插座面板注射模設(shè)計(jì)

插座面板注射模設(shè)計(jì),插座,面板,注射,設(shè)計(jì) 畢業(yè)設(shè)計(jì)（論文）開題報(bào)告 課 題 名 稱： 插座面板注塑模設(shè)計(jì) 學(xué) 生 姓 名： 指 導(dǎo) 教 師： 所 在 學(xué) 院： 機(jī)電工程學(xué)院 專 業(yè) 名 稱： 機(jī)械設(shè)計(jì)制造及其自動(dòng)化 說(shuō) 明 1．根據(jù)《學(xué)院畢業(yè)設(shè)計(jì)(論文)管理規(guī)定》，學(xué)生必須撰寫《畢業(yè)設(shè)計(jì)（論文）開題報(bào)告》，由指導(dǎo)教師簽署意見、教研室審查，學(xué)院教學(xué)院長(zhǎng)批準(zhǔn)后實(shí)施。 2．開題報(bào)告是畢業(yè)設(shè)計(jì)（論文）答辯委員會(huì)對(duì)學(xué)生答辯資格審查的依據(jù)材料之一。學(xué)生應(yīng)當(dāng)在畢業(yè)設(shè)計(jì)（論文）工作前期內(nèi)完成，開題報(bào)告不合格者不得參加答辯。 3．畢業(yè)設(shè)計(jì)開題報(bào)告各項(xiàng)內(nèi)容要實(shí)事求是，逐條認(rèn)真填寫。其中的文字表達(dá)要明確、嚴(yán)謹(jǐn)，語(yǔ)言通順，外來(lái)語(yǔ)要同時(shí)用原文和中文表達(dá)。第一次出現(xiàn)縮寫詞，須注出全稱。 4．本報(bào)告中，由學(xué)生本人撰寫的對(duì)課題和研究工作的分析及描述，沒(méi)有經(jīng)過(guò)整理歸納，缺乏個(gè)人見解僅僅從網(wǎng)上下載材料拼湊而成的開題報(bào)告按不合格論。 5. 課題類型填：工程設(shè)計(jì)類；理論研究類；應(yīng)用（實(shí)驗(yàn)）研究類；軟件設(shè)計(jì)類；其它。 6、課題來(lái)源填：教師科研；社會(huì)生產(chǎn)實(shí)踐；教學(xué)；其它 課題 名稱 插座面板注塑模設(shè)計(jì) 課題來(lái)源 自選 課題類型 工程設(shè)計(jì)類 選題的背景及意義 塑料模具在當(dāng)今社會(huì)越來(lái)越廣泛的應(yīng)用，從電腦、手機(jī)、飲料、臺(tái)燈、水筆、水盆等方面應(yīng)用極其廣泛，可以說(shuō)從我們的吃穿住行都離不開它。注射成形是成形熱塑件的主要方法，因此應(yīng)用范圍很廣。注射成形是把塑料原料放入料筒中經(jīng)過(guò)加熱熔化，使之成為高黏度的流體，用柱塞或螺桿作為加壓工具，使熔體通過(guò)噴嘴以較高壓力注入模具的型腔中，經(jīng)過(guò)冷卻、凝固階段，而后從模具中脫出，成為塑料制品。 本次的畢業(yè)設(shè)計(jì)是插座面板的注塑模的設(shè)計(jì)，該模具有重量輕、耐腐蝕老化、絕緣性好、強(qiáng)度高、使用壽命長(zhǎng)，制作方便、價(jià)格低廉等特點(diǎn)，可用于雙孔、三孔插座。 研究?jī)?nèi)容擬解決的主要問(wèn)題 課題研究的主要內(nèi)容： 本課題主要是塑料成型的工藝設(shè)計(jì)及制造，也就是注塑模的工藝設(shè)計(jì)方案分析及確定工藝計(jì)算，模具結(jié)構(gòu)設(shè)計(jì)計(jì)算等內(nèi)容。生產(chǎn)主要是為了提高生產(chǎn)效率，因此在設(shè)計(jì)是要力求結(jié)構(gòu)簡(jiǎn)單，但是一定要保證其精度要求。 擬解決的主要問(wèn)題： 先對(duì)塑件進(jìn)行結(jié)構(gòu)分析，確定型腔的布局，從各方面考慮其結(jié)構(gòu)布局，我也多次到成型部門進(jìn)行現(xiàn)場(chǎng)模具制造學(xué)習(xí)，積累了生產(chǎn)實(shí)際經(jīng)驗(yàn)，了解本課題一些相關(guān)技術(shù)要求及注意事項(xiàng)。 研究方法技術(shù)路線 1. 產(chǎn)品外形構(gòu)想，運(yùn)用Pro/E軟件生成產(chǎn)品。 2. 對(duì)塑件的工藝性進(jìn)行分析。 3. 選擇注塑機(jī)，選擇分型面，確定模具的結(jié)構(gòu)形式。 4. 成型零件設(shè)計(jì)。 5. 澆注系統(tǒng)設(shè)計(jì)。 6. 合模導(dǎo)向機(jī)構(gòu)設(shè)計(jì)。 7. 模溫冷卻系統(tǒng)設(shè)計(jì)。 8. 推出機(jī)構(gòu)設(shè)計(jì)。 9. 模架尺寸確定。 10. 