OT: Very OT. Carving up plastic project boxes

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Hi All -

Most small projects wind up living in small project boxes, usually plastic boxes from Rat-Shack or similar. Drilling holes for pushbuttons and so on is pretty easy. Lining them up usually works, more or less.

But the main problem is creating larger holes, especially rectangular ones. How do you do it ? If the box has an aluminum plate lid, it's not too hard - use a nibbler tool to nip it out. You can get pretty good results that way. Nice square corners.

The problem comes when you need to cut the plastic itself. It's (usually) too thick for the nibbler tool, at the least the two that I have. So that leave using a Dremel or similar, which has its own issues.

The main one being that the plastic melts, even at really low rpm, regardless of the tool, whether it's a cutting disc or a milling bit. Plus it's extremely hard to keep to a straight line ... So if you don't have a milling machine/lathe, how do you do it ?

* How do you cut nice neat rectangular holes in plastic boxes * ??

Dean 94TT
"Life is just one damn thing after another" Elbert Hubbard (1856 - 1915)

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I use a dremel, at very low speeds. and then using the same cutting wheel at an off angle I remove any burrs or melt. for a really clean edge I may even flame treat the edge (depends on the plastic) to return it to that smooth and glossy look.

another option is to use the dremel to get very close to teh line you want, and then using a VERY sharp xacto knife, trim away the remaining material, to leave a nice smooth cut.

Consider looking for a Bezel and lense (Digikey has them) I assume this is for your little timer project, so you're looking for a way to make the display hole look nice. The beauty of the bezel is you can use the dremel to cut the hole, but it doesn't have to be all that neat.

Writing code is like having sex.... make one little mistake, and you're supporting it for life.

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What about drilling a hol ein the center of the rectangle then getting a little hobby ?hagner? saw (the ones with the thin blades and just a handle otherwise). then take out the blade at one end, pass it throught the hole then connect it back up. Then just cut towards the edges of the rectangle.

If you take it slowly and carefully it should work out nicely, then sand off the edges etc

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Dingo_aus wrote:
What about drilling a hol ein the center of the rectangle then getting a little hobby ?hagner? saw (the ones with the thin blades and just a handle otherwise). then take out the blade at one end, pass it throught the hole then connect it back up. Then just cut towards the edges of the rectangle.

If you take it slowly and carefully it should work out nicely, then sand off the edges etc

What you're describing sounds like what we call a Dremel here in North America. Basically what it is, is a hobby rotary cutting tool, that you can get all kinds of attachments for, from cutting wheels to grinding stones.

Writing code is like having sex.... make one little mistake, and you're supporting it for life.

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Bandsaw blades (as thin as you can find), cut into two or three inch long sections are great once you have a rough cut. The finer the teeth the better. Make the square hole a little smaller than you need it (about a blades width) and then use sand paper to finish up. It takes a long time, and it's not easy but if you want a nice case you gotta spend the time on it.

-Curiosity may have killed the cat
-But that's why they have nine lives

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What Dingo was describing, I believe, is a coping saw. It's kind of like a hack saw but the blade is finer and allows you to make small radius turns while cutting. They are great for light duty work - like plastic project boxes.

Sharp and medium coarse files also are nice.

Lots of plastic shavings produced though. Not wise to do it in any inside room where the wife can see :)

Please note - this post may not present all information available on a subject.

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Deep plastic trays (cat litter boxes) and a vacume cleaner are very usefull to keep the mess down :) If you're working inside a large plastic tray I find that the plastic bits tend to statically attract inside the box, reducing the amount that is thrown out, and it also makes a nice catch for dropped bits. Vacume out the inside of the box (and the surronding area for what you missed) afterwards, and you're all set. Works for me at least.

-Curiosity may have killed the cat
-But that's why they have nine lives

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Lots of good suggestions here. Actually, I had a couple of requests for my old guitar tuner project from some friends, so I'm making a few up.

[/url]https://www.avrfreaks.net/Freaks/...

It's the cutting of the hole for the little LCD that's always a bother. As you can see from the photos in the project, my last attempt, while serviceable, was definitely not too pretty.

So far I've found the Dremel to be the best. Use a cutting wheel to get the hole in place, a little smaller than needed. Then use it face-on to start removing back to the line of the hole. Have to use the heavy-duty thicker discs for this part.

I've tried the milling cutters, but it's almost impossible to maintain a straight line. Even using the drill press. You really need a milling machine type slide.

Bezels are great, I can just never find the right size. Ever.

