Thank you very much for your help everyone!I managed to achieve some pretty good prints mostly by reducing print speed on small objects. I think you were right printbus, thanks a lot.I think i will still install a cooling fan, to see if i get better results. I'll keep you updated if you want.I stumbled upon another problem lately : when printing small objects, the extruder tends to clog, it did twice in a row yesterday printing a small figurine with a lot of support material. I think i may be printing support material too fast, what do you think?