Designing Metal project enclosures

[Sarvesaa]

Hi guys, I have recently made a variable power supply with 0.050-24 V and 0-2A current limiting function. I tested it and it works perfectly as intended.I also decided to put some standard set voltages like 3V,5V,12V on the front panel of the power supply.
I am planning to use ADS1115 for voltage and Current measurement use 16*2 display controlled by atmega 328P.

I am planning to give it a metal enclosure. I want some of your advice about that. I going to use sheet metal thickness 1mm
The enclosure's dimensions:
Length 180mm
Height 110mm
Breadth 200mm

[rdl]

Buy something off the shelf and design/modify your project to fit it. It will save you many headaches and a lot of time.

[rdl]

One thing I'll add, whether you buy or go ahead and build your own, try and make sure any parts/panels where you'll need to drill or cut openings is a completely flat and separate part.

Those 2 piece boxes where one part is the top and sides and the other forms the front, back and bottom are a real pain to work on. Anything but drilling a simple hole can get really awkward.

[coppercone2]

a good break is expensive and you should probably buy boxes

[ajb]

Seconding what rdl said.  It’s worth looking at extruded aluminum housings as well, if you can find ones that are large enough, the factory end caps can be replaced with your own metal parts or even PCBs, and the usually have a bunch of internal slots that can support PCBs or metal carrier plates for internal parts.

[Conrad Hoffman]

That thickness seems reasonable for the size you're thinking of. If you're not a sheet metal worker with a shear and brake, better off to buy a box.

[coppercone2]

Well if you don't care what it looks like (so you end up with something that looks like a old style package (imagine some 1940 brown paper wrapped cheese sent to the front as a gift), then you can make your own box pretty easy.

And if you don't mind copper its easy. Or soldered nickel silver (but that is expensive). And that's only if you can tolerate thin walls. When you make a thin box like that, you will need to make reinforcement brackets on the inside of the box for the connectors and stuff.

[SmallCog]

I think learning to work with sheet metal is a great idea, it would of course be simpler to buy a box but it would also be simpler to buy the power supply too!

One suggestion is to enrol in a class at a trade school. You may even be able to use their tools to make your box rather than the box they will inevitably have you make in class.

Otherwise a tool like this is reasonably cheap to make, and you may well learn to weld in the process 

https://youtu.be/Ggy1DHwAh_0

[BurningTantalum]

It is always worth picking up old battery chargers and other dead equipment from yard sales or the local dump. The cases are usually well made and ready fitted with panels, feet and mains cable grommets. A flat alloy front panel is easy to make to replace/hide the original, and can be glued over the original making a neat finish. The panel can be etched with caustic soda to give a nice matt finish and sprayed with lacquer.

[Conrad Hoffman]

+1 on repurposing old enclosures, but I avoid steel like crazy. I have a full shop, plus Greenlee punches, and still don't like working with it.

[mag_therm]

It was very difficult for me to learn how to braze aluminum.

So I have incentive to use that method to make boxes, even though it does not make sense compared to a die cast Hammond etc.

(posted before, a mini rack chassis on the top position): https://app.box.com/s/i0nz3v6iy9zd2nhqkac7qwlfbw3od9rv

For drilling, tapping and light milling, I have added jig and DRO scales  to the lathe milling attachment. That also is used for drilling (0.8mm)  the home brew pcbs.

https://app.box.com/s/d9dcfzw83y1q776c46prganuzfa3d0os
https://app.box.com/s/co92xg8rx98fhxgswm8eefc8le24brzp

The box material is 6061 Al. Not all alloys can be brazed. I use 1/8 (3mm) thick angle and plate. Angle mostly 1.5 by 1.5 (38 by 38)
The workflow so far, is to drill/tap the Al parts then braze together.

[coppercone2]

haha brazed aluminum box I would end up under observation if I tried that one 

whats a good sheet metal break thats under 1kusd?

[Conrad Hoffman]

You can TIG weld aluminum very nicely. It's possible to gas weld it, but the skill level is way beyond me. I've seen brazing rods at the county fair for joining it, but it seems closer to soldering than true brazing. What process are you using?

[jpanhalt]

I've seen brazing rods at the county fair for joining it, but it seems closer to soldering than true brazing. What process are you using?

