DIY resin cast project box


[Rhys] wrote in to share a custom project box he built from scratch using polyester resin. He states that in New Zealand, he tends to have problems finding the perfect project box. They are typically too big or small to get the job done, so he figured he might as well just build his own to spec.

Using Google SketchUp, he designed his ideal project box, then got busy building wooden molds. He scored some free melamine scraps from a local company, which he used to build the base of his molding rig. Once the inner and outer molds were built, he secured them to his base and mixed up some polyester resin.

A few hours later, he pulled apart his molds and smoothed out his project box with some sandpaper. He drilled and tapped screw holes, then prepared to make a lid and base for the box.

He admits that the process is quite involved, but there is something to be said for building yourself an enclosure made specifically for the project it is going to house. If you are looking to do something similar be sure to check out his blog – he offers up some sound resin casting tips, as well as some pitfalls to avoid.


  1. Tex© says:

    this is a really great idea XD

  2. eric says:

    This looks really nice! Well done.

  3. CutThroughStuffGuy says:

    3D Printer = perfect enclosure production machine.

  4. Barefoot says:

    CNC = perfect enclosure mold production machine.

    OTOH, No 3D Printer + No CNC = the average schlub who has to resort to (gasp!) *hand tools* !!

  5. Bob D says:

    @CutThroughStuffGuy Unless you don’t want it to look like it was made from spaghetti. And you don’t feel like paying $1K+ for a enclosure maker.

    I do both resin casting and 3d printing and I enjoy resin casting much better. You can get better detail than even the highest end 3d printers, and can usually produce parts much faster. And the ~doing~ of it is much more fun than watching a printer print.

    The only suggestions I’d have for Rhys is that he’s always going to have lots of cleanup when casting from wood molds. Silicone is usually the way to go. It takes a few tries to learn how to work with it correctly, and it increases the cost of the project, but they require just a little sprue cleanup and can be reused a few dozen times. (Though if you’re just doing one-offs, wood is perfectly fine, though simply coating it with Vaseline will work as a mold release without effecting the mold shape as much as tape.)

  6. Michael Nielsen says:

    How high temperature and what pressure can this final case withstand? Could it be used to build a shisha/hookah/water pipe?

    Great job – looks very pro! Gotta try to find this in some store nearby!

  7. Whatnot says:

    Ever since the chinese made me aware of how poisonous melamine is I’m hesitant to use it as a building material, I’m not sure I want the dust in my vicinity.

    If it’s really that bad? You decide for yourself:

  8. komradebob says:

    Now if someone can just come up with a good/cheap way to punch holes for DB{9,15,25} connectors.

    For better strength, add in a little fibreglass mat. Pretty soon you’ll be making your own GRP automobile bodies! :)

    • N0LKK says:

      In this method you can “cast” any holes needed for connecters etc. That or work the finished enclosure like you would wood. Greenlee chassis punched may work on thinner plastic, but at~$460 for a DB 9 punch few home shops are going to have that in the tool cabinet.

    • N0LKK says:

      Figuratively speaking the finished product feature must be bullet proof. I believe it should be possible to cast the bottom om the box at the same times the sides are cast A nice on-line write up of process that has have covered in passed in print media. The WWW has been made a bit more complete.

  9. CutThroughStuffGuy says:

    Better throw out your Mr. Clean “Magic Erasers” / aka fine white foam melamine “sandpaper”.

    “Could it be used to build a shisha/hookah/water pipe?”

    Resin is not suitable for this. It will melt and produce toxic vapors. Resins are generally BPA based epoxies or MDI/ISO based urethanes.

    I second the silicone mold idea. I was thinking more of the high end 3d printers rather than a reprap. I don’t consider those 3d printers – they are toys. Getting better but functionally limited due to limitations inherent to their design.

    You are also correct that silicone will capture more detail than the best 3d printers. Some people have taken molds of lotus leafs and the silicone will take on the “water completely beads up into a sphere” effect. It is rather neat actually.

  10. chemist dood says:


    Agreed, poly resin makes a great adhesive for laminates, but is horribly toxic and odorous. He set a good thickness as the stuff is a bit brittle when thinner.

  11. Diego says:

    I think you have to *eat* a fair amount of melamine in order to be considered harmful.

    The chinese milk scandal was about the adulteration of dairy products, adding melamine in place of genuine milk. Quite insane indeed!

