**4.2. Mass reduction of moving parts**

In moving sub-systems/parts of machine-tools, the current replacement of standard materials by lightweight alternative materials simultaneously reflects the trend to optimized material consumption, general material reduction and the introduction of high-performance materials, such as reinforced polymer-based composites or low-density metals. Although this trend is often pointed out as a positive factor pushing for new dynamics to the sector, the issue of the environmental cost of the introduction of these alternative materials should be carefully analysed, particularly regarding the lifetime and end-of-life disposition of such components/materials, although a lot of work is on-going regarding innovative end-of-life strategies for these materials.

#### **4.3. Mass reduction of structural parts**

In what concerns the assembly resources used for the machine-tool construction, the materials and process inputs associated with the base structure of the equipment tends to determine its environmental impact, due to its dominant volume and weight. When looking for high performance materials for high-accuracy processes/systems, innovative polymer concrete solutions, also referred as mineral casting, are being introduced to replace the typical steel welded main structure towards a performance upgrade even in the most conventional machine-tools. Technically, this solution is indicated to overcome the static and dynamic stiffness and vibration damping requirements (Erbe at al., 2008), reflected on Figure 5, but, indirectly, this has significant environmental, technical and cost benefits.

Polymer concrete compositions mainly integrate a set of mineral granulates dispersed in a polymer resin. Granulates are abundant and several companies even supply these mineral products with certified composition, granulometry and general quality specifications, which have the advantage of being market proven, reducing risk and time-to-market. Unfortunately, although they are about 90% of the total weight of the composition, these components represent less than 20% of the cost. In fact, polymer resins are the cost-drivers in these compositions. In general, epoxy resins are about four times more expensive than alternative polyester resins. Depending on the quality requirements, polyester could be a preferable choice, but they are less stable and present a higher shrinkage rate, which might be a problem in thicker bodies, as high shrinkage might result on significant internal stressing and subsequent cracking. Mineral casted structures can be produced in a single-step, and process time is mainly affected by the curing process, which depends mostly on the polymer characteristics (some products are presenting curing times up to 24 hrs at room temperature).

146 Metal Forming – Process, Tools, Design

**4.2. Mass reduction of moving parts** 

strategies for these materials.

**4.3. Mass reduction of structural parts** 

**4.1. Detailed analysis of assembled sub-systems components** 

is still relying on the environmentally conscious of the sub-system manufacturer.

Regarding the assembled sub-systems of the machine-tool, and considering the trend for all electric or electromagnetic versions of these, particular attention should be given to the use of advanced functional materials, particularly composites, and the increased use of additional electronic components, as these typically includes higher amounts of hazardous materials or raw materials which are hard to recover. Also on this analysis, the sub-system approach for improvement is recommended in order to favour a finer analysis of all components. In fact, while the significant impact of a housing material can be more evident from the volumetric contribution of the component, only a detailed sub-system analysis can insure that the determinant impact of a small volume component based on a hazardous material would not be missed. Although some mandatory related legislation is established for electronic components, the amount and combination of substances in a multi-component electromechanical sub-system

In moving sub-systems/parts of machine-tools, the current replacement of standard materials by lightweight alternative materials simultaneously reflects the trend to optimized material consumption, general material reduction and the introduction of high-performance materials, such as reinforced polymer-based composites or low-density metals. Although this trend is often pointed out as a positive factor pushing for new dynamics to the sector, the issue of the environmental cost of the introduction of these alternative materials should be carefully analysed, particularly regarding the lifetime and end-of-life disposition of such components/materials, although a lot of work is on-going regarding innovative end-of-life

In what concerns the assembly resources used for the machine-tool construction, the materials and process inputs associated with the base structure of the equipment tends to determine its environmental impact, due to its dominant volume and weight. When looking for high performance materials for high-accuracy processes/systems, innovative polymer concrete solutions, also referred as mineral casting, are being introduced to replace the typical steel welded main structure towards a performance upgrade even in the most conventional machine-tools. Technically, this solution is indicated to overcome the static and dynamic stiffness and vibration damping requirements (Erbe at al., 2008), reflected on Figure 5, but, indirectly, this has significant environmental, technical and cost benefits.

Polymer concrete compositions mainly integrate a set of mineral granulates dispersed in a polymer resin. Granulates are abundant and several companies even supply these mineral products with certified composition, granulometry and general quality specifications, which have the advantage of being market proven, reducing risk and time-to-market. Unfortunately, although they are about 90% of the total weight of the composition, these components

**Figure 5.** Comparative analysis of vibration dampening between conventional metals used in machinetools and a commercially available polymer composite (based on Anocast product, a Rockwell Automation product (Rockwell, 2012)).

In turn, regarding the environmental benefits related to the introduction of polymer concrete-based solutions, the following aspects are to be highlighted:

