Author Topic: Procuring or designing custom sheet metal enclosures.  (Read 2033 times)

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Offline forrestcTopic starter

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Procuring or designing custom sheet metal enclosures.
« on: May 14, 2024, 12:40:35 am »
I'm frustrated and need to try some other approach.

I've been trying to work with various sheet metal manufacturers who specialize in enclosures for electronics and similar.  Many of these have in-house design teams, but it seems like getting from "I want to put this board in an enclosure, and here's a 3d model of the PCB, and I'm happy to move mounting holes if necessary" to an actual, usable, enclosure at a price I can afford is statistically unlikely to happen.  Having wasted way too much money and time over the years with suppliers that didn't end up working out, and having the current one flame out as well, I need to try a different approach.

I'm wanting to know how others deal with this. To be clear - these are usually just garden-variety rectangular metal boxes with a single PCB inside.   Connector holes along one side, some way to mount the PCB in the bottom (pem inserts, pushed up sheet metal, side clips, don't care).  Maybe some ventilation holes, maybe not.   All should be able to be done on a cnc turret punch and brake/bender.  The most exotic thing I often ask for is if the supplier has the fancy punch which makes a 4 sided screw 'mounting' slot in the bottom to enable wall mounting---but that should be able to be loaded on the turret punch.   If they'd rather laser cut it all and use pem inserts I'm fine with that as well.

My immediate thought is "screw this, I just need to learn how to draw a manufacturable enclosure and send it off to a whole truckload of companies for a quote".  I don't know if this is practical, or if there are resources I don't know about how to actually do this successfully.  I.E. examples on what to do or not do, costs, etc.   

I've also looked at hiring a consultant to do the design, but that has it's own set of problems, not the least of which is that finding the right consultant tends to be difficult and also that some of the quotes I've gotten are so far out of our budget that I had to politely turn them down.

So, if anyone has experience in making this type of thing happen, and suggestions on how to be more successful than I have been over the last 10+ years, I'd love to hear them.   One last note:  This is for products with volumes around 500-1000/year, but with 5-10 year production runs, so something like 2500 total over the product life, but only 250 or so bought at a time.   So this is beyond "bend a few in-house" or "prototype" volumes - but also not to "can afford to spend a lot and spread it across a lot of units".
 

Offline thm_w

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Re: Procuring or designing custom sheet metal enclosures.
« Reply #1 on: May 14, 2024, 12:49:21 am »
Do you have fusion360, solidworks, or some other CAD tool that is good for sheet metal design?
What kind of design quotes are you getting that you think are unreasonable for the budget?

Laser or water jet is fairly common so odd shapes are not an issue.

We use aluminum + PEMs, then you can do whatever finishing you like if any, anodized, painted, powder coat, etc.
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Offline forrestcTopic starter

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Re: Procuring or designing custom sheet metal enclosures.
« Reply #2 on: May 14, 2024, 01:28:41 am »
Do you have fusion360, solidworks, or some other CAD tool that is good for sheet metal design?
Yes, fusion360 and a few others such as TurboCAD.

I also have SolidWorks for Makers but that isn't commercially licensed and I'd need to sort that out first.


What kind of design quotes are you getting that you think are unreasonable for the budget?

10K upwards for the consultants.   

The manufacturers have just been frustrating.   Not the current project, but for a 19" rackmount enclosure, I had one that I paid around $5K for a design and initial prototype, which they made a mess of.  Bosses weren't placed correctly - boards were crooked, etc., even though I provided them drawings, sample circuit boards, and even an existing enclosure that I was shipping.  Then, they, for whatever reason refused to let me pay them an additional $5K to fix it.  Instead they demanded that I order the first 500 enclosures (35K of metal), which they promised would be perfect.  No thank you.  $5K down the drain with nothing to show for it but a screwed up enclosure.

