A Study on the Micro Nozzle-array plate of Ceramic Powder Injection Molding

• Main Authors: Ying-Cyuan Chen, 陳映全
• Other Authors: Shi-Chang Tseng
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/35706600017667728693

碩士 === 國立雲林科技大學 === 機械工程系碩士班 === 94 === This study is to develop the micro fabrication technology to produce a nozzle-array plate for fuel injection system of SI engines. It involves micro electro-discharge machining (M-EDM) and micro ceramic powder injection molding (MCPIM) technique. Because the pitch of 180um is quite small, a reverse-duplication M-EDM was used to manufacture micro cavity which has 4 micro pillars at once. The diameter of each pillar is about 300um. To reduce manufacture cost and keep higher precision and accuracy, micro injection molding was used to do the mass production. For CIM, lower mold temperature results in faster build-up of frozen layer, which in terms to prohibit the material to fill into the micro features. And this causes lower degrees of replication of CIM. Thus a vario-thermal injection molding (VTIM) system was developed and it provides higher mold temperatures to help the polymer melt fill into micro structures more like liquid and improve the degrees of replication of micro features. In order to study the effects of different processing conditions on the diameter shrinkage of green parts, Taguchi’s design method of experiments was applied to achieve meaningful results in fewer times of experiments. From the ANOVA analyses, less shrinkage of diameter was mainly affected by the initial mold temperature. Higher mold temperature result in thinner or even none frozen layer, which helps improve the degrees of duplicating the micro features. It also helps improve the bonding strength of weld lines which occur behind the micro holes. The debonding process is to separate the binding filler from the green part and has a strong effect on the success rate of final parts. In this work, commercial pellets and recommended thermal debonding procedures were applied. More studies are still needed to achieve better debonding contents and conditions in the near future. After that, brown parts were put in higher temperature oven for final sintering. Shrinkage during sintering was usually around 12~20% and affects the dimensions and precision of final parts. After sintering, similar experiments were done in measuring diameter shrinkage of sintered parts. Again, the most significant factor to the diameter shrinkage is the initial mold temperature. Higher mold temperature help polymer melt to flow and reduce the shear strain rate and stress, which can improve sintering quality. The average diameter of micro pillars was 310um and the average diameter of sintered holes was about 270um. Average hole shrinkage is about 13%, which is less than 16.6% of overall shrinkage of sintered parts. This work has successfully produced thin nozzle-array plates by integration of M-EDM and ceramic injection molding. Further studies to test its spraying performance on a SI engine are on the way and better results are expected.