INTERNATIONAL JOURNAL OF PRECISION ENGINEERING AND MANUFACTURING Vol. 16, No. 3, pp. 509-515 MARCH 2015 / 509 © KSPE and Springer 2015 Optimum Airflow to Reduce Particle Contamination Inside Welding Automation Machine of Hard Disk Drive Production Line Jatuporn Thongsri 1,2,# and Monsak Pimsarn 1,3 1 Research Unit on Mechanical Reliability Technology, King Mongkut’s Institute of Technology Ladkrabang, Bangkok, 10520, Thailand 2 College of Data Storage Innovation, King Mongkut’s Institute of Technology Ladkrabang, Bangkok, 10520, Thailand 3 Department of Mechanical Engineering, Faculty of Engineering, King Mongkut’s Institute of Technology Ladkrabang, Bangkok, 10520, Thailand # Corresponding Author / E-mail: ktjatupo@kmitl.ac.th, TEL: +66-2-329-8271, FAX: +66-2-329-8263 KEYWORDS: Airflow, Automation, Particle contamination, Computational fluid dynamics, Fan filter units Welding automation machine (WAM), used for welding minute components to the head gimbal assembly (HGA) of a hard disk drive (HDD), needs to operate in a strictly clean environment. In today’s HDD factories, to prevent airborne particle contamination to the WAM, Fan Filter Units (FFUs) are installed on top of it to supply clean air and blow away outside airborne micro particles, keeping the microenvironment clean. Furthermore, the mass of the clean air should also carry away harmful particles generated inside the microenvironment. In this research, numerical simulation of airflow inside a WAM was performed in order to verify these cleaning functions of the airflow. A transition shear stress transport turbulence model was employed to simulate airflow from the FFUs through and out of the microenvironment. The simulation results showed that the airflow from the FFUs truly performs the two cleaning functions as intended. Moreover, they also revealed that the optimum air speed, the speed resulting in the lowest particle counts, is in the range of 0.35-0.55 m/s. Our findings can be useful for developers who may use FFUs to reduce particle counts in the environment of other types of industrial machinery. Manuscript received: May 2, 2014 / Revised: November 27, 2014 / Accepted: December 1, 2014 1. Introduction Production of electronic parts and components is an important industry in Thailand. In 2011, it generated several billions US dollars which amounted to 30% of all Thailand’s incomes from exports. This kind of production absolutely needs to be done in a clean room or a clean environment with very low particle counts. Contaminating particles are generated by various human activities. 1 Some activities may generate up to 30 million particles per minute. 2 Movement of machine parts also generates a lot of micro particles. The standards of a clean environment vary among different types of industrial production. In general, the standard of a clean room for production of electronic parts is ‘class 100’, referring to the US FED STD 209E criterion; that is, only 100 particles per cubic feet bigger than 0.5 µm are allowed. However, class 100 clean room is prohibitively costly to construct and maintain; therefore, in a real mass production facility, class 1,000 clean room is used instead, in which only 1,000 particles per cubic feet bigger than 0.5 µm are allowed. In order to achieve even lower particle NOMENCLATURE i, j = 1, 2, 3 correspond to the components of x, y and z, respectively ρ = fluid density u = velocity P = pressure t = time F = external force k = thermal conductivity E = internal energy σ ij = stress tensor T = temperature S = user-defined source term DOI: 10.1007/s12541-015-0069-2