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On 30-4-2014 20:51, Stephen wrote:
> On 30/04/2014 8:14 AM, Thomas de Groot wrote:
>> On 29-4-2014 22:19, Stephen wrote:
>>> On 29/04/2014 9:09 PM, Stephen wrote:
>>>>
>>>> Go back another twenty years and they would be mostly lead popes.
>>>
>>> I think I meant pipes. Lead pipes not lead Popes. :-)
>>>
>>
>> Somehow, those /lead popes/ trigger my imagination... :-)
>>
>> Thomas
>
> Edgar Allan Poe, anyone? ;-)
>
No not really Poe, although dark enough indeed. It combines to me more
with what in Italy were called the /Years of Lead/ (anni di piombo).
Lead popes would suggest to me a period of oppressive religion. An
interesting topic for an SF novel in a distopian world.
Thomas
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On 29/04/2014 09:23 AM, scott wrote:
>> Interesting. I was under the impression that UV-resistent coatings are
>> just overly-optimistic marketing, and in reality none of these coatings
>> actually work.
>
> One of the first image results from google gave this:
>
> http://www.alpineastro.com/filters/uv_ir_cut_specs.htm
>
> That's a pretty sharp fall-off below 400 nm. Whether it works or not is
> unquestionable, what is usually up for debate is whether it's actually
> useful on a camera. On skin, eyes or paint of course it works and is
> useful.
That's a pretty sharp cuttoff. OTOH, from this scale you can't tell
whether the filter still passes, say, 1% of the UV. 1% UV is presumably
still easily enough to utterly destroy whatever is underneith. (E.g., a
plastic coated in this stuff will get ruined in a few months rather than
a few days.)
I am not a professional chemist, but as I understand it, UV just
destroys absolutely everything it touches, and it's very hard to make it
not do this.
> Then there are all the things the consumer doesn't even notice. Like
> plastics that are easier to mould (more complicated shapes are possible
> to be made faster with finer details), possible to process in thinner
> films, flame retardants that are environmentally friendly, stronger and
> stiffer plastics that enable things to be made with less plastic for the
> same performance etc.
So... essentially you're saying the only real change is that plastic is
cheaper now?
And to think I was under the impression that plastic only exists in the
*first* place because it's cheaper...
> The software we use here for simulating the moulding of a plastic part
> (to make sure it will fill correctly and not leave any sink marks, weld
> lines etc) has a built-in database of plastic materials to choose from.
> There are over 10000 of them, and there are plenty not in the list. They
> have all been developed for a specific reason, and most of them recently
> (not 30 years ago).
I knew there were at least 6 main plastic types. But 10,000? Really? I
can imagine you could have 10,000 different compounds, with different
additives in them to adjust how springy or brittle they are, etc. But
10,000 fundamentally different molecules? Really?
Actually, I just thought of something. One thing we didn't have when I
was a kid: oven bags. As in, plastic bags that you cook things inside. I
still can't quite wrap my mind around how this works; most plastics melt
if you pour boiling water on them, never mind heating them to *hundreds*
of degrees...
(Also, if this plastic as such a high melting point, how do you mould it
in the first place??)
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> Second, you worked in the chemical industry for over 10 years. I'm sure
> you're familiar with the names 3M, Dupont and BASF, just to name those.
> Don't think for a second that these companies don't have large R&D depts
> that work round the clock trying to come up with newer compounds
I was under the impression that 3M's main business is *manufacturing*
plastics, not designing new ones. (Actually, I was under the impression
that 3M manufactures finished products that have plastic _in_ them, but
I guess they probably sell raw plastic to other people...)
> Have you noticed how nowadays most eye glasses are made of plastic?
> Clear plastics with higher IOR (sorry for getting slightly on-topic for
> P.O-T) than glass were unheard of 30 years ago. The progresses made in
> the domain of contact lenses is even more impressive than that of
> conventional glass lenses.
Really? I thought *all* transparent materials have an IOR different than
air. As in, it's impossible to *avoid* this (e.g., if you wanted to make
a kind of "invisible glass", you can't do it.)
