, acetone will make it craze into tiny easy to break pieces. Even though PC is expensive it has double the modulus of HIPS so you can make the shell thinner. Also has a higher heat distortion temp than HIPS, so if there is heat from the epoxy curing the PC mandrel should distort less than HIPS.



Interesting! But I'll need a full metal nozzle to print PC, something I don't currently have, plus likely a heated bed with temp above 120 - something my printer does not support at all :(.
Plus, I'll have mess with anti-adhesives (otherwise 'crazing' it will not help much, it will remain stuck to the laminate).

It seems that cheapest way is just printing with ABS and dissolving it in acetone. It is not even *that* bad compared to most other solvents, just smells. PVA is also highly hydroscopic (duh!) so some filament enclosure with dessicant will be required...
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Patrick Bateman
New Member

USA
72 Posts

Posted - 12/31/2019 :  14:55:35  Show Profile  Visit Patrick Bateman's Homepage  Reply with Quote
Not sure if it came up in the thread, but you really want to avoid using PLA on a bike. Basically it will melt in the sun. It's made of corn and it has a very low melting point. One of my 3D printed speaker projects melted in the sun, during the *winter!*

Another "neat" thing to keep in mind, with 3D printers, is that you can make ridiculously stiff shapes by making them large in diameter with thin walls. When I was first making 3D objects, I was making them with walls that were about 1/4" thick, but after some time I realized I might as well "go big" since there's not much downside to doing so. (IE, with aluminum or steel, there's a limit of how thin the walls can get, but with a 3D printer you can make walls that are a fraction of a millimeter thick if you feel like it.)
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Balor
recumbent guru

Russia
925 Posts

Posted - 12/31/2019 :  15:23:01  Show Profile  Reply with Quote
There is still downside of course - prone to buckling failure. But when printed with bare minimum of infill, it can be fixed as well!
Btw, PLA is really tough and rigid. If you shield it from the sun, (it has HDT of about 55 C) it is an excellent material, I've printed some COGS and they stood up to serious watts (hundreds, actually).

I need a way to properly dissicate the PVA, cause it came wet out of the box, literally steams when printed and when printed has no layer adhesion whatsoever :(

Edited by - Balor on 12/31/2019 15:24:36
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strayray
Warren

USA
23 Posts

Posted - 01/01/2020 :  17:52:41  Show Profile  Reply with Quote
Balor, see https://ultimaker.com/en/resources/52682-how-to-dry-pva

If you go the silica gel beads route (5-8 USD/lb), I prefer color changing indicator beads, so you can tell when they need to be recharged. I prefer the orange-green beads over the blue-pink beads. The blue-pink beads have cobalt chloride - a known irritant and suspected carcinogen.
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Balor
recumbent guru

Russia
925 Posts

Posted - 01/05/2020 :  17:23:08  Show Profile  Reply with Quote
Thanks, I've bought a used convection oven and it worked nicely (as well as apping temperature).

Also see this:
https://aliexpress.ru/item/32851405162.html

If that works... why not print it from CF-filled PLA? I think I'll make my own BB :).
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Balor
recumbent guru

Russia
925 Posts

Posted - 03/06/2020 :  04:39:13  Show Profile  Reply with Quote

I think I'll try replicating that some more, for actual frame joints.

I'll need to experiment with annealed PLA (unannealed will not work for sure - low creep resistance), annealead CF-pla, ABS/ABS-GF, PETG and CF-petg (annealed), and maybe I'll try polycarbonate and GF-filled PA (this one is CRAZY strong, better strength to weight then aluminium (and better than PA-CF)! http://www.esun3d.net/UploadFiles/Download/MSDS_eSUN_ePA-GF%20filament.pdf though, obviously, there is anisotropy inherent in 3d printing and needs to be dried before each print)


Too bad there are no 3d printable PC-GF filaments I can find, that would be *ultimate* 3d printing plastic! I already have an all-metal nozzle and I've made a diy enclose that works well (no warpage of ABS parts at all).
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strayray
Warren

USA
23 Posts

Posted - 03/09/2020 :  07:49:35  Show Profile  Reply with Quote
>better strength to weight then aluminium
Call me surprised. A quick lookup of 6061-T6, to pick a random alloy, has an ultimate tensile strength of 310 MPa, but a fatigue strength of 95 MPa.
Meanwhile Matterhacker NylonG is claiming a tensile strength of 95 Mpa. Derating that by 30% for fatigue (rough guess from googling), and again for 3D printing it, it is somewhat weaker. But if you scale by the 2.7x density advantage of PA-GF, PA-GF looks competitive.

I've read nylon's properties vary widely with humidity, and some with temperature. For example, straight from the mold, nylon it quite brittle because it's so dry (IIRC 0.1% humidity is a target for injection molding feedstock). It recovers after re-humidification. But that's really dry. I don't know how its properties vary across real-life biking conditions. (I do expect my days of sub-zero Fahrenheit biking are over. so I can discount those temps.)

For stiffness, (modulus of 69 GPa vs 4 GPa in NylonG), aluminum still has the advantage, even when scaled by weight. But because the plastic is less dense, you can increase dimensions to make up for much of that.
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Balor
recumbent guru

Russia
925 Posts

Posted - 03/09/2020 :  08:05:14  Show Profile  Reply with Quote
My point exactly (and esun PA GF claims to be even better). As for stiffness - that's what 'sandwich' construction is for.
Filled materials are more easily printed due to massive decreased warp factor, though require a hardened nozzle of course... still needs many hours of drying before printing unfortunately.

Edited by - Balor on 03/09/2020 08:15:16
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