Carbon Fiber cloth, once mixed with resin and cured, is just fiber re-enforced plastic. The part can then be either clear coated, powder coated or simply polished without any additional coating. The weaving pattern and thread thickness will determine the appearance of the final products. The most commonly used cloth patterns are twill and plain, in 3k thread thickness. 3k indicates there are 3000 carbon filaments in each “tow”. Often times you’ll see thicker thread on the back of the carbon parts, that’s 6k or 12k carbon which is thicker, great as backing material. A common misunderstanding is that higher “K” number gives more stiffness and strength – these two properties are indicated by other numbers, and in general is not a concern for buying motorcycle bodyworks. (It’d be when it comes to structural parts which have to bear great force, such as wheels and frames, but it’s beyond the scope of this article.)
Now let’s look at what’s so called the “autoclave” process. An autoclave is simply a big high-pressure heating chamber that opens from one end (think of a pressure cooker that fell on its side). Carbon fiber cloth that’s wetted with epoxy resin is conformed onto the metal molds with vacuum bag, laid out on a long roller cart and rolled into this big pressure cooker. Door is then locked, heat is on, pressured is applied and the timer is set. In an hour or so, parts are rolled out and checked for leaks. If everything looks good, parts are rolled back in to bake for another 45 minutes or so. After the autoclave is done, the parts are de-molded, trimmed, cleaned and clear coated. The following step-by-step photos will give you a better understanding on how this process works.
Carbon Fiber fabric is pre-pregnanted (hence the name
“pre-preg) with epoxy resin and stored in a walk-in freezer. Pre-preg carbon
fiber gives best fabric-to-resin ratio, and eliminates the resin-inducing step.
We use Toray® carbon fiber on all our bodyworks.
The roll of carbon fiber fabric is fed into our CNC router
and cut into desired shape. The cloth is then laid inside the mold and vacuum
is applied. Certain parts that have metal mounting fixtures will require
another mold on the backside to ensure precision. Parts that require smooth
backend (like windscreens or hand guards) will also use backside mold so both
sides will appear smooth.
Once parts are in their molds and tightly vacuumed, the cart
is rolled into the autoclave chamber. Temperature and pressure are all set from
the digital control panel. The baking then begins.
The operator will double check for vacuum leaks during the
autoclaving period if the panels are large and prone to air leaks. Leaked
vacuum will induce air bubble into the resin and results in weakened parts and
inferior finish.
If everything goes well (most of time it does!), we will
have a beautiful part. Shown above is the side panel for Ducati Sportclassic
1000.
Trimming is done on our CNC rig with a Mitsubishi Robot Arm.
If the part is relatively flat, we can also utilize waterjet. There are also
parts only can be cut by our skilled staff with hands.
The part will then be cleaned to remove mold release agent
and sprayed over with UV resistant clear coating. After some hand polishing, we
can finally deliver beautiful carbon fiber motorcycle bodyworks that brings
grin stretching from ear to ear.
The making of carbon fiber body panel is still a very labor
intensive process and requires a lot of skill and patience. It’s also
challenging when it comes to de-mold and trim intriguingly shaped parts. But
hey, this is what we do here and we will keep trying to bring you the best
carbon fiber products with a reasonable price, through ways of technology, experience
and passion.
