This is a carbon fiber iPhone 6 case that I made for a lab class. The following method will work for any phone case, although softer silicon based cases proved to be a bit trickier.
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Step 1: Molding
Before you begin, make sure you wear some vinyl gloves and safety goggles! Especially during later steps when dealing with epoxy you will not want direct contact with some of the chemicals used. Safety first.
First you will need to make a mold of your iPhone case:
Take some non-stick Saran wrap and very carefully try to layer it on the inside of your phone case. You are looking to encompass the sides and body tightly with nearly no wrinkles at all! If there are any holes in your case, it is important to let the wrap bulge out a little: this can be polished a bit later, and cut out when the time comes. Once you do this, pour a regular mold batter to act as a mold cavity and fill your case to the top before allowing it to dry.
Step 2: Extracting the Mold
Once the mold has hardened, you can proceed by taking it off your phone case. Try to pull the mold out evenly on all sides so that it doesn’t snap! You can go ahead and throw away the Saran wrap.
It helps to spend a little time sanding the plaster mold down with sand paper, especially the edges and the front of your case. For the back, make sure any features on the case are well defined so that they can more easily be cut out later on. To do this, take a small knife or even a key and just outline these features as above.
Step 3: Carbon Fiber Lay Up
You will need a 5:1 two-part epoxy ratio of resin to hardener, respectively, and a sheet of 3K carbon fiber. Remember to wear your gloves when handling both items.
You will cut out a sheet of carbon fiber that is the size of your phone case, leaving at least one inch on all sides. The more room you have to work with, the better.
For laying up the carbon fiber, you will start by putting a non-stick wax paper on a counter, the front of your mold down and the back side of your mold facing up. Prepare the 5:1 epoxy resin to hardener mix (the key is to eliminate all bubbles from your mix by pouring slowly and consistently, the hardener into the resin, and pushing the bubbles out of the epoxy if needed) and use brushes to wet your phone mold and the carbon fiber side you will stick onto the mold. Wet it well!
Wrap the carbon fiber tightly around the case preferably with no wrinkles at all. Also be careful to avoid folds on the edges of your mold. As long as the carbon fiber sheet wraps flatly around the edges, you’re case will turn out fine. In later steps, we will trim or cut down on the messy parts later. If it gets a little slippery, try to dry the middle portion of the front of your mold with a napkin and tape the carbon fiber sheet down to hold it.
To finish this step, tightly wrap a non-stick wax sheet followed by another Saran wrap layer to hold the carbon fiber sheet tightly to the mold while it dries. You should place your phone with all wrappings in a vacuum seal until all of the air bubbles escape, that way your case is as tightly bound to the mold as possible.
Step 4: Extracting the Case
Once your epoxy has set, you are ready to take your case out of the vacuum and remove the wax paper and Saran wrap from the carbon fiber and mold. Now you can have fun breaking apart your mold; this can be done with a hammer and a flat head screwdriver. Beat the screwdriver with the hammer and try to get as much as you can off without poking holes into your carbon fiber case. Be selective of where you are working as this can get messy!
Likely you will still be left with little bits of mold that won’t come off, for example tucked away in the sides of your case. Try to add a little water to soften these bits, get a smaller screw driver if possible, and with care, patiently continue to wipe off these final bits from your case. Sandpaper is also a good option for removing the final touches of plaster that are too thin to scrape off with a screwdriver. Give the case a final rinse and you can proceed to the final steps!
Step 5: Cleaning Up
At this point, it’s okay if your case still looks a little messy because now it is time to make it look pretty. I would recommend using a dremel and carbon fiber shear scissors if possible. You will cut off the edges of your carbon fiber case to whatever extent you prefer, trying to get rid of folds and any fibers that are still loose. Remember to leave enough on the sides so your phone doesn't just fall out. Also carefully cut out any hole features your case might have as above.
Step 6: Gloss Epoxy
This step is just as important as the cutting if you want to make sure your phone case looks good, and will also smooth out any last fibers that might poke you. We used a General Purpose One to One gloss epoxy for this step. After mixing, all you have to do is wet both sides thoroughly and you can leave it to set for a day.
*Note: Try to leave the case tilted on something so that excess epoxy can drip off and not form a strange layer at the bottom. Setting the case atop a plastic cup could prevent the entirety of the case from sticking to one surface. In case you are unhappy in any way, feel free to carefully dremel or cut off some last features.
I hope you will be happy with your final product in following this procedure; you are now ready to upgrade your phone case!