**1. Introduction**

In the last decade, significant attention has been devoted to the assessment of the environmental impact of manufacturing processes and machine-tools, defining the most important factors to be covered and proposing methodologies to support the analysis of their individual contributions. The work published has established that the environmental impact of a manufacturing process is mainly affected by the consumption of 3 types of resources, namely:


Most of the studies dealing with this triangular perspective focus the analysis of chipping processes (Dietmair & Verl, 2010; EBM, 2010; Gutowski et al., 2006; Kuhrke et al., 2010; Pusavec et al., 2010a,b; Rajemi et al., 2010). Other pure metal forming processes, such as chipless-shaping processes, typically involve no significant material waste or consumables usage, and the savings on the electrical consumption of the machine-tool become the dominant factor to analyse during the use-stage (Santos et al, 2011). As advanced by Gutowski (Gutowski et al., 2006), the total energy required for operation of a machine-tool is not constant, as many life-cycle assessment (LCA) tools assume, and instead the system total electricity consumption, *Pactive,System*, should be decomposed in a fixed and a variable parts, according to Eq. (1):

$$P\_{active, System} = P\_0 + k\vartheta \tag{1}$$

Towards Benign Metal-Forming:

The Assessment of the Environmental Performance of Metal-Sheet Forming Processes 137

Regarding this, it is important to highlight the interesting work followed by the CO2PE initiative (Kellens et al., 2012), which has been working on the definition of a methodology for systematic analysis and improvement of manufacturing unit process life-cycle inventory (UPLCI), i.e. on the deep analysis and quantification of the manufacturing processes environmental impact. To ensure optimal reproducibility and applicability, documentation guidelines for data and metadata are included in this approach. Guidance on the definition of a functional unit and a reference flow as well as on the determination of system boundaries meets the generic LCA goal and scope definition requirements of ISO 14040 and ISO 14044. Developed with the purpose to provide high-quality life-cycle inventory (LCI) data for manufacturing unit processes, this work seems to fit the needs of methodology

This chapter provides an overview on the assessment of the environmental impact of metalforming processes and machine-tools. The most important factors to be considered are discussed and some methodologies supporting the analysis of the individual contribution of energy consumption during process are presented, as this is still considered as the main detractor. Process categorization criteria and accurate modelling of the energy consumption per category are here highlighted as the basis for high quality quantitative inventory data to achieve reliable environmental profiling. Pure metal forming processes, such as bending, are covered. Overall and sub-systems accounting strategies are presented, using the case of Laser cutting as an example of multiple sub-systems with similar contribution to the total energy consumption. The main findings and conclusions, as well as some strategies favouring the environmental performance of the manufacturing processes, are here

The strategies for improvement expected from the environmental profile assessment of a process shall be based on the comparative analysis between alternative production scenarios. Relevant technologies and application ranges have been selected, considering the respective technology/application market share. Comparative studies were followed with a pre-defined job and application ranges (material, shape, process quality,…), and under

Regarding data collection, particularly on preliminary process evaluations, it seemed realistic to start focusing on energy consumption and any main consumable. The same measuring system and accounting methods were used throughout the comparative studies followed.

Special attention was dedicated to the accounting methods and assessment methodology to use. A wide discussion has been followed about the limitations of the non-standardized methodologies and the impact of the quality of the inventory and main indicators to the reliability and standardization of environmental profile assessment results. As presented in a previous work (Azevedo et al, 2010), for the purpose of the analysis of the environmental profile of a machine-tool, the contribution of the different main inputs to the overall impact

standardization for the machine-tool use-stage analysis.

discussed.

**2. Methodologies used** 

similar utilization modes.

where *P0* is the fixed part corresponding to the total stand-by power [kW], �� is the rate of material processing, typically in cm3/s, and *k* is a constant provided in kJ/cm3.

Additionally, from Eq. (1), the SPE would be built as indicated in Eq. (2):

$$B\_{elect} = \frac{p\_o}{\nu} + k \tag{2}$$

While the constant part is used to insure the active response of sub-systems, such as driving controls, exhaustion or cooling apparatus, and is independent of whether or not a part is being produced, the variable part corresponds to the energy needed to produce a work-piece and is typically proportional to the amount of material being processed or to the type of work.

As demonstrated by Santos (Santos et al, 2011) for pure forming processes with discrete loading, such as bending, the maximum value of the variable part is limited by the machine characteristics, affecting the throughput. On the other hand, this is the theoretically constant value to which the SPE model would tend to, considering the fixed consumption would be shared by an infinite throughput. In real scenarios, the rate between constant and variable contributions associated to a production cycle, as well as their respective values, is mostly dependent on the system technology. However, the full implications of technology to the environmental profile of the machine should be attained in terms of the contributing triangle referred and not only the energy-consumption during use of the machine-tool.

Another point is the guiding for environmental improvement, as the environmental impact assessment requires the application of specific methods and tools. Life-cycle assessment (LCA) is the reference tool for environmental profiling of products and processes, as it is the most effective tool for this purpose and permits the most advanced environmental analysis possible. Every LCA methods use qualitative, quantitative or semi-quantitative analysis, although the quantitative form is considered more suitable for detailed LCA studies (Curran, 1996; Hochschorner, 2003). However, LCA tools can be time and work consuming and thus have significant costs.

In recent years, there has been a trend for the development of simplified methods for LCA. These are quantitative or semi-quantitative methodologies aiming to give quick answers and suggestions. Although these methods tend to be very universal and wide-ranging, given the broad applicability of these methodologies and the strong emergence of its use, they have a strong customization potential. In fact, these simplification techniques can be adapted to provide 'customized' or 'tailor-made' perspectives in studies of specific systems or sectors, enabling to include system-specific principles and practices more relevant and appropriate to the interested LCA end-user, while still producing valid and robust results, and keeping the LCA basic conditions regarding scope and methodology (Bala, 2010; Curran, 1996). In line with this, Hochschorner (Hochschorner et al, 2003) highlighted the importance of the method applicability to the field of application as the most important selection criteria of the proper LCA method to adopt, in order to deliver the required information.

Regarding this, it is important to highlight the interesting work followed by the CO2PE initiative (Kellens et al., 2012), which has been working on the definition of a methodology for systematic analysis and improvement of manufacturing unit process life-cycle inventory (UPLCI), i.e. on the deep analysis and quantification of the manufacturing processes environmental impact. To ensure optimal reproducibility and applicability, documentation guidelines for data and metadata are included in this approach. Guidance on the definition of a functional unit and a reference flow as well as on the determination of system boundaries meets the generic LCA goal and scope definition requirements of ISO 14040 and ISO 14044. Developed with the purpose to provide high-quality life-cycle inventory (LCI) data for manufacturing unit processes, this work seems to fit the needs of methodology standardization for the machine-tool use-stage analysis.

This chapter provides an overview on the assessment of the environmental impact of metalforming processes and machine-tools. The most important factors to be considered are discussed and some methodologies supporting the analysis of the individual contribution of energy consumption during process are presented, as this is still considered as the main detractor. Process categorization criteria and accurate modelling of the energy consumption per category are here highlighted as the basis for high quality quantitative inventory data to achieve reliable environmental profiling. Pure metal forming processes, such as bending, are covered. Overall and sub-systems accounting strategies are presented, using the case of Laser cutting as an example of multiple sub-systems with similar contribution to the total energy consumption. The main findings and conclusions, as well as some strategies favouring the environmental performance of the manufacturing processes, are here discussed.