My understanding is that aluminium "brazing" rods are mostly zinc.  As alloy 2024 and many other "aircraft" alloys are not weldable or only spot weldable, Oshkosh and other shows usually have plenty of aluminum solder/brazing exhibits.  Of course, it is not structural, as a real weld can be.

[coppercone2]

You can TIG weld aluminum very nicely. It's possible to gas weld it, but the skill level is way beyond me. I've seen brazing rods at the county fair for joining it, but it seems closer to soldering than true brazing. What process are you using?

I would still recommend a break so you can weld a corner. When I tried to gas weld boxes I used angle pieces and 3x-welds (back of angle to sheet, other side of angle to other sheet and then corner to corner. Corner to corner welds are painful. What would be best is if you bend one of the sheets like you were going to rivet it, then weld that on both sides. Steel gas weld corner joint is much easier but you get disgusting distortion unless you fixture the crap out of it with reasonable gauges (say 12-8 awg).

When you try to oxy weld aluminum sheet corner to corner your exterior weld might end up looking right, but when you look at the inside you will see the penetration is spotty. Then try to gas weld the interior corner, that is just painful. I would make the box so there is no interior corner to weld. I can actually see that looking correct with aluminum oxy welding with only a modest skill level. Also don't be suprized by how malleable the aluminum is after gas welding.. very soft.. if you are used to the strength of things like extruded aluminum (that has extra strength from the extrusion) it will be mostly gone.. I read that the extrusion process gives it around 30% extra strength IIRC.. and that's what we are used to as humans dealing with regular aluminum when we design our boxes). The braze is brittle if you don't have a big lap joint area, but the aluminum is not as soft as after a weld). The aluminum oxy-welded corners also like to crack when you try to straiten out bend distortion. The post gas welded pieces remind me of lead in terms of bend strength. You  have drastically less control parameters when you work with aluminum, since you have 0 feedback from the material being luminescent. Every welder or brazer ends up looking at material color as a indicator of how things are going, and aluminum does not tell you shit compared to steel, that alone makes it like working with one eye. Maybe Jordi Le Forge can do it nicely if he tunes his visor to see near infrared. . Whatever you can visually identify  from working with hot aluminum is total crap compared to the amount of information you get from steel or copper.

Before you try to weld a corner weld make a butt joint between two pieces that looks buttery smooth so you have a reference of what you want the corner to look like, before you start post weld finishing (I never managed to get that). Bend it back and forth in a vise many times to see if the joint pops.

Take a sharp strong steel pick when you are done welding and finishing aluminum when you are learning and pry at it. you have success when you deform the aluminum and you don't pull crap out of the weld thats not actually welded but pressed into place.

[mag_therm]

Brazing 6061 of 1/8 inch 3mm thickness and below:    I use Forney 46111 filler rods, no flux, oxy-acetylene, #1 tip.
Preparation is filing or milling or grinding before the braze.

I use a sharpened toolsteel probe to scarify/stir  the parent metal under the molten filler.
I think that is important to get the oxide to break up and float up.
A white, surface after cooling seems to indicate that some oxide came up.
If the braze is shiny, it might not have properly alloyed, leading to a weak joint.
Distortion is not a problem.

These brazed joints are in my experience, by no means safe to use for structural or vehicular applications, but OK for hobby boxes.

I find there are limitations on the types of joints due to the lack of a mushy temperature range.

[coppercone2]

You know what I thought might be a good tool for brazing or soldering aluminum, a bristle brush that has very long bristles. If you try to use a typical brush while working hot, you end up smoking the handle pretty quick and too much heat transfers into the area holding the bristles. I wonder what would happen if you made a stainless bristle brush that has 2 inch long bristles so you can get at it at a little bit more. Or a ceramic handle bristle brush. Like a pool stirring tool that has more surface area then just a pick. Some kind of ceramic scraper might be interesting too. or just an aluminum  handle one.

And try alumiprep-33 for cleaning the aluminum up before brazing/welding/painting (just be careful with it), the same one you use for alodine application cleaning. I tried that for gas welding before and it came out really buttery.

Just FYI as a flux applicator I took one of those silicone basting brushes that you use for the kitchen, cut the bristles to be about 3/4 a centimeter long and use that to dip into flux and apply flux. Not too much flux gets stuck in the brush and it transfers it well (for brazing/welding flux pastes). You can also wedge it into something so you can drag your rods through it to coat them. And you can shake excess flux into the container pretty good.

