The aim of this work is to describe the formulation adopted for the numerical simulation of the Metal Deposition process (MD). MD process consists of a manufacturing technology similar to the multi-pass welding used for building features such as bosses and flanges on fabricated components. Temperature evolution as well as residual stresses and distortions due to the successive welding layers are accurately studied coupling the heat transfer analysis together with the mechanical field. A fully coupled thermo-mechanical solution is considered including phase-change phenomena defined in terms of latent heat release and shrinkage effects. The material behaviour is characterized by a thermo-elasto-viscoplastic constitutive model (at macro-level) coupled with a metallurgical model (at micro-level). Nickel alloy (INCONEL-718) is the target material of this work. Both heat convection and heat radiation models are introduced to dissipate heat through the boundaries. An in-house developed coupled FE software was the starting point to deal with the simulation and an ad-hoc activation methodology has been implemented to simulate the deposition of the different layers of melted material. Thermo-mechanical results are presented in terms of temperature evolution, residual stresses generated and prediction of the final shape. Difficulties and simplifying hypotheses are discussed. The numerical simulation of the MD process is based on an ad-hoc FE activation technology able to reproduce the deposition of the melted material along the welding path. Two basic approaches are possible. Either a model is assumed including all the elements of the analysis or the model is extended at each time-step. The first approach considers that all the elements defining the successive welding layers, which will be deposited during the process simulation, are included in the initial computational model. These elements are made passive by setting material properties that do not affect the rest of the model. Both low stiffness and low heat conductivity are considered until the welding layer is used. There are different drawbacks to be taken into account: first of all, the simulation process is performed