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D Yuniskis
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      03-19-2010, 05:32 PM
Hi,

I need a small quantity (~20) of small {plastic,aluminum}
enclosures. But, I'm looking for something other than a
simple rectangular prism shape.

So far, I haven't found anything "stock" that looks
appropriate (I did find a COTS "console-like" case but
the angle is too shallow).

If push comes to shove, I can have a friend mill them
out of blocks of aluminum but that seems terribly wasteful!

I'm wondering, instead, if I can't hack together something
with a sheet metal skeleton (or, maybe even a cardboard or
wooden form!) and fiberglass? This doesn't need to be
terribly strong, structurally. And, I could no doubt
come up with a way of mounting everything to a *base*
(i.e., to eliminate the need for fasteners *in* the skin).

Has anyone done this sort of thing before? Pointers to
helpful tips as well as things to avoid... :>

Thanks!
--don
 
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Rich Webb
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      03-19-2010, 05:58 PM
On Fri, 19 Mar 2010 10:32:42 -0700, D Yuniskis
<(E-Mail Removed)> wrote:

>Hi,
>
>I need a small quantity (~20) of small {plastic,aluminum}
>enclosures. But, I'm looking for something other than a
>simple rectangular prism shape.
>
>So far, I haven't found anything "stock" that looks
>appropriate (I did find a COTS "console-like" case but
>the angle is too shallow).
>
>If push comes to shove, I can have a friend mill them
>out of blocks of aluminum but that seems terribly wasteful!
>
>I'm wondering, instead, if I can't hack together something
>with a sheet metal skeleton (or, maybe even a cardboard or
>wooden form!) and fiberglass? This doesn't need to be
>terribly strong, structurally. And, I could no doubt
>come up with a way of mounting everything to a *base*
>(i.e., to eliminate the need for fasteners *in* the skin).
>
>Has anyone done this sort of thing before? Pointers to
>helpful tips as well as things to avoid... :>


Some possibles from my bookmarks list:
http://www.polycase.com/
http://www.rose-bopla.com/Main_Pgs/T...f_Contents.htm
and of course http://www.hammondmfg.com/


--
Rich Webb Norfolk, VA
 
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Dombo
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      03-19-2010, 06:01 PM
D Yuniskis schreef:
> Hi,
>
> I need a small quantity (~20) of small {plastic,aluminum}
> enclosures. But, I'm looking for something other than a
> simple rectangular prism shape.
>
> So far, I haven't found anything "stock" that looks
> appropriate (I did find a COTS "console-like" case but
> the angle is too shallow).


Depending on your specific requirements a 3D printer could be an option
for plastic enclosures. Companies which offer prototyping services often
have one.
 
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Charlie E.
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      03-19-2010, 06:12 PM
On Fri, 19 Mar 2010 11:02:04 -0700, Tim Wescott <(E-Mail Removed)>
wrote:

>D Yuniskis wrote:
>> Hi,
>>
>> I need a small quantity (~20) of small {plastic,aluminum}
>> enclosures. But, I'm looking for something other than a
>> simple rectangular prism shape.
>>
>> So far, I haven't found anything "stock" that looks
>> appropriate (I did find a COTS "console-like" case but
>> the angle is too shallow).
>>
>> If push comes to shove, I can have a friend mill them
>> out of blocks of aluminum but that seems terribly wasteful!
>>
>> I'm wondering, instead, if I can't hack together something
>> with a sheet metal skeleton (or, maybe even a cardboard or
>> wooden form!) and fiberglass? This doesn't need to be
>> terribly strong, structurally. And, I could no doubt
>> come up with a way of mounting everything to a *base*
>> (i.e., to eliminate the need for fasteners *in* the skin).
>>
>> Has anyone done this sort of thing before? Pointers to
>> helpful tips as well as things to avoid... :>
>>
>> Thanks!
>> --don

>
>I'm not sure what you're thinking of in terms of a "skeleton", but a
>fiberglass enclosure, by itself, would certainly be structurally sound
>enough for anything small.
>
>Be aware that polyester resin has a smell that many find objectionable
>when it's fresh, and it takes quite a while to tone down. Cheap
>polyester resin is worse (it's actually the styrene filler that smells
>bad), and applying it poorly also makes it worse.
>
>So fiberglass with some other resin may work better, if you're willing
>to dink with it, or if you can find a fabricator who is.
>
>If a sheet metal case would be acceptable, then consider finding a sheet
>metal fabricator to make you some. A run of 20 will cost a lot more in
>setup and design than in the actual case itself, but if you just gotta
>have a case, you just gotta have a case.


