Fig 7: Pressure Drop and Temperature at flow  front

Temperature at flow front result shows the temperature of the polymer when the flow front reached specified point, in the center of the plastic cross- section. The flow front should not drop more than the range shown in fig during the filling phase. Large changes often indicate that the injection time is too low, or there are areas of hesitation. If the flow front is too low in a thin area of the part, hesitation may result in a short shot. In areas where the flow front temperature increases by several degrees, material degradation and surface defects may occur. At the start of injection the result temperature is 240.1 °C which shows in red colour and at end of injection the result temperature is 214.5 °C which shows in dark blue  colour.

Fig 8: Time to reach Ejection Temperature and Weld lines

Cycle-time optimization starts at design stage. Cooling time takes up over 50% of cycle time. Therefore understanding of cooling in the mould becomes very important. Injection molding is a cycle operation. The cycle consist of Mould closed and clamp, (few second- depends on machine speeds) Injection – Fill (speed) phases, (few seconds) Switchover and pack (pressure) phases, (few seconds). Cooling time, (40 to 60% of cycle time) Actual filling time: 5.76 sec , Cool and pack time: 396.50 sec ,Mold open: 5.00 sec , Total time: 407.25 sec. The clamping force result is a time-series result which shows the force of the mould clamp over time. It is force resultant from filling and packing pressure that acts to open the mould. The clamp force is a function of injection pressure and the projected area of the part. A good clamping force results should show the maximum clamp force applied is less than 80% of the machine limits, allowing the remaining 20% as a safety force. The clamp force result can produce misleading result if the model has overlapping surfaces is added. Use pressure profiles or adjust part wall thickness to reduce the clamp force requirement. The maximum clamping force is noted as 0.194 tonnes.

7. Results and Discussions: The following result parameters that are obtained from the analysis.

Fig 9: Solid Model of Cam Bush

Sprue Bushing: The maximum diameter of the sprue should be atleast 6mm in diameter. The minimum diameter should be greater than nozzle orifice by 0.5-1mm. The length of the sprue channel should be as short as possible and never 100mm long. The sprue included angle has to be 4-5°. Design of runner: The main consideration for the designer to design a mould is the shape and cross section of the runner, the size of the runner and Layout of the runner. The different shapes of the cross section of the runner are fully rounded, semicircular, trapezoidal, modified trapezoidal, hexagonal, square and rectangular. Semi-circular cross section type runner is selected because it is easy to machine. Runner diameter calculation: D = (√W *4√L)/3.7= (√66

*4√16)/3.7 = 4.39mm, D- Diameter of runner, L- Length of Runner = 16mm, W- Weight of Cam Bush= 66g.The temperature of the mould must be maintained at some constant temperature below the heat point of the plastic, in order to chill it to a rigid state. Differential cooling strains are set, if the mould temperature is not uniform and those strains may cause distortion of the moulding after ejection. The heat input is supplied by the injection heating cylinder to plasticize the material must be removed from the mould to permit ejection.Q = m x {Cp x (Tmat  – Tmould) + Lt }= 66 x {0.4x (240 – 40) +57.8}= 9094.8cal/hr.

摘要：本文主要针对凸轮衬套生产的自动注塑模设计与分析进行了研究。Cam Bush用作高压变压器开/关分接开关装置中的分度装置，用作分度头和换能齿轮之间的连接件。注塑模是一种在短时间内大量生产塑料部件的工具。利用UnthigHICS（NX 7.5）和Auto Desk Moldflow进行建模和对凸轮衬套填充率、冷却系统位置和潜伏浇口位置进行模具流动分析。成型工具由顶板、腔板、芯板、间隔块、顶出板和底板组成。这六个芯销和六个推出销在注塑模上提供，因为所需的凸轮衬套具有六个分度孔。使用的材料是油淬非收缩钢（OHNs）的核心和空腔，选择用于拉杆，导套，型芯销，顶针，定位环和直浇道衬套的EN353以及用于其他钢板的低碳钢。设计并分析了注塑模具的各组成部分。在模具中设置了潜孔闸板和挡板圆孔冷却系统，提高了生产率和良好的表面光洁度。所需的尼龙66凸轮衬套部件将与注塑机的各种参数一起用该成型工具生产。