Introduction: Cast a USB Key in Resin
This tutorial will show you a simple and inexpensive method to cast a USB key / thumb drive in resin.
I have always wanted to cast a USB key in resin, but I wanted to do it cheaply without the complexity of creating a silicone or 3D printed mold.
- A USB key / thumb drive
- Epoxy resin mix supplies (resin, mixing cup, eyedropper, toothpicks, etc.)
- Heat gun or torch (optional for removing bubbles from resin)
- Clear plastic sheet (from packaging, laminate, 2L soda bottle, etc.)
- Hot glue gun
- Baby oil or resin mold release
- Scotch tape
- Q-tips and/or coffee filters
- X-Acto knife or razor blade
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Step 1: Prepare Your USB Key
Begin by carefully removing the outer shell of your USB key / thumb drive. Clean away any dust, rust, or debris and ensure the USB key is dry. Determine how much of the tip you want to leave clear of resin and place two layers of scotch tape across that area. The tape serves two purposes - to protect the tip from resin exposure and to suspend the USB key in the mold.
Step 2: Fold the Plastic
I used plastic from toy packaging. This plastic is frequently used to package many products like electronics, toys, and so on. You could also use thick laminating sheets or plastic cut from a 2L soda bottle. If you use plastic cut from a bottle, I would suggest gently heating it to flatten it out. You don't need much.
Cut a strip of the plastic that is wider than the length of your USB key and at least three times longer than the width of the USB key. You can always cut more off later when you're done folding, so it's better to begin with more than you need.
I creased the plastic using the edge of a table, placing my USB key on the plastic to judge the relative widths. I didn't use any markers, but you may wish to mark the edge before creasing the plastic. Use whatever method works best for you.
Leave both ends longer than needed. The starting end can be trimmed after you are done folding. The goal is to create a free-standing rectangle in which the starting end is flush against the terminal end. The terminal end should have some excess to provide support in the next step.
The plastic I used tolerated folding and unfolding well without breaking. If you make a mistake, start over with a new piece of plastic or apply some heat to re-flatten the plastic. When you're sure of your creases, you can make them sharper by sliding something hard like a pair of scissors over the edge of the fold.
Trim the width (height) of the plastic so that it's a few millimeters longer than your USB key (or as long as desired for your USB key).
Step 3: Glue the Mold in Place
Cut a second piece of plastic to serve as the base of your mold.
I used a hot glue gun to secure the plastic, but you may want to use a different type of glue depending on your needs. A glue gun worked well for me, although at the base the heat from the glue caused part of the crease to lose its sharp edges (see the third image). Something like a cyanoacrylate glue (i.e.: Krazy Glue) might work better, but it's important to control the flow of the glue to avoid getting any glue inside the mold, which will affect your cast.
I began by applying a small amount of hot glue to the corner where the starting end meets the terminal end and the base. I then drew a line of glue up the edge to secure the rectangular shape. Finally I applied glue around the base of the mold to secure it in place. Again, if you are using hot glue, be careful around the base because the heat can cause the creases in the plastic to lose their sharpness.
It is important to line the entire perimeter of the base with glue to avoid resin leaking out the edge.
Step 4: Prepare the Mold
It's important to prepare your mold before you mix the resin. This gives you sufficient time to ensure the mold is adequately coated with baby oil and to suspend your USB key in the mold.
I used a q-tip to swab a small amount of baby oil inside the mold. Because some q-tips can leave behind lint or fibers, you may wish to use another tool. Coffee filters are an excellent alternative because they leave virtually no lint behind. You can cut a piece of coffee filter and place it over the end of a q-tip or simply shape the filter paper so it can be used to swab the inside of the mold. You only need a very thin layer.
Place your USB key inside the mold to ensure it sits as expected. The scotch tape you applied in Step 1 will support the USB key. If it does not sit centered in the mold, adjust / re-apply scotch tape. Remove the USB key at the end of this step.
Step 5: Mix the Resin
If you've worked with epoxy resin before, then you know how to mix the epoxy with the hardener, typically in a 1:1 ratio. Follow the instructions for the brand of resin you use. For this project I used Art 'N Glow Clear Casting and Coating Epoxy Resin. It costs about $25 for 16oz and can be found at most craft stores or online. There are many brands to choose from.
Mixing: most resin kits include popsicle sticks for mixing. I strongly advise against using popsicle sticks because they have a lot of surface area and introduce bubbles during mixing. Instead I use toothpicks, which minimize the amount of surface area and resulting bubbles. I slowly mix for about 5 minutes until I can't see any streaks.
If you are having trouble with bubbles, you can briefly (1-3 seconds) flame torch or heat gun the surface to pop bubbles. Alternatively you may gently heat the resin by placing your mixing cup in warm water. If you heat the resin, be very careful because heat accelerates the curing process, leaving you with a more viscous liquid and less working time.
If you want to add pigments or glitter, do so now.
Step 6: Add Resin to the Mold and Cast the USB Key
The USB key will take up more volume than you might expect so begin by filling only about half the mold with resin. I used a plastic eyedropper to add the resin, being careful to avoid introducing bubbles into the liquid.
Slowly lower the USB key into the mold. If bubbles attach to the USB key, gently move the USB key up and down to dislodge them. Use an eyedropper to fill in the remaining airspace in the mold. Pop surface bubbles with a toothpick or hot air.
As with most resin casts, you want a bulge of resin at the surface, which will level out as the resin cures. Don't be afraid to use more resin than you need. I allowed resin to spill over the edge. The thin excess layer is easy to remove after the resin cures. During or after curing, if you discover the surface has sunk lower than desired, it's easy to mix a little more resin to add to the mold.
In Step 4 you checked that the USB key would stay centered on its own when suspended in the mold. Ensure the USB key is centered by viewing it from both the front and the side. It is important to watch the mold for the next 1-2 hours to ensure it remains centered. If it starts to deviate from the center, you can gently push it to return it to the center. The resin will become very viscous within 1-2 hours, so any corrections should be made in this time frame. If needed, use a piece of scotch tape to create tension on one side to help center it.
Allow the resin to cure. Most craft resins require 24 hours to cure before removing them from the mold.
Step 7: Remove the USB Key From the Mold
Most craft resin requires 24 hours to cure for mold removal and then 48-72 hours to fully solidify. I recommend removing the USB key at the mold removal cure point (24 hours). This leaves any excess resin soft and easier to cut through. This also leaves the resin more vulnerable to scratches during this process, so be careful with your tools. You may want to wear gloves to avoid scratching the resin with your nails.
Gently pull the mold apart at the seam. If you used hot glue, it does not create a strong bond, so it should be fairly easy to pull it away. The baby oil should leave a smooth, glossy finish without the need for any refinishing. Remove the scotch tape from the tip of the USB key.
I deliberately overfilled my mold, which left thin pieces of resin at the top. Use an X-Acto knife or razor blade to carefully cut away any excess resin. I found a slow and gentle back-and-forth sawing motion worked best to get a clean cut. Ensure the USB key fits in a USB port. If you placed the USB key in too deep, use your blade to carefully trim away resin until the tip fits into a USB port.
If you desire a lanyard or keychain, use a small drill bit to slowly and carefully drill a hole in the base. It's usually best to do this by hand and there are many inexpensive handheld drill options for under $10.
Allow the resin to finish curing. You will now have an awesome DIY USB key to show your friends!