• Journal of the Korean Society for Precision Engineering
• /
• v.32 no.11
• /
• pp.977-982
• /
• 2015

This study uses finite element analysis to evaluate the forming load of tool entrance angle of the cold forward extrusion molding process of helical gear; this can replace the spur gear applied to the Electronic Parking Brake (EPB) system. A cold forging process is often used in the automobile industry as well as in various industrial machines due to its high efficiency. Finite element analysis is frequently used when interpreting results of the forging process. Formality was evaluated by calculating tooth profile filling rate of helical gear. Change in required forming load was investigated when the entrance angle of forward extrusion tool die was changed from $30^{\circ}$ to $60^{\circ}$, also by finite element analysis. We suggest suitable tool entrance angles.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2012.05a
• /
• pp.1217-1218
• /
• 2012

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2009.10a
• /
• pp.387-390
• /
• 2009

This study was designed to fabricate the micro-electro-mechanical systems (MEMS) parts such as micro spur gears using hot extrusion of gas atomized Al-78Zn powders. For this purpose, it is important to develop new methods to fabricate micro-dies and choose suitable extrusion conditions for a micro-forming. Micro-dies with Ni were fabricated by LIGA technology. LIGA technology was capable to produce micro-extrusion dies with close tolerances, thick bearing length and adequate surface quality. Superplastic Al-78Zn powders have the great advantage in achieving deformation under low stresses and exhibiting good micro formability with average strain rates ranging from $10^{-3}$ to $10^{-2}\;s^{-1}$ and constant temperatures ranging from 503 to 563K. Al-78Zn powders were compacted into a cylindrical shape (${\Phi}3{\times}h10$) under compressive force of 10kN and, subsequently, the compacted powders were extruded at 563k in a hot furnace. Micro-extrusion has succeeded in forming micro-gear shafts.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.21 no.2
• /
• pp.130-136
• /
• 2022

Reducing production costs through net-shaped cold forging is an important aspect in the automobile industry. In this study, we intend to produce a net-shaped electronic parking brake (EPB) serration gear for automobiles, using multi-stage cold forging. These serrations are then assembled to the reduction gear of an EPB actuator. The forging process of the serrations and the cold forging design were verified through finite element analysis (FEA) in order to evaluate metal flow. The forging machine was selected by checking the load using FEA. Based on the FEA results, molds were designed, and parts were made using multi-stage cold forging to produce a net-shaped serration gear.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2009.10a
• /
• pp.449-452
• /
• 2009

This paper was designed to fabricate the miniature spur gear with pitch circle of 1.8 by hot extrusion process of mechanically alloyed Zn-22wt%Al powder at various temperature. The mechanical alloying was preformed for ball milled times of 8h, 16h and 32h by the planetary ball milling. Mechanically alloyed powders were compacted cylindrical performs. Extrusions of the miniature spur gear using the alloyed powder were carried out at different extrusion temperatures. The extruded spur gear was sintered for 2h at $350^{\circ}C$ in argon atmosphere. The friction between the die and the powdered billet and the internally different density due to complex product shape cause the internal crack. To overcome the mentioned problems, high dimensional accuracy at cross section of the spur gear and uniform Vickers hardness could be obtained by graphite lubricant and controlling holding time.

• Journal of the Korean Society for Precision Engineering
• /
• v.9 no.3
• /
• pp.12-28
• /
• 1992

A new helical gear extrusion process was proposed and its numerical solution program based on the upper bound method was developed. In the analysis the involute curve was used as a shape of die and the upper bound method was used to calculate energy dissipation rate. By this method the power requirement and optimum conditions necessary for extruding helical gear were successfully calculated. These numerical solutions were in good agreement with experimental data. In the experiment, die life was greatly improved compared with that of Samanta process and 4 .approx. 5 class helical gear of KS standard for automobile transmission was successfully manufactured.

• Transactions of Materials Processing
• /
• v.20 no.7
• /
• pp.485-490
• /
• 2011

The application of helical gears in crucial parts of automotive transmissions has been steadily increasing due to their higher power transfer performance compared to spur gears. However, the traditional gear manufacturing methods such as hobbing and deburring require large cycle times with expensive production lines so that there have been intensive efforts trying to manufacture gears via forging processes. Although forging processes for spur and bevel type gears have been developed on the practical level, the manufacturing of helical gears is still dependent on the traditional cutting process. Therefore, this paper seeks to develop a cold forward extrusion process for the helical gear with the pitch diameter of 43.5mm and a helix angle of $18.4^{\circ}$. A forward extrusion process was used due to the relatively small diameter of the target geometry. The material deforming behavior influenced by the die geometry was examined by using CAE analysis. Finally, it was found that the helical gear manufactured by the developed extrusion process satisfied the dimensional accuracy and mechanical characteristics for automotive transmissions.

• Transactions of Materials Processing
• /
• v.19 no.5
• /
• pp.283-289
• /
• 2010

Extrusion process in the bulk material for fabrication of miniature helical gears has problems such as a high forming load and short tool life because the cross-section is complex and asymmetry. To overcome these problems, in this study, miniature helical gears were fabricated by Zn-22Al powder hot extrusion. The included die angle for minimum extrusion load and improving die filling was determined by FE-simulation. The Zn-22Al spheroidal powder produced by gasatomization were compacted and sintered for extrusion experiment. The dimension of helical-gear is 0.3mm in module, 3.35mm in pitch diameter, $15^{\circ}$ in helix angle and the number of teeth is 12. All of the extrusion experiments were performed with internal helical gear die which was machined by precision electric discharge machining using the electrode. The experiment was conducted at $190^{\circ}C$ to $310^{\circ}C$ to obtain extrusive and mechanical properties. The extruded helical gears were analyzed through extrusion load, Vickers hardness and SEM images for each extrusion temperature. The powder hot extrusion process was successfully applied to fabricate a miniature helical gear.

• Transactions of Materials Processing
• /
• v.19 no.6
• /
• pp.352-356
• /
• 2010

This paper was designed to fabricate the micro-spur gear by the LIGA and hybrid powder extrusion process. It is important to manufacture a micro-die with a high aspect ratio and determine appropriate extrusion conditions for a microforming. Ni has been used to fabricate micro-dies. LIGA process was capable to produce micro-extrusion dies with close tolerance, longer bearing length and adequate surface quality. Superplastic Al-78Zn powders have the great advantage in achieving deformation under low stresses and exhibiting good micro-formability with average strain rate raging from $10^{-3}$ to $10^{-2} s^{-1}$ and constant temperature ranging from 503 to 563K. Al-78Zn powders were compacted into a cylindrical shape ($\Phi3\times$h10mm) under compressive force of 10kN and, subsequently, the compacted powders were extruded by the hybrid powder extrusion process controlling of the temperature holing time for a improvement on formability of Al-22Zn powder. Micro-extrusion has succeeded in forming micro-gear shafts.