How to Mold a Carbon Fiber Phone Case




Introduction: How to Mold a Carbon Fiber Phone Case

Carbon fiber is a composite material consisting of woven carbon fibers that are hardened by epoxy. The material is very tough and lightweight, making it useful for aircraft and automobile parts, and we'll be using it to make a phone case. While carbon fiber has been around for some time, carbon fiber phone cases are not very common. This makes finding pre-made ones difficult, but means that completing this project will net you a phone case unlike most others.

Step 1: Materials and Tools

Materials you will need:

  • First and foremost is the carbon fiber. This is typically purchased in large rolls, so you might want to think about other projects you might be interested in before committing to purchasing it.
  • Next is the epoxy. This is sold in two parts, the resin and the hardener, so be sure to purchase the correct hardener for your chosen resin.
  • You will need a pre-made phone case. This will be used to create a mold around which the carbon fiber will be shaped.
  • Plaster will also be needed for the mold. The brand doesn't matter and you don't need a large amount of it, enough to make several phone-sized molds will suffice.
  • Plastic wrap and wax paper are also necessary, for maintaining a clean work space and for helping the molding process. You will need both normal plastic wrap and plastic wrap with a sticky side.
  • Plastic sheets will be needed as well. These should be thicker than kitchen plastic wrap and free of cuts or tears since we'll be using them to create a vacuum bag.

Tools you will need:

  • A measuring cup will be necessary for mixing the epoxy. If possible, find disposable ones as these will help reduce preparation time.
  • Foam brushes for applying the epoxy. You will need several of these since they will most likely be ruined after applying one coat of epoxy.
  • A vacuum pump for the molding process.
  • A Dremel rotary tool for detailing the phone case. You will need a variety of tips for the rotary tool, including a cutting tip, a sanding/grinding tip, and a buffing tip.

Step 2: Hazards and Precautions

Both carbon fiber and epoxy can act as irritants if they come in contact with your skin or eyes. Thus, you should always wear gloves (Nitrile for epoxy, Vinyl for carbon fiber) and eye protection while handling these materials. You will also want to wear long-sleeve clothing and a breathing mask while cutting or grinding the carbon fiber.

The Dremel rotary tool must be handled with care. It is important to keep gloves and loose hair away from the rotating end, lest they be caught and pulled into the tool. Always grind away from yourself, both to avoid blasting yourself with carbon fiber particles and to minimize the risk of loosing your grip and hitting yourself with the rotating end.

Step 3: Making the Mold

This step is by far the most important in making a good phone case. It is crucial that your mold be as good as possible, since any defects in the mold can only get worse during the molding process.

To speed up the cleanup process later on, cover your work space with plastic wrap. The plastic wrap should be replaced between every step in this instructable.

You'll want to begin by lining your pre-made phone case with sticky plastic wrap, sticky side against the phone case. Keep the contact between the plastic wrap and the case as smooth as possible to limit wrinkles in the mold. There are no easy ways to do this, you might have to try several times before you're satisfied with the quality of your wrapping. Try to make bubbles at any place where there is a hole or indent so that the plaster can fill out these spots properly.

Once you're satisfied with the wrapping, mix approximately 1/3 cup of plaster with the amount of water recommended on the packaging. When plaster is properly mixed, it should be about the consistency of pancake batter. Next, pour the plaster into the wrapped phone case, while making sure the plaster fills out any holes or indents in the case. The plaster should reach the top of the phone case, but it should not overflow. Once the case is full, smooth the surface and leave the mold in a dry place to set.

When the plaster has set, carefully remove the mold from the phone case to avoid stressing the mold too much, or else it might crack. Next, you may want to smooth any wrinkles you missed in the wrapping process and try to define any details you want reflected in the carbon fiber later on. This can be done by gently rubbing it with a tongue depressor, wet or dry, until the wrinkles are smoothed and the edges are defined.

