**4.4. Selection of sub-systems technology and power matching**

As concluded from the study on Laser cutting, although the sub-systems dimensioning and energy-consumption could be individually optimized for a specific range according to the application conditions, these are quite technology dependent. Besides, considering that one same machine-tool model typically operates in very distinct operating modes, it is important to insure that all sub-systems are properly synchronized in each operating condition, and the respective power-consumption profiles should be matched. This is expected to contribute significantly for the reduction on the power demand and improved efficiency of auxiliary main-systems against the main energy-source sub-system.

Towards Benign Metal-Forming:

The Assessment of the Environmental Performance of Metal-Sheet Forming Processes 149

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.

Azevedo M., Oliveira M. I., Pereira J.P. and Reis A. (2011), Comparison of two LCA Methodologies in the Machine-tools Environmental Performance Improvement Process, *Proceedings of 18th CIRP International Conference on Life Cycle Engineering*, Braunschweig-

Bala, A., Raugei, M., Benveniste, G., Gazulla, C., Fullana-i- Palmer P. (2010). Simplified tools for global warming potential evaluation: when 'good enough' is best, *International* 

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Devoldere T., Dewulf W., Deprez W., Duflou J. R. (2008), Energy related environmental impact reduction opportunities in machine design: case study of a laser cutting machine, *Proceedings of the CIRP International Conference on Life Cycle Engineering*,

Dietmair A., and Verl A. (2010). Energy consumption assessment and optimization in the design and use phase of machine tools, *Proceedings of the 17th CIRP International* 

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Erbe T., Król J.; Theska R. (2008). Mineral casting as material for machine base-frames of precision machines. *Proceedings of 23rd Annual Meeting of the American Society for* 

*Precision Engineering and the Twelfth ICPE*, October 19-24, Portland-Oregon.

*INEGI – Instituto de Engenharia Mecânica e Gestão Industrial, Portugal* 

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*Conference on Life Cycle Engineering*, Anhui-China, May 19-21. Ecoinvent Centre, Ecoinvent 2.0 database, October 2010, www.ecoinvent.ch.

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**Author details** 

Marta Oliveira

**6. References** 

Germany, May 02-04.

Sydney, N. S. W., pp. 412-419.

Besides the evidences coming from the laser case analysed, the impact of the motor power to the SPE values of the bending case also reflects some needs for improvement. Although the energy models presented are able to be tuned for different motor rated power levels integrated in press-brakes of different maximum bending capacity, this is indirectly associated to the maximum loading capacity of the machine. Obviously, in order to minimize power consumption, the motor rated power installed should be as low as possible, as made evident when comparing hydraulic systems (Table 1), where the lower motor rated power of the former resulted in over 49% energy savings when comparing a 110 t equipment with that of a 170 t equivalent. Moreover, in these hydraulic systems, where the stand-by consumption contributes significantly to the SPE, the motor power related energy savings are maximized with the increase on system usage.
