A process and an apparatus for producing 3D moldings, wherein a spectrum converter is used. Said converter is defined as a means which absorbs a radiation, for example electromagnetic thermal radiation, and radiates or emits one or more defined wavelength ranges; the spectrum converter is here irradiated by an emitter of an electromagnetic thermal radiation (shortwave or longwave radiation), i.e. by a lamp or an emitter, for example an overhead emitter or a sintering unit, and then emits a defined electromagnetic thermal radiation.