Transparent rubber enclosures

This clear rubber puck serves as the enclosure for a diy mp3 player. The wires encapsulated in the rubber are just there for looks but the utility of using this material as a case is fascinating.  Alas, there’s no details on the material other than that it’s clear rubber. Update: [Reboots] picked up on some info that we originally missed. Looks like this is made from some Smooth-On PCM 780 urethane rubber.

We’ve looked into casting our own molds from silicone rubber in the past.  That may be the process used here but we can’t tell what allows the two halves to be pried apart. We’ve embedded video after the break that details casting rubber around a part in one solid block, then cutting the rubber off of that to create a mold. We’re also familiar with the mold making kits from Tap plastics but as far as we know, they’re always colored and never clear.

We keep our eyes peeled for new prototyping products and we want to know more about the materials and the process used to make this cylindrical elastomer. If you’ve got the goods on how this is done, please share them in the comments.

[via Gizmo Watch]

Comments

  1. googfan says:

    waterproof i suppose.

  2. Arcylon says:
  3. wdfowty says:

    what? no diy headphones?

  4. reboots says:

    No details unless you bother exploring the links in the article, that is.

    About Casting Materials:

    http://www.electroniccrafts.org/?n=Details.CastingMaterial

  5. The Moogle says:

    Clear casting resin nuff said

  6. bro says:

    When you have to encase something small, (like the mp3 player) you could use some hotglue as well.

    Use some oil on the inside of a tinbox, add some glue, let it dry, insert your pcb, fill the box.

    To get a nice top-surface you just have to cut off the top.

  7. dougefresh says:

    I was gonna say clear resin, but was beat to it eye c… Although the resin I’ve used turned a little yellow.

  8. SomeRandomDudeYouProbablyDontKnow says:

    if you check the photos it shows them using rubber bands to hold the two halves together. I guess they removed the rubber bands for most of the close ups…

  9. big dick johnny says:

    That hot glue yields nice results as one commenter suggested. I’ve used it before, just as rugged, even flexes a little but not enough to damage pcb

    expect thermal issues though on application processors, dsps etc

  10. chrisla says:

    I’m not sure about PMC-780, but I’ve used PMC-790 at length. It smelled HORRIBLE and outgassed forever (years later the stuff is still outgassing). Every year when we open the freshly rented truck at Burningman for inspection, they say “what’s that smell!” Also watch out for this stuff getting brittle over time if not mixed just right.

  11. overengineer says:

    I’ve used hot glue to “pot” many a small connector/adapter. If you just need a way to protect and give a durable shell to a simple circuit (that won’t ever require modifications), not a whole lot can beat hot glue as a solution. One way to get clean faces is “thermal” mats — heat-proof rubber mats often sold at hobby shops to protect your table also have the tendency to not allow hardened glue to stick to them. With a small enough application, you can just apply the glue one side at a time, using the mat to provide a flat edge. It works in a pinch, though finding a better form is a good idea for anything much larger than a little dead-bug circuitry.

  12. localroger says:

    Making the parts pry-apartable is a matter of using one part as part of the mold for the other. start with the outside mold, say a large bottle with a screw cap. Cut the bottom off so that the screw cap becomes the bottom. Affix a void form to the cap, turn it over, spray the whole thing with mold release, and pour in the silicone.

    Now when that cures, turn it over, affix a smaller void form to the inside of the hollow (you might need to make two of these outsides if the void form affixing ruins one), coat with mold release, and pour more silicone. You now have two pieces that will slip fit with a void in the center.

  13. ... says:

    One thing to watch out for with hot glue is some brands are very highly conductive, others have a huge dialectic constant. I have had good luck with polyurethane resin (you can buy gallon jugs of it for doing fiberglass work at home improvement stores)

  14. Mike LM says:

    Long time ago I used some RTV compounds from Dow Corning especially designed for encapsulating and/or protecting electronic circuits. In special, check their elastoplastic coatings.

    Please, have a look at:

    http://www.dowcorning.com/content/etronics/etronicscoat/default.asp?e=Electronics+Products

  15. charlie says:

    for hobby use, stay away from urethane and polyester resin. most or that stuff is seriously toxic, and can smell for a long time as mentioned. best to use a platinum cure silicone, and epoxy resin. i use sorta-clear 40 silicone from smooth-on, and easycast clear casting epoxy.(pigments can be added to both for desired color) the epoxy, unfortunately, is quite pliable when cast to smaller forms, and not quite “water clear”. it is, however, the best solution i have found for embedding items such as this.

