Enclosures for the midnight engineer - Page 1
Forum section: electronics / projects

author: carveone
author_rank: Contributor
timestamp: July 15, 2011, 05:03:47 pm
content: I know this has been brought up before but I'd like to add some queries about enclosure purchases. In essence, the enclosure is the item that makes the project - every pcb I've ever designed has been designed for a particular enclosure, unless I didn't care too much...There are many places you can buy boxes but, in my opinion, they don't scale well in price. If you are making 4-5 pieces then you can buy an ABS box for $3-4 and that's fine. Even though I can buy a little box at Tesco for $1 that does the same job. And even though there are a myriad of one shot plastic containers in my fridge that cost sod all and make me thing that the project boxes are a damn ripoff....But if you plan to sell your prized invention, like I do, then it's a different matter. In my case I'd like to make a low speed USB device with a 1.8" screen and a few buttons and I'd love to be able to scale.Here's an example of a nice case:Insignia Digital Photo frameOk. A low speed device is supposed to have the USB cable attached but good enough. That's a $15 product. Microcontroller, flash, lcd, case and the case isn't $3-4 of that...(I'll add that the LCD on that photoframe is a 1.8" tft with an ILI9163 controller which is available in China for $2. Amazing stuff)So what's my point? I mean, designing your own enclosure and making the injection moulds is unlikely to be feasable for someone like me. I spent last night looking at the casing on my mobile phone. No Way am I capable of doing that without a lot of training!So has anyone ever purchased and used stock enclosures of this type before? If you look at the alibaba or taobao commerce website, you'll see plenty of places (in China at least) that mass produce enclosures for specific product lines. Now there's an obvious catch - the minimum order amount is about 500 or so. But at 50c to $1 each, I can take that risk...I'd be interested to know if anyone has done anything like this before...

author: ToBeFrank
author_rank: Regular Contributor
timestamp: July 15, 2011, 05:56:07 pm
content: I have not done this, but I am looking to do the same thing. Please post back anything you find.

author: gregariz
author_rank: Frequent Contributor
timestamp: July 15, 2011, 06:21:02 pm
content: Quote from: carveone on July 15, 2011, 05:03:47 pmPlastics I think are the one big barrier to getting started I think. PCB's, nameplate,assembly and packaging services can be found on the net for not too rediculous prices usually... but plastics are PITA.All costs are for plastics are sunk on die costs if you go for a custom case - and my enquiries showed it was more like a 5000 minimum buy to make it a reasonable proposition. If you find someone who can absorb the cost of a die for 500 cases at $1 each, I'd simply love to know who they are. Sometime back I worked with a mechanical engineer who had experience doing that and his take was that costs can't really come down much because everyone is using precision ground steel or aluminium blocks for the die with the injector/ejector/cooling already included in the block. These ready-to-go blocks at the time were about $10K for the steel ones - no doubt they've come down in price in recent years but to what level I don't know. They could sometimes fit more than one job on a block if they are small enough.I haven't gone down the road any further but I did use thewww.shapeways.comservice to get an enclosure 3D printed. I used autocad to draw it. Learning Autocad can be a pain in the ass but its do-able by oneself. Usually some tutorials on the web and books at your local bookshop. I didnt have any formal training on it but am able to do most of what I need to do - ie basic mechanical 2D and 3D drawings. The rest will be up to your creativity. I would follow the design guidelines for the molder, ie minimum wall thicknesses, feature depths etc. Most I have seen seem to have a document. If you look athttp://www.protomold.com/they used to have a small cube they sent out (its sitting on my desk...may still do that) with the recommended plastic thicknesses and features molded onto it so you can get a good idea of what you are allowed to do. I think you'll find that even Mechanical Engineers do the same thing - ie follow the molders guidelines. The molder will let you know/help if anything concerns them.

author: carveone
author_rank: Contributor
timestamp: July 15, 2011, 06:22:40 pm
content: I think we're all looking to make our lives easier and save some bucks at the same time. But windowed boxes for LCD displays seem to be a special problem. If anyone thinks I'm going to mill out a box and glue a piece of transparent plastic in there for anything other than a one off prototype they're mad.Ahem. The first time this occurred to me as a possibilty was when seeed studio released a little LCD oscilloscope called the DSO nano. The case was clearly from a media player of some sort.Aside: Thanks to Dave for clarifying the whole patent thing in one of his articles. The first time I discussed my idea with someone he started on about patents. "You should patent that!".Uh. Yeah... If I had a million quid I'd be on a beach and thinking about chicks. Patents wouldn't enter into it...

