Jatuporn Thongsri

A Simulation of the Number of Particles Trapped by the Circulating Filter of a Hard Disk Drive and their Trajectories

A transition shear stress transport turbulence model and a discrete phase model of Fluent software were employed to simulate numerically the trajectories of loose particles and the number of them trapped by the circulating filter of a hard disk drive (HDD). The filter was located either at the left or the right of a 2.5 inch dual platter HDD rotating at 7200 rpm. Particles were released from the middle diameter position where four head gimbal assemblies (HGAs) were located. The simulation included airflow and particle trajectories released from any of the four HGAs. The results of this simulation can help determine the efficiency of a circulating filter and its optimal placement.

Successful Simulation of Airflow in the Microenvironment of an Assembly Automation Machine and its Implication

Today, the hard disk drive (HDD) industry is using assembly automation machine (AAM) to construct head stack assembly (HSA) from smaller parts. AAM needs to operate in a clean environment with very low particle counts. To achieve this end, fan filter Unit (FFU) is used to supply purified air into the environment by filtering out airborne particles from recirculating air. In this study, we investigated numerically the airflow induced by FFUs inside a microenvironment that houses an AAM in an HDD factory. The boundary conditions chosen for simulation were directly derived from the real ambient conditions in this HDD factory. We found that the FFUs not only filter out airborne particles from the air supplied into the microenvironment but also act as a particle blocker, pushing away the nearby particles in the air surrounding the openings of the microenvironment. The findings from this study can be applied to cases where other kinds of machinery need to be protected from airborne particles.

A Successful CFD-Based Solution to a Water Condensation Problem in a Hard Disk Drive Factory

This paper was intended as an article of a practical solution. The settings of a ventilation system for a production line in a hard disk drive (HDD) factory were inappropriate leading to a condensation problem in a work area causing the finished products to be defective and unsalable. This paper describes an attempt to solve this problem and the outcome. Computational fluid dynamics (CFD) was used to simulate the airflow from a ventilation system in an HDD factory. The simulation results were validated with actual values measured with instruments readily available at the factory. The simulation results showed that the airflow patterns and temperature distribution of the air above and around some areas in the production line were not proper. The old temperature setting of the system for the air coming out of the inlet caused the temperature of the air above the said areas to be in the range of 13-20.5 °C, which was lower than the dew point temperature thus causing a condensation problem. From the results of the simulation, we recommended the factory to increase the inlet air temperature to be around 16.5-22 °C, so that the temperature of the air above and around the work areas would be higher than the dew point temperature and more uniform. The factory implemented our recommendation and found that it not only solved the problem satisfactorily but also saved the air-conditioning cost.

Development of an industrial ultrasonic cleaning tank based on harmonic response analysis.

HighlightsWe reported actual problems complained by customers and its solution.Novel simulation based on harmonic response analysis was set to solve the problems.Acoustic pressure throughout the tank was simulated using problematic conditions.Good agreement between the simulated and experimental results was achieved.Results have already been used to develop smart ultrasonic tanks by manufacturer. ABSTRACT A small industrial ultrasonic cleaning tank, which is one of the best‐selling models, had cleaning problems. Customers sometimes complained that the tank did not completely clean all objects, or that some objects got damaged, so a solution to the problem was urgently needed. The tank has a volume of 18 L, frequency of 28 kHz, eight horn style PZT4 transducers, and a total electric power of 400 W. The cleaning occurs from the cavitation effect which corresponds to an increase in the acoustic pressure. A computer simulation is presented using a harmonic response analysis (HRA) in ANSYS to resolve and improve the efficacy of the tank. From the simulation, we found that the acoustic pressure within the tank was uneven. The distribution of acoustic pressure had a characteristic pattern depending on the placement of the transducers. When the temperature was increased, the acoustic pressure was decreased leading to a cleaning efficacy drop as well. All simulation results were correlated to the foil corrosion test and power concentration experiment. The HRA was used to redesign the tank for higher cleaning efficacy. The simulation results indicated that more suitable placement of the transducers lead to a more intensified acoustic pressure, and a better distribution throughout the tank. This research not only resolved the cleaning problems that occurred in the 28 kHz tank, but was also demonstrated that it can be applied to a 40 kHz tank as well. Results from this research were accepted and approved by the manufacturer, and were used by them to develop smarter industrial ultrasonic tanks with higher cleaning efficacy for commercial sale.

