The two-storey building of KTA Kunststofftechnologie Aurich in the East Friesian town of Aurich in the German state of Lower Saxony employs 1,200 workers in a three-shift system.
According to the plant's managing director, Jost Backhaus, it is the world's first rotor blade plant with continuous flow production. "Labour costs are high in Germany and KTA blade production will reduce cycle time to only seven-to-eight days, compared to about ten days for comparable blade manufacturing with a 'traditional' manufacturing process," says Backhaus. "At the moment we produce four-to-five blade sets a week, but we will boost this to seven-to-eight sets once all process steps have been optimised to the full later this year."
Integral to the concept are the in-house developed mobile production platforms that in seven predetermined process steps of ten hours each transport two matching blade halves in parallel over a 500-metre rail system.
Smaller composite components such as the shear-web internal reinforcements are pre-manufactured at the upper level, covering a central section of the plant floor area. These assemblies are then picked up by a portal crane, moved into position above a predetermined mould and lowered for final integration. The flow production concept incorporates a "RoundTrack" closed circuit for the mobile moulds, enabling their precise positioning without posing a barrier for forklift trucks and an easy return to the line beginning.
Following a blade's individual upper and lower shell epoxy resin vacuum-infusion and curing process completion, the halves are merged. For the finishing stages, different vehicles with a longitude-axis rotation system enable easy access to a blade's full surface for cleaning, grinding and inspection.
"Our current level of production automation is already high and includes, besides different kind of conveyor vehicles such as an automated cutting unit for glass-fibre, a glueing robot for the main moulds and a robotised blade painting portal," says Backhaus. "At KTA we had to optimise and master a completely new blade manufacturing process, and this learning curve is now about 60% completed. The introduction this summer of a surface grinding robot and a glass-fibre sheet cutting and precision mould placement robot is planned, but each additional process automation step must be implemented carefully for minimising risks of production flow disruption."
The E-101 blade has a "traditional" airfoil design, and in late March the switch to a redesigned and easier-to-manufacture second-generation E-101 blade had almost been completed. Main visible differences include a modified inner blade section with another spoiler segmentation design, and an improved mechanical spoiler attachment method. Blade mass was also reduced. A new E-101 E2 for IEC class IA strong wind sites, with a primary focus at export markets, will become commercially available in early 2016.
For the 3.0MW IEC class IIA E-115 Enercon developed new-generation slender (load-reducing) segmented rotor blades incorporating a factory-assembled integrated spoiler. Compared with the wider and partly site-assembled spoiler of E-101 blades, the E-115's blades have a "flattened" spoiler shape that extends further towards the blade foot creating an increasingly common 'flat-back' airfoil.
E-115 blades comprise a glass fibre inner section of about 12 metres and a 44-metre outer section (glass fibre reinforced composite). The sections are joined by an ingenious patented multiple-bolt method.
The overall solution is aimed at easier transport logistics especially at space constrained inland and/or forested sites.
An inner segment manufacturing novelty is the machine wrapping of pre-soaked fibreglass fabric around a cylindrical core that in ready form constitutes the load-bearing structure. In a second step the aerodynamic trailing edge, a pre-manufactured "add-on" with Enercon's integrated flat-back spoiler, is bonded with this "blank" creating the final airfoil structure and shape.
Automated wrapping offers time saving and cost benefits, high and uniform manufacturing quality and improved working ergonomics. The outer segment is built of traditional half shells with state-of-the-art vacuum-infusion technology, and can be flexibly produced at various blade production sites.
"The wrapping production method has a lot of potential for extending these inner segments of more than 20 metres in length, allowing us to utilise and adapt this new method to meet all our future blade demands," says Backhaus.