Manufacturing processes

Components may be manufactured by one of two methods.

Components are manufactured using two different methods: roll-forming or brake pressing. The components may then be used to form larger, more complex fabricated structures

Roll forming is a continuous process that shapes flat sheet or coiled, flat sheet into profiles or sections.

A typical roll former consists of a number of pairs of rolls. The sheet passes between the rolls, which rotate in the opposite directions drawing the sheet through. Each pair (or stand) of rolls slightly changes the geometry of the sheet. The number of rolls required depends on the complexity of the section and can be as much as twenty pairs. Coils are supplied in standard widths which are then slit to the required width for the profile. Roll forming is a rapid method of producing standard components, typical forming speeds are 20 - 40 metres per minute. Most roll forming machines are controlled by computer and cut the finished section to the exact length required. In order to maintain the speed of production cutting to length is done using a flying shear, which travels with the roll-former whilst shearing.

Holes and notches can also be made during the roll forming process. Each section or profile normally requires a different set of roles. The economics of roll forming relies on large production quantities. The cost of rolls is considerable and the changeover from one set to another to change profiles may take up to a day to complete. Some roll formers now produce less complex sections using adaptable rolls which are capable of producing a variety of sections with dramatically reduced changeover times. Whilst these sections may not be as structurally efficient as some sections produced using dedicated rolls, cost savings are achieved by being able to roll a wider range of sections in smaller quantities.

Press braking is used to manufacture a wide variety of components in small production runs.

Press braking is much slower than roll forming but does not need expensive tools dedicated to particular component. Sections are manufactured by pressing sheets, forming one or two bends at a time. The maximum length of a component is governed by the maximum length of the press brake, typically 6.0 metres.

 Cold-formed is supplied from the rolling mills in large coils up to 1500 mm wide. In most applications in the buildings the steel is pre-coated, either galvanised or painted. The steel coil forms the base material for a wide range of products manufactured by smaller companies using their own tools and designs. Products maybe either mass produced standard components that use dedicated tools such as cladding panels and lightweight structural sections or products may be design and fabricated to suit specific applications. Although the tools for individual cold-formed steel components can be expensive they are a fraction of the cost of tools for hot-rolled sections thus a much there is a considerably wider range of cold-formed structural sections than hot rolled.

Steel strip, which forms the basis of cold formed products, is available in various grades in flat sheet or coil form.

The coils are up to 1.5 metres wide either unpainted, galvanised or pre-painted. Typical thicknesses are between 0.4 mm and 6.0 mm. There are various grades of steel, representing different structural and forming qualities. The most common form of steel is galvanised coil with a yield strength of either 280 or 350 N/mm² and a standard zinc coating of 275 grams per square metre (taken over both sides of the sheet). This type of steel is used in structural sections and decks. The quality and specification for sheet steel is given in various standards.