Abstract: Present research in metal direct RP&M technologies all over the world is discussed. The viewpoint is presented that the strategy for material deposition to a large extent determines the process’s characteristics in the aspect of heat input and dissipation, while heat input and dissipation have a crucial influence on the parts’ microstructure, mechanical properties as well as accuracy. From this point of view, a new classification criterion for metal direct RP&M is put forward which essentially classifies the technologies according to the differences in heat influence on parts during the processes. Based on this criterion, these technologies are classified into three categories: selective deposition, cladding deposition and droplet deposition, whose technical characteristics, applications as well as developing trends are also discussed. Special emphasis is concentrated on the analysis of technical problems as well as tried solutions. The principal approach for fabricated parts to get finer microstructure, better performance as well as higher dimensional resolution is considered to be a more accurate control of heat input and dissipation. What’s more, heat input should be as little as possible.

Key words: Accuracy, Direct metal rapid manufacturing, Heat input, Rapid prototyping technology