Abstract: An apparatus for producing a three-dimensional object by successive solidification of layers of a powder material at points corresponding to a cross-section of said object using electromagnetic or particle radiation comprises support means having an upper side for supporting the object thereon at a determined elevation, elevation adjustment means for varying the elevation, means for applying a layer of the material onto the upper side or onto another layer formed on the upper side, and irradiation means for irradiating the layer of the material at the points corresponding to a cross-section of the object. For reducing the production time of the object the apparatus further comprises a prefabricated base plate on the upper side, the base plate being made of a material which the powder material adheres to when being solidified, and means for removably connecting the base plate to the upper side of the support means.