Wind power + renewable energies
Robust quality for extreme conditions

Rotor blade manufacturing

State-of-the-art mixing and dosing systems for resin, adhesive and gelcoat applications

Rotor blades are exposed to extreme loads during operation. They must be able to withstand all types of weather conditions. Wind speeds of up to 400 km/h can occur at the tips of a rotor blade. Hail, impact from birds and even raindrops can cause significant damage to the leading edges. In addition, increasingly large turbines are being produced, and the length of the rotor blades and the rotor diameter are growing steadily.

Even the smallest error in production could have serious consequences. This poses particular challenges for the construction of the systems. The components are still manufactured by hand. Although there is a tendency towards automation for certain process, this has not yet become established. For the production of fibre composite components, DOPAG offers special metering and mixing systems that can handle the large material volumes involved in the production of rotor blades and can meet all the current production requirements.

Our product range includes infusion systems with volume outputs of more than 60 l/min as well as bonding resin systems that process compounds of more than 30 kg/min. This ensures minimal mould cycle times. Due to the high resin consumption during infusion and the quality standards of the fibre composite components, resin degassing systems need to be used. DOPAG has a validated system which can degas more than 40 litres of resin per minute. In addition, there is also a wide range of gel coat systems as well as systems for mixing erosion coatings and putties for finishing the rotor blades.

We offer metering technology for these applications:


Metering infusion resin

Rotor blades must be able to withstand extreme loads and demonstrate high strength and rigidity. The infusion process ensures optimum cohesion of the internal components. This involves impregnating the semi-finished fibre products with infusion resin. Here, dry woven or non-woven (non-crimp fabrics/NCF) fibre materials are placed in an open mould and a vacuum build-up is prepared with infusion tubes and valves. The main infusion tube is then connected directly to a metering system, which dispenses the infusion resin and applies it into the mould. The DOPAG metering systems eldomix or compomix can be used to optimally dispense the material.

Filament Winding

Filament winding with DOPAG metering systems

In the case of the filament winding technique, cylinders, tubes and vessels are wound. The composite components can then withstand high pressure in spite of their low weight. In filament winding, the fibres, such as carbon or glass fibre, are continuously fed from a roll through an impregnating bath and then wound onto a winding mandrel, resulting in a fully wrapped profile. The fibres are first impregnated in the bath. It is filled with materials such as polyurethane or epoxy resin and must be kept at a constant level during the winding process. The DOPAG metering system eldomix can perform this task, for example.


Manufacture of pultruded composite components

Rotor blades contain composite components produced through a pultrusion process. They are installed inside the rotor blades to ensure a higher rigidity of the rotor blade. Carbon or glass fibres are fed from a roll and passed through an impregnating bath filled with epoxy or polyurethane resin. The impregnating bath is kept at a constant fill level with DOPAG eldomix, for example. The fibre composite is subsequently pulled through a heated moulding tool, which has the negative shape of the generated profile. The endless profiles in T, U or O-form are then individually cut to length.

Adhesive Bonding

Bonding fibre composite components

Adhesive bonding involves bonding smaller composite or metallic components. The application is also used in the manufacture of rotor blades for wind turbines. DOPAG systems dispense the adhesive either manually or fully automatically. For example, the application can be conducted in point and/or bead form. The DOPAG gluemix, for example, is used in the wind power industry. This was specially developed for use in the production of rotor blades and is capable of metering large quantities of epoxy resin precisely and reliably.

LEP + Putty

Protecting edges and smoothing out irregularities

Rotor blades are exposed to extreme loads. It is therefore very important that the leading edges are protected from damage. A two-component polyurethane is applied to the leading edges of the rotor blades. This is known as leading edge protection (LEP). Even in the high-precision manufacturing process, small irregularities may occur on the surface of the blade at the end of the production process. In the putty process, these cavities are filled with a putty based on 2K polyurethane, ensuring that the surface of the rotor blade is smooth throughout. The two-component material can be prepared with eldomix from DOPAG for both applications.


Surface protection for composite components

As composite components are exposed to extreme weather conditions, corresponding surface protection is necessary. This is either applied to the composite material as a gel coat or applied beforehand as an in-mould gel coat. This means that the surface protection is applied in the mould, e.g. before the infusion or RTM process. DOPAG developed the metering and mixing system gelcomix for gel coat applications in rotor blade production. It is used to prepare the two-component material, an epoxy resin or polyurethane, and then manually applied to the mould surface.

Reference projects


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Expert in wind turbine rotor blade production

Trends in rotor blade production

In recent years, the rotor blades of wind turbines have been getting even larger. Carbon fibre semi-finished products in combination with standard glass fibre materials enable blade lengths of more than 100 metres. Due to the increased need for reinforced fibre layers, mould occupancy times are getting longer. Tonnages for infusion and bonding resins as well as coating materials are increasing. Consequently, the systems for providing mixed materials must meet these growing demands. This also applies to the very high quality standards involved in offshore.

A rotor blade typically consists of glass fibre composites and reinforcement materials such as balsa or foam materials in order to transmit the shear stresses. The production process begins with the manufacture of the upper and lower shells. For the first layer, a gel coat is applied using the gelcomix metering system to give the component a high-quality surface finish. Dry semi-finished fibre products are then placed in the mould, auxiliary materials are added, and then the entire component is sealed vacuum-tight with a film and evacuated. This ensures the maximum freedom from pores.

Further steps include degassing the infusion resin and the actual infusion process. Degassing is necessary because some air bubbles can collect in the material due to contact with the air and due to transportation, which can result in undesired air pockets in the fibre composite during vacuum build-up. Degassing reliably removes even the smallest bubbles from the material. The compomix BL infusion system is connected directly to the vacuum build-up by means of tubes. Alternatively, buffer tanks are also possible, which are supplied with mixed material and also connected using infusion tubes. The mould is set after infusion. The temperature is closely monitored and controlled during this process in order to prevent material damage due to the exothermic reaction of the resin.

Once the component is fully set, all auxiliary materials are removed and the bonding process of the stiffening elements and the two shell halves begins. The adhesive beads are applied with a gluemix binding mix system. Once this process is complete, the two halves of the mould are closed up and a complete rotor blade is created.

DOPAG offers reliable solutions for the manufacture of fibre composite components, for example RTM, Filament Winding, Infusion, Pultrusion, etc.

  1. compomix


    The compomix DI was developed for dispensing epoxy and PU in infusion processes in the production of rotor blades.

  2. eldomix


    The eldomix 100/600 range of systems are compact, solvent free, gear pump driven metering and mixing systems.

  3. gelcomix


    The gelcomix is a gelcoat application system, especially developed for surface production of rotorblades and composite parts.

  4. gluemix


    The gluemix was specially configured for the application of two-component adhesives in rotor blade production.