【正文】 常州工學院畢業(yè)設計（論文）外文文獻 學 院 機電學院 專業(yè)班級 10成型一 學生姓名 高麗君 指導教師 陳懷國 A. Mold ComponetsMolds used in injection molding consist of two halves。 one stationary and one movable. The stationary half is fastened directly to the stationary platen and is in direct contact with the nozzle of the injection unit during operation. The movable half of the mold is secured to the movable platen and usually contains the ejector mechanism. There are many possible mold designa, including multiple piece molds for plicated parts. On production molding equipment many articles may be shot at the same time by the use of multiple cavity molds. The use of a balanced runner system carries the plastic from the sprue to each individual cavity. At this poin the material passes through a gate into the cavity. The gate is a restriction, smaller then the runner, to provide for even filling of the mold cavity and to allow the products to be easily removed form the runner system. With most injection molding system, the articles can be snapped away from the runner or sprue without additional trimming. Prouducts that have been injection molded can usually be identified by finding where the gate was broken off. The gate will usually be located at the edge or parting line of an object or in the center of cylindrical product. Molds are expensive, as are the machines. Yet, once the product has been designed, molds made, and production stared, articles can be produced in quantity at low cost. Virtually all thermoplastics can be injection molded through variations in mold and machine design. Mold (and die) parts that are massproduced and standardized in shape and dimension are referred to as “standards” (or “standard parts”). Specialized operators of milling machines, lathes, lathes, electronic discharge machining (EDN) equipment and grinders produce mold ponents independently of each other, following detaied mold part drawings. Finally, all these items e together with the standard mold base and hardware and are assembled by the mold maker. Today, standard ponents for the moldmaking industry are marketed by a number of panies. illustrate the standard ponents for Molds.Table Status of standardization (1998) ponents for Compression, Injection, and DieCast MoldPos. No.DenominationStandardDINISO1Plate, plain167601675322Plat, drilledV 167602/3Support pillarDIN ISO 10073100734Centring sleeve1675994495Locating guide pillar1676180176Locating guide busch1671680187Ejector pin, cylindrical head1530A67518Shouldered ejector pin, cylindrical head1530C86949Ejector pin, conical head1530D/10Flat ejector pin1530F869311Ejector sleeve16756840512Sprue puller insert16757/13Sprue bushing1675211007214Angle pin/840415Locating unit, round and falt/840616Locating ring1676310907110907217Thermal insulating sheet167131560018Cooling connectors16766/29 / 31B Mold Construction The construction of the mold for injection molding begins with the working drawing. From it the tequirements for the mold can be specified. These would include the material from which the mold should be made, the availability of equipment for machining the mold, and the mold capacity of the die set on the machine. Cold rolled steel is an ideal material for laboratory molds, since it machines well, is fairly inexpensive, and holds up well for nozzle pressure and wear. Its major disadvantage is that it will rust quickly unless protected by mold telease or wax during storage. Complicated mold cavities need specialized machining and polishing, therefore, circular cavities which can be turned and polished on the lathe require less equipment and machining skill. Similar molds may also be machined from aluminum, and they have the advantage of not rusting. Excessive wear develops on the sprue due to the high nozzle pressure on the soft aluminum, but this can be overe by the use of a steel cover plate on the top of the mold. Another method of mold construction is by the casting process using an aluminum filled epoxy resin. This type of mold is particularly suited to products of intricate design and products that are difficult to machine. The cast epoxy is strong and gives good surface detail, however, it is brittle and should have a steel top plate attached to absorb the wear of the nozzle. A pattern of the product must be secured or made and placed on a mold plate. The drag of a small steel flask is placed around the pattern and the epoxy resin is poured to fill the mold half. When this half of the mold has been cured, the cope is placed over it and the remainder of the mold poured. Upon curing, the flask is removed, all surfaces machined smooth, dowel pinholes drilled, and dowels inserted. A steel cap plate should be bolted to the top halves and the sprue, runners, and gates machined. Instructions for mixing, pouring, and curing the aluminum filled epoxy should be followed according to the manufacturer’s specifications.2. Hot Runner Systems Hot runners are classified according as they are heated: insulatedrunner systems (it is not described in this article) and genuine hotrunner systems. The latter can be further subclassified according to the type of heating: internal heating, and external heating. Heating is basically performed electrically by cartridge heaters, heating rods, band heaters, heating pipes and coils, etc. To ensure uniform flow and distribution of the melt, usually a relatively elaborate aontrol system prising several heating circuits and an appropriate number of sensors is needed. The operating voltage is usually 220 V to 240 V, but small nozzles frequently have a low voltage of 5 V, and also 15 V and 24 V opera