In the past series production of structural composite parts for example of a wind turbine was done in three steps. First, a master plug was produced which was used for making a mould, as the second step. The final parts were built from this mould. Following these three steps it took sometimes a few years from ready to use CAD data to the start of a series production.
Using a direct female tool made by Knierim Tooling reduces cost and time of production significantly and allows a fabrication of at least 100 pieces without any decrease of quality.
Direct female tools are built in a similar way as master plugs. Except the outer layer of the sandwich construction is different. According to customer’s requirements it will be a laminate of GRP or CFRP with epoxy resin. This layer is machined into the final shape and the surface will be finished to customer’s needs.
In case a heating is requested it can be done either with a wire mesh or a layer of carbon fibre (which requires a CFRP laminate). The heated layer will be covered with a laminate which is machined into shape precisely to a tenth of a millimeter and finished as desired. The wire or carbon fibre will be connected to an extra-low voltage (48 to 60 V) power supply providing, together with the cover layer, an evenly heated surface.
To further improve the durability of the tool the surface can be treated with a special topcoat.