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Construction of Steel Railway Bridges
Published in John F. Unsworth, Design and Construction of Modern Steel Railway Bridges, 2017
Plate and shape cutting methods used in preparation for steel shop fabrication¶ depend on edge preparation specification, dimensional tolerances, and material thickness. A common steel cutting method is thermal flame cutting with oxy-acetylene or pure oxygen gases. Metals may also be cut by thermal plasma gas cutting. Plasma cutting is fast and provides smooth and clean cut surfaces but is typically less effective than flame cutting for steel plates in excess of about 25 mm (1 in.) thick and effectively limited to cutting plates less than about 65 mm (2.5 in.) thick. Thermally cut surface roughness in the form of small notches (potentially detrimental stress raisers depending on the service load stress state of the component) may be precluded with speed- and direction-controlled automatic cutting (Figure 10.4). Otherwise, supplemental trimming of rough cut surfaces by grinding or machine planing may be required. Automated or mechanized thermal cutting also increases shop productivity [e.g., girder flanges can be economically flame cut at same time using guides (Figure 10.5)].
Metals
Published in Christopher Beorkrem, Material Strategies in Digital Fabrication, 2017
For their strength and durability metals are often deployed in materially parametric compositions. For its flexibility and simplicity of machining, sheet steel is often the material of choice. Metals require a layer of post-processing after cutting adding significant production time compared with wood. Sheet steel is most often processed using a CNC plasma cutter, laser-cutter, or water-jet. Each machine type comes with both strengths and weaknesses. Plasma cutting is quick and dirty, superheating the material through an electrical current, this process leaves a proportionately wider cut line. However, a plasma cutter is capable of cutting thick sheets of steel significantly cheaper than any other method. Laser-cutters require significantly more investment to reach the strength where they are capable of cutting through thicker metal. Additionally, they require a punch of ignitable gas to pierce the material quickly, but they do create relatively thin cut lines. Water-jet cutters provide a clean even cut, but require significantly more investment. They require a high-pressure system to deliver a tiny piercing stream of sand and water. They also require a bathtub to collect the spray following cuts. In addition to cutting machines there are certain types of CNC bending tools that can be used to form certain extrusions into both two-dimensional and three-dimensional shapes.1 There are also processes for creating custom componentry through conventional casting processes with CNC tooling, vacuum forming, and explosion forming.2
Development of an intelligent model to optimize heat-affected zone, kerf, and roughness in 309 stainless steel plasma cutting by using experimental results
Published in Materials and Manufacturing Processes, 2019
Soroush Masoudi, Mostafa Mirabdolahi, Mohammad Dayyani, Farshid Jafarian, Ana Vafadar, Mohammad Reza Dorali
The main advantages of plasma cutting are its high cutting speed, efficient material removal rate, the lack of use of highly flammable gas, the possibility to cut a wide range of thickness (1–150 mm), and high energy concentration.[4] However, plasma cutting is categorized as a rough cutting process due to its extremely high energy concentration and the formation of irregular edges.[5] In new technologies such as high-tolerance plasma arc cutting (HTPAC), higher density and efficiency can be obtained compared to traditional technologies due to the use of smaller and optimized torch diameters. In this process, the plasma beam stays in direct contact with its axis and its divergence is minimized.[6]
Investigation of different cutting technologies in a ship recycling yard with simulation approach
Published in Ships and Offshore Structures, 2022
Sefer Anil Gunbeyaz, Rafet Emek Kurt, Osman Turan
Results of this study show that plasma cutting is a viable alternative to commonly used oxy-fuel cutting for the daily metal cutting tasks in the yard. Plasma cutting can provide around 60% improvement in the productivity of the primary and secondary dismantling zones of the ship recycling yards for the selected case study. Even though the initial capital and consumable costs of the plasma cutting is more expensive compared to the oxy-fuel cutting, plasma cutting is superior to the oxy-fuel (LPG in this specific case). The initial cost of the plasma cutting is around €10,000 that is high compared to the €300 investment cost of the oxyfuel cutter. Moreover, on the operation expense, oxyfuel cutting (€21/hour total operation cost) is also much cheaper compared to plasma cutting (€33/hour). However, using plasma cutting, the difference in investment and operation be compensated due to the high performance, which compensates through the lower operation time, lower worker cost and higher throughput of the yard. One of the causes for performance difference is the fact that the oxyfuel requires the metal to be preheated before cutting, while plasma does not have this requirement. This also improves the quality of the steel as there is minimal slag on the cut edges. Even though it is generally not crucial for ship recycling, sometimes plates are sold as it is for direct reuse if they are in good condition. Plasma torches can cut non-ferrous metals and stainless steels while oxy-fuel torches cannot. This is important for the ship recycling business as some ships contains stainless steel parts (equipment, pipes, cargo holds, and so forth), as well as aluminium or cast-iron parts. Plasma torches can operate on these metals without any loss of productivity.
Computationally intelligent modelling of the plasma cutting process
Published in International Journal of Computer Integrated Manufacturing, 2020
A. Lazarević, Ž. Ćojbašić, D. Lazarević
The plasma cutting process is widespread in manufacturing and construction industry. The process is well suited for automation, which increases its efficiency and productivity, making it even more competitive. The continuous improvements of the plasma cutting process have had a positive impact on the capabilities and quality of plasma cutting, making their adjustments easier and faster. Plasma cutting systems do not require intensive operator training, therefore, they are easily applicable in the production environment.