Purpose

Machine tools are the equipment used for the cutting and shaping of materials, like metals, which generate greenhouse gas (GHG) emissions across their life cycles due to material use and energy consumption. The life cycle emissions of machine tools are distributed over time and may vary with technology advancement. This paper aims to incorporate these temporal factors into the global warming impact (GWI) assessment of machine tools and further reveal their influences on the results.

Method

Incorporating emission time into the GWI assessment of machine tools is based on the following dynamic life cycle assessment (LCA) framework. First, compute temporally differentiated GHGs of machine tools based on the activity-based modeling. And then, use time-dependent characterization factors (CFs), which are developed based on the radiative forcing concept, to assess their GWI. By using this framework, a dynamic life cycle GWI assessment of machine tool is conducted using two gear hobbing machines. Both the emission time and the potential changes of life cycle emissions due to the improvement of electricity mix and the variation of machine tool use modes are considered.

Results and discussion

The results demonstrated that when the emission time was considered, both machines offered 3% of reduction of GWI, compared with their static results, respectively. Further reductions were found for the two machines, when the electricity improvement and the changes of the machine tool use modes were considered. All the differences between the static and the dynamic environmental impact results become smaller with the extension of the time horizons (THs) that accounted for the evaluation.

Conclusions and recommendations

The conventional static LCA has the potential to overestimate the real GWI of machine tools. It is more important to account for the emission time in GWI assessment at shorter THs or for a longer lifetime of machine tools. This work offers a method to dynamically assess the real GWI of machine tools. The proposed method helps to make robust decision-making for environmentally friendly machine tool selection and support sustainable production.

中文翻译：

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一种考虑时间效应的机床生命周期全球变暖影响动态评估方法

目的

机床是用于切割和成型材料（例如金属）的设备，由于材料使用和能源消耗，这些材料在其整个生命周期中会产生温室气体 (GHG) 排放。机床的生命周期排放随时间分布，并可能随着技术进步而变化。本文旨在将这些时间因素纳入机床的全球变暖影响（GWI）评估中，并进一步揭示它们对结果的影响。

方法

将排放时间纳入机床 GWI 评估是基于以下动态生命周期评估 (LCA) 框架。首先，基于基于活动的建模计算机床的时间差异化温室气体。然后，使用基于辐射强迫概念开发的瞬态特征因子 (CF) 来评估其 GWI。通过使用该框架，使用两台滚齿机对机床进行动态生命周期 GWI 评估。由于电力结构的改善和机床使用方式的变化，排放时间和生命周期排放的潜在变化都被考虑在内。

结果和讨论

结果表明，当考虑排放时间时，与静态结果相比，两台机器分别提供了 3% 的 GWI 降低。考虑到电力的改善和机床使用方式的变化，两台机器都发现了进一步的减少。随着考虑评估的时间范围（THs）的扩展，静态和动态环境影响结果之间的所有差异变得更小。

结论和建议

传统的静态 LCA 有可能高估机床的实际 GWI。在较短的 TH 或较长的机床寿命下，在 GWI 评估中考虑排放时间更为重要。这项工作提供了一种动态评估机床真实 GWI 的方法。所提出的方法有助于为环保机床选择做出稳健的决策并支持可持续生产。