模具设计技术3-(注塑不良分析)TROUBLE SHOOTING(164页PPT)

(164页)

'模具设计技术3-(注塑不良分析)TROUBLE SHOOTING(164页PPT)'
学习模具 设计 (三)Troubles hootin(g一)?防氣閥(空氣阱) Air traps? 防氣閥(空氣阱) ? Air traps? 什麼是空氣阱? ? What is an air trap?? 空氣阱是陷入模穴內的空 ? An air trap is air that is caught inside the mold 氣. 它是由聚合物熔融流 cavity. It becomes trapped 動會集成的或不能從模具 by converging polymer melt 排氣口或模具鑲件氣孔逃 fronts or because it failed to 逸形成的. 空氣阱位置通 escape from the mold vents, 常位于最後充填的區域.在 or mold inserts, which also 這些最後充填區域缺乏排 act as vents. Air-trap locations are usually in 氣口或排氣口不夠大都是 areas that fill last. Lack of 造成空氣阱的普遍原因并 vents or undersized vents in 導致不良.另一個普遍原因 these last-to-fill areas are a 是由較大的厚度比率造成 common cause of air traps 的競爭軌道 聚合物流動的 and the resulting defects. ( Another common cause is 趨勢是在較厚處優先通過). racetracking (the tendency of polymer melt to flow preferentially in thicker sections), caused by a large thickness ratio. ? FIGURE 1. 由計算機預測的熔融前端推進顯示的空氣阱位置. (點擊REPLAY重放動畫)? FIGURE 1. Air trap locations indicated by the computer-predicted melt-front advancements. ? (To replay the animation, click Replay)? 空氣阱造成的問題 ? Problems caused by air ? 模壓產品內陷的氣體會導 traps 致空白點與氣泡,短射(不 ? Entrapped air will result in voids 完整的充填),或表面不良 and bubbles inside the molded 如瑕疵或燒痕 為了消除空 part, a short shot (incomplete fill), . ? or surface defects such as 氣阱,你可以通過減少射出 blemishes or burn marks. To 速度,放大排氣或在模穴處 eliminate air traps, you can modify 設置合適的排氣孔來修改 the filling pattern by reducing the injection speed, enlarging venting, 充填模式. or placing proper venting in the? 在以下的圖形中,空氣阱由 ? cavity. In the figure below, an air 帶較大產品厚度比率的競 trap results from race-tracking in a part with a large thickness ratio. In 爭軌道造成.在這種情形下, ? this case, the entrapped air can be 陷入的氣體可以通過改變 vented by changing the thickness 厚度比率或通過增加空氣 ratio or by placing a vent 阱位置處的排氣孔來通氣 ? (e.g., via an ejector pin) at the air trap location. (如通過頂針)空氣阱.? 補救措施 ? Remedies? 改變產品設計 ? Alter the part design 減少厚度比率 ? Reduce the thickness ratio.? ? This will minimize the race-? 會降低聚合物流動競爭跑 tracking effect of polymer melt. 道的效果. ? Alter the mold design 改變模具設計 ? Pay close attention to the proper ? placement of your vents.? 注意排氣孔的放置位置 ? Place vents in the areas that ? 將排氣孔放在最後充填的 fill last. 區域 ? Vents are typically positioned at . discontinuities of mold material, ? 排氣孔典型定位于模具材 such as at parting surfaces, 料的中斷處如在分模面上, ? between the insert and mold wall, 鑲件與模壁中間,在頂針處, at ejector pins, and at mold 在模具滑塊上. slides. ? Re-design the gate and ? 重新設計灌點與傳輸系統 delivery system.? 改變傳輸系統能改變充填 ? Changing the delivery system 模式 通過這種方式 最後 can alter the filling pattern in , , such a way that the last-to-fill 充填區域就位于正當的排 areas 氣位置. ? are located at the proper venting locations.? 确保排氣孔足夠大以 ? Make sure the vent size 便模穴氣體能在射出 is large enough so that 時跑出來. the air present in the cavity can escape ? 然而需小心,排氣孔不 during injection. 要太大,不然會造成模 ? Be careful, however, that 具邊緣的毛邊.建議結 the vent is not so large 晶性聚合物排氣孔大 that it causes flash at the 小為0.025 mm (0.001 edge of the molding. inch), 無定形聚合物 ? The recommended vent 排氣孔大小為0.038 size is 0.025 mm (0.001
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模具设计技术3-(注塑不良分析)TROUBLESHOOTING(164页PPT)
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