learning about making carbon parts

[warrenpenalver]

Doing this thread separate from my car thread as its going to be about carbon bits rather than just my car. The idea being it documents how ive made bits and progress as i learn and hopefully it inspires others to do the same and demistifies some of it as in its simplest forms its just playing with plastics!!

Some of the parts i want to make are specific to my car and some are not but specifically ideas for me to work on to improve my skills/learn more and to help out mates etc.

Ive played with glassfibre before as well as playing with resins so moving onto carbon was kind of the next stage. Also carbon parts can be both stronger and lighter than the original parts so win on all rounds.

Ive got a string of parts ive got hold of to make moulds including the following:

mirror baseplate.

chosen as its relatively simple shape but with some fixing points to fix to car so needs practice with combining different laminates and ensuring structural strength around the fixing screw hole as well as the cosmetic finish

steering column upper shroud:

chosen as several tight curves and sharp edges as well as screw fixings underneath so needs to learn skills of combining carbon/resin with accurately positioning screw threaded metal.

steering column lower shroud:

relatively simple shape, but with ignition key recess requiring two part mould to prevent "mechanical lock". Needs hooks making out of carbon sheet to latch with upper shroud. Also matches up with upper shroud.

Door handle

chosen because it is complex injection moulded plastic. The aim being to design either the complete unit in carbon or a combination part where the mechanism remains plastic but the visual surfaces carbon for cosmetic reasons. will need a multitude of skills combining basic moulding, thought about screw fixings, making strong yet light levers and support arms and accuracy in locating the multiple moulded parts to make a working mechanism. probably one of the last things i do as its the most complex!!

I might have a go at some larger panels and parts at a later date but while im learning, the moulding costs of big panels makes it prohibitively expensive for experimenting and i dont fancy spending 2 hundred quid on a mould for a part im just messing with and might not work!!

ok to make carbon bits you need some specialist equipment and an array of common workshop tools and materials so you can make moulds, sand bits, cut things, etc etc

To choose your equipment you need to decide which method of part making you will use. There are 3 core methods for making carbon parts namely wet lay, vacuum resin-infusion and pre-preg.

Wet-lay
in simple terms you have a mould, brush in resin for the gel coat, then lay in your laminate layers wetting out each layer with more resin then finally allowing the part to cure.

This is the simplest method to use and needs no special equipment but it is also hard to achieve cosmetically pleasant results as well as the parts will likely be fairly resin rich meaning not as light or as strong as they could be. It takes a lot of practice and patience to get a good cosmetic finish with the key being a good even gel coat layer and careful application of the first visible layer of carbon.

Vacuum Resin Infusion
The name gives it away here. In essence the part is made in a vacuum and resin is sucked through the part by the vacuum pump. It is then left to cure under vacuum either at room temp or in an oven.

This method is more complex yet can achieve very good results. The mould has to be constructed with a large flange to enable the bagging and infusion materials to fit in. The carbon is laid in dry, then a stack of peel ply, infusion mesh and bagging film is laid on top. The bagging film is sealed either to the mould or as a bag (supplies as open ended tube) to make a air tight bag. You have a vacuum outlet and a resin inlet on the bag. Vacuum is then drawn to help hold all the material layers in place as well as promote resin flow. Then a resin is drawn through the whole mould by the pump. The infusion mesh has the gaps needed to allow it to flow. once resin has reached all parts of the mould it is then cured either at room temp or in an oven. roomtemp curing can be further strengthened by postcuring in an oven.

The advantage over wetlay is much lighter and stronger parts due to the method ensuring the correct ideal resin/carbon ratio and also parts with a better cosmetic finish due to the vacuum ensuring no bubbles or pin holes. It is also easier to learn with less emphasis on fiddly skill but more emphasis on being systematic in making sure you have a good bag stack and air tight bag. The disadvantage is it requires some specialist kit so is not ideal if you just want to make one or two things.

Pre-preg.
This method uses carbon fabric that already has the resin in the fabric. It is laid in moulds in a similar way to resin infusion and then bagged under vacuum. It is then cured in an autoclave both under pressure and temperature.

This is the ultimate in strength and lightness and hence often used in top flight motorsport, aerospace etc. But it is beyond the capabilities of the home enthusiast due to the sheer expense of the equipment. The much more expensive pre-preg material and process makes the final parts sometimes several times the price of equivilant resin infused parts.


Specialist gear.
I have chosen to use vacuum resin infusion as my method because although it has a small initial outlay on equipment (£200), can achieve far better results than wetlay and with careful planning and sticking to routines can achieve good results without the need for fiddly intricate abilities of the dummy doing the work (ie me!).

The key bits you need are firstly the vacuum pump:

does what it says on the tin really. key to making the process work!

Catch pot:

catches the excess resin drawn out of the bagging stack and stops you killing your pump with resin!! Also has the vacuum guage so you know when youve achieved the good vacuum.

Bagging materials:

resin infusion mesh: plastic mesh that allows resin to flow across mould
peel-ply: Stops the bagging material sticking permenantly to the part
bagging film: seals the mould and enables a vacuum to be made
gum tape: seals between bag and mould flanges
infusion spiral tube: similar to spiral cable wrap! Allows resin to flow easily from resin inlet
inlet and vac ports: allows tube to go through bag for resin inlet and vac outlet
6mm pvc tube: links resin to bag, bag to catchpot and catchpot to vac pump
masking tape: helps hold things in place!
Breather fabric: sometimes used to absorb excess resin or to allow resin to flow in places.
infusion resin: epoxy resin with a low viscosity so it flows easily
carbon fabric: the laminate! different styles used include 4x4 and 2x2 twill as well as unidirectional or plain weaves
release agent: designed to stop the carbon sticking to the mould.


Mould Making:
For this thread i will be making a mould of a cosworth brake fluid resevoir. Its got a few curves as well as a flat edge where i make it a 2 part mould and some fixings/screw threads so will involve a bit of skill.

First of all you need to decide how you will make a mould. In this case you can copy ford as it was made in 2 halves then bonded together, so you have a good line for making a mould flange. In this case i decided i will also need to make the screw threads and fluid oulets out of black resin plastic as those parts cannot be made in carbon easily.

First of all i made moulds of the resin parts. I did this using a 2 part silicone moulding putty. You just measure out equal quantities of each silicone, mix it then press it over the part and it cures within 5 minutes! the mould is then ready to pour resin into!
These are the simple moulds made:

quite hard to see whats what due to the silicone on the edges but all the detail is there deep in the silicone.

The second stage is making a flange. I have used plasticard and made a start in this photo:

when its finished it will go all round the edge. You can hold the flange on with plasticine and glues and tapes. Ive used pasticine and tape. I have also filled in the lid recess as that cant be made easily in carbon, and cut off the screw thread as it just gets in the way of making a mould and is replicated in resin later. Plasticine is a good material for filling holes or making edges and flanges as it does not stick to epoxy resins and is firm enough to survive the moulding process.

I will update this thread more as i go along the process.

 

[Scotty1.7]

Cracking work warren looking forward to this stuff.

Might have to ask you about some costs for afew little bits

 

[Vitch-w]

looking forward to seeing this as a finish top work k:

 

[warrenpenalver]

Might have to ask you about some costs for a few little bits

would likely be more than you thought as despite being home made parts there is still the cost of making a mould, although if its a item others want of course moulding costs reduce.

 

[PumaJay]

get on the wing mirrors.... id deffo be interested in those and the steering colum shrouds!!

 

[warrenpenalver]

i wont be making bits to sell until easter probably. want to play first.

 

[warrenpenalver]

Time for the first update!

carried on with the flanges. Note in this pic the gaps between the sheets are filled with plasticine:

also I filled the very edge where the flange meets the part with plasticine. This has been done so no resin bleeds under the part causing a mechanical lock of the part to the mould.

Also from underneath i have used plasticine again to stiffen the flange against the part.

