Comparative study of selected indoor concentration from selective laser sintering process using virgin and recycled polyamide nylon (PA12)

Abstract

Additive manufacturing (AM) stands out as one of the promising technologies that have huge potential towards manufacturing industry. The study on additive manufacturing impact on the environment and occupational exposure are attracting growing attention recently. However, most of the researcher focus on desktop and fused deposition modelling type and less attention given to the industrial type of AM. Usually, during the selective laser sintering process, recycle powder will be used again to reduce cost and waste. This article compares the PM 2.5, carbon dioxide (CO2) and total volatile organic compound (TVOC) concentration between virgin and recycles powder using polyamide-nylon (PA12) towards indoor concentration. Four phases of sampling involve during air sampling accordingly to the Industry Code of Practice on Indoor Air Quality 2010 by DOSH Malaysia. It was found that PM 2.5 and CO2concentration are mainly generated during the pre-printing process. The recycle powder tended to appear higher compared to virgin powder in terms of PM 2.5, and CO2. The peak value of PM 2.5 is 1452 µg/m3 and CO2 is 1218 ppm are obtained during the pre-printing process during 8 hours of sampling. TVOC concentration from recycling powder is slightly higher during the post- printing phase where confirm the influence of the powder cake and PA12 temperature from the printing process. In summary, this work proves that elective laser sintering (SLS) machine operators are exposed to a significant amount of exposure during the SLS printing process. Mitigation strategies and personal protective equipment are suggested to reduce occupational exposure.

State of the art in additive manufacturing and its possible chemical and particle hazards—review

“…TPE can undergo repeated melting and crystallization cycles, allowing them to be processed, for example, by SLS. For instance, PA12 is a material with increased chemical resistance, allowing to produce elements with good mechanical properties, and matt, rough surface 49,50 . A mixture of powdered polyamide and aluminum (alumide) is also used.…”

“…It was identified that the most emissive particle size range was 205–407 nm, and the number concentrations of particle sizes of 352 and 407 nm were highest during the ejection stage (~4.4 × 10 4 particle/min). The increase in dust concentrations was observed during powder preparation or post‐processing of parts produced by powder bed fusion 50,109,122 . The particle emission from the powder jet printers are strongly influenced by the powder properties as well as the powder dispersion process.…”

“…For instance, PA12 is a material with increased chemical resistance, allowing to produce elements with good mechanical properties, and matt, rough surface. 49 , 50 A mixture of powdered polyamide and aluminum (alumide) is also used. Other materials applied in AM on an industrial scale are synthetic plastics polysulfone (PSU) and poly(phenyl sulfone) (PPSU) but their processing requires respective safety measures.…”

“…The increase in dust concentrations was observed during powder preparation or post‐processing of parts produced by powder bed fusion. 50 , 109 , 122 The particle emission from the powder jet printers are strongly influenced by the powder properties as well as the powder dispersion process. In case of powder jet printing machines with a constant spreading mechanism, the particle emission can be very different between different powder types.…”

The Effects of Virgin and Recycled PA12 Powders in SLS Processes on Occupational Exposures

“…The results conform well with those of Dadbakhsh et al [32], who found that there were no significant differences in the size and shape between the virgin and recycled PA12 powders. Based on the particle size distributions, the particles for both virgin and recycled PA12 powders are fine particulate matter, which identify as potential occupational exposure to the SLS operators especially during powder handling [33]. Fig.…”