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VIDEO TUTORIAL

How to Make a Mold for a Carbon Fiber Hood (or Similar Panel)

In this example we make a carbon fiber car hood but the exact same process could be used to make a roof, trunk, wings or doors. In this case we used an original panel from a modern Fiat 500. However, any finished pattern could be used at this stage if you have not got an original to copy or your design is unique

TUTORIAL BREAKDOWN

1. Preparing the hood

Ideally choose a panel in good condition with minimal paint blemishes or defects on the surface. The better the quality of the panel now, the better quality the mold surface will be and less need for repairs and polishing later.

Remove any parts that are not to be molded - such as the hood latch. Create templates for and create the mold flanges. Gaps around the flanges can be filled using filleting wax to get a sealed gap and smooth transition to the flange.

2. Applying release agents

To ensure the best possible chance of a successful release, it is wise to use 2 release agents at this point. First EasyLease is applied to the hood with 5 layers being applied. Secondly this is backed up with 2 layers of mold release wax

3. Making the outer skin mold

The mold for the outer skin is then made using the Uni-Mold Mold Making System. The lay up for this mold is standard for the Uni-Mold system and consists of Tooling gelcoat backed up with coupling coat and 100gsm CSM, finally finished with the Tooling resin and 4 layers of 450gsm CSM to add the backing strength to the mold

The Outer skin mold is left to fully cure before turning over the whole mold to make a start on the Inner Frame Mold.

4. Preparing inner frame

The flange barrier material is now removed, exposing the flange of the hood skin mold. The Filleting wax around the outside of the flange is trimmed and neatened to ensure the same good seal between the Outer skin mold and the hood itself. The holes and slots on the frame underside are sealed over with Release Tape to keep the resin out and produce a smooth neat finished mold.

The entire hood underside is then coated in release agent just as the outer skin, with extra care taken to ensure the new flange is properly coated in release agent,

5. Making the mold for the inner frame

The mold making process for the inner frame is identical to that of the Outer Skin. Once complete, the mold is allowed to cure fully before it can be trimmed and demolded.

6. Demolding and trimming the molds

Mark around the outer edge of the flange with a marker pen as a cutting guide. The rough edges are then cut off using a jigsaw to reveal the neat edges of the mold. Using a chisel or demolding tool, carefully pry between the upper and lower molds to open up a small gap, Carefully widen this gap and separate and demold the outer skin mold and inner frame mold from the original hood.

Once demolded, any rough edges can be tidied and the wax removed prior to inspecting the molds for damage.

7. Repairing the mold damage

A small patch has been damaged and will need a gel coat repair. Using tools and sandpaper, the damaged material was removed and prepared for repair. A small batch of Tooling Gel Coat is mixed up with some MW1 Wax Additive Solution to avoid a tacky surface finish.

Once cured, the repair was carefully sanded flush with the surrounding area before being polished back to a high gloss.

8. Sanding and polishing the mold

To get a very high quality professional finish, the mold was sanded and then polished. The mold surface has very fine print through from the mold process and some small marks and blemishes from the imperfections on the original hood. The imperfections were removed by wet sanding the surface working through the grits from coarse to fine. It was then machine polished to give the high gloss finish.

DISCUSSION (12)

Please share any questions or comments you may have about this video tutorial.

Volodymyr Tykhenko9/6/2023

If I need to make a mold thicker than on video can I also put all layers at one time with Uni-Mould system or at some point I have to pause and let resin cure/shrink and proceed with some layers later?

Easy Composites› Carl

Really, any more than 4 layers at a time would be risking the mould overheating. If you wanted to go thicker, then you will need to wait for the first 4 layers to cure, then key the surface and apply another 4 layers (you need the 4 layer thickness to give you the heat to cure the resin)

Harrison Mast

How long did the process of the mold take??? Would love to lean but maybe start with little parts first...

Easy Composites› Matt

About a day per mould half, including curing time.

DavidGP

At 14:31 wouldn't the wax leave an unwanted large void between upper and lower mold after it's been removed?

Easy Composites› Matt

No because the 'wax' is only there to extend the edges of the mould. Once the component is demoulded it will be trimmed back to the original component line.

DavidGP

Why is the Uni-Mould Tooling Resin 'filled'? What is the reason for that?

Easy Composites› Matt

It's filled to reduce shrinkage. A typical polyester laminating resin cannot be used to laminate 4+ layers of CMS all in one go because it would shrink badly and distort the mould. The filled resin used in the tooling mould system is very low shrink and designed to be applied all in one go. This speeds the process up greatly. It also makes the moulds suitable for higher temperature use as well, if needed.

Lesley B

What is the weight difference between the carbon bonnet and the steel please?

Easy Composites› Matt

The original steel bonnet was 20kg, our carbon fibre one was just 3kg, so 17kgs lighter.

Stefan Baier

How many bonnets could be made with one mould?

Easy Composites› Matt

There wouldn't really be any limit Stefan. Realistically, accidental damage to the mould is more likely to limit its lifespan than anything else but certainly we'd expect to be making hundreds of parts using a mould like this and if treated well it could be several hundred.

Paulina de Luca

Why do my parts warp when out in direct sunlight, or when interior gets too hot for interior parts..?

Easy Composites› Matt

It's likely that your parts need a 'post cure' in an oven to cure them fully. The reason is that epoxy is not fully cured at room temperature for quite some time. Doing a 'post cure' at elevated temperature forces the resin to fully cure and also helps improve the heat distortion temperature. Once a post cure is done, the part is unlikely to soften and warp in the sun again unless the part is exposed to temperatures which exceed the Tg (maximum temperature) of the resin you're using.

cegla cegla

Could you explain different between coupling resin and resin used later on to build up layers?

Easy Composites› Matt

The purpose of the coupling resin is to enhance the bond between the gelcoat and the tooling resin as well as providing a resin to wet out the 100g CSM to prevent print through.

D-dog Jackson

So how much less strong is carbon fiber if you don’t give it the vacuum and heat cure treatment?

Easy Composites› Matt

Certain strength properties, like tensile strength, are 90% determined by the fibre and so there's not much difference between different laminating/cure processes in terms of their effect on tensile strength. Other properties, like inter-laminar shear are more affected by the resin system and void content and you might see as much as a 20-30% difference in this property between a hand lay, no post cure laminate vs a resin infused then post cured laminate.

JoshHefnerX

How thick were the finished molds? At what point do you add reinforcement to the molds so they aren't flexing under their own weight? Also, how much if any, shrinkage is happening to the molds as they cure?

Easy Composites› Matt

There is almost no measurable shrinkage. The Uni-Mould system is a specialist very low shrinkage system. No extra reinforcement was added other than that shown in the video.

Jim Tyson

I don't understand why you don't use PVA mold release spray?

Easy Composites› Matt

It's very rare you'll see PVA used these days to be honest. I guess the main reason is the swirls or satin finish (or both) that it leaves on the mould (or component) surface. That all needs to be flatted and polished out. Wax and chemical release agent (or, really, just either of these on their own) are more reliable and leave a better finish.

ExistancelsPain

How would you install nuts into the inside of the mold for the hinge mechanism?

Easy Composites› Matt

You can use pre-made fixings which have a nut or stud on a load spreading plate which you can bond or laminate into place. You can make them yourself of you can buy them off the shelf from us. The main brand on the market is called Big Head Fasteners.