Simulation of ultrasonic cleaning and ways to improve the efficiency

Based on practical problem in industrial ultrasonic cleaning, this research has an objective to simulate acoustic pressure leading to cavitation in a cleaning tank. By using Harmonic response in ANSYS as simulation software, acoustic pressure distribution has been simulated at different position in the cleaning tank. The result has been confirmed by aluminum foil corrosion test. The simulations show that increasing power of piezoelectric transducers can lead to increasing the power of acoustic pressure; however, it cannot lead to the change of acoustic pressure distribution. To change the acoustic pressure distribution, the difference of frequencies is required. For such typical ultrasonic cleaning tank, the position of the highest cleaning efficiency is at the middle of the tank. Finally, the result can lead to the optimization between the power and frequency of ultrasonic to reach the maximum cleaning efficiency.

A Problem of Particulate Contamination in an Automated Assembly Machine Successfully Solved by CFD and Simple Experiments

Assembly of hard disk drives (HDDs) needs to be done in an automated assembly machine (AAM) virtually free of particulate contamination that can cause them to malfunction. Fan filter units (FFUs) are installed above the AAM to reduce the number of suspended particles in the recirculating air flowing over and around them. At one time, several HDDs were found to be defective. To find out the root cause of this problem, computational fluid dynamics (CFD) was used to investigate the airflow over and around the AAM. It was found that the cause of the high particle counts was improper air speed from the FFUs. The optimal FFUs air speed needed to be in the range of 0.35–0.65 m/s in which the airflow would block out nearby airborne particles and purge away particles generated by the AAM effectively which would, in effect, reduce the particle counts down below the threshold level of class 100 clean room. A few available measurement tools at the factory were then used to perform validating measurements against the simulation results, and the validation was positive. This optimal speed range was implemented at the factory after which the level of contamination was reduced to an acceptable level.

Feasibility Study for Installing Machine in Production Line to Avoid Particle Contamination Based on CFD Simulation

Ventilation system inside production line for electronic component production needs to meet the factory standard. Because it can eliminate small particles which may cause of human or machine in production as well as it can distribute the circulating air temperature uniformly. CFD is used in this research in order to study the feasibility and plan for machine layout in production line before actual installation. The simulation shows the airflow in every area inside production line. From simulation with releasing the particles from human and machine is found that this ventilation system generates airflow that makes most particles float out of the machines and no particle downs to the conveyor, it results to contamination. In addition, the simulation also shows the range of 19-26 °C air temperature that meets the factory standard. The results of this research are the parts of the data to renovate the production line to get more efficiency and proper on the production.

Effect of Grain Size on Effective Permittivity of Ferroelectric Films Based on Effective Medium Theory

Based on effective medium theory, the temperature dependence of effective dielectric permittivity, εe(T), on core radius (a) and thickness (t) of non-ferroelectric dead layer (DL) on the surface of inhomogeneous grains of ferroelectric film made up of cylindrical ferroelectric grains was theoretically investigated. It was found that εe(T) increases with increasing core radius but decreases with increasing DL thickness. In this work, an equation expressing the relationship among εe, a and t was derived. This equation is very useful for the preparation of a ferroelectric film to desired properties.

Simulated Trajectories of Particles and the Number of Particles Trapped by the Circulating Filter in a Hard Disk Drive

The particle trajectories and the number of them trapped by circulating filter of a 2.5 inch dual platter hard disk drive (HDD) were numerically investigated using a transition shear stress transport turbulence model (transition SST). Four head gimbal assemblies (HGAs) were placed at the outer diameter positions where tiny particles of alumina were released. The simulation revealed the results of airflow, particle trajectories and efficiency of a circulating filter. This result can be applied as fundamental information to design HDD layout in order to reduce its contamination. Keywords: Airflow, Circulating Filter, Hard Disk Drive, Particle Trajectory, Computational Fluid Dynamics

Numerical Investigation of Airflow Pattern inside Environmental Chamber

In industrial hard disk drive research and development laboratories, an environmental chamber is normally used to perform a mechanical verification test of Head Gimbal Assembly (HGA). It is very important to verify that the airflow pattern in the chamber is comparable to that in a real hard disk drive. Hence, we applied a transition shear stress transportation turbulence model (transition SST), one of the robust mathematical models in computer fluid dynamics, to simulate the airflow behavior inside both an environmental chamber and a hard disk drive (HDD). We found that, overall, the two patterns of airflow were not comparable at all. The air velocity vectors around the HGA in VENA were smaller than that in HDD. The reason for this is likely to be that there was more space between the top cover of the chamber and the platter than the space between the top cover of the hard disk drive and its platter.