author: gregariz
author_rank: Frequent Contributor
timestamp: July 15, 2011, 06:28:15 pm
content: Quote from: carveone on July 15, 2011, 06:22:40 pmWell I decided on a pre-molded enclosure which would need to be customized. Ie let your local machine shop make up a jig to cut any custom features in the standard enclosure.If you get lucky you'll find something you can use. In my case the enclosure dictated alot of things ie the display, what controls could be fitted, what connectors could be fitted and where.

author: carveone
author_rank: Contributor
timestamp: July 15, 2011, 06:31:01 pm
content: Quote from: gregariz on July 15, 2011, 06:21:02 pmThat definately seems to be the case. (Ouch)QuoteSlight misunderstanding there. I meant stock cases. In other words these guys already had the dies and were willing to turn out a 500 part order for $500. If you look around the China plastics websites you can recognise some of the parts they are that generic.I guess some big company initially made a 100,000 or million part order, shipped them the dies and then wasn't interested in getting the dies back. Or maybe some companies make up generic dies for media players or generic mobiles and once they done that then your cost is simply for the plastic...QuoteThat is one way to reduce small unit custom costs alright. Premold insertions or post molding trimming or milling... I like the idea of getting a local shop to use a jig to do the repetitive cutting, that makes more sense.

author: carveone
author_rank: Contributor
timestamp: July 15, 2011, 06:35:23 pm
content: Quote from: gregariz on July 15, 2011, 06:21:02 pmYes indeed. I've heard good things about them (The Rossum's Posterous website has a recent article). I'd also like to play at my local fablab. Which is across the sea in Manchester, England unfortunately but I still want to visit it to see a laser cutter and cnc machine at work!

author: gregariz
author_rank: Frequent Contributor
timestamp: July 15, 2011, 06:46:51 pm
content: Quote from: carveone on July 15, 2011, 06:35:23 pmMy take is (and is just my opinion) is that its no longer worth buying either a 3D printer or a Laser cutter. I've found shapeways are cheap enough that if I only use them a couple times a year then I still won't have forked out more than a couple hundred. Likewise with laser cutting. I use pololu.com for that and again same amount of money. Prices have really come down for this stuff

author: gregariz
author_rank: Frequent Contributor
timestamp: July 15, 2011, 06:48:09 pm
content: Here is just a small list of enclosure makers I made some time back (Fry's and Jameco are my local suppliers here so you can ignore that)UPDATE: I moved the updated list over to the manufacturing and assembly group...

author: deephaven
author_rank: Frequent Contributor
timestamp: July 15, 2011, 07:07:43 pm
content: Have a look at this:http://www.bafbox.co.uk/

author: Unknown
author_rank: Unknown
timestamp: July 15, 2011, 07:15:45 pm
content: BOPLAhttp://www.bopla.de/andOKWhttp://www.okwenclosures.com/index.htmwere recently mentioned in the Open Source Multimeter thread. Both good.

author: Semantics
author_rank: Contributor
timestamp: July 15, 2011, 07:45:48 pm
content: There's a lot of molding and casting techniques that can probably be adapted for your needs. None are as efficient as pro injection molding, but for the midnight engineer...You can do what movie prop folks do and master vacuum forming. It's quite doable at home, all you need is an oven, a vacuum cleaner, and build yourself a vacuum box. Lots of info on those on Instructables.com and my favorite ones usually end with "... and now you have your Stormtrooper armor."Generally, it involves a sheet of thermoplastic that's heated up and placed over a positive mold and then the table "vacuums" the plastic to make it readily take the shape of the mold.Miniature gaming and board gaming folks do something else entirely. They often do stuff with silicone molds and pourable resins and polyurethanes. With a clever "sandwich" of opposing negative molds for each side of your case, you can probably cast some hollow things. The depth limit may not apply, but you'll probably have a little more clean up to do pruning the trees required to pour everything where it needs to go. Nice part is that these use resins which are doable at room temperature and you could wind up with something with more thermal resistance than thermoplastic. One thing to watch for is picking up a resin or polyurethane or whatever that needs "degassing". But there are "degassing-free" chemicals that don't need such elaborate equipment.The vacu-form process, IMO, is probably the best suited for home building of project cases, as long as you are careful not to make each side too deep, because the plastic will stretch and become thinner the farther it travels. Given my art skills, I'd probably buy a one-off from Shapeways or Pokono and then use that as a master from which to make a negative silicone mold, or do it twice to get a positive mold of form suitable for use with vacuumforming.If you're ambitious, there's also backyard metalcasting - It's pretty simple to melt aluminum and iron. You can make stamp a model mold of your plastic parts and basically pack in special sand tightly around it to make a mold. Make a few holes, pour the metal in, let it cool (and refinish because it will be a little rough), and then just repeat the process to get a negative metal mold. I guess from there you can work out a way to melt plastic (as to avoid pouring resins which have a much narrower range of physical properties) and use it in the molds as a poor-man's injection molding. It would probably be tough to get the "injection" part of it due to the pressures needed, but, hey, if you're got more time than money...After all that... I personally love electronics in nice natural wood enclosures.I like it so much that it's depressing to realize I have no wood working skills whatsoever. But you might.

