**5. Smart production innovations**

*Mass Production Processes*

(DMF) [61].

not been extensively examined [47]. The focus of research has been on sustainable development through additive manufacturing by (1) improved resource efficiency permitted by redesign of both products and processes for in-house waste minimisation; (2) product life extension using technical approaches and stronger personproduct relation; and (3) simplified value chains by reduction of logistic complexity

Environmental effects such as biodegradability and ecotoxicity are not fully understood. Similarly, little is known about the chemical solvents used for removing excess material during the steriolitography (SLA) process as well as environmental effects related to selective laser sintering (SLS), laser additive manufacturing (LAM), dynamic magnetic compression (DMC) and direct metal fabrication

Evaluation of the energy consumption has not been thoroughly investigated [51] nor has water consumption and treatment [61]. Polymers, the most processed type of powders in SLS, have quite a low sintering temperature (<200°C). A partial consideration of SLS which does not include the efficiency of the laser source or auxiliary energy finds a low energetic intensity of the process, but there is no direct comparison possible with other rapid prototyping techniques or conventional manufacturing processes from the quality perspective [62]. Smaller thickness layer and optimal part orientation may overcome surface quality issues, but processing

Additive as opposed to subtractive manufacturing may help to reduce material input into production. Not all material from DDM is reclaimable. Powder bed processing of polymers causes up to 50% of the build volume in waste which cannot be reused. Significant energy may be required in the production of the required raw materials (feedstock), but there may be significant saving if recycling is possible [47]. There is potential to combine surplus agricultural materials such as soybean to create composites of comparable strength to those made from petroleum-based

Energy savings may be obtained through reduced material demand and use phase savings due to lighter weight. However, the benefits of components produced through additive manufacturing versus traditional manufacturing are questionable for automotive components when considered in the context of additional manufacturing impacts caused by powder production, processing and post treatment [65]. Some authors have concluded that it is not possible to determine whether 3D printing is more environmentally friendly that machining or vice versa [66].

It is likely that hybrid additive manufacturing and subtractive manufacturing will be desirable so there will be a need for intelligent algorithms to determine process parameter combinations. With multiple additive manufacturing systems, an intelligent factory with resource allocation and self-organisation capabilities would be optimal [58]. An investigation of DDM-based operational practices to build sustainability capabilities anticipates increased local supply chain partners, reduced material flows, inventory and transport operations, and more sustainable product lifecycle management [67]. However, many of these operations are likely to be complex such as the addition of sensors to products, the extent of customer control over the production process and dynamic supply chain reconfiguration.

Distributed manufacturing may significantly reduce transports over centralised

manufacturing [68], however, raw material transport may offset some of these benefits. There is a significant risk that additive manufacturing may trigger a rebound effect through an increase in overall consumption, especially in fashion products [69]. It is also not clear whether mass customization in DDM will precisely match consumer needs and thus eliminate waste, or if the availability of DDM will increase waste through trial productions. Environmental sustainability benefits are

and placing production nearer to the consumer [60].

time and thus energy consumption is increased [58].

resins [63] or to utilise local waste streams (mussel shells) [64].

**70**

Cyber-physical systems (CPS) facilitate the connection and communication of software and mechanical or electrical elements using wired or wireless data infrastructure. This technology makes it possible to monitor and direct production systems with complex processes at all hierarchy levels and with high product varieties. The anticipated paradigm shift in manufacturing to Industry 4.0 or smart factories and production systems will decentralise traditional centralised applications for production control [71]. Industry 4.0 innovations/technical developments which will enable this paradigm shift include [72]:


The effect of Industry 4.0 on sustainability is unknown in detail. Smart production systems are expected to reduce waste, overproduction and energy consumption. The following section will introduce the sustainability hierarchies and apply them to mass production, mass consumption and DDM to determine which of the above Industry 4.0 innovations would be of greatest benefit with respect to the financial, environmental and social sustainability needs of manufacturers.
