MOLDING YOUR OWN CARBON FIBER COMPONENTS
Author: James Sparkes, Newcastle, Australia.
TOOLS / EQUIPMENT REQUIRED:
Small hand held rotary tool with cutting disks and sanding / grinding wheels (a Dremel
type tool with a flexible shaft is recommended),
Wet / Dry abrasive paper (240 grit, 400 grit and a polishing grit - say 1200),
Pane of glass (say 1.5 ft by 1 ft and thick enough to take reasonable handling loads
without breaking - I used my wife’s glass chopping board),
A few clothing vacuum bags (this is a must if you want to get a reasonable end product),
A powerful vacuum cleaner (I used my wife’s with the filters removed to improve the
vacuum),
A sharp pair of scissors (for cutting the glass and carbon cloth),
Hot water bottle and blanket (to speed up cure times),
A dust mask / respirator and eye protection (use when cutting / sanding).
MATERIALS REQUIRED:
Fiberglass cloth (6oz weight should be fine),
Carbon fiber cloth (I used a plain weave which was all the shop had - at $60 AU per roll
metre it’s not cheap),
Two part epoxy resin (I used WEST System epoxy which is a marine grade epoxy.
Don’t be tempted to use the cheaper polyester resin as this is not as strong as epoxy, does
not wet out carbon as well as epoxy and cannot be exposed to high temperatures.),
Mold release wax (a carnauba based wax specific for mold release - do not use car
polish),
Liquid PVA (for mold release - this is a specific PVA for mold release not the glue
kind).
Thin PVC plastic sheeting (to avoid having resin sticking to things you don’t want it to),
Roll of cling film (to use as a peel / release film),
Cotton cloth (to use as breather fabric),
Popsicle sticks (for mixing resin),
Some wax free plastic cups (for larger amounts of resin),
A small medicine cup (to measure out resin and hardener - I used a 50ml one and
usually only mixed up small batches of 30ml or less),
Acetone (for clean up of uncured resin),
Some short length bristle brushes (use some that will not loose all their bristles when
cleaned),
Latex gloves (to avoid a gooey mess all over your hands).
GENERAL SAFETY AND HEALTH PRECAUTIONS:
The reader of this article takes full responsibility for their own actions when following
these procedures. Uncured resin and the resulting dust from cured resin and glass /
carbon fibers may be toxic and have harmful effects when inhaled. Use common sense
and follow the manufacturers guidelines.
Notes on resin mixing. Always add the hardener to the resin, not resin to the hardener.
Use small quantities, i.e. only mix what you can use during the pot life (pot life is the
time taken for a standard volume of mixed resin to “gel” at a standard temperature).
Large volumes of mixed resin (say 100ml or more) generate excessive heat during the
chemical reaction. This heat build up will cause to resin to gel quicker, may cause the
mixing container to MELT and cause excessive resin vapors.
Notes on cured glass and carbon fibers: Take care when handling cured parts during
sanding and cleanup. Fine fibers with cured resin act as splinters and may break off
when imbedded in your skin. Carbon dust if left to sit on bare skin will cause a mild
irritation - wash off with soap and water.
Notes on sanding / grinding carbon fiber: Carbon fiber dust can conduct electricity.
Take precaution to prevent carbon dust from entering electrical equipment as this may
cause short circuits and expensive repair bills.
MOLDING BASICS - Plug Preparation
A warning on part molding. Mold only parts with a positive draft angle, i.e. the part
will not be locked into the mold due to it’s shape. For complex parts I suggest multiple
piece molds which can be disassembled for part release. These molds are beyond my
current experience. Also note that the clutch cover has a positive draft and can be
molded using a single piece mold. The original cover did prove to be difficult to remove
from the mold. The carbon part was also difficult remove and I ended up destroying the
mold in the process.
You can use you own original parts to create a mold. Start with smaller simple parts
which are flat or have small uncomplicated curves. The first part that I attempted to
make a mold from was the clutch cover and after three attempts I gave up and moved on
to the heel plates.