繪零件圖和裝配圖 研究的總體安排和進(jìn)度計(jì)劃 第一周 查閱資料，對(duì)塑件的工藝性分析 第二周 選擇注射機(jī)，選擇分型面，確定模具的結(jié)構(gòu)形式 第三周 成型零件設(shè)計(jì) 第四周 澆注系統(tǒng)設(shè)計(jì) 第五周 合模導(dǎo)向機(jī)構(gòu)設(shè)計(jì) 第六周 模溫冷卻系統(tǒng)設(shè)計(jì) 第七周 推出機(jī)構(gòu)設(shè)計(jì) 第八周 模架尺寸確定 第九周 查閱資料，翻譯英文資料 第十周 繪零件圖 第十一周 繪零件圖 第十二周 畫裝配圖 第十三周 畢業(yè)論文初稿完成 第十四周 畢業(yè)論文定搞 第十五周 準(zhǔn)備答辯 第十六周 答辯 主要參考 文獻(xiàn) 1、《塑料成型模具與設(shè)備》 夏江梅 機(jī)械工業(yè)出版社 2005 2、《模具工程》 H. 瑞斯 化學(xué)工業(yè)出版社2005 3、《實(shí)用注射模設(shè)計(jì)手冊(cè)》 賈潤(rùn)禮、程志遠(yuǎn)編，中國(guó)輕工業(yè)出版社 4、《注射模具設(shè)計(jì)與制造實(shí)用技術(shù)》王樹勛編，華南理工大學(xué)出版社 5、《Pro/ENGINEEG野火版3.0——模具設(shè)計(jì)篇》李翔鵬，人民郵電出版社 6、《模具設(shè)計(jì)與制造簡(jiǎn)明手冊(cè)》 馮炳蕘，蔣文森等編 上海科學(xué)技術(shù)出社 指導(dǎo)教師 意 見 指導(dǎo)教師簽名： 年 月 日 教研室意見 學(xué)院意見 教研室主任簽名： 年 月 日 教學(xué)院長(zhǎng)簽名： 年 月 日 徐州工程學(xué)院 畢業(yè)設(shè)計(jì)（論文）任務(wù)書 機(jī)電工程 學(xué)院 機(jī)械設(shè)計(jì)制造極其自動(dòng)化 專業(yè) 設(shè)計(jì)（論文）題目 插座面板注射模設(shè)計(jì) 學(xué) 生 姓 名 朱偉偉 班 級(jí) 04機(jī)本（6）班 起 止 日 期 2008.02.25至2008.06.02 指 導(dǎo) 教 師 張萬(wàn)利 教研室主任 李志 發(fā)任務(wù)書日期 2008年 2月 25日 1.畢業(yè)設(shè)計(jì)的背景： 模具工業(yè)是國(guó)民經(jīng)濟(jì)的基礎(chǔ)，而塑料模具又是整個(gè)模具行業(yè)的霸主。我 國(guó)的塑料成型模具設(shè)計(jì)，近幾年發(fā)展迅速。目前塑料模具在當(dāng)今社會(huì)越來(lái) 越廣泛的應(yīng)用，從電器、手機(jī)、飲料等方面應(yīng)用極其廣泛可以說(shuō)離不開它。 注射成型是把塑料原材料放入料筒中經(jīng)過(guò)加熱熔化，使之成為高黏度的流 體，用柱塞或螺桿作為加壓工具，使融體通過(guò)澆嘴比較高壓注入模具的型 腔中，經(jīng)冷卻凝固階段，而后從模具中脫出，成為塑料制品。本設(shè)計(jì)的是 聚乙烯塑件（插座面板），采用一模二腔注射。該產(chǎn)品采用側(cè)澆口注射， 2.畢業(yè)設(shè)計(jì)(論文)的內(nèi)容和要求： 主要內(nèi)容：分析塑件的工藝性，選擇注射設(shè)備，選擇分型面，設(shè)計(jì)注 射模成型零件，設(shè)計(jì)澆注系統(tǒng)，導(dǎo)向機(jī)構(gòu)，推出機(jī)構(gòu)，冷卻系統(tǒng)。 基本要求:通過(guò)畢業(yè)設(shè)計(jì)，掌握注射模設(shè)計(jì)的基本步驟，熟悉塑料注 射模的各個(gè)組成部分的設(shè)計(jì)要領(lǐng)，能獨(dú)立設(shè)計(jì)注射模模具 3.主要參考文獻(xiàn)： 1、《塑料成型模具與設(shè)備》 夏江梅 機(jī)械工業(yè)出版社 2005 2、《模具工程》 H. 瑞斯 化學(xué)工業(yè)出版社2005 3、《實(shí)用注射模設(shè)計(jì)手冊(cè)》 賈潤(rùn)禮、程志遠(yuǎn)編， 中國(guó)輕工業(yè)出版社 4、《注射模具設(shè)計(jì)與制造實(shí)用技術(shù)》 王樹勛編， 華南理工大學(xué)出版社 5、《Pro/ENGINEEG野火版3.0——模具設(shè)計(jì)篇》 李翔鵬 人民郵電出版社 6、《模具設(shè)計(jì)與制造簡(jiǎn)明手冊(cè)》 馮炳蕘，蔣文森等編 上?？茖W(xué)技術(shù)出社 4.