A system and method for the manufacture of a wind turbine blade component is described, preferably a shear web component for a wind turbine. The shear web is manufactured by using a forming tool to define a flange-shaped cavity at an end of a web member. A resin is injected into the cavity and cured to form a flange cast onto the web member. The forming tool is subsequently removed from the web member to provide a component having a load-bearing flange formed from a cured resin.