Now the flange is mostly done, we want to make a bigger flange plate to form the edge of the mould. You dont strictly need to do this but when vacuum bagging its often easier if your doing one sided bagging to have a straight edged mould to work from. You dont need to be very neat or accurate as none of what this flange will do will be seen on any final parts.

Cardboard cut to a rough shape at first with a hole for the part to come through:

then adjust the hole until the part fits through:

then mark with a pencil round the flange and draw some trim lines on the cardboard to give a small a piece as practical:

Then when cut, cover the card in selotape so that it is easier to wax and wont stick to the mould:

Then tape the flange on both sides to the cardboard:

The next step is to make an edge for your mould. Again this is just being neat and tidy and will just make it easier to use as it will sit nice and flat on the table while you make parts. You can use anything reasonably stiff for this. I have used balsa as its what i have lying around and constructed a edge.

I then used some nails to hold corners together:

it was then taped to the flange and the edge sealed with plasticine to make demoulding easier:

The next thing i have done, which again is optional at this stage, is to screw in some screws at the side of the flange. This is so that when i have put in the resin and start laying in the fibreglass, the edging will be tied into the mould by the screws embedded in the fibreglass. Of course you could do all of the edging at the end but this saves time now.

So the plug mould is now complete!!

The next stage will be to wax the mould, coat it in mould release then make the mould itself!!!

 

[andyc1230]

you can also make your own prepreg,sort of, get your sheet of cloth,you can use as plies as you want just make sure the weave is in diferent directions ie, 90/45/90,wet the cloth out,we use 3m 9323,or for high temp work use 9396,both of these will air dry & you can use it in your equipment as vac-ing down does produce the best results, then put it between 2 sheets of bagging material and on a flat surface squeeze the resin out using a plastic filler spreader,once fully wetted you can the draw on the plastic with a fine paint pen any shape you want & cut it out with a pair of scissors.Any leftover material can be put in the freezer for use at a later date. Dont try & make the parts spot on to size,run over the edge of your mould, get yourself a pencil grinder & an array of diamond bits to trim up with also a set of diamond needle files will be usefull.
once you get the hang of it you will be turning out some great parts.

 

[warrenpenalver]

In this post we are making the actual mould.

First of all we take the completed plug then polish the part and apply mould release wax. Build up to about 5 or 6 layers. Then with moulds like mine, you will want to make some legs on the underside so it sits level. I used old toilet rolls! Anything will do really!!

Next apply liquid mould release agent PVA to the mould in as much of an even layer as possible:

you can see here how on the waxed parts it tries to run off but you just keep moving it around. I do a second coating after 15 minutes as it fills in any gaps. As long as there is a coat all over then the part shouldnt stick.

The next stage is mix up the epoxy resin tooling gel coat. If you look in this photo you can see small bubbles in the mixed resin. You will almost always get some regardless of how careful you are. Most of it will brush out when you apply it to the mould but i leave it 5-10 minutes to degas. The pot life is about 30 minutes so plenty of time!

next start applying it to the mould. Nice and thick, as thick as you can get it on without it massively running off.

cover the whole part well and cover the flanges too. The reason you want it thick on the part is so you can sand it down nice and smooth to remove any imperfections. The flanges dont need to be soo thick.

Leave the mould for between 1 and 3 hours until the resin is tacky. Every now and then touch your gloved finger on the resin and it is ready when it sticks but leaves no residue on the glove. Do this on the flange so you dont accidentally push through the resin to the part if you screw it up.

When the resin is tacky, mix up your strengthening material. Im using a fibreglass embedded epoxy putty instead of fibreglass matting. Its much easier to use and less messy. Press the putty into the mould and cover the whole part in a layer approx 1cm thick for small to medium parts and upto 2cm for thicker parts. Ive also added some balsa stiffening between part and side walls. You dont have to do that for most parts but i want the mould to be nice and strong.

Now I just need to leave it for upto 24hours to cure and then demould the part from the mould!

 

[warrenpenalver]

Now its time to see the finished mould!!

