Many already know about how Giant is one of very few companies that manufactures carbon frames from raw fibre instead of ready-made pre-preg materials. What isn't as well known, though, is that Giant also uses a similar in-house approach for its aluminium bikes, too. Take a walk with us as we give you an in-depth look at how it's done.
That Giant builds such a staggering number of carbon fibre frames in-house from raw fibre – not ready-built pre-preg shipped from suppliers – is impressive on its own. What's even more incredible, though, is that the company adopts a similar approach with its aluminium frames, too.
Video: Inside Giant's Taiwan factory
Giant's alloy frames start life about 800km (500mi) north in Kunshan on mainland China at a facility called Giant Light Metal. Here, Giant actually smelts its own alloys, casts its own billets and extrudes its own tubing. In other words, when the company slaps its house-brand 'ALUXX' label on a frame, it really is a Giant product and not simply a rebadged item from someone else.
Heavyweight tubing sheds some weight
Raw tubing is shipped from Giant Light Metal over to the frame factory in Taichung, where it undergoes more rigorous forming operations. As it arrives, the tubing is all round, relatively thick and straight-walled, and far too heavy for use in higher-end bicycles.
Raw aluminium tubing racked up and waiting for its turn through the machine
Once in Taichung, that tubing is cut to manageable lengths and then forced through a number of dies that reduce the wall thicknesses and refine the grain structure to make it both lighter and more durable than before. As this point, the tubing can already be used to build high-quality frames.
Giant receives raw aluminium tubing into its Taichung factory from another facility operated by the firm, which smelts its own alloys
Giant goes further yet, however, with additional shaping that gives the tubing more direction-specific properties. Hydroforming (which uses pressurised oil to push the tubing outward against a steel mould) is the preferred method for higher-end frames while air forming (which uses hot, pressurised air instead of oil) is used for mid-range models.
The machinery involved in hydroforming is absolutely enormous compared with the parts being formed
In either case, the result is complex tube shapes with very good tube wall thickness control. In many cases, the tubes can emerge from the press with hard points, such as suspension pivot mounts, built right into the structure of the tube, thus cutting down on subsequent forming and welding steps.
Giant's hydroforming process can create surprisingly intricate shapes out of essentially round blanks
Afterwards, tube ends are mitred and deburred, and holes are drilled for water bottle bosses, internal housing ports, and suspension hardware. Each process is done on a dedicated jig to help ensure repeatability and accuracy.
All cleaned up and ready to mitre
Once the shapes are formed, all tubing is prepped for welding. It's given a rough polish and is chemically treated to remove any surface contaminants that might otherwise preclude a reliable joint.
The welded joints on giant's hydroformed aluminium frames require complex mitres
Makers at work
Now that all preparatory steps have been completed, it's time to set everything up in jigs and do some welding. Contrary to popular misconception, these frames aren't built by robots. Instead, Giant employs banks of actual people to lay down the welding rod.
Giant has a veritable army of welders on hand in its Taiwan factory
As one would expect in an operation of this size, though, there are some processes in place to boost efficiency. While each frame isn't completely welded from start to finish by one worker, they're not done in full-on assembly line style, either.
Front triangles sit on this rotating rack as they transition from the tacking station
Rather, frames progress in a handful of steps through several workers. For example, jigging and tacking is done in one area, one worker might weld an entire front triangle, and then another might do the rear end.
Welders are mostly supplied with individual cubicles so they can work relatively undisturbed
Alignment is checked at several points during the process, too, using a mix of manual gauges and laser sights.
Checking dropout alignment
Once welding is completed, frames are sent off for the first round of heat treatment (to T4 spec, for those that are interested), checked again for alignment, then sent for the final round of heat treatment (T6 spec).
After all that, the frames are off for final polishing, cleaning, and prep for painting.
Some welds are left raw while others are sanded down
From the time the raw tubing arrives in Taichung to finished product, Giant says an aluminium frame can theoretically be manufactured in about two hours.
In our fourth and final installment of this exclusive factory tour, we'll take you through the painting process and show you how Giant builds up all of these frames into complete bikes.