Drilling and customizing enclosures - tips please

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Hi,

I want to house a circuit board in a small enclosure (3" x 2" x1" or so).
The enclosure will needs 5 holes with the largest one 1/2 inch diameter.
Three holes are round but two should be rectangular cutouts but not sure the
best approach for them.

I am on a tight budget per unit and I want to make about 10 or 20 of these.
I have no experience of drilling cases so I am wondering what is the easiest
low cost material to work with? I am thinking of some kind of plastic since
it is lower cost than metal, but which types are best (or best avoided)?

I am also thinking of using a case with a removable front panel (or
removable front and rear panels) so I can drill them while flat and use a
template to get the holes in the right place (hopefully) each time. If you
have any tips on this so I can get a reasonably professional looking
finished item would be extremely welcome, thank you very much!

-
Jim



Re: Drilling and customizing enclosures - tips please
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Jim,

 From what you describe, I doubt you'll get "professional" results in
your own shop.  (You say you don't have experience, which means probably
not the tools either.)

At a minimum you need a drillpress; you'll lose a lot of accuracy trying
to hand-drill.  You'd need to use a nibbler, hand file, or maybe a
Dremel to finish the square holes.

Really sharp results call for a CNC mill, water jet, or laser cutter
would be used.  This means paying a shop to do it.  The fact that you're
making many of them is a benefit - you can spread the setup costs across
several pieces, making it more economical.

I'd suggest laser cutting on a metal enclosure.  The shop will likely
take a DXF formatted file, charge you a flat setup fee, and then charge
for time on the machine (which will be minimal for such small parts).
You can also have them engrave your labeling, perhaps avoiding
silkscreening.  (Finish-quality of etching on plastic will vary by
material, so ask the shop.)

Removable panels will be easier all around to work with, but I'd suggest
finding a shop first and getting their feedback.  It may/may not make a
significant difference in the cutting costs, and will limit your choice
of enclosures.  Removable panels can be stacked / clamped and all cut in
one pass, which can save on time and cleanup.

You may also be able to cheaply buy extra panels and have, say, 100x cut
in one batch for economy, buying the enclosures later.  You can also
select alternate panel material, supply it in sheets to the shop and
have them cutout the entire panel with cutouts (in fact, this will be
much easier / faster for them to process instead of small individual
panels).

Plastic will be easier to tool yourself, but will require more cleanup
(e.g., the drill will melt the ejecta, leaving a ring of buildup around
the hole that needs to be cleaned up (so drill from the backside).
Metal will be cleaner to mill, but will take more effort; aluminum being
easier than steel, but also less robust.

In short, plastic is probably your best bet if you mill it yourself.
You might get better results from a shop with metal.

Cheers,
Richard

Re: Drilling and customizing enclosures - tips please
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I would suggest putting the PCB in an aluminum extrusion cut to the
desired length, and screwing aluminum ends on. Use a drill and nibbling
tool to generate the desired holes. Considerable careful sanding of the
ends will be necessary, and you'll need to paint it.


Re: Drilling and customizing enclosures - tips please
Use a Hole Punch (Greenlee) and a drill press... Get a few extra boxes
'cause you're going to ruin them as you get started.
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the
these.
easiest
since



Re: Drilling and customizing enclosures - tips please

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For the rectangular parts you want to have enough of a bezel on the
part that goes in that you don't have to be dead nuts on the holes.

If you use a crappy plastic utility box with a cheesy aluminum
removable panel you can easily drill the holes (umm.. 1/2" drills grab
something nasty when they break through, make sure that it's well
clamped and ease up as the drill is breaking through). You can do this
with a $40 drill press, no problem. Use good drills (but remember,
sharp drills grab really well). Start with a small (eg. 1/8" pilot
hole and open it out. Use a sacrificial backup material such as wood.

You can use a hand nibbler from Rat Shack to open out round holes to
rectangular. It leaves a rough edge, which you should deburr with a $6
deburring tool (available from any industrial supply place) and by
draw filing (get a good file, preferably with a "dead" edge with no
teeth on it).

Draw the panel layout in a CAD program, print it out at 100% (check
that it's accurate), spray glue it to the panel and machine that. Then
remove the paper with solvent.

Always wear safety glasses and make sure the parts are properly
clamped.


Best regards,
Spehro Pefhany
--
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Re: Drilling and customizing enclosures - tips please

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I find it's much easier to print it out reversed using a laser printer
and heat-transfer it onto the metal. The toner sticks well to surfaces
like anodized aluminium.


Re: Drilling and customizing enclosures - tips please

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How do you mask the surface from scratches due to swarf on the drill
or slips of the file?


Best regards,
Spehro Pefhany
--
"it's the network..."                          "The Journey is the reward"
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Re: Drilling and customizing enclosures - tips please

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This is why, in my initial response to the OP, I said you need to paint
it.

I've tried gluing templates to metal and plastic housings, and always
made a complete dog's breakfast of the job because the templates flex
and tear.