I've also struggled with companies which would say "oh yeah, your budget shouldn't be a problem at your MOQ" only to find that the final quote (after again paying some NRE fees), either is like 10x the cost I indicated was my target (not much of an exxageration), or that they had a MOQ of 10K.  In fairness to the last one, they decided to change their focus to larger orders in the middle of the whole engineering process. 

Laser or water jet is fairly common so odd shapes are not an issue.
We use aluminum + PEMs, then you can do whatever finishing you like if any, anodized, painted, powder coat, etc.

Yeah, these enclosures seem like what you'd normally do.   Nothing high tech about these - take aluminum or sheet metal, cut into the flats, add pems, bend, finish.   No welds, no exotic inner pieces, no complex bends.   It's just frustrating that I can't seem to figure out what from the outside shouldn't be anything hard. 
 

Offline DiodeDipShit

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Re: Procuring or designing custom sheet metal enclosures.
« Reply #3 on: May 14, 2024, 02:50:38 am »
Forrest, It comes down to a good print, a better cost estimator / programmer and a great setup person. Box Radius's require careful Setback calculations.
https://www.thefabricator.com/thefabricator/article/bending/sheet-metal-bending-calculation-basics
Design all Your dimensions from the inside. Draw or CAD the print clearly. Specify material and thickness. Be reasonable with inside tolerances.
For short orders....Give lots of tolerance for the outside; I.E. +/- .06
Accommodate for these tolerances by opening up mounting holes.
Let the Fab shop figure the rest.
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Offline loki42

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Re: Procuring or designing custom sheet metal enclosures.
« Reply #4 on: May 14, 2024, 10:14:27 am »
Enclosures like that are pretty easy to design in fusion 360 with the sheet metal tools especially if you export the 3d file from your ecad program and design around it.  You can then send it off to any of the sheet metal people in China etc and get quotes that should be pretty cheap. Quality from larger Chinese firms is very good. 

You know that turret punches exist so your miles ahead of most designers.  To make the job easy to load on a punch,  keep your radius corners to a standard radius, and things like bend relief.  You can check out catalogs from the tooling manufacturers for ideas. Mate,  Amada and Wilson are big ones. With bending,  deeper flanges are easier than really short ones,  at least on my brake. If it can be bent without special sectional tooling that helps too. 
 

Offline jmelson

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Re: Procuring or designing custom sheet metal enclosures.
« Reply #5 on: May 14, 2024, 02:57:58 pm »
There are extruded enclosures that have grooves in the sides so that a board can be slid into the slot.  Then, there are end plates that can be machined with connector cutouts, and these are screwed to the open ends of the extrusion.  I used these for a project I did.  The one issue was I was machining the end plates which were anodized, and the hard anodizing destroyed my solid carbide end mills so fast that I could only make one plate per end mill!  The plan for future production was to make the connector-side plate out of unanodized aluminum sheet and then apply a label that matched the color.  These enclosures are plentiful and surprisingly cheap.  I think I got mine from Newark for about $12 each.
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Offline SMTech

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Re: Procuring or designing custom sheet metal enclosures.
« Reply #6 on: May 14, 2024, 03:37:03 pm »
There are extruded enclosures that have grooves in the sides so that a board can be slid into the slot.  Then, there are end plates that can be machined with connector cutouts, and these are screwed to the open ends of the extrusion.  I used these for a project I did.  The one issue was I was machining the end plates which were anodized, and the hard anodizing destroyed my solid carbide end mills so fast that I could only make one plate per end mill!  The plan for future production was to make the connector-side plate out of unanodized aluminum sheet and then apply a label that matched the color.  These enclosures are plentiful and surprisingly cheap.  I think I got mine from Newark for about $12 each.
Jon

Extruded cases are indeed very handy. They come in all shapes and sizes, when dealing direct with the manufacturer they can also handle customizing the end plates with the required apertures and printing.

