Enclosures

[D Yuniskis]

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

 

[Rich Webb]

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/Table_of_Contents.htm
and of course http://www.hammondmfg.com/

 

[Dombo]

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.

 

[Charlie E.]

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

 

[Hans-Bernhard Bröker]

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?

 

[D Yuniskis]

Hi Tim,

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" :-/

 

[D Yuniskis]

Hi Charlie,

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![/QUOTE]

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 :-/

 

[Hans-Bernhard Bröker]

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.

 

[D Yuniskis]

Hi Rich,

Some possibles from my bookmarks list:
http://www.polycase.com/
http://www.rose-bopla.com/Main_Pgs/Table_of_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.

 

[hamilton]

D Yuniskis schreef:

Depending on your specific requirements a 3D printer could be an option
for plastic enclosures. Companies which offer prototyping services often
have one.

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

Its great for a sales guy showing off a NEW product, but the strength of
the model is still not what I would expect for a real case.

hamilton

 

[D Yuniskis]

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.

Ooooh! That's an idea! Much less work than fiberglass,
too! (though I suspect relying on gravity means you
need to constrain your "shape" somewhat -- e.g., I imagine
there are "minimum sag radii" :> )

 

[Rich Webb]

Hi Rich,



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.

The "how big" question is still out there. A non-rectangular shape could
also be a pretty big animated head for a carnival float... ;-)

There are some "craft" approaches, like a papier mache shell over a wire
armature or a putty build-up over an existing form. Use that as a
positive to create a negative mold and then a small production run using
cast resin. http://www.micromark.com/Casting-and-Molding-Supplies.html
has the supplies to get started.

Or, talk to the folks at http://www.protomold.com/

 

[D Yuniskis]

Hi Hans-Bernhard,

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?

Apparently, *other* have managed to do so! But, if you
need more details...

What actually is the shape you're trying to get?

Klein bottle

What size?

3 gills

What colour / surface finish?

Must not reflect any light in the visible specturm

How good does it have to look (e.g.: visible screws, tool marks)?

See above

Any requirements about sharp edges / curve radii?
Yes

What's it allowed to weigh?

< 0.0375 stone

How tightly does it have to fit the content?

tight enough to keep the contents from escaping!

What tolerances (i.e. how equal do those 20 units have to be)?

racial, ethnic and religious

What's the budget, both in terms of money and time?

3 peng, less than a hebdomad

What skill level can be expected from the person building it?

Somewhere between rocket-scientist and cancer-curer

Does any of this change your potential solution?? :-/
(If I could boil it down to "X = 2 * 3 + 4 / 5" then
I wouldn't need to ask for suggestions, would I? :< )

 

[D Yuniskis]

Hi Tim,

By "drape" I sincerely hope that you mean "take a cured molded top piece
and bolt it to the metal chassis piece".

Refering to the P in which I used the term, I meant "mold the
fiberglass around that skeleton". E.g., deliberately design
the skeleton's shape so that the fiberglass shell "klinged"
(klung?) to that shell. So, the shell/skeleton could have
bits fastened *to* it and then *it* fastened to a base.

In the second P, fasten everything to a base and then
"place" the fiberglass shell on top of it (so the fiberglass
is just a cosmetic cover only supporting itself and loosely
fastened to the rest of the lot)

Free-form fiberglass layup can be done, but it's a tremendous amount of
work. If you do something like this in fiberglass you want to make a
plaster (or wood and Bondo, or wax, etc.) mock-up, then take a mold off
of it, then make your fiberglass parts in that mold.

Yes. Hence my original comment re: wood (machining out of plastic
would require going the full CNC route whereas you can "eyeball"
something out of wood)

If you say "fiberglass housing over a metal chassis" then you start
making lots of sense. It may not be the best solution, but you're
getting into a tolerably wide range of solutions.

As asked somewhere else -- how big is this thing?

"3 gill" :> Figure the volume of two (respectible) fists.

 

[D Yuniskis]

Hi Rich,

The "how big" question is still out there. A non-rectangular shape could
also be a pretty big animated head for a carnival float... ;-)

There are some "craft" approaches, like a papier mache shell over a wire
armature or a putty build-up over an existing form. Use that as a
positive to create a negative mold and then a small production run using
cast resin. http://www.micromark.com/Casting-and-Molding-Supplies.html
has the supplies to get started.

Ah, excellent! Thanks!

Or, talk to the folks at http://www.protomold.com/

<frown>

 

[D Yuniskis]

Have you looked at PacTec Enclosures yet?
Link: http://www.pactecenclosures.com/

Ah, I had forgotten about them! But, no, they don't have
anything "stock", either. Everything COTS seems to be
"a box" -- with only minor deviations on that "rectangular
prism" theme.

 

[Grant]

Ooooh! That's an idea! Much less work than fiberglass,
too! (though I suspect relying on gravity means you
need to constrain your "shape" somewhat -- e.g., I imagine
there are "minimum sag radii" :> )

It is easy. Vacuum forming! You make the mould from wood and
body filler, drill small holes through the mould and suck the hot
plastic sheet down onto the mould and into the contours.

Then you cut the flat plastic from around the edges of the moulded
plastic to make the one-piece sides and top of your box. Mount the
plastic over a metal base with edges turned up for mounting holes.

I was a plastics worker prior to switching to electronics a few
decades ago, that's roughly how the moulded illuminated advertising
signs are made.

ABS is good for this as it's not brittle, doesn't smell bad, and
can easily be worked for display cutouts and so on.

Grant.


Grant.

 

[Spehro Pefhany]

It is easy. Vacuum forming! You make the mould from wood and
body filler, drill small holes through the mould and suck the hot
plastic sheet down onto the mould and into the contours.

Then you cut the flat plastic from around the edges of the moulded
plastic to make the one-piece sides and top of your box. Mount the
plastic over a metal base with edges turned up for mounting holes.

I was a plastics worker prior to switching to electronics a few
decades ago, that's roughly how the moulded illuminated advertising
signs are made.

ABS is good for this as it's not brittle, doesn't smell bad, and
can easily be worked for display cutouts and so on.

There are some inexpensive vacuum formers for hobby use available
on-line, not sure how well they work. It's also possible to make
creative use of inexpensive PCBs and stick-on labels for very small
quantities.

 

[Fred Abse]

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).

Have you looked at OKW?

http://www.okwenclosures.com

 

[Anton Erasmus]

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... :>

Try

http://www.tekoenclosures.com/
(USA site, actual fabrication in Italy)

RS Components and Farnell sell some of their enclosures.

Regards
Anton Erasmus