An important parameter for the production of wood based panels is a steady supply of material, evenly distributed over height and surface. This article presents the working principles of an automatic mass controlling system developed by Grecon Inc. The system uses X-radiation to continuously measure the surface mass density along the production direction in a non-contact way. The measured results are the basis for the regulation of the belt speed and/or the height of the rake, though which controls the material quantity to an even level. Target optimization helps customers save material and other costs.