Taking into account, as soon as possible in the product design process, specific manufacturing constraints is a major stake in the current economic context. In the specific field of forging part design, i.e. the modification of the initial shape of the tooled part into a forgeable shape, our recent developments show the necessity of knowing the way the material flows during the process. To this end, we are developing a fast-simulation deformation tool (two dimensional, isothermal) based on the extension of Chamouard's model. This tool allows us to simulate the evolution of the forging force, as well as to visualise the intermediate shapes during the operation in order to identify the critical zones in terms of filling. In this paper, we present our latest developments about this subject. First of all, we deal with the problem of the upsetting of a billet, recalling the model used and in particular our original approach to the evolution of the tool/part contact diameter. Then we present the extension to the flashless forging of a billet and we compare our results to experimental ones from the literature. This comparison relies on the correlation between the forging force and the unfilled volume, i.e. a measurement of the corresponding corner radius. The integration of the flash calculation is the third main point of this paper. After a detailed presentation of the model, we show its sensitivity to the flash position on the part. Then we also compare the obtained results with those in the literature. We end with the presentation of an example showing the current abilities of the program in terms of algorithm's performance, interface facilities and result handling.