> The "technical" garment industry has also greatly benefited from these
> new polymers. You're a skier, so you've most certainly seen the
> 74732327523 tags that are sewn or attached on a new ski jacket or
> gloves, touting the amazing breathability, yet still impermeable,
> feather light, yet warm as a mammoth pelt, machine washable, yet won't
> fade properties these clothes now offer.
I thought that all of those claims were radically exaggerated marketing,
and that these materials are basically identical to what we had 40 years
ago.
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On 29/04/2014 03:21 PM, scott wrote:
> Or surely you've heard about 3D printers recently? The materials they
> use (the professional ones, not the hobby ones) are state-of-the-art
> polymers to give the final piece properties as close as possible to
> traditional injection moulded plastics. It's not like those materials
> existed 30 years ago.
Granted I don't work in the manufacturing industry. But I would have
expected that the market for rapid prototyping is utterly *tiny*
compared to the market for actual finished goods.
Does anybody really use 3D printers much? I mean, I can imagine there
are products for which this might be really useful, but if you're just
making (for example) plastic sandwich boxes, do you really need to
prototype that?
Also: I was given to believe that 3D printed objects have approximately
the structural rigidity of jellybaby. It's strong enough to see if
various printed parts will fit together right, but if you stare at it
too hard you're gonna break it. But hey, it's only a *prototype*, right?
It's not like the finished item will be made of the same gel...
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On 01/05/14 18:41, Orchid Win7 v1 wrote:
> Granted I don't work in the manufacturing industry. But I would have
> expected that the market for rapid prototyping is utterly *tiny*
> compared to the market for actual finished goods.
>
> Does anybody really use 3D printers much? I mean, I can imagine there
> are products for which this might be really useful, but if you're just
> making (for example) plastic sandwich boxes, do you really need to
> prototype that?
>
> Also: I was given to believe that 3D printed objects have approximately
> the structural rigidity of jellybaby. It's strong enough to see if
> various printed parts will fit together right, but if you stare at it
> too hard you're gonna break it. But hey, it's only a *prototype*, right?
> It's not like the finished item will be made of the same gel...
YABAMBA
--
Protect the Earth
It was not given to you by your parents
You hold it in trust for your children
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On 01/05/14 18:37, Orchid Win7 v1 wrote:
>
> I was under the impression that 3M's main business is *manufacturing*
> plastics, not designing new ones. (Actually, I was under the impression
> that 3M manufactures finished products that have plastic _in_ them, but
> I guess they probably sell raw plastic to other people...)
>
YABAMBA
>
> Really? I thought *all* transparent materials have an IOR different than
> air. As in, it's impossible to *avoid* this (e.g., if you wanted to make
> a kind of "invisible glass", you can't do it.)
>
YABAMBA
>
> I thought that all of those claims were radically exaggerated marketing,
> and that these materials are basically identical to what we had 40 years
> ago.
YABAMBA
Sorry Andy but it has to be said
John (recovering from his stroke)
--
Protect the Earth
It was not given to you by your parents
You hold it in trust for your children
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On 1-5-2014 19:41, Orchid Win7 v1 wrote:
> Does anybody really use 3D printers much?
My dentist.
>
> Also: I was given to believe that 3D printed objects have approximately
> the structural rigidity of jellybaby. It's strong enough to see if
> various printed parts will fit together right, but if you stare at it
> too hard you're gonna break it. But hey, it's only a *prototype*, right?
> It's not like the finished item will be made of the same gel...
My dentist makes bridges and crowns with a 3D printer, and the products
are no jellybabies, thank God. :-)
Thomas
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> I was under the impression that 3M's main business is *manufacturing*
> plastics, not designing new ones.
It's both - if they didn't do the latter they would be no different to
the other 10 million plastic manufacturing plants. If you've ever dealt
with 3M (as a supplier for volume manufacturing) you would know they are
not the cheapest, but they often have materials and technologies that
nobody else has. This is their business model, it is not making
bog-standard plastics cheaper than everyone else (they would never win
this).
> (Actually, I was under the impression
> that 3M manufactures finished products that have plastic _in_ them, but
> I guess they probably sell raw plastic to other people...)
