A method for non-destructive evaluation of a manufacturing process when forming a three-dimensional article through successive fusion of parts of a metal powder bed, which parts corresponds to successive cross sections of the three-dimensional article, the method comprising the steps of collecting an X-ray signal, created by the electron beam, from at least one position of the first and/or second metal powder layer and/or a melt pool of the first and/or second metal powder layer and/or a fused first and/or second powder layer by an X-ray detector, comparing the X-ray signal with a reference signal, alarming if the generated X-ray signal compared to the reference signal is indicating contamination material of larger amount than a predetermined value and/or a deviation in Atomic % of the powder material larger than a predetermined value.