They even scale up to the 19" size suggested here, we used to build assemblies full of backplanes and drive control modules in enclosures made by Schroff  e.g RS 487-551. RS I note has plenty of rackmount steel cases too, again potentially reducing your requirement to sending a panel of to get punched appropriately.

However I do feel your pain, the complaints people have on this forum about subcontracting electronic assembly are nothing compared with the joy of sourcing metalwork, be it stamped or machined. Many of them simply cannot be bothered, deliver poor quality, don't respond to quote requests or have no clear scheduling or interest in delivering when promised. Anodisers- even worse, every issue they blame the machining or the batch of Aluminum.

As a contractor we typically end up dealing with a customer specified metalwork shop, one is excellent, the rest not so much. In all cases they are supplied with complete CAD.
 

Offline thm_w

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Re: Procuring or designing custom sheet metal enclosures.
« Reply #7 on: May 14, 2024, 09:02:04 pm »
10K upwards for the consultants.   

The manufacturers have just been frustrating.   Not the current project, but for a 19" rackmount enclosure, I had one that I paid around $5K for a design and initial prototype, which they made a mess of.  Bosses weren't placed correctly - boards were crooked, etc., even though I provided them drawings, sample circuit boards, and even an existing enclosure that I was shipping.  Then, they, for whatever reason refused to let me pay them an additional $5K to fix it.  Instead they demanded that I order the first 500 enclosures (35K of metal), which they promised would be perfect.  No thank you.  $5K down the drain with nothing to show for it but a screwed up enclosure.

I've also struggled with companies which would say "oh yeah, your budget shouldn't be a problem at your MOQ" only to find that the final quote (after again paying some NRE fees), either is like 10x the cost I indicated was my target (not much of an exxageration), or that they had a MOQ of 10K.  In fairness to the last one, they decided to change their focus to larger orders in the middle of the whole engineering process.

Sounds like your anecdotes reinforce keeping the design work and metalwork separate.
$5k seems alright if it was done correctly + cost optimized. But I have never contracted out these designs, only done in house. So its just a guess.

If you design/dimension the part correctly in F360, its not hard to go back and tweak sheet metal thickness or other details that the manufacturer might suggest. You can let them know you are open to design suggestions to make it easier to manufacture.
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Offline T3sl4co1l

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Re: Procuring or designing custom sheet metal enclosures.
« Reply #8 on: May 14, 2024, 10:39:03 pm »
What kind of suppliers have you been working with...?!

Last time I had an enclosure made, I scratched up some basic drawings by hand, brought them to a small local fabricator, they charged I think $200ish /ea (gosh, that'd be more like $300 now) for time and materials, and boom, I had five sets or whatever of the thing.  Would've been a 10 x 16 x 7"-ish box with a couple interior panels.  Forget if that was a two-C-shape assembly or one five-side box with cover or-- no, it had a faceplate at least, it could've only been four at most; but yeah, they figured it out and it worked great.

It pays to have some basic knowledge of drafting.  Not even to the point of like GD&T (geometric dimensioning & tolerancing) but to know what lines to draw where, in what weight (heavy = outline, light = feature e.g. edge of a face, bend line, dashed = hidden i.e. backside light line), and the spacial awareness to draw it from multiple angles and use sections to eliminate ambiguity.

Nowadays, you would be best designing it in SolidWorks, Fusion360, etc., using sheet metal commands (cut, bend, drill, etc.), and sending the file directly to a fab -- there are numerous online fabs that do this, even one-stop sources like PCBWay these days.  You might check for one local-ish (same or neighboring state, say) to save on shipping or ease communication if anything needs to be done in person.

If you don't have the mech software and how to drive it, of course this gets more difficult, but you can always ask several shops if they'll make sense of your chicken scratch, maybe even have them turn it into models for you -- or hire someone for the same task, which should be pretty straightforward, and you can ask for clarification and tolerancing in the process, making sure everything is sensibly sized, fits together, tolerances are achievable, etc.  Doesn't even need to be the service of an ME, but an ME might be able to do it faster / more accurately than a more informal / hobby / novice type.

