Resin Cast Project Enclosure

Project boxes available off the shelf always seem to be just too smahttp://blog.rhysgoodwin.com/wp-admin/post.php?post=973&action=edit&message=1ll or way too big!  This is especially true here in New Zealand where the options between JayCar and SurplusTronics are fairly limited.  I needed a specific size to house a project I’m working on so I decided to cast my own in Polyester Resin.  I hope the details which follow will prove helpful.

 

 

Draw up a design – I used Google Sketch up.  Make a box of which the inner dimensions represent the outer dimensions of your final enclosure.  I used blocks of pre-dressed pine.  You’ll want to use something reasonably solid and screw it down to a base board so you get nice square vertical sides.  For a base I used melamine board – it’s nice and smooth and the resin won’t bond to it.  Your local kitchen builder will give you off cuts for free if they’re nice.

 

Wrap the blocks with masking tape.  This provides three benefits:

  1. The waxy surface of the tape acts as a barrier between the wood the resin and makes de-molding easier
  2. It creates a nice flat surface to mold against
  3. Reduces the chance the resin leaking out because it forms a seal as the blocks are pressed together then screwed down

 

 

 

Put a mark on the side of at least one of the walls to indicate the height of the enclosure, this is where you will pour the resin up to.

Accuracy when cutting the wood is important if you want a professional looking result.  Decide on a tolerance and stick to it.  If you cut a length and it’s not within tolerance then re-do it.  If you don’t, you’re sure to be disappointed with the end result.  Resist the “She’ll be right” temptation – it won’t be right!  Errors are amplified at each stage of the process.  I worked to 0.5mm.  For me this was an excellent practice exercise in hand-saw and measuring accuracy.

 

Make a shape of which the outer dimensions will represent the inner dimensions of your finished enclosure.  This is where you decide on the thickness of the enclosure walls.  I made over-sized corners so that I had solid pillars to screw into.

 

Unless you’ve got a dead level work bench you’ll probably need to set up a little platform that you can level off with screws – like this:

 

 

Mix up some resin and pour it into the mold up to the height you marked.  Mix the resin and MEKP as per the instructions.  I mixed towards the higher end of the 1%-2% ratio, about 1.7%.  And please be careful with the MEKP.  Don’t even think of going near it without eye protection and gloves.  MEKP is a severe skin irritant and can cause progressive corrosive damage or blindness.

 

 

Now the fun bit.  After a few hours the resin will be hard enough to remove it from the mold.  Unscrew and remove the inner blocks and as many outer blocks as you need to get the enclosure out.

It will be a bit hard to get out because the resin shrinks a little bit as it cures.  It will probably also still be a bit sticky when it comes out.

 

 

Now on to the top and bottom sections.  You could just cut some flat plexi-glass for this but while we’re at it we might as well just cast them.  Clean up the enclosure with sand paper.  I used wet/dry from 120 grit up to 400.

Drill and tap the corners.

 

 

Use making tape to mask off the areas where the resin will touch.  Screw in 4 countersunk lid screws leaving them out to the height you want the thickness of top lid to be (I made mine 4mm).  Make sure they are all exactly the same height.

 

 

Reassemble the outer box of the mold on a new piece of melamine and place the enclosure back in, screws down.  The enclosure will have shrunk since it was last in the mold so use multiple layers of masking tape as packers to center it (use an even number of layers on each opposing side).

 

Make sure your platform is dead level and pour the resin into the mold so it just comes up over the sides of the enclosure.  This will make a locking lip on the lid.

 

After a few hours you can de-mold the box with lid attached.  It will be stuck to the board but just slowly ease it away, you almost have to peel it up. Don’t try to knock or tap it.  With a bit of luck you’ll be able to remove the screws from lid and take the lid off without too much difficulty.  Making the lid this way takes care of the screw holes and countersinking.

 

Now repeat the process for bottom lid.  For the bottom I didn’t mask it off because I wanted it sealed on – I don’t need to remove it.  I also made it a bit thicker so it’s nice and solid for mounting to.

 

Once you’re all done you can sand/polish the enclosure as much or as little as you like.  I left it with a frosted look but you could shine it up to be completely transparent if you wanted.  I also removed the thread from the holes in the lid.