  12. Hacksaw says:

    @Whatnot…the State of California has determined Oak to be a carcinogen…

  13. Renee says:

    I like multi-discipline stuff like this. Mold making is extremely useful.

    I’ve thought about getting a reprap/makerbot in order to make master molds and then casting them in whatever material I want.

    Imagine making a complex shape on a makerbot and then casting it in aluminum.

  14. Pedro says:

    My resins usually turn out a bit yellow. I normally add a fair amount of MEKP (2.5%/3%) to make the resin cure faster (it’s occasionally kinda cold out in my workshop in the UK). Would using a slower cure improve the colouring of my resins, or should I just start buying more expensive resin?

  15. Luke says:

    Polyester resins are nasty, styrene-offgassing stuff. Vinylester resins are not much better, though more waterproof and stronger. If you want something safer, use a proper epoxy. Modern epoxies like MAS, East Systems, West Systems, Raka etc are low in VOCs and such and much stronger than polyester resin. While somewhat more expensive, the cost for small volumes is not prohibitive ($50/liter vs ~$20 IIRC).

    Rather than using fiberglass mat, consider woven fiberglass. If low strength is required and you want near transparency, very sheer fiberglass fabrics are available at RC model shops at less than one ounce per yard (think window sheers or panty hose). These can make a resin quite strong, though not as strong as a heavy 3+ oz. fabric. Those epoxy companies can provide lots of useful info online on how to use their products.

    Neither the resins nor epoxies are UV resistant, so if your project is going to be in the sun, paint it or cover with a clear UV absorbing urethane varnish.

  16. Raab says:

    @ whatnot

    the melamine wiki page you referenced differs from the melamine veneered board used in the casting. the veneer is a polymer of melamine and would have different properties to melamine compound

  17. CutThroughStuffGuy says:

    “Resins” almost always yellow or come with a yellow tint. There are some clear ones available though but you will probably have to look for them specifically.

    Resins can be lots and lots of different chemistries though.

    Epoxies are low in VOC, yes, but they almost always contain bisphenol-A (BPA).

  18. xoxplox says:

    Is there any nontoxic resin?

  19. Whatnot says:

    @raab Thanks for actually thinking about it and taking note of what I talked about, and I’m not saying the stuff is so dangerous in its normal proper use, but if you start drilling and sanding and such you just get situations I myself would not feel comfortable with, and I’m not sure it being a polymer helps when it’s ground to a fine dust and inhaled and absorbed through the skin and depending on the circumstance maybe even ingested.
    Now I’m not saying you are doomed when you do but to me its something I’d prefer to avoid by looking for alternative materials.

    To the others that commented on my comment:
    No I don’t use a mr clean magic eraser.
    And you could actually take a look at the link I provided, and see how all countries and the WHO set limits and how the FDA even drastically revised theirs to make a much smaller amount safe than they advised beforehand (and if you then still mock it as if the concept of toxicity is a fable I can safely relegate you to belonging to the extremely dumb and perhaps even insane).
    And you would also have noticed that it can be harmful when ingested OR inhaled OR even can pass through the skin..
    There are mitigating factors though, it’s a natural stuff and it should not be a problem at all in normal levels, but seriously you can’t say it’s can’t possibly be a problem either, and why take the risk? Surely there are other materials you can use that don’t have such known risks when you start grinding and drilling and filing away at it.

  20. rickroll says:

    Nice project. Thanks for posting.

    For squarish boxes though, wouldn’t it be easier to cut pieces from a sheet (eg. Plexiglas), and then fasten/glue/fit/weld to get the box?

    Also I don’t know about New Zealand, but you can usually get suitable enclosures ready made from retail sources, mail order if necessary.

    Ultimately it might be cheapest and easiest to just buy it.

  21. cgmark says:

    The only downside I see to this is the cost of the resins. I have looked at casting things in resin in the past and the cost just doesn’t seem to justify it.

    A much cheaper approach is polymer clay. Polymer clay is basically powdered plastic mixed with a mineral oil that evaporates when heated and made into a clay. Roll out some sheets flat and bake in the oven for 15 minutes. Join the sheets together with the same clay, make rounded corners or special shapes and then bake again. It can be drilled, sanded, painted. Cost is about $6 in the USA for enough to make a decent enclosure and no toxic chemicals involved.

  22. Leithoa says:

    Vacuforming would be faster for all but the most complex enclosure designs. As with the casting, creating the molds is the most time consuming step.

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