It's probably harder nowadays to find local suppliers, than it used to be.  The internet is clogged up with SEO and generated results.  You can scroll for dozens of pages looking for anything smaller than an international supplier -- someone who's actually only interested in big bucks and production quantities and will jerk around little players until they pay up or leave for something else.  More traditional discovery methods may be necessary to fall back on.  Location searching at least can help, but also consider ye olde Yellow Pages (well, maybe not, they're commodified too these days, aren't they?...who actually has a phone book anymore?), or similar methods.  Check newspaper ads in local areas?  Check maps.  I don't think there's a trade association that might index such suppliers, but that also works for certain kinds of business.  And, if you post state/region, you might get tips here.  Or really even just stateside in general, shipping smaller packages across the country doesn't cost extra.

As for the rackmount:

The cost seems ludicrous, and, I don't really know how much stuff you have packed into the thing, but just for point of reference, a typical empty box runs $100 e.g. https://www.digikey.com/en/products/detail/bud-industries/CH-14404/428959 and you can just drill all the holes yourself if it's simple, support boards/panels on standoffs, that sort of thing.  Step up would be drilling holes more precisely and pressing in inserts -- or getting a shop to do it, and next after that would be, take these basic outlines and make me a custom with x-y-z features, panels, etc. included.  Like, some things like slots and precise large holes/openings will be much easier to do, particularly in production (laser or CNC punch) on flat sheet, than modifying an already-bent box, and a shop so equipped will know how best to do it.

Tim
« Last Edit: May 15, 2024, 01:01:34 am by T3sl4co1l »
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Offline forrestcTopic starter

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Re: Procuring or designing custom sheet metal enclosures.
« Reply #9 on: May 15, 2024, 12:03:41 am »
What kind of suppliers have you been working with...?!

Obviously the wrong ones.

I've always provided some drawings. For the bad rackmount experience, it was even completely dimensioned, as opposed to the "rough sketch" I've done before. More recently, I also provided a correct 3D model of the circuit boards for electronic fitment along with any drawings.   

However, I have also always expected the manufacturer to work with me on what makes the most sense in their manufacturing flow and do the actual manufacturing plans.  This means that my drawing is going to be largely a rectangular box indicating hole and mounting locations and some notes about features such as "ventilate this side - open up at least 25% of the surface area".  I have always felt this was the best way since the manufacturer knows more about their tooling and flow than I do.  Starting to think this might be the wrong way to do this.

Nowadays, you would be best designing it in SolidWorks, Fusion360, etc., using sheet metal commands (cut, bend, drill, etc.), and sending the file directly to a fab -- there are numerous online fabs that do this, even one-stop sources like PCBWay these days.  You might check for one local-ish (same or neighboring state, say) to save on shipping or ease communication if anything needs to be done in person.

Yeah, I'm coming to this realization.  Just trying to figure out the best way to be successful in making a good looking enclosure.  Even a half-dozen prototypes have to be cheaper than what I've been doing though.

As for the rackmount:
The cost seems ludicrous, and, I don't really know how much stuff you have packed into the thing, but just for point of reference, a typical empty box runs $100 e.g.

We've been using a stock enclosure modified by the manufacturer for years, and continue to do so.  Costs us about $70 at the quantities we are using.   25 pem inserts in the bottom for PCB mounting, holes cut in the front panel, some silkscreening, nothing else special.   We just wanted/needed to move to something which resolved a few minor nits our customers continue to bug us about, such as easier cover removal for maintenance/reconfiguration tasks and so on.

We were expecting the fully custom unit to be more, but we also felt that it improved product quality so we were ok with it.  We didn't expect the project to go sideways like it did, especially since we were able to provide an existing enclosure, production circuit boards, dimensions of all of the boards, holes, etc., and so on.  It's pretty obvious that something is horribly wrong when you stack the prototype they provided on the existing enclosure we provided to them.  As in the entire thing is like a full inch wider, including "rail to rail" spacing for mounting.
 

