The invention relates to a method for establishing a sectional or modular wind turbine blade. The method comprises the steps of transporting at least two blade sections of said wind turbine blade and a mobile factory for joining blade sections to a location at or in proximity of a wind turbine site, positioning said blade sections with two blade section ends facing each other and supported on a platform in said mobile factory, moving said platform in relation to the ground at the location for levelling said platform, aligning said blade section ends in relation to each other, and establishing said sectional or modular wind turbine blade by joining blade sections in an area of connection at said blade section ends.
The invention also relates to a system for establishing a sectional or modular wind turbine blade and a mobile factory for joining sections of a wind turbine blade.