• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.62-65
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• 2009

There have been strong demands for micro size screw with high precision due to miniaturization and integration trends for electronic products such as Hard Disk Drives. The thread rolling process for screw manufacturing are lower unit cost, reduced material utilization, and superior mechanical properties compared to the machining process. But little work has been done on the thread rolling of micro size screw. In this paper, we investigate thread rolling process using Finite Element Analysis (FEA) and parameter study for screw manufacturing. And we also carried out compression tests to obtain the material property and to implement into the FE tool for the numerical simulation. In case that parameter of relative position oldies is half length of pitch for maintaining the continuous thread profiles, we found that shear friction factor was 0.9 during the thread rolling process using FEA. We are trying to develop the thread rolling process using the FE-simulation to manufacture screws which have been commonly produced from the industrial level fabrication at present.

• Transactions of Materials Processing
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• v.21 no.3
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• pp.179-185
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• 2012

In this paper, it is proposed to produce high precision screws with a diameter of $800{\mu}m$ and a thread pitch of $200{\mu}m$ ($M0.8{\times}P0.2$) by means of a cold thread rolling process. In this part II of the study, the focus is on the production and reliability testing of the prototype $M0.8{\times}P0.2$ micro-screw. Designs for two flat dies were developed with the aid of the literature and previous studies. Process parameters during the cold thread rolling process were established through FE simulations. The simulation results showed that the threads of the micro-screw are completely formed through the rolling process. Prototype $M0.8{\times}P0.2$ micro-screw were fabricated with a high precision thread rolling machine. In order to verify the simulation results, the deformed shape and dimensions obtained from the experiment were compared with those from the simulations. Hardness and failure torque of the fabricated micro-screw were also measured. The values obtained indicate that the CAE based process design used in this paper is very appropriate for the thread rolling of micro-sized screws.

• Transactions of Materials Processing
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• v.20 no.8
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• pp.581-587
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• 2011

The production of high-precision micro-sized screws, used to fasten parts of micro devices, generally utilizes a cold thread-rolling process and two flat dies to create the teeth. The process is fairly complex, involving parameters such as die shape, die alignment, and other process variables. Thus, up-front finite-element(FE) simulation is often used in the system design procedure. The final goal of this paper is to produce high-precision screw with a diameter of $800{\mu}m$ and a thread pitch of $200{\mu}m$ (M0.8${\times}$P0.2) by a cold thread rolling process. Part I is a first-stage effort, in which FE simulation is used to establish process parameters for thread rolling to produce micro-sized screws with M1.4${\times}$P0.3, which is larger than the ultimate target screw. The material hardening model was first determined through mechanical testing. Numerical simulations were then performed to find the effects of such process parameters as friction between work piece and dies, alignment between dies and material. The final shape and dimensions predicted by simulation were compared with experimental observation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.10a
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• pp.189-190
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• 2009