[themadhippy]

Does it have to be all metal? woods much easier to bodge,use it for the sides and top and bottom,and just use metal for the front and rear panels.If however your set on all metal buy the 6  sides as  individual pieces,to join them together  , square blocks of ally  with suitable threaded holes, at each corner.Assemble the sides ,top and bottom  and fill any gaps with  body filler  ,sand and paint.Front and back panels can be built up and screwed into place.No expensive tools needed,just a drill and a tap

[coppercone2]

and line it with copper sheet or nickle silver sheet and solder a shield on the inside like genrad. staple it into the wood for holding it in.

[jpanhalt]

I would still recommend a break so you can weld a corner. When I tried to gas weld boxes I used angle pieces and 3x-welds (back of angle to sheet, other side of angle to other sheet and then corner to corner. Corner to corner welds are painful. What would be best is if you bend one of the sheets like you were going to rivet it, then weld that on both sides.

When you try to oxy weld aluminum sheet corner to corner your exterior weld might end up looking right, but when you look at the inside you will see the penetration is spotty. you don't pull crap out of the weld thats not actually welded but pressed into place.

The way to TiG weld anything so that the back side looks like the front, so far as I know, is to add shielding gas to the back side.  That is simple with some projects, such as welding aircraft mufflers, but is a bit more complicated with flat sheets.  Still, it can be done.

[coppercone2]

there are alot of youtube videos showing how to make gas diffusers out of stainless steel for that kind of tig welding, but keep in mind compounds like solar-flux B that are meant to act as shields that are flux based rather then gas based.. they do look cool

I see people make custom diffusers for torches for various welds too, but it looks like you need to be really into tig, I can't even get my machine to run after thinking about it for almost a year, and it looks like tig prices went through the god damn roof. I had to pick between some microwave test equipment over tig lol

[Nominal Animal]

I love Hammond die-cast aluminium boxes for single-board computers.  They're relatively cheap and moddable with hand tools (anything sharp that can cut wood, can basically cut aluminium too).

What I lack is a small milling machine to mill customized lids with bosses inside for interfacing to hot chips.  In other words, I like to use the boxes upside-down, with the board sitting on top of the lid (or more properly, hanging off the lid, right way up).  Before milling one from aluminium stock, I do recommend 3D printing one first (with low infill, for speed).  I have almost a dozen different Linux SBCs, mostly older cheaper ones.

I've looked at Proxxon mills (MF 70, FF 230, FF 500/BL), but as I currently live in a flat without suitable shop/workspace, this is on hold for now.

[rdl]

I have a Proxxon MF 70. I don't use it a lot, but it's been pretty handy to have over the years. Most of the time it's just stored on a shelf above my bench. When I need to use it I take it to the bathroom and set it on the counter next to the sink. The mess that gets made is pretty easy to clean up in there.

[Nominal Animal]

It's the structurally conducted noise in the apartment building that stops me, actually.

I've had a disabled "neighbour" who had some kind of a wood/metal shop in a 10-story apartment building, somewhere around the 6th floor.  They used some kind of a impact drill and a hammer several times each week, but never longer than half an hour at the time.  The sound was so loud that it was impossible to tell the exact apartment or even floor; as loud as if someone was doing it in the same room.  Because the neighbour belonged to a protected class, neither the landlord nor the police were willing to do anything about it, this being Finland.

I will not do that, not even if I utterly disliked my neighbours.  The noise is too much.  (Plus, my current flat is in a building where you can hear your neighbours washing machine when it's on.  New building, horribly poor sound proofing.)

[PaulAm]

+1 on having separate front and rear panels.

A fairly easy to fabricate box can by made by making 2 "U" sections for the top and bottom and using a piece of aluminum bar as a joiner by drilling holes along the edges of the sections and drilling/tapping corresponding hole in the bar.  Make the bar long enough so you can drill/tap holes on the ends for the front and rear panels to attach.

It helps to have a brake, but with aluminum sheet you don't need much and could probably do OK with a couple pieces of wood and a vise.  Use button head screws, paint and use some decent graphics on your front panel and there you go. 

Here's a pic of a project I'm working to allow remote control of an Acme PS2L electronic load.  In this box I elected to place the joiners vertically on the sides so the panels would have some backup and not get pushed into the box.

All in all, if you can find something to repurpose or buy, it will make your life a lot easier.  It will probably take you longer to make a nice looking cabinet than it took to design and build your power supply