Two-level factorial design of the pre-processing activities of polyamide 12 powder in selective laser sintering three-dimensional printing process

Powder exposure during selective laser sintering (SLS) three-dimensional (3D) printing process is detrimental to the health of workers in the indoor workspace and those in surrounding areas. To date, there is a paucity of studies concerning the factors involved in the SLS 3D printing process that have a significant effect on the indoor air concentrations. Hence, in this study, two-level factorial design was conducted to identify the factors that have a significant effect on the indoor air concentrations (particulate matter with a diameter less than 2.5 and 10.0 μm (PM2.5 and PM10), ultrafine particles (UFP), and total volatile organic compounds (TVOC)) during pre - processing activities of the SLS 3D printing process. The exposure during handling of polyamide 12 (PA12) was simulated in a 24-m2 SLS 3D printing chamber. The following factors were investigated: (1) Factor A (air velocity (fan speed of the split air conditioner), (2) Factor B (refresh rate (the use of recycled PA12 powder), (3) Factor C (collecting powder from the mixing machine), (4) Factor D (transferring powder to the SLS 3D printing machine), and (5) Factor E (pouring powder into the feeder chamber). The sampling methods were conducted according to the Industry Code of Practice on Indoor Air Quality, Department of Occupational Safety and Health, Malaysia. Based on the analysis of variance results, Factor B was the most significant factor that contributed to the PM2.5, PM10, UFP, and TVOC concentrations during the pre-processing activities of the SLS 3D printing process. In conclusion, proper handling and the use of an automated vacuum conveying technology for the pre-processing activities will help prevent the spreading of gaseous and aerosol particles to other areas within vicinity of the SLS 3D printing process

Development Of TEG Peltier Device For Heat Harvesting From 1.5 HP Split Unit Air Conditioning System

In today’s world, recycling energy would be alternative in achieving green environment. Air conditioning shows the biggest energy consumption worldwide. Commonly air conditioning used to maintain indoor temperature. In Malaysia, split unit air conditioning system are famous for small area application. However, the heat release by condensing unit are wasted to the environment. Therefore, one peltier device using thermoelectric generator (TEG) module were develop in this experiment. The aim of this paper are to present the development of peltier device to harvest heat from condensing unit, hence convert it to electricity. The peltier device were sandwich among copper plate sizing 120mm x 60mm x 2mm. The copper plate were brazed at the discharge pipe of compressor and the other side of copper plate were attach to the heat sink where flow through by condensing water from evaporator. Six peltier were arrange respectively between copper plates. 3 case were monitor depended on the ΔT of cooling coil and condenser temperature. The maximum ΔT were observed at case 1, and simultaneously monitored voltage output for each peltier. The maximum 1.61V were collected from the split unit air conditioner after 30 minutes of operation with around 9-10 °C of ΔT. The application of TEG to harvest heat and turn into electricity shows the promising alternative for heat recovery. The current generated may useful for small scale used of electricity for household usage

Emission Of Selected Environmental Exposure From Selective Laser Sintering (SLS) Polyamide Nylon (PA12) 3D Printing Process

Indoor Air Quality (IAQ) is very important to the health and comfort of occupants inside building. The quality of indoor air depends on the air pollutant inside the building. A bad IAQ in workplace will lead to negative impacts to the operators such as dizziness, irritation, headache and others. Additive manufacturing is one of the emerging technologies that has been discussed recently. However, the study on emission from 3D printing process are still focusedon FDM type 3D printer. Less attention given to the other type of 3D printing especially powder bed fusion particularly selective laser sintering (SLS). Therefore, this study aims to investigates the emission from selective laser sintering of 3D printing process. The design calibration block from SLS printer’s manufacturer is selected to be printed to measure the emission from SLS printing. The powder material use in this research was polyamide nylon (PA12) powder material. The data collected for 8 hours during whole printing process. Temperature, relative humidity, carbon dioxide (CO2), total volatile organic compound (TVOC), and formaldehyde were measured and compared to the acceptable limit for Industrial Code of Practice (ICOP) DOSH 2010. The highest concentration of carbon dioxide CO2 is at preparation for during printing phase 999 ppm and almost exceed the limit of 1000 ppm. Meanwhile, TVOC, formaldehyde, RH and temperature were measured at 1.7 ppm, 0.05 ppm, 70.6%, and 27.6 °C accordingly. The concentration of TVOC and formaldehyde are in the range of acceptable limit. RH and temperature meanwhile slightly over acceptable limit during SLS machine operation due to laser temperature. The data collected from the emissions of selective laser sintering (SLS) 3D printing by polyamide nylon powder suggest that ventilation system of the location should be improved to remove excess pollutant air and fresh air is suggest to supply constantly to the occupant

Mechanical properties of oil palm frond wood filled thermoplastic polyurethane

The problem of the biomass waste produced from palm oil plantation is present today. The biomass waste typically is sourced from oil palm trunk (OPT), oil palm frond (OPF) and oil palm fruit bunch. Considering the huge amounts OPF wood waste from palm oil plantation, the waste can have other added value if they can be used as in polymer composite materials. This study is subjected to investigate the effect of oil palm frond (OPF) fiber and powder loading to hardness, toughness, tensile and flexural strength of thermoplastic polyurethane (TPU) as wood polymer composite. Frond fiber with size of 2-3 mm and frond powder with size of 60-90 micron were used as filler materials. The TPU/OPF composite samples were fabricated by compressive molding approach. The result shows that hardness of TPU based composite increased by 48% with the addition of 30 wt.% of OPF powder. Ultimate tensile strength of TPU increased by 26% with addition of 30 wt.% OPF frond powder. The impact strength of TPU increased by about 50 % by the addition of 30 wt.% of OPF frond fiber, while the flexural strength of TPU/OPF composites increased by about 86% by the addition of 30% OPF frond fiber. The microstructure of TPU/OPF composite samples shows good interfacial bonding between TPU matrix to OPF powder and OPF fiber, which represents a significant improvement of mechanical properties of TPU/OPF composites. It can be concluded that both, OPF powder and fiber addition significantly improved the mechanical properties of TPU. The OPF powder improved hardness and tensile strength, while the OPF fiber improved on the impact and flexural strength of the TP

