【正文】 ating cavity springs should be strong enough to give an initial impetus to the floating cavity plate to ensure it moves away with the moving is normal practice to mount the springs on the guide pillars（ Figure32） and acmodate them in suitable pocket in the cavity plate. The major part of the feed system（ runner and sprue） is acmodated in the feed plate to facilitate automatic operation,the runner should be of a trapezoidal form so that once it is pulled from the feed plate is can easily be that if a round runner is used,half the runner is formed in the floating cavity plate,where it would remain,and be prevented from falling or being wiped clear when the mould is opened. Now that we have considered the mould assembly in the some detail,we look at the cycle of operation for this type of mould. The impressions are filled via the feed system（ Figure31（ a）） and after a suitable dwell period,the machine platens mence to force is immediately exerted by the pression springs,which cause the floating cavity plate to move away with the moving half as previously sprue is pulled from the sprue bush by the sprue the floating cavity plate has moved a predetermined distance,it is arrested by the stop moving half continues to move back and the moldings,having shrunk on to the cores,are withdrawn from the pin gate breaks at its junction with the runner（ Figure31（ b）） . The sprue puller,being attached to the moving half,is pulled through the floating cavity plate and thereby release the feed system which is then free to fall between the floating cavity plate and the feed moving half continues to move back until the ejector system is operated and the moldings are ejected（ Figure31（ c）） .When the mould is closed,the respective plates are returned to their molding position and the cycle is repeated. Feed System It is necessary to provide a flowway in the injection mould to connect the nozzle（ of the injection machine ） to each flowway is termed the feed the feed system prises a sprue,runner and terms apply 3 equally to the flowway itself,and to the molded material which is remove from the flowway itself in the process of extracted the molding. A typical feed system for a fourimpression,two platetype mould is shown in is seen that the material passes through the sprue,main runner,branch runner and gate before entering the the temperature of molten plastic is lowered which going through the sprue and runner,the viscosity will rise。在大型注塑機上常帶采用螺桿式的注入方式，如圖 21所示。通?？拷?jīng)驗來決定塑件所需要的鎖模力總噸數(shù)，一般在塑件投影面積上每平方英寸需要作用兩噸鎖模力。模具由三個基本部分組成，分別是動模部分、浮動型腔板和定模板。限位釘必須有足夠的長度為定模板和浮動型腔板之間提供足夠的空間，從而使?jié)沧⑾到y(tǒng)的凝料順利脫落。注意，如果采用圓形分流道，分流道的一半開設(shè)在浮動型腔板上，開模時，分流道可能留在浮動型腔板，將阻礙凝料的脫落或去除。 安裝在動模部分的拉料桿脫離浮動型腔板，澆注系統(tǒng)凝料由此脫下，然后在浮動型腔板和定模板之間自由落下。熔融塑料通過主流道和分流道時溫度降低而使熔體黏度升高，然而，熔體通過澆口填充型腔時，由于剪切作用產(chǎn)生的熱量又使黏度降低。 、冷料井 冷料井正對著主流道。 注塑機為推出系統(tǒng)提高了自動推出力，其推出動力裝置安裝在注塑機移動板的后面。裝配機構(gòu)（見圖 52）由推板、推板固定板和注塑機頂出桿組成?；镜耐瞥龇绞接幸韵聨追N：（?。┩茥U脫模；（ⅱ）推管脫模；（