Then

Hot-rolled process

• Steel ingots are rolled into any shape imaginable (i.e. I-beams, Ts, channels, angles, flat bar, and sheet products).
• Controlling tolerances allows bow, twist, and sway in the final product.
• Not possible to precision roll the shape to the point where their use in curtain walls is practical.

 Cold-drawn process

• Physically pull steel through a shaping die without heat.
• Ideal for smaller shapes, such as bars, wires, and general shapes with smaller cross sections.
• Sharper corners than possible with the hot-rolling process.
• Not ideal for exterior façades as their structural requirements dictate larger shapes.

 Now

Cold-rolling process

• Flat steel sheets or continuous coils are fed through a series of rollers to desired shapes for curtain walls and windows.
• Allows for the development of larger sections out of thin-gauge carbon or stainless material (material thickness ranges from 24 gauge 0.6 mm [0.024 in.] to 6 mm [¹/₄ in.]).
• Rollers can introduce complicated shapes into the material (gaskets, box screws).

 Laser cut, laser-welded shapes

• Process takes long, flat carbon or stainless plates in lengths ranging from 12 to 15 m (38 to 49 ft), in thicknesses from 4 to 50 mm (⁵/₃₂ to 1 ¹⁵/₁₆ in.), and laser cuts them into bars or strips in the size required for the desired shape.
• Once cut, the bars are assembled into the required shapes, with joints laser welded into the desired profile, such as rectangles, channels, Ts, angles, square tubes, and I-beams.
• A shape can meet the required width and depth, and also change the wall thicknesses to develop the necessary structural properties for the application.