First we must get all the flanges, plasticine and part off!!

First start lifting the card:

As you can see it starts to come off easy, a good sign that enough wax and PVA was used.
As i lifted the card, even the plasticard flange has begun to come away:

Again a good sign we havent permenantly bonded a load of resin to the part!

Finally get the whole card off and as you can see it came off intact with no sticking anywhere:

You now need to dig up some of the plasticine holding the flange in place and remove the flange working your way around the mould.

once that is done you need to dig out ALL of the plasticine around the edge of the part.

something like a small screwdriver is ideal just dont press hard as you dont want to damage anything.

Then we are ready to pop the part out. Give it a good tug and see if it comes out. If not try a bit of leverage with a screwdriver but be careful you dont damage edge of the mould. if youve PVA'd and waxed correctly the part will not be stuck to the mould, we just need to break the vacuum. If that fails, get a rubber mallet and give the part a few light taps. Few light taps later and the part has broke the vacuum:

Then just lift out the part!

You now need to clean up all the plasticine from the edges and the mould:

Once that is done get a bowl of warm soapy water and a cloth and wash the mould thoroughly to remove all the PVA residue:

Once that is done you are left with a nice clean mould ready to be fettled for use:

Then inspect the mould for defects. Looking at this picture you can see how crisply the fine detail on the part has been copied into the mould:

That is where the preparation has paid off.

Another picture to note is this one:

You can just about make out the matt finish of the flange at the top and the shiny finish at the bottom. The Plasticard was at the top and the shiny tape covered card was at the bottom. As you can see the surface finish of the two componants has been transferred to the mould. Obviously this is the flange area so irrelevant but the point is that the better the finish of the part/plug then the better the finish of the mould and the better finish of the mould, the better finish of the final carbon part. So preparation is key.

The final step is to mix a little more gel coat resin and fill in any rough edges on the flange and the edges of the flange. This is just so i have a slightly smoother edge for the gum tape to seal against when vacuum bagging.

The part was then left to cure overnight. You can speed up the cure and "Post cure" in the household oven at about 80 degrees for a few hours. That way you can be certain the mould is fully cured and ready to be prepped for use.

The next stage will be final prepping of the mould for use, so polishing up and applying the release agents.

 

[warrenpenalver]

polish up the mould then clean it and apply your release agent. You can do light sanding and any fettling you need to do now so the defects are not transferred to the carbon parts.

Next measure up and cut out your reinforcement layers. Measure using a piece of cloth or a sewing tape measure to ensure you account for all the recess' and edges. Make it a bit oversize for your flange too. Its always better to have it too big than too small!! you can revise the size of sheet if massively too big the next time.

Next lay your first layer of carbon into the mould. Press it deep into the recess's then trim the edge and tape it down to hold it in place. For deep recessed moulds like mine, you can insert a cloth into the carbon to push it into the recesses properly and hold it in place as you trim and tape.

Once your first layer has been done, get your gum tape out.

Tape around the entire edge of the mould. Doing this now also gives you an idea of how close you can go with tape etc.

Next keep adding additional layers of reinforcement. My final layer is of kevlar to give better durability of the part and give it a good impact and fracture resistance so even in a smash the tank should stay in one piece.

Next add peel ply in a layer just bigger than the carbon. The peel ply is there just to stop the rest of the bagging stack sticking to the part.

Next layer is the infusion mesh. this has lots of gaps to allow the resin to flow across the part. You may need to cut lines into corners etc to help it fit. Does not matter if it overlaps.

Add a double layer of mesh from the offcuts to one end of the mould. This is where the vacuum connector goes. The double mesh aids air flow. Ive added extra mesh around the sides due to shape of my part. Then place the silicone vacuum connector onto the double strip of mesh.

The next part is fitting the resin inlet and infusion tubing. The resin inlet is a silicone part and the infusion tubing is basically spiral tube to allow resin to flow easily. You can see from this pic of the parts on the desk how the two pieces interact:

On my infusion, instead of having the inlet at opposite side of mould, ive placed it in the centre of the part so i have no problems getting resin all the way in the part. On shallowish parts, having the vac port at one end and resin inlet at the other is adequate.

