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How do we design a box (enclosure) for an electronic product ?

Discussion in 'Electronic Basics' started by Ray, Oct 4, 2003.

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  1. Ray

    Ray Guest

    Hello all,
    I want to design a power supply enclosure which would look
    professional. The front panel will be from plastic, the rest will
    be metalic. I don't know where to start really, is there some
    software that will enable me to make the design on a file so that
    I can send it off to a company that would manufacture it ?
    Tia.
     
  2. Rich Webb

    Rich Webb Guest

    Unless you can recover the non-recurring engineering costs of designing
    a custom enclosure, find an off-the-shelf one that works.

    You can often get custom front panels made fairly cheaply (basically
    holes in sheet goods), painted or anodized, and with silk screened
    markings. Check with Elma Electronic UK.

    If you want to design your own, you'll either need to provide complete
    manufacturing drawings or add the cost of the production of the drawings
    (and the inevitable revisions) to the NRE.
     
  3. Ray

    Ray Guest

    How do I create a drawing, we never learnt how to do this in EE.
    Is there some software we use to design boxes. I heard of
    autocad, is this the tool, if so, do I need to get special customisation
    for box/panel production ? Is there a free evaluation version ?
    Tia
     
  4. This is for a one-off or a production design?

    If the former, look at as many commercial units as you
    can and decide what you like best, then copy it as well as
    possible (assuming you can open it up and see how the
    airflow, connection, and similar problems are handled). FTM
    you may like the guts of one and the outside of another.

    Have you ever done any sheet metal work? It's not all
    that hard, and a useful skill. The tools can get expensive
    though.

    BTW, a plastic faceplate is a bad idea for a SMPS as they
    can radiate lots of EM noise. A plastic _cover_ on a metal
    plate works if it stays cool enough.

    If the latter, you must work for a very small company.
    EEs are rarely tasked with enclosure design. ;>)

    Mark L. Fergerson
     
  5. JeffM

    JeffM Guest

    we never learnt how to do this in EE.
    Shame on your instructors.

    CAD packages are expensive and the learning curve is outrageous
    (especially AutoCAD). There are other vector-based alternatives:
    http://www.engineering-group.com/ENGINEERSMALL/cad.htm

    If, however, all you need is a line drawing that is easily printed/replicated,
    a bitmapped paint package is an easy option.
    MSPAINT is already on your Windoze box.
     
  6. Ray

    Ray Guest

    Shame on your instructors.
    hi, thanks for the link which I will look up. Regarding your suggestion to use
    mspaint how will I know if production companies accept bitmap files. Also,
    bitmaps are 2 dimensional, some features of my plastic from panel will have
    3D designs, for example the panels will need to have a raised frame. How
    will I know how to draw the things that I want in a 2 dimensional sheet, surely
    there are some convensions ( which mspaint will not be able to enforce ).
    A library of designs will also be useful. What do the professionals use ?
     
  7. Ray

    Ray Guest

    no as yet...
    I'm am talking about a low voltage/low current one.
    So who then is tasked with enclosure design ?
    Is that something I need a degree for as well ?
     
  8. If this is a one-off or small production job, I'd strongly recommend
    using a ready-made box, available from Farnell and other electronic
    distributors (I normally use Hammond boxes, because the distributor I
    normally work with carries them - don't know what makes you'll have in
    the UK). If you use a ready-made box, then you just have to design
    the front and rear panels.

    AutoCad is a very common mechanical drafting package - but it is
    EXPENSIVE. There are cheaper mechanical drafting packages available
    (search for Intellicad - an AutoCad clone) - many offer
    ACad-compatible output, which may be desirable if you are sending the
    job to an outside company that wants machine-readable drawings.

    There are certainly drawing conventions in mechanical drafting, but I
    wouldn't expect ACad or other programs to enforce them.

    I have recently started using Front Panel Express
    (http://www.frontpanelexpress) - they supply the design program, and
    deliver panels in a few days. That URL will get the US office in
    Seattle WA - the parent company is in Germany.
     
  9. JeffM

    JeffM Guest

    |strongly recommend using a ready-made box...
    |I normally use Hammond boxes...
    |Peter Bennett

    Well said; Stay away from custom anything if possible.
    Take this advice with you throughout your life.

    This is the easy way to minimize the custom stuff;
    plastic is much easier/cheaper to fab than metal.
    In addition, would you like this enclosure to trap a fire inside it
    should something go terribly wrong? 6 metal sides are mandatory for this.
    If you are going to be doing designing/engineering,
    you will have to start considering worst-case scenerios.

