I made a mold over the weekend and figured it would be a nice how to. It's for a 2010 camaro trunk insert. The factory one is carpeted. I didn't have pics of the begining so here is how I made the plug. I put resin down over the carpeted piece and sanded it smooth. The key here is your mold will only be as good as your plug is so spend as much time as needed to make it flat and as smooth as glass. I sand all my plugs up to 2000 grit and polish them before doing anything else. This is a very rough how to since it was just me in the mold shop on the weekend so had limited pics. If you want any other pics on how to do a step just ask and I am sure I will have one of a different mold we have done. So on with the pics.
In this pic it shows the plug all sanded down. The aluminum around it is called a flange an is used so you can have a edge to trim off the actual carbon part when you make it and for applying vacuum bag tape later on. It is just aluminum flashing purchased at home depot and it is attached with hot glue on the back.
Now to keep the gel coat from getting under the edge of the part causing it to lock the two parts together we use a non hardening clay. For most parts that need a nice rolled edge we use as little clay as possible but for this part the part just stopped and didn't need a rolled edge like on a hood or trunk so we made it so gel coat wouldn't get stuck. Nothing pretty but works just fine for this situation.
This is the tool we use to shape the clay. Got it from a arts and craft store for $15 or so.
After you put the clay around the edge you need to fill any holes that will be cut out later. I usually just use clay but you can use hvac tape as well. This is where the trunk latch goes through the insert.
Next we tape off all the seams where the aluminum flashing meets up so the gel coat once again doesn't get stuck between the two layers. It is just hvac tape.
Next step is to take wax and grease remover and go over the entire part and make sure everything is clean. After that you need to put on some sort of release agent to allow the plug to seperate from the mold when its dry. You can use mold release wax but on plugs I always use PVA. Some don't like it but I have had situations where plugs have gotten stuck to molds and it's tough to see both get destroyed after all the work spent on making a plug. I have had plugs take up to a month to make just right so it's a risk I wouldn't take. You can brush on pva but we spray it. 4 very thin coats letting each coat dry. The pva creates a thin film that is water soluble between the gel coat and the plug. I have never ever had a part stick with this stuff. This it what the bottle looks like.
Next we apply gel coat. This is tooling gel coat and it's a bit stronger then normal gel coat. It also sticks to vertical surfaces better. This stuff is pretty nasty smelling we always use gloves and proper breathers to be safe. You can brush it on or spray it. We usually spray it but the part was small enough that I didn't want to bother having to clean the gun after.
Now you let this cure till it is a B stage. You will know when it's there because you can leave a fingerprint but no gel coat comes off on your finger. We usually let it cure for about 2 hours at this point depending on temp.
Next step is to apply fiberglass or carbon fiber on top of the gel coat. There are alot of different types of fiberglass you can work with such as Chopped Strand Mat and woven. Most of our molds are made from woven glass or carbon fiber. For this mold I chose chopped strand mat since cost was a issue and there wasn't a need to have it made out of carbon fiber or woven glass. The method here is to lay down the fiberglass and soak it with a ester based resin. The binders in the chopped strand mat break down when they are soak in ester resin. Make sure there is NO trapped air in between the gel coat and the fiberglass this would cause voids that you will have to repair later on. Spend alot of time on the first few layers as they are very important to having a strong mold. This mold was made with 6 layers of fiberglass total but only applying 3 layers at a time. The reason you don't want to have to many layers on at once is because the chemical reaction that cures the resin creates heat. Enough heat can cause problems such as warping the mold. So we put 3 layers of fiberglass on let it cure for a day and put 3 more on the next day. Here is what the mold looks like after 6 layers are on it.
After the mold is cured this was about 24 hours we popped the mold from the plug by putting plastic wedges between the two. I take my time here and gently work my way around the part edges until it pops apart. Here is what the mold surface looks like when it comes out and is washed off with water to get the release agent off all the way.
At this point you can do any repairs to the mold using more gel coat. If it's ready to go I polish it up again to be sure the mold surface is like a mirror. The surface of the part will only be as good as the surface of the mold.
Now it's time to apply more release agent to it so your carbon fiber part can pop out of the mold after its dry. We have used alot of different types of release here are a few examples. Mold release wax (you apply this just like car wax. On new molds its 6 coats letting each one haze up and buffing it out to a shine), pva just like we used before (I don't use it here because it can leave a weird finish on the carbon parts but it does work) and a Semi Perm release (this is my favorite stuff. We have never ever had a part stick to the mold before and the parts just pretty much fall out of the mold when done.) Here is the exact stuff we use applying three coats. The benifit to the semi perm stuff is they tend to allow up to 30 releases between coats so it saves time and money if you are doing decent production runs.
Now to make a part you just apply clear gel coat to the mold by spraying it. You can brush it on but I have never had success with doing it that way. Let the gel coat b stage and apply your carbon fiber to the mold. Here you spend lots of time making sure it is firmly pressed into all the corners and edges. If you don't you will end up with a hole between the fabric and the gel coat. next apply your choice of resin (If you are using epoxy make sure that it is compatable with your gel coat since some epoxys don't react well to polyester based gel coats. If you are using a ester based resin you will be fine) Apply as many layers as needed which will depend on what you are making. Most parts that are cosmetic will use 3 or 4 layers you can use one layer of carbon and a few layers of fiberglass. Most carbon products out there are made this way and is a huge reason why some hoods are $600 and the full carbon ones can be over $2500 (high quality hoods can consist of 10 layers of 3k carbon fiber and is why a high end hood can cost upwards of 2000 or more but they tend to weigh in at very little compared to the one layer carbon and rest fiberglass version). Let the resin cure and pop out your part.
I didn't get any pics of the part we made from this mold but I will take some tomorrow when the weather is better here.
There are a few different ways of making the part such as vacuum bagging or infusion and if anyone wants to see pics of it let me know and I will take some while we make a part and post them up.