I don't think they do much of that, maybe for some specialised areas but
I've never heard or seen anyone sourcing raw plastic from 3M.
> Really? I thought *all* transparent materials have an IOR different than
> air. As in, it's impossible to *avoid* this (e.g., if you wanted to make
> a kind of "invisible glass", you can't do it.)
You can create a cone structure on the surface of the material (with the
points upwards so it's pointy to touch). Now so long as the size of the
cones is smaller than the wavelength of light then you get a continuous
smooth variation of IOR from the air to the solid. This prevents any
reflections, so the glass looks invisible. I've seen prototypes of this
and it really does look invisible (you can stick a patch of it on glass
and it looks like someone cut a hole in the glass). The obvious problem
with this is the tips of the cones wear off quite easily which starts to
reduce the effect. Again, it's all about developing new materials and
processes to achieve this kind of product.
There are other anti-reflection coatings already in use, with varying
degrees of performance. One of them works by destructive interference
and is used on glasses, outdoor displays etc, you can tell by the
characteristic purple tint of the remaining reflection (it blocks green
reflection mainly).
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On 1-5-2014 22:38, Doctor John wrote:
> On 01/05/14 18:41, Orchid Win7 v1 wrote:
>> Granted I don't work in the manufacturing industry. But I would have
>> expected that the market for rapid prototyping is utterly *tiny*
>> compared to the market for actual finished goods.
>>
>> Does anybody really use 3D printers much? I mean, I can imagine there
>> are products for which this might be really useful, but if you're just
>> making (for example) plastic sandwich boxes, do you really need to
>> prototype that?
>>
>> Also: I was given to believe that 3D printed objects have approximately
>> the structural rigidity of jellybaby. It's strong enough to see if
>> various printed parts will fit together right, but if you stare at it
>> too hard you're gonna break it. But hey, it's only a *prototype*, right?
>> It's not like the finished item will be made of the same gel...
>
> YABAMBA
not sure what that acronym means but if it means something like GIYF or
'why don't you just think before you post' or 'have you heard of the
concept of newspapers and magazines', I agree.
Anyway, we use our 3D printers a lot in the hospital, e.g. to plan
operations. Also, have a look at shapeways.com . Do you want plastic
(several varieties) , sandstone, metals, or ceramic?
--
Everytime the IT department forbids something that a researcher deems
necessary for her work there will be another hole in the firewall.
---
This email is free from viruses and malware because avast! Antivirus protection is
active.
http://www.avast.com
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> That's a pretty sharp cuttoff. OTOH, from this scale you can't tell
> whether the filter still passes, say, 1% of the UV. 1% UV is presumably
> still easily enough to utterly destroy whatever is underneith. (E.g., a
> plastic coated in this stuff will get ruined in a few months rather than
> a few days.)
I don't think many dyes fade within a few days of sunlight exposure. A
few months maybe, but then a 1% UV filter will allow them to last a few
decades, which is actually useful for something like a car or a photo.
> So... essentially you're saying the only real change is that plastic is
> cheaper now?
Not really, what I'm saying is that the development of plastics and the
processes that use them have allowed *products* to become cheaper. But
that's pretty much the entire purpose of engineering, to make a product
that meets all the requirements for as low a cost as possible. If you
can come up with a new material (or a variant on an existing one) that
allows an existing product to be made cheaper you will be collecting the
$$$.
> I knew there were at least 6 main plastic types.
Correct, there are at least 6 :-) Here's a list of the common categories:
http://www.efunda.com/materials/polymers/history/history.cfm?list_order=name
There are about 40 there. If you click on each one it will give you a
list of common grades, about 20 for each of the ones I clicked on.
That's already 800 different grades without even considering various
combinations of other additives to aid manufacturing or specific
properties needed. My point is that if you plot all of these on a
timeline you'll see that most have been developed fairly recently, it's
not like there's no development in plastics.
> (Also, if this plastic as such a high melting point, how do you mould it
> in the first place??)
Make your manufacturing machinery from something with a higher melting
point, say steel? How do they make the steel in the first place? :-)
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