 

 

 

Well that’s quite a process! But the result is good and it’s good practice for accuracy, woodwork and resin casting.  I tried a number of methods before I came up this and it’s by no means perfected – as always I’m keen to hear your ideas.

casting, electronics, enclosure, mold, plastic, polyester, project box, resin

38 Responses to Resin Cast Project Enclosure

  1. Joel September 27, 2011 at 11:39 pm #

    I’m trying to make CNC part with resin. This article inspired me. Thanks for sharing!

    • RhysGoodwin September 30, 2011 at 10:48 am #

      Cheers Joel! Thanks for stopping by.

  2. Sergio May 2, 2011 at 11:28 am #

    Great work! Hello from Wellington.

  3. Erwin Ried April 30, 2011 at 7:13 am #

    Wow! congrats, looks very nice. Can you provide the exact resin name? so I can look it in eBay or some online store?

    Thanks!

    • RhysGoodwin May 2, 2011 at 11:54 pm #

      Hi Erwin,

      It’s called water clear polyester casting resin.

      Cheers,
      Rhys

  4. A.Wyatt April 27, 2011 at 3:21 am #

    Pam if I’m not mistaken is a NON-Stick Cooking spray. here you can check it out online.

    http://www.pamcookingspray.com/pages/history/index.jsp

    also Rhys, you did an outstanding job, i will using your technique with something other than the poly resin. thank you for posting this.

  5. Carlo Calica April 26, 2011 at 7:56 pm #

    What was the weight and dimensions of the final box? It looks like it might be a bit heavy (but very strong). Great job, very inspiring.

    • RhysGoodwin May 2, 2011 at 11:50 pm #

      Hi Carlo,
      Yeah it’s not light – just under 500 grams. Fortunately for my application weight is not an issue.
      Outer dimensions: 180x95x40(mm)
      Inner dimensions: 160x75x30(mm)

      Cheers,
      Rhys

  6. jd April 26, 2011 at 7:33 pm #

    That’s a spiffy box! Learned a trick or two, thanks for sharing!

  7. Tom April 26, 2011 at 4:16 pm #

    Brilliant! Thanks for taking the time to document this.

  8. Andrew April 26, 2011 at 3:27 pm #

    Nice work, which store/stores/brand do you buy your resin from? I’m curious to give something like this a go – cheers ;)

    • RhysGoodwin April 26, 2011 at 7:48 pm #

      Hi Andrew,

      I get all my supplies from New Zealand Fibreglass in Panmure, Auckland. The resin is about $30 NZD for 1KG and comes with the MEKP. No specific brand, I guess they just buy it in bulk and put it into smaller tins. They have all the fibre glass reinforcing, waxes, tools etc too.

      Cheers,
      Rhys

  9. sky17 April 26, 2011 at 1:05 pm #

    Nice work, might be able to strengthen it by dropping some fiberglass before you pour in the resin.

  10. nobody April 26, 2011 at 11:29 am #

    maybe put a bit of grease/oil on the screws, just enough to make removing them from the lid easier.

    i had this vaguely in mind but this is a very nice idea.

    • RhysGoodwin April 26, 2011 at 12:19 pm #

      Yeah good idea. Release wax would be best probably. I’m guessing you have to be a bit careful as some oils or greases might affect the curing. Thanks for stopping by.

      Cheers,
      Rhys

  11. Wouter April 26, 2011 at 11:04 am #

    Does the box continue to smell like polyester for a long time?

    • RhysGoodwin April 26, 2011 at 12:13 pm #

      Hi Wouter, It has a slight smell for a few days but eventually goes away.

  12. Steve April 26, 2011 at 8:37 am #

    Nice work. That turned out really well. @ Jonathan, you can get dyes and tints from resin suppliers to make the resin whatever color you want. Dyes are transparent while tints block light. Or the other way around, I can never remember.

    • RhysGoodwin April 26, 2011 at 12:10 pm #

      Cheers Steve. I think I’ll have to have a go at coloring it next time.

  13. Bradley G April 26, 2011 at 7:55 am #

    Urethane resins are very user-friendly and a lot less fumey than Polyester. Smooth-On’s Smoothcast series are a favorite among moldmaking/casting geeks. No toxicity concerns, either. MEKP is nasty stuff.

    • RhysGoodwin April 26, 2011 at 12:08 pm #

      Thanks Bradley. I’ll look to that, the polyester is pretty strong smelling stuff. I also wouldn’t mind a resin that was a bit tougher the polyester can be a bit brittle.

