At 7:02 AM -0800 1999/11/08, Marshall Burns wrote:
>Hi folks,
>
> First question: Does anyone know the technical numbers that describe the
>material properties required of a SCUBA FIN? Properties such as modulus,
>elongation, tensile and flexural strength, etc. and also surface smoothness?
>Primarily, I see a need for a material that combines being SOFT and
>TOUGH, but I'd like to be able to express that quantitatively if I can.
>
> Second question: How close are we to being able to deliver those
>properties straight out of a fabber today? Many of you are experienced in
>using flexible materials on today's fabbers (SLA, Sinterstation, maybe some
>on LOM). How close could you come to making a scuba fin that you could put
>on your foot and go diving in?
>
> I'm not talking about a secondary process that casts in a different
>material after fabbing a mold or master on the fabber. I'm talking only
>about materials that come directly out of the machine.
>
>
> (This posting carries on with the discussion last week about direct
>manufacturing of products in fabbers. I've told you that I'm writing about
>this for an upcoming issue of the RP Report. You may have seen a TV
>commercial by UPS that shows a scuba fin being delivered from an Internet
>vendor by a fabber in the customer's home. I'll be writing about how far
>that fantasy is from becoming reality. Thanks for your help with my research
>on it.)
>
>Best regards,
>Marshall Burns
>President, Ennex Corporation
>
>Marshall@Ennex.com
>Los Angeles, USA, (310) 824-8700
>www.Ennex.com
>
>
>
>For more information about the rp-ml, see http://ltk.hut.fi/rp-ml/
Marshal,
Think "Glass-reinforced silicone rubber." I could build one this
week, given access to a LENS or FDM -- assuming that there is a
silicone-rubber-like material out there.
Essentially, that's what they are making the better fins out of
today. Though, the cup that the foot is inserted into is usually a
softer material, naturally to protect the diver's skin from abrasion
(I usually wear boots, so maybe that's a moot point). So you are
actually talking two different materials here.
Probably the best candidate for creating this would be Optomec's LENS
machine, as it allows the blending of two or more materials during
the build process. Can FDM do this as well? Admittedly, it seems the
application of LENS is better geared towards metals -- but reduce the
laser temp, and simply shoot a powdered silicone rubber/fiberglass
mix from one tube, and a softer silicone rubber from the other tube.
FDM might be easier to use the softer, more organic materials, but
maybe not be able to blend them as well at the interface.
Heck! Why stop there? Give me a cheap digitizing arm, I could plunk
it down on the counter at the local scuba shop, and digitize the
diver's face and create a mask that is so perfectly matched to the
face, wide or thin, that it won't leak. I could even take the
eyebrows and the hairline into account -- a constant source of slow
leaks! Much better comfort, no leaking. I could also position and
increase the size of the lens to increase visibility maybe 50%.
Perhaps use a curved lens instead of a flat plate, better optical
quality and less distortion. Since I would know the curve of the
diver's face, and where the eyes are located, the position of the
lens could be optimized for that diver. Maybe even have it set up to
accept corrective lenses.
The big question is, naturally, are the MATERIALS available to do
this? I've never dealt with molding items out of surgical-grade
silicone rubber -- is it powdered/pelleted in its raw form, or a
liquid that needs to be cured?
The biggest problem to making this a commercial success would be
price. It would probably cost me between $1500 and $2000 to make it,
and naturally, I would want to increase the price to make a good
profit. That's about 10 times the cost of a quality mask. I don't
think the average diver would want to fork over that much for a
regular diving mask, no matter how comfortable. $800 to $900 might be
a bit easier to swallow. But why spend that much when you could buy a
technical diving mask for the same price, and be able to speak to
your buddies while underwater?
It is easy to justify the above price when creating a prototype to
test and demonstrate. But when you go into production, you must make
the product at a cost that will allow you to sell it at a price that
the customer will buy it and you can still make a decent profit!
Face it, I would rather cough up $300 to buy a high-quality
production mask, and then use the rest of the $2000 towards a week in
Aruba to use the mask, than to buy the super-custom RP mask and then
have no money left to go anywhere to use it.
Bill Richards
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For more information about the rp-ml, see http://ltk.hut.fi/rp-ml/
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