I like the kitty-litter pan idea - great way to keep the plastic dust down.

One neat trick I use for positioning the holes is to photocopy the bare board, or the populated board if you really need the component sizing. Then tape the photocopy onto/into the box - you can see exactly where to cut.

Works well for face-on parts like LCD screens as in the tuner, as well as for edge-on items like side-mounted pushbuttons. Just photocopy the board edge-on ...[/url]

Dean 94TT
"Life is just one damn thing after another" Elbert Hubbard (1856 - 1915)

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What Dingo forgot to mention is that, here in Australia, we can buy plastic boxes from Jaycar which have cutting lines already moulded in the inside of the lid of the box. They are about 10mm apart. Just run a sharp Stanley knife in the groove and you have a perfect square hole....well provided it's in 10mm spacings incrememnts... :D

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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Yep, a coping saw. But I agree with previous poster, the cuttable-boxes are the best.

- Dean :twisted:

Make Atmel Studio better with my free extensions. Open source and feedback welcome!

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Hi,

I have always used a hot exacto blade to work with plastics and a file.

I think you can get soldering irons with hot knifes on them or buy hot knifes seperately, but I have always just used a normal exacto knife (ones with all metal handles like this image) and heat it up in a flame.

Anyway then you just cut through the plastic like a dull knife through very hard butter, except with somewhat noxius fumes. Then you use a cold knife (probably not the same one - the act of heating the knife seems to dull the blade a lot) to cut away some of the residue of the melting, and finally a file to smooth it all out a bit.

Works for me!

-Colin

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I like how this guy does it:

http://www.hobby-elec.org/e_acry...

Not sure I can build the bending machine though. Anybody knows where I can buy one and what's the price?

Bogdan

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I don't know if they're tempature controlled but this is a Hot Box. You can buy them at stores that sell PVC pipe and tools (it's used to heat PVC up to a bendable tempature) Not sure how well it'd work on other materials but they might know.

-Curiosity may have killed the cat
-But that's why they have nine lives

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This might not be of interest for low volume projects but I did find it quite interesting. A while back I came across http://www.emachineshop.com. They offer services in the mechanical area in a manner similar to what companies like Olimex, pcb4u, pcbfabexpress, etc., offer for printed circuit boards. You can download their CAD software, design your widget using one of the materials they support, and then get an online quotation. I haven't tried it yet but I really like the idea.

Dave

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Sceadwian wrote:
I don't know if they're tempature controlled but this is a Hot Box. You can buy them at stores that sell PVC pipe and tools (it's used to heat PVC up to a bendable tempature) Not sure how well it'd work on other materials but they might know.

I think it is temperature controlled. I'll take a look at this, thanks.

Bogdan

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js wrote:
we can buy plastic boxes from Jaycar which have cutting lines already moulded in the inside of the lid of the box. :D

John, I took a quick look on Jaycar, but couldn't find what you describe. Can you supply a link to one of these boxes? Thanks!

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dksmall wrote:
[John, I took a quick look on Jaycar, but couldn't find what you describe. Can you supply a link to one of these boxes? Thanks!
Heres a link, hope it works because of their filemaker pro web server/database....
link

If not, just on the "category search" select "Enclosures" and second line "Jiffy". They even have some funky clear/coloured ones.

Ah, at last, a topic I can comment on without showing my lack of skill/understanding!

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Poundy got there before me! :D :D

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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I have had good luck with the following:
drill plenty of relief holes near the perimiter
get a reeely sharp wood chisel
tap lightly on the first pass round the perimeter
tap harder the next pass
after several passes the inside falls out, a little sanding is all that is left.

the key is sharp chisel - box must be soft plastic - not acrylic

for bigger rund we just bought a CNC router.
the jig is the hard part.
run g codes and voila.

run at 5000-6000 rpm, use standard end mill fairly small (1/16)
run air hose right to the bit to keep scrap out of the hole &
keep the bit cool
cut as fast as you can without binding anything

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The best way to do it is ofcourse to use a real milling tool.
It need not be that expensive. I've see the A5 size tool form max-computer in action, and I'm definitely getting me one !!
Cost about 1500 Euro.

http://www.max-computer.de/

/Jesper
http://www.yampp.com
The quick black AVR jumped over the lazy PIC.
What boots up, must come down.

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The December issue of Circuit Cellar (http://www.circuitcellar.com) has an article on Building Boxes by Ed Nisley.

It looks like a very good article.

Please note - this post may not present all information available on a subject.