Application of Gas-assisted Injection Molding on the Lightweight Push-bike Frame Design.

• Main Authors: Wang, Chi, 王齊
• Other Authors: Hsu, Pe-Ming
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/7mkm34

碩士 === 遠東科技大學 === 機械工程研究所在職專班 === 107 === Balanced scooter is a popular children's car. The pedal-free bicycle that is born because the child's muscles are not yet mature makes it use step by step. The finished product needs to be firm and beautiful. In order to get the best appearance, the finished product is usually as much as possible. Integrally formed, but at the same time, the thickness of the finished product is too thick, resulting in an increase in weight and failure to meet the requirements. Therefore, the internal hollowing of the finished product is performed by means of gas-assisted injection molding, and attempts are made to reduce the weight of the finished product. The gas-assisted injection molding process firstly performs the injection of the plastic into the film cavity, and then introduces the gas into the melt. The commonly used gas is an inert gas of nitrogen, and the gas flows to the low pressure and high temperature regions of the product along the direction of the least resistance. As the gas flows through the article, it hollows out the cross-section beyond the thick wall by melting the plastic. These hollowed out plastics fill the rest of the finished product. When the filling process is completed, the gas continues to provide the holding pressure to solve the problem of volume shrinkage during the cooling process of the material, but it is difficult to control the gas-assisted injection molding. If the traditional method is used, it is necessary to carry out experiments to find the best gas assist. State, for this reason, this simulation experiment decided to use the mold flow analysis software Moldflow for simulation. Moldflow mold flow analysis software performs gas-assisted injection molding simulation on the actual finished product, which can save the cost of large test and modification of the mold, and can find possible problems and the best choice first. The finished product used in this discussion is the rocker body. The original meat thickness and weight exceed the customer's requirements. It is difficult to solve in the past. I decided to use Moldflow for gas-assisted injection molding to simulate the hollowing out and try to find the best flaw. Empty state. The process of this discussion is to fix the injection velocity value and the injection pressure value, and modify the gas pressure to 10 bar, 15 bar and 20 bar, and the injection capacity is 60%, 65% and 70%. The injection position is the end injection and the central injection, the gas inlet. The position is at the end and the center, and finally the overflow channel is added for experiment, and the content is discussed to distinguish the injection position from the gas inlet position, and the gas pressure and the injection capacity are respectively discussed in three different states. The results show that under the condition that the finished product is selected at the end of the finished product and the position of the gas gate is not good, the amount of gas-assisted injection can be hollowed out, and the end of the flow is insufficient, which causes it to fail to meet customer demand. After maintaining the original gate position and changing the gas gate position, the amount of voiding is significantly improved but the flow end is easily vented, and the addition of the overflow passage does not help. To this end, the gate position is changed to the center of the finished product, so that the flow at both ends is balanced. After changing the position of the gas gate, it is found that the amount of hollowing is still insufficient, so the overflow passage is added at the end of the finished product, and the result shows that the gate position and the air pressure position are displayed. Change to the center of the finished product, and add the overflow channel. After adjusting the gas pressure to 15 bar and the filling amount of 70%, you can find the best hollowing state of the finished product 30% hollow.