author: carveone
author_rank: Contributor
timestamp: July 15, 2011, 07:59:10 pm
content: Wow. First I didn't realise there were that many box manufacturers around although some are well known like Hammond and Bud.Thank you Semantics. That's a lot to think about. I'd just come back from watching a youtube video of some guy heating up some acrylic in a little oven and thermoforming it on a wooden mold. He did show the limitations but it's quite interesting. I really do like the idea of a wooden box too though. I'd also thought of a box made of foam and material like polycotten. A soft cuddly electronic project! It's been a while since I picked up the razor plane and sandpaper but it's worth a go.Green sand and lost wax. Whew. That's a good many years ago in my Mech Eng degree days!For small amounts I think it's also worth investigating surplus. There are an awful lot of tiny cheap little lcd media players around with little buttons and all for not much money. You get buttons, case, lcd and often a little battery for a few dollars. I'm sure if you like the case, one can track down the original manufacturer of said case....

author: gregariz
author_rank: Frequent Contributor
timestamp: July 15, 2011, 08:12:21 pm
content: If you've got the space...http://www.mediummachinery.com/index.html

author: Zero999
author_rank: Super Contributor
timestamp: July 15, 2011, 09:28:23 pm
content: It looks like 3D printing is the future for producing enclosures in small volumes and it will one day become as cheap as PCBs.Have you ever tried vacuum forming? I've seen it been done by hobbyists on the Internet. It looks cheap but you can't get complicated shapes.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 16, 2011, 09:40:58 am
content: Unless you have the volume to do a mould, pretty much the only option is an off-the shelf case with machining to do the holes. Even then there will likely be a setup cost. If possible keep all the holes on the same face as machining multiple faces will cost more.One cheap option is to find case that has a flat removable panel, and replace the panel with a PCB. Dave's ucurrent is one example, here's another I did recently:

author: Unknown
author_rank: Unknown
timestamp: July 16, 2011, 12:44:26 pm
content: Nice channel Mike.Subscribed.

author: carveone
author_rank: Contributor
timestamp: July 16, 2011, 01:28:42 pm
content: I must investigate molding and the like and Mike's pcb method is a nice one to keep in mind for small volume. Lots of smart people out there! There's different strategies to bear in mind for volumes in the units, 10s, 100s and 1000s....

author: hisense999
author_rank: Contributor
timestamp: July 16, 2011, 03:21:29 pm
content: Quote from: gregariz on July 15, 2011, 08:12:21 pmHehe is quiet funny, but anyway final plastic injection is the most simple step in whole design, same as outlook design, small details and mould preparation this is most complicated and expensive. By the way machine of this size looks more as for rubber injection for compareable price chinese market is flooding by even more advanced equipement but even Chinese don't try sell it as hald-professional plastic injection cuz machines with this kind of power are only for rubber injection.But I suggest to look at 3D printers for plastic UP! have before limited offer for 1400USD if I'm not wrong now cost 2700 USD and have very good feedback I will receive mine in next days and can post more about it.

author: Zero999
author_rank: Super Contributor
timestamp: July 16, 2011, 04:48:20 pm
content: Quote from: Squonk on July 15, 2011, 09:45:50 pmInteresting. That would inidcate that the plastic which is good for 3D printing isn't very stable. I wonder if that will improve in the future?I know there are things which can be manufactured with 3D printing that can't be made any other way.

