Usage of thin panels is constantly increasing in shipbuilding since it provides better performance with lower fuel consumption, faster speed, and agility for ships. Even though deformation and productivity challenges are common in thin panel fabrication, they can be solved with dedicated automated production.
Towards thin panel production
In modern shipbuilding, ships are built lighter to increase the speed and agility while still appreciating the green values, such as better fuel economy. Moreover, ship-owners are looking for faster delivery times with reduced investment, and the same ship functions and functional constructions should be maintained. This requires ship designers to ﬁgure out ways to meet the demands and e.g. reducing plate thickness even down to 3mm everywhere that is possible.
Reduced plate thicknesses are not only a big challenge for ship engineering but also for automated manufacturing. In order to answer the demands on today’s shipbuilding, it’s needed to make a shift from traditional methods and processes to modern automated shipbuilding.
Thin plates and stiffeners
In special ships like navy, cruise, ropax, and ferries, the main amount of interior panels can be built from thin plates – the target being 3-4 mm. By decreasing material thickness the length of welds is increasing – more stiffeners and more butt welds. Preparation for weld edges must achieve machining tolerances to able succeed in welding – poor edge preparation cannot be corrected by welding. The welding process must be controlled on-line to keep the heat input on the optimum level to avoid deformations. For secondary elements like T-beams and Bulkheads, the same laws apply – dimension tolerances must be under control all the time.
The production from the cutting to the block assembly must be under good dimensional control and all work phases must be predictable. Interfaces to and from the MES system, even up to the 3D design system, thanks to digitalization are available. By digitalization, it is possible to run panel lines nearly fully automated and also to gain a high level of productivity with on-line feedback.
Advanced T-beam manufacturing line.
Automation enables a high level of productivity
During past years Pemamek has developed and made a full set of machinery and HMI to support the thin material steel production together with the world’s leading yards in navy and cruise shipbuilding. Fast material handling with minimum operator interfering, material preparation, automatic material dimension control, WPS process control, operation free welding processes, quality control, and communications with superior MES systems.
Modular and proven panel line machinery is always done by listening to customer wishes and with modern welding processes combined with the PEMA ideology.
To ensure productivity and quality also at the end of the production line, T-beam assembly and T-beam welding stations need to be established and automated. This is something that differs from the existing traditional panel lines.
Especially in cruise shipbuilding the ratio of transversal and longitudinal Tees is quite high compared to the traditional tanker or bulk carrier manufacturing.
Research & Development in LHAW and GMAW
The latest research and development have been the integration of Lincoln Electric’s high-end welding processes together with PEMA’s high-quality welding technology. For plates one-sided butt welding with a single pass, PEMA has developed a process library for laser-hybrid welding to cover plate thicknesses from 4 mm up to 25 mm for high strength steel. The nominal work cycle for normal thin panels within 20-25 m plate length is around 30 minutes.
For stiffener ﬁllet welding, the high quality is achievable with LHAW or advanced MAG process. With the LHAW process, the welding speed ~2-3 m/min and with advanced MAG ~1.5-2 m/min can be achieved. According to the chosen profile handling configuration and amount of welding heads, the cycle time in this process per profile is changing from 6 to 15 minutes.
Using the high-speed Lincoln welding GMAW/MCAW process for secondary elements together with PEMA WeldControl 200 robot on-line programming and controlling software, we are again stepping ahead to control the productivity and quality of thin panel production.