Introduction: Arduino-Powered Automated Epoxy Resin Dispenser + Turned Skateboard Tap Handles

By Narwhal Labs
About: Narwhal Labs is a community and makerspace that encourages and supports creative building, learning, and experimentation.
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Ever try and dispense and measure your epoxy and get the ratio wrong? Spend lots of time pushing individual pumps only to get a few milliliters of resin at a time? Well have we got a solution for you! Our friend Umit dropped by Narwhal Labs and built this awesome automated epoxy dispenser inspired by everyone's favorite adult beverage dispenser, and powered by an Arduino to do the hard work for us. Follow along in this project to see how we built it. This involved CNC work, laser engraving, electronics, 3d printing and resin - really ran the gamut of STEAM fields here. We provide all of our files freely and open source including models, schematics and code so you make your own and maybe even iterate on Umit's design. And of course, check out our full build video below.

Supplies

Step 1: Making and Obtaining Parts

We love to teach and show off as much of our projects as possible, but we're going to quickly glance over the parts themselves. We cut our plywood on an AvidCNC PRO2448 CNC router and did some hand sanding and roundovers after. Our acrylic panel was cut on our Thunder Laser Nova 35 100W, and our 3D printed parts were printed on our CR-10 variant printers. That said - the attached vectors can be printed on a plotter and used as templates for manual processing of your parts, and printing services, local makers, libraries, or makerspaces would be a great way to get your STLs made if you don't have a 3D printer at home.

Fusion 360 compatible step archives, vectors, and ready-to-print STLs are attached here. Our basic BOM is in the intro. There may be some small things - wire, solder, generic pin and spade connectors, standoffs, etc that you'll need to obtain on your own or pull from your spare parts.

We dispensed the resin and hardener from their original bottles with the cap-barb adapters shown. Full disclosure - this did initially work, but the super low viscosity and surface tension of our thickset hardener basically meant that it leaked out of any place it could possibly leak. We recommend rethinking the solution for the resin and hardener reservoirs.

Attachments

Step 2: Electronics Prep + Code

This epoxy dispenser uses a super simple feedback loop with a load cell to meter epoxy by weight. Both bottles sit on a platform on top of a load cell. As resin is dispensed, the weight dispensed is measured, and multiplied/divided by the right ratio, and hardener is automatically dispensed in the correct amount by weight when the hardener tap is pulled.

*Note!* Epoxy ratios by volume and weight are different! We used TotalBoat Thickset, which is 3:1 by volume, but 100:28 by weight. The ratio is changed by a single line of code - just uncomment the right line for the resin system you're using from this section:

//double mixRatio = 0.45; //TotalBoat High Performance 2:1 Slow or Medium
//double mixRatio = 0.46;//TotalBoat High Performance 2:1 Fast
//double mixRatio = 0.18; //TotalBoat Traditional 5:1 Slow or Fast
//double mixRatio = 0.27; //TotalBoat Traditional Crystal Clear
//double mixRatio = 0.28; //TotalBoat Traditional Tropical Extra Slow
//double mixRatio = 0.83; //TotalBoat TableTop
//double mixRatio = 0.84; //TotalBoat MakerPoxy
//double mixRatio = 0.28; //TotalBoat ThickSet
//double mixRatio = 0.44; //TotalBoat Penetrating Epoxy


Please refer to the attached schematics and code when building your own system. There's some room for improvement in flow rates and dispensing, so we'd love to see what you figure out. This might even be able to be done with peristaltic pumps, compressed air, and more.

Attachments

Step 3: Turned Skateboard and Epoxy Tap Handles (Not Just for Epoxy Dispensers!)

Thanks to our friend Ben at Woby Designs, we have no shortage of broken skateboard cut-offs for fun projects like this. A simple rectangular glue up of some skateboard pieces was cut on an angle at the end, wrapped in polypropylene tape, and filled with some resin to make a cool clear end-cap.

The handle was turned into a more traditional tap handle. The end of our resin was cut on the same angle as the wood block, sanded, polished, and some small vinyl decals were cut to denote the resin and hardener.

A small 1/4-20 insert nut was installed in the bottom. This process isn't just applicable to an epoxy tap - you can use this for your homebrew keezer, brewery or more.

Step 4: Final Assembly

With all of our parts made, code coded, electronics soldered - it's time to assemble everything. The basic structure is essentially a box. We assembled most of it with glue and brad nails, and the occasional self-sealing stem bolt (any trekkies out there?). Kidding - self-drilling trim screw. Please reference our model and photos for assembly of the components. be sure to appropriately hose clamp your vinyl hoses to the barb fittings, and use thread sealant PTFE tape on any plumbing threads. The barbs/solenoids are a nice friction fit into the frame of the dispenser.

Step 5: Dispense Your Resin!

But first - a party trick. Our friend Xyla also happens to be friends with Umit, and we wanted to do a little homage to her clear, LED lit "party kayak". A simple strip of some inexpensive RGBW LEDs with the cheap controller they came with under our acrylic panel made for an awesome edge-lit effect. And even better - they're powered by the same 12V power supply that runs the rest of our contraption!

You'll also notice a melamine drip tray - we recommend making one for any stray epoxy. It's also the perfect size to fit a disposable paint tray liner under it for easy cleanup.

We appreciate you checking out our video and project! We know this isn't something most will replicate exactly, but we hope there's some helpful information here for your own projects. Were you able to improve on our design? Do you have any suggestions? Let us know in the comments and be sure to tag us on social media!