author: gregariz
author_rank: Frequent Contributor
timestamp: July 18, 2011, 06:28:12 am
content: We have one of these printers at my work that we use for Proto Cases. It does a decent job, the plastic (ABS or similar I believe) is not as strong as a molded case but it does just fine for prototypes. The idea is that you use this and get your plastics just spot on before forking out to have a mould die made. I've had the printed cases outside in some fairly decent heat and it has held up. The main problem with 3D printing is that it does leaves a rough surface. That is to say it doesnt have the smoothness or texture you would find on a finished product. In order to finish it you would have to sand it smooth and then paint it.When thinking about what level of finish you could reasonably expect from a product using an off the shelf case, I remembered the Peak Atlas series of component testers. I noticed that Alex did a tear down of one here...https://www.eevblog.com/forum/index.php?topic=3256.0Now I could swear I saw that plastic enclosure being advertised by one of the Case manufacturers years ago - meaning that is an off the shelf case. I could be wrong but I'd probably be prepared to put money on it because I noticed it not long after the meters came out. That case was nice because it had a pair of buttons moulded into it and a LCD cutout.All the designer of that unit needed was some minimal machining for the wires to come out, an LCD that fitted in the case and a Lexan labelIMO that product is a pretty good example of what should be possible with an off the shelf case.

author: hisense999
author_rank: Contributor
timestamp: July 22, 2011, 05:45:02 pm
content: My first results with 3D print:I can say part is very strong this can resist a lot for midnight engineer this is more than perfect.Second part on second picture which is more smooth is just printed in different direction which give more smooth results.

author: gregariz
author_rank: Frequent Contributor
timestamp: July 22, 2011, 06:14:05 pm
content: cool.. what package did you draw it up in Hisense?

author: hisense999
author_rank: Contributor
timestamp: July 23, 2011, 01:35:03 pm
content: Quote from: gregariz on July 22, 2011, 06:14:05 pmSolidWorks was used for drawing this, just it need to follow "cheap mould" rules, this printed part was half prepared for real mould so follow basic rules of mould for reasonable price.SolidWorks is quiet simple to make basic boxes etc. after few lessons.If someone want to make a quiet complicated enclosures using 3D printing I suggest some basic lectures about mould preparation for know what is quiet simple what complicated and which details are impossible to get for price lower than new house in real mould, then you can get a clue how to make usefull part with 3D printer.B.R.

author: Zero999
author_rank: Super Contributor
timestamp: July 24, 2011, 03:14:21 pm
content: What about making your own metal case?Apparently, it isn't that hard to do!You could use 3D printing to create the moulds.http://www.backyardmetalcasting.com/http://myhomefoundry.com/

author: Unknown
author_rank: Unknown
timestamp: July 24, 2011, 05:31:09 pm
content: Casting is fun......if you don't mind molten metal on your feetWhere I live, it's almost cheaper to to submit your model to the foundry and have it cast for you. What I learned from the foundry guys is that thin features are no good for casting in sand. They have some aspect ratios for surface area/volume but it isn't trivial arithmetic. So if you ever dream of cast enclosures think thick features, and I mean thick ass features. For example for a bearing cover the size of a CD they refused to make it thinner than 6mm and they will charge me for the failed parts too, unless I raise the thickness to 8mm. The failure rate was around 40% so next time around I raised the thickness to 8 and brought snacks and drinks too.If you want more delicate parts there are two ways to go. Either lost wax casting or injection molding at high temp. Both are expensive. But there is slight possibility one can make lost wax casting at home.

author: ivan747
author_rank: Super Contributor
timestamp: July 26, 2011, 01:40:34 am
content: Quote from: mikeselectricstuff on July 16, 2011, 09:40:58 amBRILLIANT!As much as Dave's uWatch and uCurrent designs.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: July 26, 2011, 02:01:35 am
content: Semantics has some very good points.FWIW, every company I've worked for that paid the big $$ for a mold would have saved money if they had every injection molded plastic part CNC machined. The success of products isn't predictable, product life today is very short even if successful, and nobody ever paid off the molds and went on to make profits. Even with low volume aluminum tooling it's too expensive.I've never vacuum formed, but believe it's a very good alternative.CNC machines are super fast if the people know what they are doing. I'd always get a quote to have the whole thing machined from a block or maybe a cast part made of ABS or similar. Always talk to agoodshop before making assumptions about cost.I've cast very good gears and such using silicone molds. No doubt you could do a nice enclosure, but once you get beyond about 10 parts, it's way too tedious. The resins and colorants are also quite expensive.The 3D printed parts I've seen over the years just aren't of sufficient quality or durability for anything other than prototypes.Sand casting is great for heavy wall stuff that needs a lot of machining but lost wax is capable of much finer detail and smaller sections. There are people who do lost wax commercially and it's very very good, but could be too expensive.I typically use PacTec enclosures if I want plastic and Lansing enclosures if I want metal. These are both good commercial quality, reasonably priced, decent looking and I wouldn't consider anything else until volumes hit several hundred.