Method and device for calibrating multiple energy rays for the additive manufacturing of an object

A method for calibrating a device designed for manufacturing at least one object by an additive manufacturing technique starting from a raw material, the method comprising:

• applying the raw material in successive layers in a construction zone wherein each of these successive layers defines one and the same build plane;
• after the application of each layer, moving several energy rays over this layer so as to form successive cross-sections of said object and to thus build the latter layer by layer;
• wherein, in said construction zone, several sectors are determined extending at least in this construction zone, wherein every sector is covered by at least one corresponding energy ray;
• wherein, for every sector, corresponding scan means are controlled to move the point of incidence of the ray in the construction zone over said sector according to a predetermined pattern so as to form said successive cross-sections;
• wherein for every sector a sector coordinate system is associated with the corresponding scan means of this sector, and a relation between each sector coordinate system and a single reference coordinate system is determined by an initial transformation function;
• wherein at least one of said sectors extends at least partially over two or more of the other sectors;
• moving said point of incidence by said scan means to at least one measuring position;
• wherein the at least one measuring position has sector coordinates which are defined in the sector coordinate system associated with said scan means;
• determining reference coordinates of the point of incidence in this measuring position in said reference coordinate system;
• determining for at least one measuring position, deviation between said reference coordinates of the point of incidence and coordinates in said reference coordinate system of said measuring position, obtained by applying said initial transformation function on said sector coordinates;
• calculating a corrected transformation function on the basis of the thus determined deviation for at least one measuring position, and preferably for two, three or more measuring positions, such that the coordinates of said measuring position in said reference-coordinate system are substantially equal to the coordinates obtained by applying the corrected transformation function to the sector coordinates of the measuring position.