1、编号： 毕业设计 (论文 )外文翻译 （ 译 文） 学 院： 机电工程学院 专 业： 机械设计制造及其自动化 学生姓名： 学 号： 指导教师单位： 艺术与设计 学院 姓 名： 梁惠萍 职 称： 讲师 2012 年 5 月 15 日 The Effects of Mold Designon the Pore Morphology ofPolymers Produced withMuCell_ Technology ABSTRACT: In this study two molds were designed and used in MuCell_technology to generate im
2、plants with a porous structure. To arrive the desiredpore structure many process parameters were investigated for indicating theeffects of process parameters on the pore morphology. This process parameterinvestigation was performed on each mold respectively, so that the influencesof the mold design
3、on the pore morphology have been researched by the sameprocess parameter setting. It was found that the mold design also had effectson the pore structure in MuCell_ technology. A proper mold design couldimprove the generated pore structure, such as porosity, pore diameter, andinterconnectivity. KEY
4、WORDS: mold design, cell morphology, MuCell_, injection molding,medical implant, porous polymer, polyurethane. INTRODUCTION MuCell technology, as an effective microcellular injection moldingprocess, is widely used in automobile and furniture industries.In most cases, MuCell_ technology is used to sa
5、ve raw materials, but itis also used to produce implants with closed porous structure 1. It usesCO2 as blowing agent, which is injected in the plasticization section ofthe injection molding machine (Figure 1). The blowing agent is injectedinto the polymer melt through the gas supply line and injecto
6、r, in itssuper critical state, by the plasticization phase of the injection moldingmachine. After the plasticization the mixture of polymer melt and gas isinjected through the nozzle into the mold, where the foam structure canbe generated due to the quick pressure drop in the mold. The mainproducts
7、which are produced today with MuCell_ technology have closedcellular foam 24. The MuCell Microcellular Foam injection molding technology is a complete process and equipment technology which facilitates extremely high quality and greatly reduces production costs. The MuCell Process involves the contr
8、olled use of gas in its supercritical state to create a foamed part. The MuCell Technology is targeted at precision and engineered plastic components with maximum wall thicknesses of less than 3mm.The MuCell Process generally offers a 50-75% improvement in key quality measures, such as flatness, rou
9、ndness, and warpage, also eliminating all sink marks. These improvements result from the fact that relatively uniform stress patterns are created in the molded part rather than non uniform stress characteristic of solid molding.As a direct result of the uniform stress and shrinkage associated with t
10、he MuCell Process (which occurs because the pack and hold phase of the molding cycle is eliminated), the parts that are produced tend to comply far more closely with the mold shape and, presumably, the dimensional specifications of the part itself. This means that when using the MuCell Process, fewe
11、r mold iterations are needed to produce a compliant part, saving time and cost.The quality advantages of the MuCell Process are complemented by certain direct economic advantages, including the ability to produce 20-33% more parts per hour on a given molded machine, and the ability to mold parts on
12、lower tonnage machines as a result of the viscosity reduction and the elimination of the packing requirement that accompanies the use of supercritical gas. This 25 page processing handbook covers all aspects of the process from set-up to troubleshooting to optimizing results. It is primarily useful
13、to companies who are manufacturing or are planning to manufacture parts using the MuCell Injection Molding Process. Please contact Trexel for a copy of this publication.The MuCell Injection Molding Process involves the highly controlled use of gas in its supercritical state (SCF) to created millions
14、 of micron-sized voids in thin wall molded parts (less than 3mm). With the correct equipment configuration, mold design, and processing conditions these microcellular voids are relatively uniform in size and distribution.The voids are created or nucleated as a result of homogeneous nucleation that o
15、ccurs when a single-phase solution of polymer and gas (commonly nitrogen, but occasionally carbon dioxide) passes through the injection gate into the mold.The single-phase solution is created through the operation of a conventional injection molding machine which has been modified to allow the creat
16、ion of a single-phase solution. The key modifications to the system involve the use of a precision SCF delivery system to deliver SCF to special injectors based on mass flow metering principles. The SCF is then injected into the barrel where it is mixed with the polymer via a specially designed scre
17、w. A shut off nozzle maintains the single phase solution while the injection molding screw maintains sufficient back pressure at all times to prevent premature foaming or the loss of pressure which would allow the single phase solution to return to the two phase solution. Trexel has recently publish
18、ed a comprehensive MuCell Process Guide in English, Chinese, Japanese, and German which explains in step by step detail how to apply the MuCell process in the manufacture of MuCell Injection Molded components. This 25 page processing handbook covers all aspects of the process from set-up to troubles
19、hooting to optimizing results. It is primarily useful to companies who are manufacturing or are planning to manufacture parts using the MuCell Injection Molding Process. Please contact Trexel for a copy of this publication.The MuCell microcellular foam injection molding process for thermoplastics ma
20、terials provides unique design flexibility and cost savings opportunities not found in conventional injection molding. The MuCell process allows for plastic part design with material wall thickness optimized for functionality and not for the injection molding process. The combination of density redu
21、ction and design for functionality often results in material and weight savings of more than 20%. By replacing the pack & hold phase with cell growth, lower stress parts are produced which have enhanced dimensional stability and substantially reduce warpage. Cell growth also results in the elimination of sink marks.
