An additive manufacturing machine for building objects by layerwise melting of powder material includes a build chamber containing a build platform, a powder dispenser depositing the powder material in layers across the platform, a high energy beam selectively melting powder material in each layer and a control device controlling a property of the powder material given by build particles in the powder material below a specified upper particle size limit. A method includes controlling a property of the powder material given by build particles below a specified upper particle size limit. A method carries out successive builds, wherein in-between the builds, particles are added to or removed from the powder material to effect a property of the powder material given by build particles below a specified upper particle size limit. Further, adding or removing particles ensure that a sufficient proportion of micro build particles are present in the powder.