If you really need something custom, then consider clear plastic, like
you can get at Home Depot. It is easy to cut, and you can get plastic
glues that bond it like it is all one piece. If you don't want it
transparent, get some plastic spray paint and paint the inside to any
color you want!

If you are careful, you can even drill and tap it, although I would
recommend using a nut glued and embedded in the plastic as more
reliable.

Charlie
 
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Hans-Bernhard Bröker
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      03-19-2010, 06:34 PM
D Yuniskis wrote:

> I need a small quantity (~20) of small {plastic,aluminum}
> enclosures. But, I'm looking for something other than a
> simple rectangular prism shape.


So now we know what you're _not_ looking for. But we don't know what
you _are_ looking for. How is anybody supposed to be able to offer
meaningful suggestions based on that?

What actually is the shape you're trying to get?
What size?
What colour / surface finish?
How good does it have to look (e.g.: visible screws, tool marks)?
Any requirements about sharp edges / curve radii?
What's it allowed to weigh?
How tightly does it have to fit the content?
What tolerances (i.e. how equal do those 20 units have to be)?
What's the budget, both in terms of money and time?
What skill level can be expected from the person building it?
 
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D Yuniskis
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      03-19-2010, 07:27 PM
Hi Tim,

Tim Wescott wrote:
> D Yuniskis wrote:
>> I need a small quantity (~20) of small {plastic,aluminum}
>> enclosures. But, I'm looking for something other than a
>> simple rectangular prism shape.
>>
>> I'm wondering, instead, if I can't hack together something
>> with a sheet metal skeleton (or, maybe even a cardboard or
>> wooden form!) and fiberglass? This doesn't need to be
>> terribly strong, structurally. And, I could no doubt
>> come up with a way of mounting everything to a *base*
>> (i.e., to eliminate the need for fasteners *in* the skin).

>
> I'm not sure what you're thinking of in terms of a "skeleton", but a
> fiberglass enclosure, by itself, would certainly be structurally sound
> enough for anything small.


The "skeleton" idea would allow me to fasten things to
that skeleton and drape the fiberglass around it.
(i.e., instead of trying to fasten to the fiberglass
itself)

The other option was to fasten everything to a "base"
and hang the fiberglass shell over that.

> Be aware that polyester resin has a smell that many find objectionable
> when it's fresh, and it takes quite a while to tone down. Cheap


Yes. But time "cures" that problem ;-)

> polyester resin is worse (it's actually the styrene filler that smells
> bad), and applying it poorly also makes it worse.
>
> So fiberglass with some other resin may work better, if you're willing
> to dink with it, or if you can find a fabricator who is.
>
> If a sheet metal case would be acceptable, then consider finding a sheet
> metal fabricator to make you some. A run of 20 will cost a lot more in
> setup and design than in the actual case itself, but if you just gotta
> have a case, you just gotta have a case.


Sheet metal as the *exposed* case makes it a bit more
difficult to get nice edges, etc. (unless you are extruding
something). "Seams" would need to be finished (filler?)
and then painted, etc.