Re: Drilling and customizing enclosures - tips please

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Yup, it's really only good for situations where 0.5mm isn't that big a
deal (no exposed edges, substantial bezels on all the parts that go
through the panel). In the bad old days I used to lay out industrial
control panels by hand with pencil after covering them with masking
tape. Ugh.


Best regards,
Spehro Pefhany
--
"it's the network..."                          "The Journey is the reward"
snipped-for-privacy@interlog.com             Info for manufacturers: http://www.trexon.com
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Re: Drilling and customizing enclosures - tips please


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You can often use router or mill bits to good effect - they reduce grabbing.

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Re: Drilling and customizing enclosures - tips please

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I think what you are looking for is a "Bug Box" [a registered trade mark]
A Google search hit on Jameco Electronics (jameco.com). But their site
appears to be unavailable. I cannot recall manufacturer of Bug Boxes so
can't say where else to purchase. At one time (I reveal my age) many
high volume electronics supply houses ( Arrow etc ) stocked them as a
catalog item. They were a collection of standardized enclosure with one
or two removable aluminum panels.

You omitted the specifications of the required rectangular cutouts. If
they are for a some what standard purpose, as others have said, there is
probably an appropriate Greenlee punch.

Other specs omitted:
  dollar value of panels
  definition of "reasonably professional"
  your geographic location




Re: Drilling and customizing enclosures - tips please
[...]
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I think you probably mean "Bud Box", named after the manufacturer, Bud
Industries, Inc.  They're still sold through most electronics supply
houses.  For low-volume orders, digikey.com and mouser.com are
probably your best bets.  You probably want one of their "mini boxes",
but they have quite an extensive line of metal (sheet, extruded, and
cast) and plastic enclosures to choose from.  The sheet aluminum boxes
(which is what the mini boxes are) are pretty easy to make holes and
cutouts in.  (Of course, you can also build your own pretty easily
from plain sheet aluminum if you have the tools.)

As others have said, if you're making 10-20 of them, you should look
into finding a local metal shop to make them for you, if you want
professional results.  It might be cheaper than you think.

Re: Drilling and customizing enclosures - tips please

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I think "Bug Boxes" were little compartmentalized
plastic cases for storing DIP IC's.

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That's probably what you were thinking of.


Re: Drilling and customizing enclosures - tips please
On Sun, 04 Sep 2005 15:42:52 GMT, in comp.arch.embedded "Jim"

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it might be worth costing these people.
http://www.frontpanelexpress.com /



martin

Re: Drilling and customizing enclosures - tips please

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In addition to all of the other folk's excellent suggestions, you might
want to consider using an electric scroll saw for the square cutouts.
They're not terribly expensive and don't require a lot of space. As long
as you make a pilot hole (that does not need to be tangent to the final
outline) large enough to thread the saw blade through, you're in
business.

Cut just shy of the final outline and finish with a file or two.

Slower than the Greenlee punch/die sets but versatile.

Here's an example but shop around, there are many others.
http://www.deltawoodworking.com/index.asp?e13%6&p93%1

--
Rich Webb   Norfolk, VA

Re: Drilling and customizing enclosures - tips please
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the
<snip>

Many thanks for everyone's help on this. A drillpress and the other tools
recommended sound very good. I will make sure I have a few spare enclosures
at hand too, to practice on. I've used Front Panel Express before, and would
recommend them highly. But I would like to do these for less if possible, so
keen to make them myself. We'll see...maybe Front Panel Express will be back
on the cards depending on how well it goes. ;)

Thanks again.

- Jim



Re: Drilling and customizing enclosures - tips please
For large round holes in thin sheetmetal, I highly recommend using "Unibit"
type stepped bits.  They are a little pricey, but one of them will do many
different size hole.  The great part about them is that they cut like a
milling machine with virtually no grabbing and leave a nearly perfect hole.

Homebuilt aircraft guys use them all the time to put holes in thin aluminum.

Dave Lundquist



Re: Drilling and customizing enclosures - tips please

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"Unibit"
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hole.
aluminum.

I've got a couple of them - sold as "step or conduit drills" in Oz. There
are also some with a continuous taper - I think they are called "cone bits",
useful for prototyping work.

A machinist where I once worked showed me how to drill through thin metal.
He put a scrap of emery paper, say 1" x 1" between the 1/2" inch bit & the
work. It left a clean round hole - not "triangularish" & didn't grab/bite. I
was impressed.




Re: Drilling and customizing enclosures - tips please
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many
bits",
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Many thanks, Rob and Dave. They sound really useful.

Jim



Re: Drilling and customizing enclosures - tips please

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If I were you, I would order a custom punch.  For a few hundred
dollars, a punch can do 20 in a few minutes or upto 100,000.  We
ordered a punch for a slightly smaller part.  It could cut identical
parts in 0.3mm steel or 0.5mm aluminium.  The worst part was waiting
for them to make the punch.  After that, we can make hundreds in a day,
for pennies each.

Believe me, we hand-cut some while waiting for the punch.  As soon as
the punch is ready, all the hand-cut parts are trashed.

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