Muhamad Damanhuri, Amir Abdullah (2021) PA12 nylon dust reduction of selective laser sintering reprocessing by optimization of refresh rate and powder handling. Doctoral thesis, Universiti Tun Hussein Onn Malaysia.
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Abstract
Despite advantages of selective laser sintering (SLS) to print complex and highvolume products, major concern in SLS process are exposures during handling especially during pre-processing. This study aims to formulate percentage of refresh rate with powder handling settings with the introduction of enclosure during preprocessing stages to reduces dust exposures using response surface methodology (RSM) of central composites design (CCD) techniques. This research divides into three phases, as the first phase involves a pilot study to select pre-processing as the main contribution of emission. Analysis of variance and 95% confidence interval were used to identify factors and responses that significantly contributed to the IAQ in SLS workplaces involving 56 set of screening experiments using factorial design. Next, second phase involves series of experiments to formulate refresh rate, collecting powder from mixing machines and transferring activities due to enclosures settings using RSM techniques. Finally, the third phase involves assessing gravimetric based on personal sampling (based on NIOSH 0500 and 0600) for using enhanced model suggested by the RSM. Through screening analysis, it was obtained that refresh rate give significant percentage of contribution (72.73%) to the emission followed by collecting powder from mixing machine and transferring activity. From CCD analysis with 0.816 desirability suggested 100% refresh rate, 32.8% enclosure for collecting powder from mixing machine, and full enclosure for transferring process to reduce PM2.5, PM10, UFP and TSP. The confirmation experiment was also conducted to verify the prediction result using percentage of absolute error (%) with 4.33,3.57, 4.56 and 2.38 for PM2.5, PM10, UFP and TSP. Based on the enhanced model from RSM, performance experiments show acceptable percentage of reduction for 40.6 and 28.8 % of reduction for NIOSH 0500, and 22.7 and 27.3% for NIOSH 0600, respectively. The mathematical model from RSM shows promising strategy in term of control measures in protecting operators in SLS manufacturing industry from occupational exposures.
| Item Type: | Thesis (Doctoral) |
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| Subjects: | T Technology > TJ Mechanical engineering and machinery |
| Divisions: | Faculty of Mechanical and Manufacturing Engineering > Department of Mechanical Engineering |
| Depositing User: | Mrs. Sabarina Che Mat |
| Date Deposited: | 26 Feb 2023 02:48 |
| Last Modified: | 26 Feb 2023 02:48 |
| URI: | http://eprints.uthm.edu.my/id/eprint/8397 |
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