Once you have chosen a part to mold you need to decide whether you want a female or a
male mold. A female mold will give a smooth surface on the exterior side of the end
product. So with that in mind I assume you’ll use a female mold.
Take your chosen component and give it a good clean. The surfaces on both sides should
be spotless and free of nicks, gouges or blemishes as these will turn out on the mold.
If your part has any fastener holes, you can fill them with plasticine or a similar material.
This will prevent resin flowing through the hole and locking your part to the mold. It
also makes a nice impression in the mold and the final product so you know where to
drill any fastener holes.
Apply mold release wax to the part in accordance with the product instructions. It’s
generally wax on and allow to dry, polish off and then allow to dry for 10 to 20 mins then
apply another coat. Apply five to six coats and allow the final coat to dry for about one
hour.
Apply a coating of liquid PVA release agent to the part and allow to dry. This allows the
part to come away cleanly from the mold. It will wash off with soap and water or will
peel away like a layer of “cling wrap”.
MOLDING - Laying up and Vacuum Bagging
Before you mix any resin, ensure you have cut the required amount of glass cloth
(sufficient to cover the part with an overlap of about 1.5 inches), prepared an area to put
your vacuum bag where it can sit for a few hours and you have boiled the kettle (if you
want to use a hot water bottle for a faster cure).
Have your bristle brush ready and a cup of acetone to clean the mixing cup and brush
immediately after use.
The vacuum bag is required to hold the cloth in position and against the part / mold while
the resin cures. The application of the vacuum also draws any air bubbles out of the
layup ensuring a smooth mold surface. The vacuum also pulls out excessive resin and
compacts the layup which gives a lighter and stronger part.
A basic vacuum bag configuration is shown in the Figure 1 below.
While I don’t expect you go to the effort of replicating the configuration shown in the
figure above, we can make do with our clothing vacuum bag, some cling film as peel ply
release film and some cotton cloth as a breather fabric ply.
Have your vacuum bag and vacuum cleaner (remove the filters to allow greater suction to
be applied to the bag) ready. Have a friend ready to help you seal the bag and hold the
vacuum cleaner to the bag port while you work the wrinkles out of the bag. I placed an
old towel on the bottom side of the bag to protect it from being pierced by the glass plate.
The towel will also prevent the bag from sealing within itself, i.e. it gives a route for the
inside air to escape to the vacuum, i.e. a breather fabric.
Place a layer of the PVC sheeting on the glass plate or you can use cling film if you wish.
Place your waxed part in the center of the plate.
Mix the required amount of resin for a single layer of glass cloth. Mix the resin well and
let it sit for a bit to allow any entrapped bubbles to rise to the surface.
Place a single layer of glass cloth over the part and apply some resin with the brush
(applying a single layer at a time allows the cloth to conform to the part better). Use a
stippling action (dabbing action) rather than a brushing action as a brushing action will
generally just move the cloth around. When the glass is completely wet out by the resin
(it is no longer white but transparent), and you are satisfied with the work, place a layer
of cling film (peel ply - see Figure 1 above) over the layup and then put a piece of cotton
fabric over the top (this acts as a breather fabric ply to help the air within the bag escape
Place your part in the vacuum bag and seal. Apply the vacuum to the bag and slowly
draw the air out, as the bag closes in on the part manipulate the bag to conform to all the
curves and any tight radii of the part. Try to smooth out any wrinkles over the part as
these will create resin ridges and will need to be removed before the next layer of glass is
Once you are satisfied with the vacuum bag, let the resin cure overnight or if you prefer
you can use a hot water bottle a blanket to allow enough heat to cure the resin in about
1.5 to 2.0 hours. Periodically check on the bag to ensure that it has not lost its vacuum,
this is crucial in the first 30 mins of curing. Figure 2 shows a photograph of a vacuum
bagged heel plate molding. Note that the blue color is the dye in the PVA release agent.
The dye helps to show where you have applied the PVA.
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