| Fabrication of structural steel elements has historically | | | | For cutting irregular openings or non-uniform ends on |
| been performed by sequential operations involving | | | | dimensional (non-plate) elements, a cutting torch is |
| sawing, drilling and high temperature flame cutting to | | | | typically used. Oxy-fuel is the most common type and |
| remove material, each operations being performed on | | | | range from simple hand-held torches to automated |
| special purpose machinery. | | | | CNC 'coping machines' that move the torch head |
| Developments in plasma cutting of metals, combined | | | | around the structural element in accordance with |
| with computer motion control, accomplish the | | | | cutting instructions programmed into the machine. |
| sequential operations on a single machine. This has the | | | | Plasma Technology Applied to Industrial Metal Cutting |
| advantage of minimizing the non-productive loading | | | | Plasma Cutting emerged as a very productive way to |
| unloading/transport time between machines. | | | | cut sheet metal and plate in the 1980s. It had the |
| Background: Structural Steel Elements | | | | advantages over traditional "metal against metal" |
| Structural steel - the "skeleton" of multi-story | | | | cutting of producing no metal chips and giving accurate |
| construction - provides a framework on which floor, | | | | cuts, and produced a cleaner edge than oxy-fuel |
| wall and exterior cladding systems are affixed. | | | | cutting. |
| Individual structural steel elements are produced in steel | | | | As with other machine tools, CNC technology was |
| mills or foundries, conforming to chemical composition | | | | applied to plasma cutting machines in the late 1980s |
| and geometric/dimensional specifications established | | | | into the 1990's, giving plasma cutting machines greater |
| by regulatory agencies and industry associations. | | | | flexibility to cut diverse shapes "on demand" based on |
| The most common structural steel elements are | | | | a set of instructions programmed into the machine's |
| beams (I-beams, H-beams or girders), channels, HSS | | | | control. These CNC plasma cutting machines were, |
| (hollow structural shapes), angles, columns and plate. | | | | however, generally limited to cutting patterns and parts |
| These elements are cut to required lengths and joined | | | | in flat sheets of steel, using only two axes of motion. |
| together, either by welding or bolting in the manner | | | | Multi Axis Plasma Cutting of Structural Steel Sections |
| prescribed to achieve objectives for supporting both | | | | Starting in the late 1990s, programmable industrial |
| static and dynamic loads. | | | | robots were integrated with plasma cutting to |
| Traditional Fabrication MethodsFabrication of structural | | | | accomplish more generalized cutting of non-flat |
| steel elements has always been performed using | | | | shapes. These "3D Systems" use the robot to move |
| "metal against metal" techniques, and these remain the | | | | the plasma cutting head around the element to be cut, |
| most widespread methods today. The emergence of | | | | so the cutting path may encompass the entire outer |
| CNC (computer numerical control) technology brought | | | | surface of the element. Many systems also grip the |
| automation and greater accuracy to these techniques, | | | | element to be cut in a "chuck" so the element itself |
| resulting in special purpose machines dedicated to | | | | can be rotated or indexed forward or backward with |
| performing individual fabrication tasks. | | | | the cutting head. |
| The most common such machine is a bandsaw. A | | | | Robotic plasma cutting is widely used for cutting of |
| bandsaw employs a continuously rotating band of | | | | pipe, including HSS, used as structural steel elements. |
| toothed metal to saw through the structural steel and | | | | The task of robotic plasma cutting of more diverse |
| is generally used to cut through the entire cross | | | | shapes, such as beams and channels, has proven to |
| section of the element. | | | | be more challenging. The large sizes and variety of |
| A beam drill line has long been considered an | | | | shapes involved make the technique of gripping the |
| indispensable way to drill holes and mill slots. CNC | | | | structural steel element in a chuck impractical. This |
| beam drill lines are typically equipped with feed | | | | places the entire burden of cutting motion back on the |
| conveyors and position sensors to move the element | | | | robot. In order to have the cuts and features placed |
| into position for drilling, plus probing capability to | | | | where they are intended on the element, the robot |
| determine the precise location where the hole or slot is | | | | must be given some instruction as to the location, size |
| to be cut. | | | | and shape of the element. |