That's why I came up with the fiberglass-over-skeleton
approach -- let the skeleton (aluminum/sheet metal)
give a basic form and some support for the internals
and then let the fiberglass "sex it up" :-/
 
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D Yuniskis
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      03-19-2010, 07:32 PM
Hi Charlie,

Charlie E. wrote:
> On Fri, 19 Mar 2010 11:02:04 -0700, Tim Wescott <(E-Mail Removed)>
>
>> D Yuniskis wrote:
>>> I need a small quantity (~20) of small {plastic,aluminum}
>>> enclosures. But, I'm looking for something other than a
>>> simple rectangular prism shape.
>>>
>>> I'm wondering, instead, if I can't hack together something
>>> with a sheet metal skeleton (or, maybe even a cardboard or
>>> wooden form!) and fiberglass? This doesn't need to be
>>> terribly strong, structurally. And, I could no doubt
>>> come up with a way of mounting everything to a *base*
>>> (i.e., to eliminate the need for fasteners *in* the skin).
>>>

>> I'm not sure what you're thinking of in terms of a "skeleton", but a
>> fiberglass enclosure, by itself, would certainly be structurally sound
>> enough for anything small.
>>
>> If a sheet metal case would be acceptable, then consider finding a sheet
>> metal fabricator to make you some. A run of 20 will cost a lot more in
>> setup and design than in the actual case itself, but if you just gotta
>> have a case, you just gotta have a case.

>
> If you really need something custom, then consider clear plastic, like
> you can get at Home Depot. It is easy to cut, and you can get plastic
> glues that bond it like it is all one piece. If you don't want it
> transparent, get some plastic spray paint and paint the inside to any
> color you want!


I've used lexan in the past for this sort of approach. Solvent
weld the "corners", file to debur, paint.

But, it's hard to get anything other than a bunch of "planar
surfaces". (well, maybe if you used *thick* plastic and
filed/sanded away a *lot* you could get to an arbitrary
curved surface)

The fiberlass advantage -- especially over a wooden form -- would
let me "sculpt" the outer surface instead of relying on how
many flat "facets" I wanted to glue together :-/

> If you are careful, you can even drill and tap it, although I would
> recommend using a nut glued and embedded in the plastic as more
> reliable.

 
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Hans-Bernhard Bröker
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      03-19-2010, 07:38 PM
hamilton wrote:

> I have seen 3D printer cases that I would not give to a customer.


Strongly seconded. 3D printer output material tends to be _way_ too
brittle to actually expose to customer hands --- and it's usually in the
wrong colour or opacity, too.

It's good to _show_ a shape, but sucks at _holding_ that shape.

As a rough reference point, you shouldn't try to hold an LCD's
zebra-rubber connectors in place using 3D-printer pieces only. At least
those parts of the setup experiencing pull-stress will break almost
immediately.
 
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D Yuniskis
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      03-19-2010, 07:41 PM
Hi Rich,

Rich Webb wrote:
> On Fri, 19 Mar 2010 10:32:42 -0700, D Yuniskis
>> I need a small quantity (~20) of small {plastic,aluminum}
>> enclosures. But, I'm looking for something other than a
>> simple rectangular prism shape.
>>
>> So far, I haven't found anything "stock" that looks
>> appropriate (I did find a COTS "console-like" case but
>> the angle is too shallow).

>
> Some possibles from my bookmarks list:
> http://www.polycase.com/
> http://www.rose-bopla.com/Main_Pgs/T...f_Contents.htm
> and of course http://www.hammondmfg.com/


I had already checked ploycase and hammond -- no joy there.
I chased the second link you provided and they don't seem to have
anything either.

I'm pretty sure I am going to have to roll my own.
So, it boils down to figuring out what the limitations
of any process I might adopt would be.
 
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whit3rd
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Posts: n/a
 
      03-19-2010, 07:52 PM
On Mar 19, 10:32*am, D Yuniskis <(E-Mail Removed)> wrote:

> I need a small quantity (~20) of small {plastic,aluminum}
> enclosures. *But, I'm looking for something other than a
> simple rectangular prism shape.
>
> So far, I haven't found anything "stock" that looks
> appropriate


Three ideas: sheetmetal work is fairly easy, if you can
find a shop with brakes and shears, they
can whip up a variety of flat-surfaced boxy things.
Spotwelding or POP rivets or PEM nuts are suitable
for the fastenings.

Polycarbonate or acrylic sheeting can be heated in an
oven to sag into any mold shape (or over any interior
shapes), at modest temperatures.

Lots of 'box' items are available for lots of purposes,
can you get a file-card box or a lunchbox to suit your
purposes? How about an Altoids tin? Hubcap
from a '57 Chevy?
 
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