**5. Conclusion**

The environmental impact of a manufacturing process is strongly determined by the basic features associated to the characteristics of the machine-tool selected to execute the process. The analysis of the machine-tool assembly is supported by the inventory of all substances used as components' materials or production consumables. In addition, the analysis of a specific manufacturing process corresponds to the collection of all substances used during utilization of the machine. In a full LCA of the machine-tool, this would correspond to the use-phase of the machine-tool life-cycle.

Machine-tool technology is the factor determining the assembly components type, amount and arrangement, and consequently the energy consumption profile of the machine, which rules the environmental performance of the manufacturing process. Modelling the energy consumption of a process firstly requires an adequate process categorization based on the technology of the main functional sub-systems. Other categorization criteria, such as the utilization mode, are also interesting, but more extensive work is needed to validate and reveal the most relevant sub-categories and associated environmental features. Attention should also be paid to the exergy reference unit used to define the specific process energy indicator. In the case of pure metal forming processes, which includes a set of chiplessshaping processes, some applying only discrete loads, typical units based on the amount of material removed are not appropriate. In such cases alternative units can be introduced, such as the energy per bending cycle proposed for bending.

In the future, the environmental impact of the manufacturing processes will be strongly affected by the trend for sub-systems modularisation, higher accuracy and versatility, as well as legislation and cost factors. The particular optimisation of the energy consumption of the machine-tools during process will require a strong awareness of machine-tool manufacturers and end-users, as the continuous improvement will not depend on a single measure. Proposed measures to be combined include solutions of alternative materials, either for small components or main structures, moving or structural parts, matching of sub-systems power profile and conditions of application, operating modes, maintenance needs and process chain shortening. Many high potential measures towards metal forming, and general manufacturing processes, are being revealed by dedicated groups, but extended work focused on the development and standardization of accounting and assessment methods customized for the purpose of evaluating the environmental profile of each manufacturing process category must be followed.
