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The resin 3D printer is a relatively simple beast. There is a plate
above a screen with a small (~0.2mm) gap between the two.
Into this gap flows a resin. The screen displays an image and
where the image is light, the resin polymerizes into a solid. The
plate moves up one step and the whole process
is repeated until
a 3D part is constructed layer by layer.
Attempts to reinforce parts by incorporating short glass fibers in
the liquid resin have been made, however, due to the small gap
under the build plate, these fibers line up only in the x-y planes
and the part gains no strength in the z axis.
To address this, let's incorporate magnetically sensitive
reinforcement particles. The obvious candidate would be short
steel fibers, but magnetically functionalized antibodies exist so
it's clearly possible to make other things react to magnetic
fields, e.g. small carbon fibers.
Now, our first layer is about to start, the build plate is 0.2mm
off the screen, steel particle laden resin fills the gap. At this
point an electromagnet mounted on the build plate switches on
and all the steel particles stick to it in a vertical orientation.
We turn on the screen/UV and the resin polymerizes around the
particles. Now we have vertical reinforcement.
More sophistication could be added by having electromagnet
pairs in various positions so that several particle orientations
could be achieved.
The main problem will be ensuring the steel particles don't
settle out or accumulate quickly in the first few layers.
Have them shaped such that they're structurally linked together.
https://www.amazon....id=pla-812529524153
Maybe more hook shaped than the straight ones in this example. [doctorremulac3, May 06 2022]
Cold Welding
https://en.wikipedi...g/wiki/Cold_welding
Possible solution to the "melting plastic" problem. Not sure how plastic behaves under very low air pressure... [neutrinos_shadow, May 12 2022]
[link]
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I'll have to give this some thought. |
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What if you have the very tiny metal pieces shaped
like
jacks so they sort of interlace with each other? Not
sure how you'd shape them being as small as they'd
need to be but there's probably a way. Interesting
idea. [+] |
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Wait. The whole process is still done in non-overlapping
0.2mm layers, right? So, supposing that the steel particles in
a given layer coalesce into vertical filaments, all those
filaments still stop abruptly at the edge of the layer, and
there's nothing joining them on to the filaments in the next
layer. So, surely, the resulting structure will simply shear
apart at the layer boundaries, won't it? |
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Or is there some clever stuff about field lines that I'm not
visualizing properly? |
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I was thinking that they'd be attached magnetically
so they're hang between the solidified and liquid
portions of the progressively hardening piece linking
the layers like that. |
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Maybe I misunderstood. If not that's the way it should
be done. |
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I thought it's ferrous microparticles aligned in a resin. |
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//The whole process is still done in non-overlapping 0.2mm
layers,// |
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I'm aware of this, I'm in an odd situation where my brain
thinks it's a solved problem, but it's not letting me know
exactly how yet. |
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The solution is something to do with either recesses in the
build plate or longer than 0.2mm particles. |
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//I'm in an odd situation where my brain thinks it's a solved
problem// |
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From what I read I thought that the ferrous particles would be aligned to alternate polarity with the layers above and below adding magnetic attraction to the bond. |
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hmmm, if the particles are conductive then a very tiny current would heat a 3d print from the inside to solidify it into a single piece after printing. |
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I thought of that but couldn't think of any binding
material surrounding it that wouldn't melt. You're
welding and melting metal after all. |
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What about having a metal matrix that the shape is
built around that you then use corrosive chemicals to
remove? The plastic object shaping material could be
impervious to the chemical that would remove the
metal. |
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The heat of the metal particles might be the different enough that that it allows these particles to melt further into the previous layer making a deeper zig zag join. Especially, if they are being pulled to the previous layer ones by an attractive magnetic field. There would be no complete sheer line. |
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They will probably rust out over time. |
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What about dropping the temperature of the whole thing down to -300 or 400 degrees Fahrenheit then just blast the welding current in just long enough to weld the touching metal parts? |
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You wouldn't need to weld them, thermoplastic melts at a fairly low temperature. If you heat the metal up enough to weld you will just Swiss-cheese your print. |
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Just the right amount of heat on the other hand would cause roughly half of the magnetized particles to be drawn slightly towards one layer or the other depending on proximity. They would grip each layer after the print and solidify acting as vertical re-bar. |
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//you will just Swiss-cheese your print.// |
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What I'm saying is get the whole thing down to -200 degrees
or so so when you put the current through to weld the
metal pieces you turn it off before it gets to the plastic
which is so cold it'll take a measure of time to heat up. The
metal will too, but before the heat expands outwards to
the plastic you turn it off. |
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Electrical welding of metal happens very quickly. Zap it,
bond the piece, continue freezing everything, zap it again
till all the metal connected. |
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Well sure you could be left with a welded scaffolding afterwards but any plastic around the welds would melt leaving hollows. If you want the 3d print to structurally strengthen between layers then you just want the particles to heat to a specific temp. just enough to barely melt between layers and anchor each one to the next.
Any more heat and the thermoplastic will just bubble where you don't want it to. |
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On a side note this procedure would be a very cool way to create an intricately formed single piece of metal using negative space to create that which could not be formed without using negative-space removal. |
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Well that's my question, to what extent can the
forming of those
hollows be mitigated by split second welds
happening
in plastic that's frozen at -200 degrees or more? It
takes
some
measure of time for the plastic to absorb that heat
and change state from solid to liquid. |
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Does latent heat enter into the calculation? |
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Again, this is where 8th would roll his eyes and say
"Stand back amateurs, here's the formula." and
we'd both watch with our fingers crossed to see of
whose take 8th's evaluation confirmed. Very weird,
you'd think for him being such a
smartass know-it-all who was less than subtle in
pointing out he knew more than most people here,
we'd have hated the guy, but we all loved him. |
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Maybe it's because he was funny as hell. Everybody
loves a person
with a sense of humor, especially a sick one like
8th's. |
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//thermoplastic melts at a fairly low temperature// |
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You're in two different worlds here. Once cured resins,
acrylates in this case, aren't thermoplastics. They won't
melt/re solidify, if you heat them, they'll just eventually start
to thermally degrade. |
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But can whatever material we're talking about be
frozen enough to stem the effects of the heat from
fusing of the metal grid inside when you're essentially
welding
them together? Just zap it long enough to weld the
metal part without hurting the surrounding material
because it's so cold? |
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//stem the effects of the heat from fusing of the metal
grid// |
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I think size is critical here. My idea was all about short, iron
filing-sized particles. I don't think it's practical to weld
anything that small. Or, beyond practicality, is it even
possible? If you're thinking about a spot-welding type
technique, then that requires relatively high current. Steel
is a poor conductor and you'd get a lot of heating when
moving current to the center of a part. That, and like
lightning, there will be a more conductive path and that's
where all the current will go. |
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Laser welding might be possible, but how many are we
doing? Getting that right deep in a resin will be tough.
Easier to make a mold and cast the damned thing in metal
in the 1st place. |
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