    Don't mind Mark. He's just spoiled. ;-)
    Some engineers/techs actually enjoy branching out.


    ~how will I know if production companies accept bitmap files ?

    Ask them--and remember they're working for you.
    A piece of paper is all a good fabriction man needs.
    (Doing it on the computer just makes it easy for you to make 92 copies.)
    If they want to get paid, they'll accommodate your needs.
    You can always find someone else to take your money.


    ~How will I know how to draw the things that I want in a 2 dimensional sheet,
    ~surely there are some convensions [sic]
    ~Ray

    Yes there are. A visit to google.com could be educational.
    (search terms) Drafting OR "Mechanical drawing" Basics OR Beginning

    To get you started, the simplest standard drawing looks something like this:
    --------------
    | TOP |
    | VIEW |
    | |
    --------------

    -------------- --------------
    | FRONT | | SIDE |
    | VIEW | | VIEW |
    | | | |
    -------------- --------------
    Drawing Title
    Engineer's name
    Draftsman's name
    revision # date
     
  10. Ray

    Ray Guest

    Yes there are. A visit to google.com could be educational.
    What uni degrees teach you this ? are there reccomended books ?
     
  11. Fred Abse

    Fred Abse Guest

    Disagree. Most plastics don't fold worth a damn, and can be difficult to
    join with "normal" workshop methods.
     
  12. Fred Abse

    Fred Abse Guest

    What's wrong with good old-fashioned drawing instruments and paper for a
    quick simple box?

    IMO, nobody should go near a CAD package until they've learnt the
    fundamentals of engineering drawing.

    QCAD (free for Windoze and just about every flavor of Unix) is a good
    starting point, if a little basic. Learnt in a couple hours to a
    reasonable level of fluency.

    CAD - "Can't anybody draw?"
     
  13. Agree, on the condition that the "standard part" is built
    appropriately for the application.
    Cheaper ain't always better, though.
    Good point, and better than mine re: radiated EM.
    And never stop.
    Moi? I just wanted to point out that most companies
    allocate tasks according to resumes er skills.
    Hey, that's why I asked the OP if he'd ever bent metal.
    Aside from the skills acquisition, it's extremely satisfying
    to build something unique that not only works, but does so
    better than anything you could have bought ready-made.

    Getting the pro look merely requires inspiration,
    practice, and the "right" tools.
    Or at least tell you what they can and can't do. OTOH
    smaller companies claim they can't afford the software
    (anti-"bells & whistles" mentality) and larger ones won't do
    small runs or one-offs.
    <rant begins>

    The World Is Going To Hell In A Handbasket.

    By the time I'd graduated High School (1970), I'd had two
    years each of Mechanical Drawing, Metal Shop, and Radio Shop
    (among other things). What the HELL are they teaching these
    days??? I know, shop classes are "hazardous"; I blackened,
    cut, and burnt my fingers in those classes, but the benefits
    far outweighed the harm. I guess we make better consumers if
    we aren't allowed to learn how to build our own stuff.

    <rant ends>

    One can always haunt used-book stores for decent texts on
    Mech Drawing (and other stuff they used to teach)...

    Mark L. Fergerson
     
  14. JeffM

    JeffM Guest

    I didn't get my sheepskin until I completed 2 of these courses
    (and that was in the pencil & paper days).

    It wouldn't seem to be that hard to find.
    A check with a junior college which has any technical courses or an
    extension course thru your local government's/school's continuing
    education program
    should do it.
    A high school drafting teacher could point you in a direction.
    If Devry or ITT Tech is nearby, ask them.
     
  15. Bob Masta

    Bob Masta Guest

    To echo what others have said, look for a pre-made
    box where all you need to do is punch/drill the front
    and rear panels.

    You may also be upset, as I was in my early days,
    to discover that for many projects the enclosure and
    controls can end up costing far more than the
    electronics inside. This is a fact of life that I just
    had to get used to, but it sure grated on me!

    Of course, it's no problem if you are building
    expensive systems and can easily absorb
    enclosure costs, but it always seems that there
    a lots of good ideas for smaller products that die on the
    vine once you figure in these little details of
    rea life.





    Bob Masta
    dqatechATdaqartaDOTcom

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    www.daqarta.com
     
  16. Ray

    Ray Guest

    To echo what others have said, look for a pre-made
    I was more interested in the process involved. Telling me to buy
    a ready made box is I suppose not a bad idea, but it doesn't
    teach me anything new. Assume I can absorb the cost and all the
    rest of it, what tools do I need for the design, what experience
    do I need for the design, what knowledge do I need for the
    design, what materials are available, if plastic - what sort of
    materials, what sort of colors, transparant/non transparent,
    patterns and textures. Certain plastics are softer than others.
    How do the design packages/software change when I choose
    different materials.

