Wanted info on fabrication of a case/enclosure for an commercial electronics project

Your initial choice is between modifying an off-the-shelf case or getting a full-custom one. Full-custom will typically be injection moulded, which will involve high tooling costs ($10K upwards, possibly a LOT upwards), but will give low unit cost and allow flexible choice of materials (e.g. transparent).

As it sounds like your volume is fairly low (hundreds to low thousands), and budget limited, your only sensible option is likely to be a standard case, cut as required. Spend a few days getting hold of every enclosure catalogue you can lay your hands on so you can look at the widest possible selection. Here's a list to start with (mostly European) : Teko, Hammond, Bopla, Fibox, OKW, Pactec, Boss, Vero, Rose & Kreiger.

It is often possible to get standard cases moulded in different plastics (e.g. transparent) if you order enough - thos can sometimes be viable for a few hundred.

You don't have the money to pay someone to do the work. I'd focus on getting the money to have the product development done right.

-- Paul

Hi Reza, There was very low budget project I worked on earlier this year that incorporated two AAA batteries and a USB connector. The enclosure was semi transparent blue and the right size to have two PCB mounted AAA battery holders inside. (I think it was a Serpac C-4 or C-6 series) The only downside to using the enclosure was a single screw had to be removed to change the batteries. One thing that helped was placing the PCB near where the two halves of the enclosure separated. A hand nibbler tool and hole punch was used to make the cutouts for the PCB mounted connectors and push buttons. This might be something you could do with a "small version" prototype. Shameless self promotion: There was a small article I did on a cadence counter for bicycles a few years back. It didn't have an LCD display, but the data could be uploaded to the desktop computer. See the online edition of Circuit Cellar at:

Please tell me that you've done market research - i.e., identified and gained the interest of if not letters of intent from likely customers - before doing all this work. If not, you should now, before investing any more time and money. misc.entrepreneurs.moderated and misc.business.marketing.moderated are good resources.

Also, the impression I get from your post is that packaging is an afterthought. It shouldn't be, especially for a consumer device and/or one that will see rugged use, such as on a bicycle. Even if it's going to sit on a shelf and look good, your laundry list of packaging details isn't trivial. The R may be done, but the D isn't.

Sorry for being presumptuous. You may have already done the research and thought all these things through.

Rob Campbell

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trivial.

Ditto Rob's comments. Assuming the best case, look for an off-the-shelf package that will do your job, as fabricating from scratch will be long, involved and costly. Minimum tailoring should be the goal. There's bound to be case or plastics suppliers in your area who can supply you a standard weatherproof product without too much drama.

Ken

We've talked to a lot of people and there seems to be sufficient interest. We're looking at selling this via word-of-mouth and magazine advertisement initially, and if it takes off there, then to ramp up production and pursue retail outlets. The largetst complication with regards to existing cases is that it somehow needs to mount on a bicycle handle. Ideally, it would need to integrate with existing harnesses to reduce cost.

One thought I had was to carve out a rough design in some soft material, make a mold of it myself, and use some resins to make a small number of cases. This seems like it's the most labour and time intensive, but the cheapest option and I dont see why it couldn't work.

So far, we've worked primarily on the electronics. But the form factor can be any shape now. So I suppose we are now doing that aspect of the research.

Also, as this product will be sold for $300-$400, I just see people as being more interested in the product if it looks more "polished" and "professional". This is why I am opposed to the modification of existing cases idea, as it will not look as "professional". But it is worth investigating, so I'll start checking out some suppliers.

Finally, I called up a tooling shop to see what the cost of the mold would be. based on what I described to him, his best guess is around $3k for the mold, and possibly $2k if he can use a unit dye (though that would limit where I can use the mold).

Also, does anyone know if it's supposed to be spelled mold or mould. I've seen it both ways.

thanks again, reza

Reza, Slightly Off topic... I recently return from a Trade Show IN Philadelphia. On South Street Party district, I happenstanced into a no cover bar with a Rap group. Now most radio Rap is vile and I don't normally listen to it. What I heard that night was wonderful. On tune went something like this, " Opinions... everyone's got em.... Opinions... aint facts..."

and then went onto the story line.....

There lots of ideas on exactly how a business should run, and given the aide range of solution and outcomes,, " Opinions... everyone's got em.... Opinions... aint facts..."

Happy selling, sell sell sell that's the focus.

