【正文】 越大，所需斜導(dǎo)柱就越短。圖11選斜導(dǎo)柱公稱直徑為20mm，進行強度校核。斜導(dǎo)柱與定模板采用過度配合H7/m6，由于斜導(dǎo)柱在模具工作過程中主要用于驅(qū)動側(cè)向滑塊作往復(fù)運動，故側(cè)型芯的壓緊以及滑塊的導(dǎo)滑等問題均與斜導(dǎo)柱的安裝配合關(guān)系不大，所以斜導(dǎo)柱與滑塊斜孔之間可以采用過孔單邊間隙1mm。楔緊塊鎖緊形式，見圖12，給出三種形式。 （a） （b） （c） 圖12楔緊塊的楔角β必須大于斜導(dǎo)柱的傾角α，這樣才能保證模具合模時壓緊滑塊，開模時楔緊塊讓開，否側(cè)斜導(dǎo)柱將無法帶動滑塊完成抽芯動作。=25176。合模導(dǎo)向機構(gòu)在模具中，用來保證動模和定模或模內(nèi)其它零部件之間準確對合，在模具中起定位、導(dǎo)向和承受一定側(cè)壓力的作用。為了使成形后的塑料制品能自動脫模，就需設(shè)置推出脫模機構(gòu)。因此，必須設(shè)有復(fù)位裝置或復(fù)位桿。因此，必須將推桿及復(fù)位桿布置在與側(cè)型芯不同合模方向投影面內(nèi)，保證抽芯時不會發(fā)生干涉現(xiàn)象。其中包括模內(nèi)澆注系統(tǒng)和飛邊所用的的熔體量。 kV≥V=ΣV+V式中 V為注射機的最大注射量，單位為cm； V為制品總體積（包括制品、澆注系統(tǒng)及飛邊在內(nèi)），單位為cm； V為一個制品體積，單位為cm，圖13所示塑料零件尺寸 ；n為型腔數(shù)， 圖13k～～注射機最大注射量利用系數(shù)，取k=；V～～澆注系統(tǒng)及飛邊體積，單位為cm。模具的閉合高度應(yīng)在注射機最大與最小閉合高度之間，即模具的厚度應(yīng)在注射機允許的模具最大厚度和最小厚度之間。此次設(shè)計的模具為單分型面模具。帶有側(cè)向抽芯機構(gòu)的模具，其開模行程的校核必須考慮側(cè)向抽芯距離。討 論設(shè)計模具是一個精益求精的過程，從掌握塑料知識開始，到掌握模具設(shè)計的相關(guān)知識，只有比較和創(chuàng)新才能適宜當今模具設(shè)計的發(fā)展。 hence, the solidifying casting is subjected to a higher rate of cooling, which in turn affects the microstructure and grain size within the casting.3. Composite molds, which are made of two or more different materials (such as sand, graphite, and metal) bining the advantages of each material. These molds have a permanent and an expendable portion and ate used in various casting processes to improve mold strength, control the cooling rates, and optimize the overall economics of the casting process.The general characteristics of sand casting and other casting processes are given in Table . Almost all mercially used metals can be cast. The surface finish obtained is largely a function of the mold material。 the seam between them is the parting line. When more than two piece are used in a sand mold, the additional parts are called cheeks.2. A pouring basin or pouring cup, into which the molten metal is poured.3. A sprue, basin or pouring cup, into which the molten metal is poured.4. The runner system, which has channels that carry the molten metal from the sprue to the mold cavity. Gates are the inlets into the mold cavity.5. Risers, which supply additional molten metal to the casting as it shrinks during solidification. Two types of risers, a blind riser and an open riser, are shown in .6. Cores, which are inserts made from sand. They are placed in the mold to form hollow regions or otherwise define the interior surface of the casting. Cores also are used on the outside of the casting to form features such as lettering on the surface of a casting or deep external pockets.7. Vents, which are placed in molds to carry off gases produced when the molten metal es into contact with the sand in the mold and the core. Vents also exhaust air from the mold cavity as the molten metal flows into the mold.Patterns. Patterns are used to mold the sand mixture into the shape of the casting and may be made of wood, plastic, or metal. The selection of a pattern material depends on the size and shape of the casting, the dimensional accuracy and the quantity of casting required, and the molding process. Because patterns are used repeatedly to make molds, the strength and durability of the material selected for a pattern must reflect the number of casting that the mold will produce. Patterns may be made of a bination of materials to reduce wear in critical regions, and they usually are coated with a parting agent to facilitate the removal of the casting from the molds.Patterns can be designed with a variety o f features to fit specific applications and economic requirements. Onepiece patterns, also called loose or solid patterns, generally are used for simpler shapes and lowquantity production。 the majority is made with shell (see Section ), nobake, or coldbox processes. Cores are shaped in core boxes, which are used in much the same way that patterns are used to form sand molds. Sandmolding machines. The oldest known method of molding, which is still used for simple castings, is to pact the sand by hand hammering (tamping) or ramming it around the pattern. For most operations, however, the sand mixture is pacted around the pattern by molding machines. These machines eliminate arduous labor, offer highquality casting by improving the application and distribution of forces, manipulate the mold in a carefully controlled manner, and increase production rate.In vertical flaskless molding, the halves of the pattern form a vertical chamber wall against which sand is blown and pacted (). Then the mold halves are packed horizontally with the parting line oriented vertically and moved along a pouring conveyor. This operation is simple and eliminates the need to handle flasks, allowing for very highproduction rates, particularly when other aspects of the operation (such as coring and pouring) are automated.Sandslingers fill the flask uniformly with sand under a highpressure stream。 in this way, castings with plicated shapes can be produced. Matchplate patterns are a mon type of mounted pattern in which twopiece patterns are constructed by securing each half of one or more split patterns to the opposite sides of a single plate (). In such constructions, the gating system can be mounted on the drag side of the pattern. This type of pattern is used most often in conjunction with molding machines and large production runs to produce smaller castings.An important development in molding and pattern making is the application of rapid prototyping (Chapter 20). In sand casting, for example, a pattern can be fabricated in a rapid prototyping machine and fastened to a backing plate at a fraction of the time and cost of machining a pattern. There are several rapid prototyping techniques with which these tools can be produced quickly.Pattern design is a critical aspect of the total casting operation. The design should provide for metal shrinkage, ease of removal from the sand mold by means of a taper or draft (), and proper metal flow in the mold cavity. These topics are described in greater detail in Chapter 12.Cores. For castings with inter