Step 4: Carbon Fiber Layup

Part 1: Shaping the Carbon Fiber

Begin by wrapping your completed mold in wax paper. This needs to be done so that the epoxy cannot seep into the pores in the plaster, binding the plaster to your phone case. The wax paper should be taut around the back side of the phone mold, but should not completely cover the front side. You can secure it in place by placing a few pieces of tape across the front opening.

Next, cut a piece of carbon fiber that is large enough to have 1 inch of overlap when wrapped around the mold. You can reduce fraying in the weave by taping around the section you want to cut and the cutting through the tape. You may also want to try cutting slivers of material from the corners to reduce overlap when you fold the piece around the mold.

You can then wrap the carbon fiber around the mold. It should be pulled taut around the back of the mold, but don't apply to much force or the weave might begin to separate. Secure it in place by taping across the front, but don't completely cover up the opening on the front and try to avoid getting tape anywhere that you intend to keep as part of your completed case. The opening is needed to get the plaster out later, and if you get any tape on your actual case, the epoxy will make it very difficult to remove.

Once the carbon fiber is wrapped and secured, you can mix the epoxy. You will only need 30-40 milliliters of mixed epoxy, so separate the total volume into resin and hardener based on the ratios on the can. Make sure to close and store the resin and hardener cans before continuing.

Using a foam brush, you can apply the epoxy to the carbon fiber. The best way to do this is to pour some epoxy over the surface and use the brush to push it into the fibers. Your goal should be to get a layer of epoxy on the inside of the case as well as outside it. You should coat all of the carbon fiber on the back, sides and front of the case, but try not to coat the opening on the front or the plaster will be harder to remove.

With the carbon fiber completely coated and full of epoxy, you are ready to vacuum pump.

Step 5: Carbon Fiber Layup

Part 2: Vacuum Pumping

Begin by cutting a section of the plastic sheet and folding it over on itself to form two layers. Pierce the top layer and attach the vacuum pump nozzle. Seal all but one of the edges with putty or two sided tape, thus forming a bag.

You can then place your fully-epoxied carbon fiber case inside the bag. Be careful not to get any epoxy on the entrance or it won't seal properly. In order to avoid ruining the vacuum pump, you should place a paper towel or a piece of felt close to the nozzle to absorb excess epoxy. Seal the entrance and attach the vacuum pump to the nozzle.

Begin running the vacuum pump and check for any leaks. Also, use this time to press down the plastic around your mold to help push out excess epoxy and to tighten the case around the mold. Once there are no leaks and the vacuum is steadily increasing, you can let it sit, preferably overnight.

Once the epoxy has set, you can remove the case from the bag and it is almost ready for the finishing touches.

Step 6: Finishing Your Phone Case

The first step here is removing the plaster from the case. This can be done by simply hitting it with a hammer until it breaks enough to be removed. You can use a screwdriver or pick to remove any stubborn corner pieces. You'll also have to remove the layer of wax paper on the inside, which is best done with some sort of scraping tool, or even a flat head screwdriver.

With the case free of the plaster mold, you can begin to put in the finishing touches. You'll want to begin by using the rotary tool with a cutting head to cut away the excess on the front. You can then use a small cutting grinding head to poke holes for the camera, the buttons, and the charging port. Finally, buff away any excess epoxy on the surface using the buffing head. How far you go with the rotary tool is entirely up to you and depends on how good you want your case to look.

Once your case is shaped to your satisfaction, apply a second coat of epoxy and let the case sit and dry on a sheet of wax paper. Once it has set, buff away the excess epoxy again and the case is complete.

You now have a homemade Carbon Fiber Phone Case.

Be the First to Share


    • Puzzles Speed Challenge

      Puzzles Speed Challenge
    • CNC Contest 2020

      CNC Contest 2020
    • Secret Compartment Challenge

      Secret Compartment Challenge

    3 Discussions


    3 years ago

    nice. i might try it with fibre. i hadn't realised fiber was a thing.


    3 years ago

    What a fun concept!