The final layer in the stack is the vacuum bagging film that seals the mould. Cut it much bigger than the mould so it will fit into the deepest corners of the part. Then working at one corner start sticking it down and work your way around the mould. You will need to add pleats using more gum tape to take up the slack length:

Keep working your way around until the entire mould is sealed. Next, above the vacuum outlet, cut through the film to insert tubing. Cut an appropriate length of pvc tube to reach port and to catch pot. Cut end at an angle so it doesnt seal on mould surface. Then Wrap gum tape around the end of the PVC tube so just enough tube pokes through to go into the fitting fully:

Then press fully into position and press the tape down to seal the tube:

do the same for the resin infusion port and you will be left with a complety prepped and bagged mould ready for drawing a vacuum.

Fit a line clamp to each port. I have also began to draw a vacuum with my mouth to show how the bagging materials move:

Looking inside the recess, you can see that even with only a small vacuum pressure applied, the bag has tightly begun to press the bagging stack against the mould.

The next stage will be using a pump to draw a proper vacuum, leak testing, adjusting bag to fit and press carbon into mould fully, then the final infusion of resin and curing of the part.

 

[jacko]

sweet!! see you sat

 

[warrenpenalver]

Did the resin infusion tonight.

First of all set up the mould and the catch pot with a cup to catch the resin in.

Then connect it to the vacuum pump:

Start drawing the vacuum on the pump then adjust the bagging material and the tweak the fabric until it is pressed under vacuum tightly into the mould. Ensure there are no voids as any voids will ruin the part.

Once you are happy clamp the vacuum line and stop the pump. leave it 15 minutes to check you have no leaks. If you have a leak press down the tapes on the edge until it is sealed. You want there to be no visible presure drop on the pressure gauge in 15 minutes.

Once you are happy, mix your resin and leave it to degas for 10 minutes then fit the resin feed hose into the resin pot and clamp/tape it so it doesnt fall out and suck in air. when you are happy turn on the pump, let the vacuum draw on the mould then slowly open the resin line valve and let resin in.

You will see the resin flow into the mould and as it wets out the mould you will see the white peel ply thin as the colour of the material underneath shows through.

The yellow shade is the kevlar showing through.

Watch the vacuum line and you will see the bubbles of resin begin to fill it. It will be full of bubbles at first!

Watch the catch pot. Despite the tube being deep into the cup, it will still spatter everywhere!

As the resin fully reaches the edge of the carbon all around, you will see the line of resin on the material.

Keep an eye on both the resin pot and the vacuum line. make sure the resin pot does not empty or you will suck air back into the mould!!!

looking at the vacuum line you want to see it mostly clear of bubbles:

When you are happy clamp off the resin infusion line and the vacuum line and leave the part to cure for 24 hours. Some people leave the pump connected which is fine if you have a good vacuum pump, but not strictly needed if your mould is properly sealed.

 

[warrenpenalver]

Sorry for delay in update! have been waiting for the resin to cure at room temperature.

Also made another part with no kevlar to test an idea. And it gave me an opportunity to show you what it looks like as the resin infuses across the part. with yellow kevlar its hard to capture on camera the line of resin moving across, however with a carbon part its dead easy to see as the resin soaks out the peel ply making the black carbon show up.

so in this photo you can see the infusion is about 2/3rds done and the resin line is clearly visible.

And the final part. Its not perfect but TBH it would be too good to be true if it was 100% perfect first time!! Ive got a few pinholes which can be filled with gelcoat and it needs a polish up to really shine but im very pleased.

Here's the fluid resevoir top half:

and some close ups.

Here you can see a couple of pin holes:

and the other side.

Overall im massively impressed. Im getting some professional advice later in the week to see where i can improve in the mould and preparation to get perfect results.

oh and for a laugh i wanted to see exotherm of resin as id not seen how cool it was before. So take a half cup of resin left over after an infusion. Put it in a microwave for 30 seconds to get a bit of heat into it to start the chemical chain reaction.