Offline T3sl4co1l

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Re: Procuring or designing custom sheet metal enclosures.
« Reply #10 on: May 15, 2024, 01:28:58 am »
Ahhh, got it.

Yeah, they were... I suppose you wouldn't be able to refund the NRE anyway, but, delivering an article that's grossly out from the reference? You literally didn't pay for that...

For stuff like ventilation, it probably helps to add a note to the effect of, "perforations in [highlighted] area, acceptable patterns: grid/checkerboard/polar; holes: round/oval/slot/diamond/etc.; other sizes/options by approval; maximum opening width/diameter: [finger-safe dimension [meets IEC 60529 something, etc.]]" and so on.  Also probably something about omitting vs. truncating the openings on the boundary of the region, or if they should be aligned to anything in particular (X, Y offset and pitch, centers, top/bottom/length, axis angle, etc.).  Just to fully describe and constrain the feature.

If they're laser cut, it probably doesn't matter what the holes are like, or, a slight preference for slots (fewer plunge + lead-in cuts?); for punched, whatever dies they have should be fine, but beware warpage due to all the working, it can end up domed; drilled is probably out for being slower overall, but, Idunno, maybe it can be done pretty fast in aluminum anyway, nice high spindle speed and a CNC, maybe questionable in steel depending on thickness (since you can't really drill large holes in thin stock, and thick stock will take longer compared to Al).  Or, can call up and ask if they have a preference, or, kinda sorta worst case, just make all the drawing variants yourself and quote them all -- the spaghetti strategy might be a tedious one, but... yeh.

And there's always I guess, solutions like cutting a big gaping hole and using a filler panel of perforated stock or expanded mesh, but that likely won't look as good here.  (The best case would probably be like, cut a disc barely undersize of the hole, and spot-weld joining tabs on the backside to mount it. The face can then be flush, but a seam is left (and probably burrs) that probably won't feel good, bare; it might fill in alright with powder coating or something, though.)

It is unfortunately hard to put "no particular requirements, just make it usable and look good" on a proper drawing.  It can perhaps be explained in order notes, or in person, but it takes a good fab to really understand that.

Tim
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Offline loki42

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Re: Procuring or designing custom sheet metal enclosures.
« Reply #11 on: May 15, 2024, 01:04:19 pm »
I've found that its much easier to get good quotes on a very specific enclosure.  I'd model the whole thing in fusion 360 or solid works and send the flat pattern and drawings to people. Try some local shops and International ones.  I find very few smaller sheet metal places here do much with punching and mostly do lasers for smaller numbers.  You pay more for lots of holes as piercing is slow. If you've got mesh vents it'll be faster on a punch. I switched from cnc router,  to fiber laser and then to turret punch.  There are places that do online sheet metal if you've got all the drawings with almost instant quotes.
 

Offline jonpaul

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Re: Procuring or designing custom sheet metal enclosures.
« Reply #12 on: May 15, 2024, 01:19:29 pm »
see the old ready made aluminum BUD Industries electronic enclosures.

Used these many times.

https://www.budind.com/



Perhaps you can adapt.

Jon
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Offline mon2

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Re: Procuring or designing custom sheet metal enclosures.
« Reply #13 on: May 18, 2024, 08:01:38 pm »
TLDR. Need a box / enclosure company? Contact Jenny - have used this company for 2-3 custom enclosures and did a plant visit (Shenzhen) last October. Excellent products with laser markings - we sourced extruded aluminum enclosures. They are the real deal and have MANY capabilities and enclosures. We are reviewing them now for a pseudo-custom rackmount enclosure.

https://www.hongfabox.com/

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Add: A1-A2 Building, Xiufeng Industrial City, Buji Subdistrict
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T: +86 (755) 82579946    Email: sales002@hfjxkt.com
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