There are many companies that have plastic work boxes. Good one in east coast USA ..name escapes me at present.. sola? They had an upscale version of the radio shack boxes. some with battery compartments and others, you may have to buy a shell ,and have it "worked" and then use it as your housing.... till if ever you tool a plastic mold and customize things.

I may have missed it, but has anyone else in the thread mentioned FCC requirements for radio/TV interference? ( Assuming that you're targetting sales in the United States.) I thought any digital product (barring something with a clock frequency lower than some very low number that I don't recall) had to be tested for RF interference before it could be sold in any volume.

Perhaps you've already looked into this but if not, a little research now might save some trouble later on.

Bill

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There is a exception if the unit is battery powered , an unintentional radiator ( like this unit ) and is only to be used in moving vehicles ... BUT if you take the unit off your vehicle and plug it into your computer for download whamo you now have to be tested.

( note FCC testing and fixing problems gets expensive fast and it is much wiser to carefully package up front )

You must have the unit tested BEFORE it is marketed ! yup hard to believe , the FCC handed out fines at the CES show of $10-20K for marketing of untested units.

KB

Does anyone have an idea of how much it costs to test a product for compliance?

Thanks!

Carlos Antunes

the testing is relatively inexpensive for fcc filing of simple license free (part 15) items, figure 1-3k for the event and the report and filing.

However, this assumes that your products already MEETs the FCC requirement. The testing is only a test and cannot CRWEATE compliance. Compliance comes from managing the frequency plan, harmonics, etc.. first to insure compliance... then you go to the test range and Verify the you compliance and the third party supplies the drat and report. Nice and cozy process.

Marco

Great advice! It's been on the back of my mind to have some testing done, but I assumed that it wouldn't be an issue 'till we went fully retail with the product. The product already has sheilding on the potential problem points (the GPS unit & antenna amplifier). However The unit will be plugged into a PC to download data. Does anyone know what type of testing is required, how to do it, and how much it costs? If it is radiating, can we supply a metal box to put the device in when plugging it into a PC? And what about metalic paints? Can I get the inside of the case sprayed with such paints to add shielding? What's the easiest way to test the unit myself before submitting it to the FCC for their testing?

Also, on the case front, there are some pictures of a laser cut acrylic case that looks great on this website :

I now need to make calls to find out pricing information.

Thanks everyone for the input so far!

Reza

$800 - $1600

Yes , I have worked with case suppliers who charged $150 setup and a couple of $ per piece to spray. Conductive paints have several issues including cracking if the plastic case can flex , and flaking of the paint over time leaving little conductive particles floating around inside the electronics.

At a minimum you need a good spectrum analyzer and the appropriate antenna(s) / lna / cabling ( costing $15-30 thousand $ ) and the appropriate knowledge and test space. Antenna must be able to be moved and rotated. The correct answer here .... it's time to find a local test lab , give em a big hug , tell then you will bring them some business and make them your buddy and you will probably be able to do some quick checks at a decent price.

KB

( obtw ... if you are designing a nifty little gps logging box for your bicycle I hope you have reviewed the little garmin bicycle unit and others in the pipeline , I only say this because I suspect they will sell on the market for less than you can buy your parts for , well good luck )

Well if the product sells for that much, perhaps in the beginning you could just buy an off the shelf bicycle computer, remove it's innards and use that case. You should be able to find a suitable donor for $20.

Ralph

Declaration of Conformity

Same procedure, but there are, as far as I know, now exemptions. But the standards and limits against which the device is tested, are roughly the same for FCC part 15 class B and the corresponding IEC standards used for CE marking. These are IEC 61000-6-3 (compatibility) and EN/IEC 61000-6-1 (emission). The IEC standards are a bit 'tighter than those for FCC, so if you measure for IEC, you're automatically ok for FCC.

Meindert

Why not? I have seen GPS work in my house (wood frame, cement tile roof) and in the top floor of a standard So Cal office building (steel frame, wood/tar roof).

On 7 Jul 2003 23:58:32 -0700, Reza Naima wrote: : Now, our device has a GPS unit in it which might also clasify it as a : Receiver, but the GPS will never be used inside home (it can't : anyhow..), so I'm guessing (hoping) that I dont need full catagory b : testing.

You could be shocked at what passes category B testing. I sure was, most recently with a clone 386 on ISA board with ISM radio, GPS, and DC switcher, all in a plastic case with zero shielding and near contempt paid towards lead dressing and other normal levels of good hygiene.

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