  16. Steve says:

    Sometimes we make rubber molds around IMU’s to reduce vibrations in the sensors.

  17. Headbonk says:

    I was thinking of encasing the circuit board of a thumbdrive I have that lost it’s case in resin, but I wasn’t sure that it wouldn’t screw things up (corrosive, conductive, heat, etc…)

    Looks like I’ve got lots of choices…

  18. Daniel says:

    Another vote for hotglue. I used it back in the day to mold garman gps data connectors. I have also used a pill bottle and epoxy to seal a home made diode block for my 82 XJ650 Maxim.

  19. Stunmonkey says:

    I am a jeweler, we use this stuff to make molds of delicate items. You can make them separate down the middle quite easily.

    When you use clear RTV, pour one half first, wait the 24 hours for the cure, spray on a light coat of mold release spray, then pour the second half.

    When that cures you have a two-part clear rubber unit that opens right up.

  20. Gert says:

    I just use transparant epoxy.
    Cut out the bottom of a bottle and i form a layer of expoxy then i put in the chip and put on another surface of epoxy.

    Then i let it cure in my fridge at a temperature of 10 to 15 Celsius/
    50 to 59 Fahrenheit/
    283,15 to 288,15 Kelvin.

    The low temperature will slow down the curing process and give the air in the epoxy the time to escape. Thus preventing ugly bubbles.

    I’d also advise to cut down any sharp corners, it can cut you like a knife.

  21. Nigel says:

    Nice one Hackaday. I was looking for a pourable silicone product to make a mould.. i came across one which lets you paste it on.. it wasnt clear though.

    im not sure any of these links carry food grade ‘silicone’

  22. Patrick says:

    We use a lot of Flexane-80 at work for potting small circuits, cable splices and so forth. Hardly outgasses at all, takes a while to harden and a release agent is HEAVILY recommended but, well, when you need something to be pretty resilient and absolutely and undoubtedly watertight at 4000m/13000ft depth at sea it’s hard to beat.

    As a footnote, machined/CNCed Delrin makes fantastic molds.

  23. bothersaidpooh says:

    Shapelock for the base box, then silicone over the top to form a lid.. :)

    If you are clever you can also make a custom two part enclosure with a reprap to hold the components securely, that provides some measure of shock protection.

    If you are using resins etc the “secret” of making perfect bubble free enclosures is to pull a vacuum on the parts using a bicycle pump or car compressor in reverse.

    Oh and don’t forget that many resins heat up when curing, use thin layers or you may crack the resin or components on the PCB. One way to avoid this is to pre-encase the delicate parts in silicone droplets before encapsulating.

  24. Jerzee says:

    I wonder how well a product like Envirotex Lite® (http://www.creative-wholesale.com/Envirotex%20Lite.htm) would work. My father uses it for decks when building R/C sailboats. It seems easy enough to work with and produces a beautiful clear finish.

  25. Stunmonkey says:

    Um, I already pointed out how it was done.

    Put in form. Pour fist half. Cure. Mold release spray. Pour second half. Cure. Remove form. Wipe hands on pants.

    Urethane, RTV, or anything similar, it works.

  26. Oren Beck says:

    Next time you’re in a car junkyard, look at the Mopar external alternator regulators or Ford “Large Die Cast Box” ignition modules. They are an example of combining Thermal Paths with Encapsulation.

    One module I used to pot for Mocom VHF gear needed waterproofing and Thermal Path. We embedded it in a soft,stays flexible HV Silicone Putty before potting the blob in ordinary Bondo. With a Thermal path made from thinnish sheet metal extending from the Transistor’s tab. and the unembedded end of that metal strip Thermal Grease coupled to the Radio’s frame.. IIRC that they tended to outlast the radio’s remaining service life.

  27. bob says:

    I found a number of casting resin manufacturers, this is just one example:

    http://www.alumilite.com/

    I thought polyurethane products involve the use of can be dangerous isocyanate though.

    Barring that, you can always use solid diamond, just be aware that diamonds are really HARD to machine.

  28. moe_hominid says:

    Sometimes we make rubber molds around IED’s to reduce vibrations in the sensors.

  29. jeditalian says:

    Plasti-dip? pretty sure they make it in ‘clear’ nowadays. i wish they would fill those fm radio wristwatches & stuff with this because if i take them apart i permanently F up the tinymagnetwirecoils.

  30. CH says:

    @jeditalian
    Plastidip sticks well to itself, so maybe encapsulation would be OK, but It can peel when wrapped around objects. Also, A bit expensive, no?

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