      Cheers,
      Rhys

      • Bradley G April 26, 2011 at 2:39 pm #

        I like Smoothcast-300 for general purpose applications like this. It’s a two part system mixed 1:1 so it’s very easy (mix REALLY thoroughly however) it has no noticeable odor at all. It is opaque (white) however, so if you’re in love with the semi-transparency of the polyester you’ll have to use a different system. They also sell it in very fast (5 min) setting time as 300Q (presumably for Quick?)

        Where brittleness is concerned, you can get Urethane resins in levels of flexibility from stuff they use (i kid you not) for impact tooling, all the way down to stuff so soft as to be nearly rubber (this is what they make a lot of gun props out of in the movies so they don’t hurt clumsy actors)

        • RhysGoodwin April 26, 2011 at 7:40 pm #

          Cheers Bradley, I’ll have to try to hunt down some of this stuff over here which I suspect is going to be a bit difficult.

          • Mark May 1, 2011 at 10:41 pm #

            Try topmark and Sculkpture workshop. Both have urethanes and smooth-on. But her ein NZ this stuff is super expensive… :-(
            http://topmark.co.nz/articlelive/pages/Products/
            Thanks for the link to NZ fiberglass. Did not know that.
            Also check out these guys for epoxy
            http://www.hardcoresurf.co.nz/products/manufacturing/manufacturing-materials.aspx

          • RhysGoodwin May 3, 2011 at 12:00 am #

            Thanks Mark. Yeah that’s the problem sometimes in NZ, cost makes these thing a bit prohibitive or non-sensible. At the end day this project has certainly cost me more than even getting a box from overseas but it was for the interest of doing it and developing the methodology too.

            -Sorry just realized your comment wasn’t approved because it had links-

            Cheers,
            Rhys

  14. Chris W April 26, 2011 at 7:34 am #

    That sir is awesome. I like this idea even better than my idea of making vacuformed custom enclosures. I’ll still be using the vacuform for certain situations, but this will be more useful for projects that don’t need a fancy box.

    • RhysGoodwin April 26, 2011 at 12:05 pm #

      Thanks Chris. I just had a google of vacuforming, looks very interesting I’ve not seen this before. Definitely something to keep in mind. Cheers!

  15. Jonathan DeWitt April 26, 2011 at 7:24 am #

    This is an AMAZING idea! Can’t wait to try this myself. Any idea what you would have to do to color the resin black or any other color?

    • RhysGoodwin April 26, 2011 at 11:58 am #

      Cheers, Jonathan. You can get pigments and dyes which you add to the resin although I’ve never tried them.

  16. DrF April 26, 2011 at 7:05 am #

    You make that look too easy, I can see my attempt ending in a very deformed mass thats meant to be a box :)

    • RhysGoodwin April 26, 2011 at 11:56 am #

      Haha, yeah I can tell you I had a few “deformed” attempts before I got it to look like this! :)

  17. iToast April 26, 2011 at 7:03 am #

    i LOVE it. But how toxic is the stuff after it hardened? Like if i touch it and work with it, do i have to wash my hands before touching other things as it leaves a toxic thing on your hands? Cuz i wan’t to use this for a different project, with more steps D: btw, try pam for a small small mold,it might work better! or a whole melane box!

    • RhysGoodwin April 26, 2011 at 11:54 am #

      Hi iToast,

      Once it cures it should be fine, I can’t see it being toxic in any way. It’s just like any other hard plastic. Although I’m no chemist and I’d certainly be doing some research if I intended to drink out of it. You mention ‘pam’ as a possible mold medium, could you explain? (Maybe called something different over here). What project do you have in mind?

      Cheers,
      Rhys

      • Odomus April 27, 2011 at 1:27 am #

        PAM, is a Non Stick Cooking Spray for Releasing foods off pans, so they wont burn. If anything, aerosol vegtable oil will work just as good…. they sell oil sprayers for cooking tha tyou add your own oil too…. especially where you live. So you should be ok if you dont have a specific kind of non stick cooking spray.

        Mind you I have used PAM, dont get the butter or flavored sprays(i figure any brand as well not just PAM), for one, it tends to stick to the resin, and 2 if it doesnt stick, THe Resin HOLDS the smell, so if you like the garlic oil spray and it releases by all means use it(could keep away some critters if you use it outside theres a thought).

        If I dont want it to smell, I usually use the Veg Oil straight sprayed. Or I use EV Olive Oil, which is a little smellier, but I find it washes off the Resin eaiser. But thoes 2 are the best I have found out for all my Resin Castings from FG, to Straight Polys to Plastic, to Rubber, to Jello ;)

        Hope this helps.

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