Drilling and customizing enclosures - tips please

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

Reply to
Jim
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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

Reply to
Richard H.

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.

Reply to
larwe

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Reply to
Jona Vark

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.

Reply to
larwe

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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Reply to
Spehro Pefhany

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

Best regards, Spehro Pefhany

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Reply to
Spehro Pefhany

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.

Reply to
larwe

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

Reply to
Richard Owlett

it might be worth costing these people.

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martin

Reply to
martin griffith

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.

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Rich Webb   Norfolk, VA
Reply to
Rich Webb

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

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Reply to
Spehro Pefhany

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

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Reply to
Baxter

the

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

Reply to
Jim

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

Reply to
Dave

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.

Reply to
linnix

"Unibit"

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.

Reply to
Rob

many

bits",

Many thanks, Rob and Dave. They sound really useful.

Jim

Reply to
Jim

Thank you. That's an excellent I hadn't considered, especially for a different job with a few hundred panels to make. I wonder what is the thickest ally it would go through?

Jim

Reply to
Jim

You can calculate the pressure required by totally up the circumference/perimeter of all the cuts and multiplying by a suitable factor for the material.

Eg. 2024-T4 aluminum has a shear strength of 41,000 PSI. If you have

20 gauge material (0.038") then the force required to punch a single 0.5" diameter hole would be 2446 lbf ~= 1.2 tons.

I use a relatively small 4-ton hand press (weighs about 500lbs with stand) to punch individual holes for prototypes, but it's perhaps a bit much to invest in that just to do a few panels. What's nice is that once you set it up the punching goes fast and the holes generally require no deburring or other finishing, nor is there any swarf. For prototypes, most of the time is spent in setup.

For more than a couple (from hundreds to thousands), we usually go to a specialist supplier with the proper CNC equipment to deliver clean accurate parts to the drawings, the handwork is used to create prototypes, one-offs or could be used for rework if changes were required. For huge quantities, hard tooling (rather than CNC) is better again.

Best regards, Spehro Pefhany

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Reply to
Spehro Pefhany

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