Development of insulation material using bamboo fibers for thermal and sound properties

Currently, fiberglass is used as an insulation material, and this synthetic fiber is categorised as nonbiodegradable and causes air pollution. This study compared the thermal and acoustical properties of Betong bamboo (Dendrocalamus Asper) and fiberglass. Conductivity (K-Value) and sound absorption coefficient (SAC) were measured for both materials. The SAC was calculated using an impedance tube at low and high frequencies in accordance with EN ISO 10534-2:2001, while thermal conductivity was measured using Solteq HE110 thermal conductivity apparatus. From data analysis, the k-values of bamboo and fibreglass were 0.05 and 0.04, respectively. The analysis also showed that the difference in k-value between natural and synthetic fibers was 0.01 at 25 mm thickness, while fiberglass was 4.986. For sound acoustic, bamboo fibre showed 0.54 and 0.86 SAC between 2000 Hz and 2500 Hz, while 0.47 and 0.71 SAC were recorded for fibreglass. It can be concluded that bamboo fibre could be used as thermal and sound insulation, with performance equal to or better than fibreglass. Further research can be extended to make bamboo fibers as natural insulation for ducting, or in building. This study recommends refining bamboo fibres using different binders to increase durability and be used as insulation in the futur

Pilot study on investigation of Thermal Sensation Votes (TSV) and students' performance in naturally ventilated classroom

Thermal comfort is essential for students' wellbeing, health, and performance. A conducive classroom must consider the acceptable range of heat and its impact on student performance. The study aims to conduct a pilot test for the determination of thermal acceptability and student performance in existing Malaysian classrooms using physical and subjective assessments. The methodology requires physical measurement using KIMO AMI 310 instrument, as well as subjective assessment via satisfaction survey adapted from ASHRAE 55 and performance assessment adapted from WHO Neurobehavioral Core Test Battery (WHO NCTB). Physical measurement parameters, such as indoor temperature, air velocity, relative humidity, and prevailing mean outdoor temperature, were measured in parallel with subjective assessment of thermal acceptability and performance assessment. Three days of data collection were conducted in the secondary school located in Endau, Johor. There are three classes involved with a total of 46 students. Each class was equipped with two ceiling fans and both ceiling fans were regulated to the speed of four. The overall physical and subjective assessment procedure took approximately 60 minutes per classroom. The findings showed that all the investigated classes were in the range of acceptable operative temperature and complied with ASHRAE Standard 55 for both 80% and 90% acceptability limits. Pearson correlation analysis showed a small positive relationship between thermal sensation vote (TSV) and learning performance was obtained. The results also showed a higher performance score at the TSV value of -1 suggesting the students tend to have higher performance scores when they voted feeling slightly cool. Thus, the results of the pilot test gave new insight into the effective method to improve the methodology for the actual data collection

The Comparison Study of Handgrip Pressure on Steering Wheel National Cars / Mohd Hidayat Ab Rahman ...[et al.]

The steering wheel is ergonomically designed to provide optimal comfort to the drivers while grip the steering wheel, especially on the long journey. There are significant design differences between the steering wheel car models. Therefore, the objective of this research are to analyze the data of handgrip pressure towards national cars which is Proton and Perodua. The experiment will be performed by using type 2 (two) cars, Proton Saga and Perodua Myvi. Tekscan Grip System is a system that will be used to perform this analysis. Data of handgrip pressure are collected during driving when the device are installed and connect to the respondents. Selection of the road for this experiment will start at 92.1 KM intersection traffic lights, entering North-South Highway, and will end at Tangkak Toll Exit. During the experiment, all volunteers need to maintain speed in the range of 80-100km / h and most of the time, they have to drive in the left lane unless overtaking other vehicles. Distance from beginning to end is about 68.8km and the time taken is about 30 minutes. Drivers will be driving with the hands on the steering wheel 9 and 3 because it is the safest position to hold the steering wheel. The finding from this study will give a better insight on the effect of steering wheel design to the grip pressure of the driver

Influence of Air Velocity on Thermal Comfort and Performance of Students in Naturally Ventilated Classrooms in Tropical Climate

Air velocity is among the most important factors influencing thermal comfort in naturally ventilated spaces in hot and humid tropical climates. It is important to have air velocity that suits comfort needs and enhances the student's learning performance in the classroom, especially in schools that rely only on natural ventilation assisted by ceiling fans. In this study, the thermal comfort and learning performance of students in a selected naturally ventilated classroom at a secondary school in Segamat, Johor, Malaysia, were experimentally evaluated under different air velocity conditions during the peak temperature period during the school session. Throughout the experiment, physical measurement and a subjective evaluation questionnaire were conducted for thermal comfort analysis and to gather the student’s thermal environment evaluation in the classroom. Students’ learning performance was assessed through simple reaction and digit span tests based on the WHO Neurobehavioral Core Test Battery (NCTB). All the assessment results were statistically analyzed, and the relationships among indoor air velocity, thermal comfort, and learning performance were obtained. The result showed optimal learning performance was significant when students felt “slightly cool” and air velocity was more than 0.95 m/s. Hotter environments and a lack of air movement were found to be causes of declining student performance. In conclusion, it is suggested that the comfort zone in a naturally ventilated classroom for school students should be set within the range of -1 (slightly cool) with an air velocity greater than 0.76 m/s