Tuesday, March 9, 2010

The Making of a Carbon Fiber Frame

Let's face it: just about every "Italian" carbon frame is made in Asia. Yes, some are really "Made in Italy" and buyers should shop carefully if that is important to them. BICYCLING magazine recently had a straightforward photo series explaining how a carbon bike is made which I found interesting:

Carbon fiber composite frames require an astounding amount of hand labor from start to finish; there is almost no automation in their production. At Giant's C-Tech factory in Taiwan, workers make hundreds of frames a day for Giant and other companies that sub-contract their production.

Part of C-Tech is the Techno Center, where engineers create the designs for the frames using Computer Aided Design software and virtually "test" the frames in simulated software. Nixon Huang, R&D Advanced Engineer, is one of the lead engineers on many Giant projects.

There are only a handful of companies in the world that actually manufacture the raw carbon fiber used in frames and parts. In its most basic form, it looks like a spool of fat thread. This is a spool of Toray's T700S fiber, a major workhorse fiber of the bike industry.

Among bike companies, only Giant and Time use raw carbon thread (other companies buy sheets of fiber pre-impregnated with resin). Here, 96 spools of carbon thread feed through the loom at C-Tech, where they're flattened and coated with resin to make a sheet of "prepreg".

The three-foot wide sheets of prepreg are then cut into the pieces needed to assemble a frame. Each piece is cut not just according to size, but the direction or orientation of fiber. At Giant, the pieces, or plies, are placed in boxes in the layup room where workers will grab the right pieces for assembly.

Each part of a frame is assembled from a "kit" of plies of prepreg carbon composite. Quality control at this point is paramount. Giant's system uses a physical layup tray with size-specific slots for each ply. This kit is for a bottom bracket section for a medium TCR composite road frame.

Workers assemble the kits in order on the tray, using molds shaped to look like the eventual frame part. The worker strips the paper backing off the composite ply and sets it on a warming plate, then applies it to the mold, which is also often warmed to help make the composite more workable.

The black plate these composite plies are sitting on is the warming plate. Most of the workers in the layup room are women; men sometimes don't have the temperament for the exacting nature of the work.

Tubes are often roll-wrapped from larger pieces of composite. This is where the majority of the intermediate and high-modulus fiber goes in a frame, because tubes are ideal locations for adding stiffness and don't have to deal with the same kinds of complex forces that you find in a bottom bracket area.

Once all of the individual sections of the frame — bottom bracket, tubes, etc. — are laid up, a worker in the layup room assembles them in a plastic layup mold. A flexible urethene bladder is threaded through the entire frame, with an inflation tip at the seatpost clamp. Steel mandrels are inserted in the bottom bracket and head tube area for precise control of surfaces where bearings will sit. Excess fiber is trimmed to fit.

The prepped frame is then sent to the oven area, where it's held in a refrigerated rack until it's ready to bake.

At the oven stage, a worker fits the frame into the baking mold. It's a time-consuming process. Each of the mold sections you see with the dark circles in them are movable "stops" that must be precisely arranged around the frame section and then bolted in place with impact drivers. Once the frame is securely fixed in the bottom half of the steel clamshell mold, the top half is hydraulically lowered and clamped in place. Then the frame is shipped off to the oven.

The same frame emerges from the mold. Note how the tube shapes have been pressed out into the shape of the mold by the pressure of the internal bladder. Overlapping edges have been blended together as the resin melts and spreads throughout the matrix. Frames are pried from the mold and sent to finishing.

A worker hand-files excess resin, or flash, from the frame. The finish process is surprisingly rough — rubber-coated deadblow mallets are used to smack mandrels from the frame. Standard-looking rasps and files shave off flash and fiber ends.

A worker applies decals to a finished fork. All painting and finish work takes place at C-Tech. Finish-filing releases carbon dust into the air, and paint is similarly hazardous. Workers here wear jumpsuits and paint masks, while fans blow particulate matter away from the workers toward walls with water cascading down. The water traps the particles so that workers don't breathe them.

One last, important phase: testing. Here, a technician drops a weight from a preset height onto a fork to gauge impact resistance. Testing — both lab and real-world — is an essential part of the quality control process to determine if a physical product matches the predicted computer models.

Take a look at how Bianchi stress tested in 1981 here.

Frames made in Asia can be legally labeled "Made in Italy", according to EU rules, if they undergo a certain degree of "transformation".

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1 comment:

  1. Nice post. It's interesting to see how these "plastic" things are created but after seeing the photos we're probably less interested in riding one. On the "Made in Italy" issue, it seems more and more makers are now claiming "100% Made in Italy" to eliminate confusion. I would guess the carbon "pre-preg" material is still mostly from Asia but the construction and forming of the frame, as well as finish work is done entirely in Italy if the maker claims "100% Made in Italy" as more and more ads in Bicisport proclaim these days.