Put it outside.

watch the fun!!

Smoooooookkkkkkkiiiiiinnnnnnnn!!!

its given me some great ideas for home made incendiary devices or maybe even a smoke bomb!!

 

[jacko]

awesome!!!

 

[warrenpenalver]

took it to the manufacturer local to me to have a look and the pin holes were cause by 2 things: in areas of dense holes its bridging of the bagging stack and the tiny pin holes were caused by me putting the vacuum on too long and hence sucking out the resin!

So the next one i need to be more careful putting the material and bagging stack in place so its perfectly against the mould and turn the pump off pronto as soon as the resin has infused fully.


oh and for those who are thinking of doing this themselves this photo is a great example of how the resin infuses on a panel. You can easily see the resin line progressing across the flat part.

 

[Vitch-w]

looks very hard and complex but the results are gunna look stunning k:

 

[warrenpenalver]

ok time for an update!!

After getting some professional advice on improving the cosmetic appearance i have had another go!

Came out much better letting the resin come in slower and turning off the vac pump earlier.

only a couple of repairable defects in the cosmetic appearance now!! Almost all the pinholes are gone so im almost there with getting the parts close to that perfect cosmetic finish people like.

overall im quite pleased. Took the new moulding down to the composites place for more advice and they were quite impressed saying that if id chosen a simpler part then i would have it perfect by now Also they said that by the time ive completed the brake resevoir there will be very little left for me to learn in terms of making moulds and resin infusion and basically i should be able to mould most things by adapting what ive already learnt.

oh on a weight saving perspective, done some checks.

original plastic part weighs 322g. the top half of my tank weighs 82g and it still needs the edges trimming.

I reckon by the time the smaller bottom part has been moulded and all the fittings added then i can keep it significantly under the original weight.

 

[warrenpenalver]

Time for the next update!!

At the moment ive delayed the making of the bottom half of the brake resevior as ive got another carbon project which is on a tight deadline as its a gift for someone!!

ok the point of this post is to show a different (and more traditional) mould making technique of using fibreglass.

ok first you need to make a plug to take a mould from. So make a baseboard of some kind, add the part, plasticine to seal any overlaps/undercuts and polish it and wax it as you would for any mould.

Then add your tooling gel coat.

Ive used 2 layers to guarantee I have plenty of material to sand as the shape is not critical for this part but its nice to have a perfect shiny finish. Ive also started making my own tooling gelcoat by using epoxy and adding a colour dye to it.

Then when that has dried to being tacky, mix up some epoxy and wet the gelcoat then add 6 layers of woven fibreglass. Wet out each layer using your brush as you go, making sure its pressed down properly into the plug.

Ive added a layer of kevlar as the last layer for 2 reasons, a) add extra strength to mould and b) to ensure there are no loose strands of fibreglass poking up as i intend to vacuum bag the mould for resin infusion and a single strand of sticking up fibreglass is enough to puncture the bag and cause a loss of vacuum.

Then leave it to cure. Once cured, remove the base board and you should see something like this:

All i need to do is dig out the plasticine and the plate will come out leaving a mould ready for cleaning up. 2 minor defects for you to note when making your own, the grooves on the right side of the mould are slight creases in the selotape i coated the card base board with. they will need filling with resin to ensure its easy for me to get a seal. second, note the area of plasticine on the left: some of the gelcoat has bled under the plasticine creating a "mechanical lock". Plasticine will come out anyway. That was caused by flex in the card allowing the plasticine to pull away. So you should use a rigid base board if you can. I just didnt have one that big.

Anyway once that is done i shall trim the mould, polish it and be ready to make carbon plates

 

[warrenpenalver]

Here is what it looks like once the plate and plasticine is removed:

needs trimming and a clean up, but note how shiney the mould surface is. That is good news as there will be less sanding and polishing of the mould needed and the surface quality of the mould directly impacts surface quality of the finished part.