# The Analysis of Key Technologies for Sustainable Machine Tools Design
## 4 Strategies and Technologies for Sustainable Design of Machine Tools
### Lightweight Techniques of Structural Components  
The high speed and high-accuracy performance need a moving component with less mass and high stiffness. Therefore, increasing the specific stiffness in moving components (such as bed, beam and spindle box) has become a significant issue. Lightweight and high stiffness of structural parts such as a bed and column are benefits to quality, speed and accuracy, as well as improving environment and economy performance through reducing energy consumption and raw material. Lightweight machine tools mainly focus on the optimization of structure components, moving components, whole structure, as well as material selection. The new structure emerging continuously like parallel kinematic machines (PKMs), box-in-box contribute for reducing weight. Meanwhile, new material also promote lightweight development like new aluminum alloys, quasi-isotropic fiber-reinforced plastics, and resin concrete (or man-made granite). The group of [PERSON] and [PERSON] make a great contribution to promoting machine tool performance on preventing chatter vibrations of large horizontal lathes [89], on the condition of high productivity and surface finish with greater stability. The dynamic performance of the servo drives is also analyzed by [PERSON] [90]. Additionally, lightweight milling machines are designed by [PERSON] [91] in order to obtain targeted productivity with minimum structure mass as well as energy consumption, which has been applied in the redesign of actual machine tools. The core concept related to lightweight parts include:  
1. Machine tool moving parts are light as possible for reducing driving power, increasing energy efficiency, and decreasing production and transport costs. 2. The structure components should have enough effective stiffness in order to guarantee machining precision. 3. The structure components should have good damping and vibration reduction performance avoiding chatter to improve the metal cutting rate. Currently, the lightweight method mainly focus on decreasing energy consumption and carbon emission. Because MT components lightweight could promote directly and indirectly energy efficiency through analysis energy losses of feed drives and auxiliary systems, reducing the basic load of MT. Meanwhile, the lightweight design of structure has also great significance to reduce manufacturing costs of machine tool factory as well as promote whole machine performance. Structural components such as bed and feed drive components could be redesigned employing corresponding lightweight strategies based on static stiffness, then the complete machine tools could be implemented considering dynamic behavior. Moreover, the light weight of machine tools could increasingly reduce material consumption. The reduction in mass has the benefit of reduction in reactive energy and friction losses, increasing the axis acceleration and guide bandwidth. The increase in stiffness could increase the process stability and guide bandwidth. The realization of lightweight design in machine tools could be achieved by material selection and structural optimization design such as topology and bionic design [68; 92]. Benefits of light weight for the sustainability of machine tools in each life cycle phase are shown in Table 3. \begin{table}
\begin{tabular}{l l l l} \hline \hline  & \multicolumn{1}{c}{**Sustainability for**} & \multicolumn{1}{c}{**Sustainability for**} & \multicolumn{1}{c}{**Sustainability for**} \\  & **Environment** & **Economy** & **Society** \\ \hline \multirow{3}{*}{Production} & Raw material reducing & Material cost reducing & - \\  & Energy efficiency & & process cost reducing & \\  & increasing & Energy efficiency & Energy cost reducing & - \\ \cline{1-1}  & increasing & Productivity increasing & - \\ End-of-life & Recycle, waste reducing & Disposal cost reducing & - \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Benefits of light weight for sustainability of machine tools in each life cycle phase.