neglected. The authors emphasized that these should be included for a robust assessment of energy consumption in BJ process.
Kellens et al. (2014) presented parametric models to quantify the environmental footprint based on energy and resource consumption. The models were developed considering build height and volume of the parts to be produced. Power analyser was used to measure the power consumption for different components of the machine. The environmental impact was assessed based on the energy consumed during printing, compressed air consumption to produce inert atmosphere inside the chamber and leftover powder after printing. Although polyamide powders have negligible environmental and health effect, even then the authors suggested to use ventilation system to extract the dust particles during the removal of the product from the chamber.
Peng (2016) analysed the energy consumption of FDM process. The energy consumed was categorised as primary energy and secondary energy. Primary energy represents the energy consumed during heating and melting the thermoplastic material. The secondary or the indirect energy represents the energy consumed during product design, printing settings, warming up of the build platform and geometrical parameters.
Yang et al. (2017) proposed a mathematical model for the energy consumption of vat photopolymerisation based AM process, i.e., stereolithography (SLA). The overall energy consumption (Eoverall) was obtained as
overall curing platform cooling,
E E E E (2.15)
where Ecuring is the energy consumed during the curing process by UV light source, Eplatform is the energy consumed by the build platform and Ecooling is the energy consumed by the cooling system. Experiments were conducted to validate the model and design of experiments (DOE) was implemented based on controllable parameters, viz., layer thickness, curing time and orientation. Using optimal set of parameters, the energy consumption was reduced to 127.7 kJ compared to the default conditions where energy consumed was 278.7 kJ. The authors also stated that industries equipped with SLA based AM machines can reduce CO2 emission from 415 pounds to 191.5 pounds for monthly production of 3000 parts.
highlighted that with the development of AM, the need for training and developing new technical skills in educational field has risen. Students who are familiar with this technology can test their creativity and make innovative products. Trained individuals can also deploy low-cost 3D printers in small businesses (Matos and Jacinto 2019).
AM has proved to be instrumental in providing efficient as well as quality health care. For example, after the outbreak of Corona Virus disease (COVID-19) in December 2019, there was an urgent need of personal protective equipment (PPE) in the form of facemask and face shields. During this urgent need, a FDM based 3D printer was able to manufacture 112 ready-to-use face shields (Armijo et al. 2020). Bio-medical products such as orthosis, limbs and implants can be effectively fabricated as per patients’ requirement (Huang et al. 2013). Also, in the process of drug delivery, AM can produce ready-to-use tablets oral tablets in high quantity (Shahrubudin et al. 2020). Despite some benefits offered by AM, some detrimental effects of AM are also reported. Huang et al. (2013) investigated the ill effects of material handling during AM process. They highlighted that the effects of materials like epoxy resins used in SLA, polyamides and ABS used in SLS have not been explored much. For example, a liquid resin named “TuxedoTMG3-HCM” undergoes alteration and mutation that can cause serious health related issues. In another study, Bours et al. (2017) developed an approach to assess the risk of exposure to raw material used in 3D printing. They considered two materials for comparison. One was liquid resin used in SLA and the other is polylactic acid (PLA) used in FDM. Three levels, viz., level 0, level 1 and level 2 were considered to assess the sustainability. Level 0 and 2 describe the worst- and best-case scenarios, respectively. In the evaluation of the post-processing stage, the material waste was addressed by Efactor:
factor m 1,
p
m
E m (2.16) where mm is the total mass of the material to make the part and mp is the final mass of the printed part. Based on the comparison of the two materials in different life cycle stages, PLA was categorised as level 2 while the resin was categorised as level 1.
Ma et al. (2018) explored the ill effects of PLA material used in FDM process on the human health. For this, they evaluated a quantity referred as human toxicity potential (HTP) during the manufacturing a gear. HTP was evaluated for several stages during manufacturing, viz., design, printing phase, service and end of life. HTP is zero for the activity that does not have any ill effects to human health, e.g., design stage. HTP was evaluated as
a a w w s s,
HTPw t w t w t (2.17) where ta, tw and ts are the toxicity potentials with respect air, water and soil, respectively, ta, tb and ts are the weights for emissions to air, water and soil, respectively. It was found the HTP score for printing, service and end of life was 1.84, 5.82 and 15.65, respectively.
Overall, the HTP score was obtained as 23.31.
Matos et al. (2019) explored how AM influence social well-being, quality of living, working condition and economic well-being. For this, they conducted interviews in four Portuguese organisations that use AM technology. Several opinion-based questions were asked and mixed responses were obtained. The viewpoint of the interviewees was analysed as positive, negative, null and mixed. Interviewees said that AM can have a positive impact on the quality of life. It enables the production of customized products and medical products such as prosthetics. Also, it encourages the concept of “do it yourself” (DIY). This enables several educational activities and also improves the learning process. However, the opinion on economic well-being and working conditions is adverse. AM may promote jobs but its digital nature can also increase unemployment. It requires comparatively less skill to operate as compared to CNC lathe or mill (Faludi et al. 2015). Hence, the workers have to settle with the salary of low skilled jobs.
Another major social concern with the growing popularity of AM is authorisation and legal issues. The increasing application of AM has raised several issues on the interpretation of intellectual property rights (IPR) system (Hornick and Roland 2013). IPR is a legal right that aims to protect the creations and inventions resulting from intellectual efforts in the field of technology, design, artistry and literary works. Some concerns of IPRs specific to AM comprise copyright, patent and trademark (Ballardini 2019). The digital feature of this technology permits everyone to re-design an existing model, produce the product and even sell the product along with its associated CAD model. Steenhuis and Pretorius (2017) reported that the ability of AM to produce the model digitally also raises questions on patent infringement. Production of guns and weapons that are illegal as per government directives can be easily created in the CAD format. The circulation of such files and their availability on the internet also poses threats to the defence of a country.
Hence, some restrictions must be imposed on the legality of CAD files to avoid misuse of AM.