primarily dependent on the depth of the cavity and the shrinkage rate of plastic materials. The mold is usually designed so that the molded part reliably remains on the male mold when it opens. Ejector pins or ejector plate is placed in either half of the mold, which pushes the finished
molded product or runner system out of a mold. The standard method of cooling is passing a coolant through a series of holes drilled through the mold plates and connected by hoses to form a continuous pathway. The
coolant absorbs heat from the mold and keeps the mold at a proper temperature to solidify the plastic at the most efficient rate. To ease maintenance and venting, cavities and cores are pided into pieces, called inserts. By substituting interchangeable inserts, one mold may make several variations of the same part.General mold design process contains two parts [19]:part design and mold design. The part design process contains five major procedures: defining main pulling direction, defining core and cavity, calculating shrinkage rate, defining draft angle, and then defining parting line.The mold design process mainly includes choosing a mold base, positioning the molded part, designing core andcavity, designing components, designing coolant channels,creating returning pin, adding ejector pin, creating gate and runner, adding locating ring and sprue bushing in sequence.
3 Applying modular design for beverage containers
    This study applies modular design to beverage-container injection molds via a five stage process, as follows: (1) product classification and machine specifications, (2) pision of injection molds into modules based on functionality, (3) pision of inpidual modules into multiple
units with sub-functions, and the relationship between design and assembly for each unit, (4) standardization of structural units, and (5) coding of standard structural units.

3.1 Product classification and machine specifications
This step classifies all of the beverage containers based on their geometry and dimensions, and selects the machine with the most suitable specifications for production. There are five major qualifications for an injection molding machine, including sufficient mold clamping force, sufficient theoretical shot volume, sufficient distance between tie bars, sufficient range of mold thickness, and sufficient mold clamping stroke.

3.2 Division of injection molds into modules based on functionality
This step pides a mold set into several modules with inpidual functions. The principles of pision include general rule, pision rule, applicability rule, and interchange rule. In general rule, modules must contain all the functions of beverage-container injection molds. In pision rule, each functional module must contain at least one
fundamental function and each unit must fulfill its own specific functions. As to applicability rule, units fulfilling a single function are preferred. For interchange rule, fundamental units should be interchangeable among modules after piding molds into product families.
3.3 Division of a module into multiple units with sub-function and the relationship between design and assembly for each unit.
The structure of a beverage-container mold that includes several functional modules. The functions of inpidual modules are further extended to the structural unit via sub-functions or sub-sub-functions. The pided modules include clamping module, hot-runner module, molding module, ejecting module, and guiding module. The clamping module functions for precisely positioning inpidual units and modules on an injection molding machine. The hot-runner module is to maintain the
flowability of molten plastics via heating. The molding module controls the geometry and dimensional accuracy of injection-molded parts. The ejecting module ejects injection-molded parts from the mold cavity. The guiding module works for accurately positioning the female and male molds during mold closing.
3.3.1 Geometrical design of structural elements 注塑模具英文文献及中文翻译(2):http://www.751com.cn/fanyi/lunwen_14352.html