    Sorry to be so boaring (probably), but I have absolutely no
    knowledge on the subject and I need a sort of overview of
    the process.
     
  17. If you have no mechanical design or drafting experience, go to a
    library and look for books on the topic. You can do entirely adequate
    drawings with pencil and paper - and it might be best to start that
    way, rather than trying to learn a CAD program at the same time.
    I suppose I started (several centuries ago) using commercial cabinets,
    and seeing what materials they used, and how they were put together
    (as well as observing how instruments I used or worked on were
    packaged).

    You might have a look around http://www.hammondmfg.com/ and other
    enclosure manufacturers' sites to see what products are available, and
    what materials are used. Hammond has mechanical drawings of some of
    their products on-line, so you can see what a drawing should look
    like.
     
  18. SammyD

    SammyD Guest

    You can download an extended eval copy of IntelliCAD from www.cadopia.com .
     
  19. So, you want to learn all the stuff a company knows about
    enclosure design, to get "the pro look"? I concur, some
    (paper) drafting texts and/or CAD practice ought to do you a
    lot of good for the final design stage. But before that, you
    also need to consider some other things like:

    Heat management (will the case temp damage any cosmetic
    plastics, do you provide ventilation, active or passive, how
    much, do you need to add a fan, how do you wire it in, will
    you need a bigger fuse, [which gets recursive because you
    have to modify the power supply], is heatsinking components
    to the case OK, are insulators needed, what kind and so on)

    Mechanical issues (how to mount the circuitry bits to the
    box, is it OK if screwheads show, how to stabilize/isolate
    anything vibrating inside, is it gonna sit on anything else
    so will it need antislip feet, if so how large and how
    "nonslippery", will anything sit on it so how strong does it
    need to be, is servicing an issue so how difficult should it
    be to get to replaceable parts like fuses)

    "Real estate" competition on the floor/desktop it'll
    occupy (is a particular shape dictated by styling or is it
    dictated by components)

    and so on.

    That's the main reason prebuilt boxes are so often
    recommended for DIYers; a lot of that work is done for you.
    Granted they're sorta generic, but you can dress them up any
    way you want.

    That's just some of the engineering details. As for
    plastic/metal, the Big Boys often start with styling;
    Marketing cobbles up a shape, texture, and color scheme,
    then Engineering has to contort the hardware to fit. For a
    DIY, it's largely a matter of taste once you get the other
    issues settled (or you can do it like the Big Boys do if you
    don't mind the recursive headaches). Selecting materials to
    satisfy your esthetics then depends on your confidence in
    your abilities to work a given material. I don't know why
    you ask about this re: software; in the Corporate CAD world,
    a solid is a solid in most packages and AFAIK nobody cares
    until the actual toolmaker has to specify drills, punches,
    dies, and so on because as you mention, some are softer,
    brittler, etc. and need special (read expensive) handling.
    As this info comes back to Accounting, they may sign on to
    changes which Marketing has to approve, and so on. Besides,
    if you're gonna do this yourself, why learn something you
    won't need (like expensive software)?

    So look at some commercial "pro look" stuff and think
    about the manufacturer's priorities; was form more important
    than function, the other way around, or did they strike a
    balance? What would you do differently, and why? Is what
    you'd do feasible and/or cost effective?
    Many of us have held jobs in all the fields involved
    (and/or overheard skull sessions in other departments), so
    that's how we got our overview. Nothing teaches like
    experience, but you can try plowing through texts on all
    these subjects and learning at home.

    OTOH depending on your age, lots of companies hold open
    house days where students can tour various departments to
    see how the Big Boys do things. Hell, sometimes they even
    let adults in...

    Oh, and as Bob Masta says, the package may end up costing
    more than the contents. OTOH if all you're investing is your
    time, and you reap all that knowledge, it may be worth it.
    Accounting departments like OJT, too. ;>)

    Mark L. Fergerson
     
  20. ddwyer

    ddwyer Guest

    Sorry to be so boaring (probably), but I have absolutely no
    Your questions demonstrate that the process is working.
    Tooling for unique plastic case is only OK for 100k+
    Entrepreneurs adapt surprising alternative cases check buying a mass
    produced high volume finished product removing the innards and placing
    your circuit inside like a cuckoo
     
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