畢業(yè)設(shè)計(jì)(論文)進(jìn)度計(jì)劃(以周為單位)： 起 止 日 期 工 作 內(nèi) 容 備 注 第一周 第二周 第三周 第四周 第五周 第六周 第七周 第八周 第九周 第十周 第十一周 第十二周 第十三周 第十四周 第十五周 第十六周 查閱資料，對(duì)塑件的工藝性分析 選擇注射機(jī)，選擇分型面，確定模具的結(jié)構(gòu)形式 成型零件設(shè)計(jì) 澆注系統(tǒng)設(shè)計(jì) 合模導(dǎo)向機(jī)構(gòu)設(shè)計(jì) 模溫冷卻系統(tǒng)設(shè)計(jì) 推出機(jī)構(gòu)設(shè)計(jì) 模架尺寸確定 查閱資料，翻譯英文資料 繪零件圖 繪零件圖 畫裝配圖 畢業(yè)論文初稿完成 畢業(yè)論文定搞 準(zhǔn)備答辯 答辯 教研室審查意見： 室主任 年 月 日 學(xué)院審查意見： 教學(xué)院長(zhǎng) 年 月 日 附錄 附錄1 An experimental study of the water-assisted injection molding ofglass fiber filled poly-butylene-terephthalate (PBT) composites Abstract：The purpose of this report was to experimentally study the water-assisted injection molding process of poly-butylene-terephthalate(PBT) composites. Experiments were carried out on an 80-ton injection-molding machine equipped with a lab scale water injection system,which included a water pump, a pressure accumulator, a water injection pin, a water tank equipped with a temperature regulator,and a control circuit. The materials included virgin PBT and a 15% glass fiber filled PBT composite, and a plate cavity with a rib across center was used. Various processing variables were examined in terms of their influence on the length of water penetration in molded parts, and mechanical property tests were performed on these parts. X-ray diffraction (XRD) was also used to identify the material and structural parameters. Finally, a comparison was made between water-assisted and gas-assisted injection molded parts. It was found that the melt fill pressure, melt temperature, and short shot size were the dominant parameters affecting water penetration behavior.Material at the mold-side exhibited a higher degree of crystallinity than that at the water-side. Parts molded by gas also showed a higher degree of crystallinity than those molded by water. Furthermore, the glass fibers near the surface of molded parts were found to be oriented mostly in the flow direction, but oriented substantially more perpendicular to the flow direction with increasing distance from the skin surface. Keywords: Water assisted injection molding; Glass fiber reinforced poly-butylene-terephthalate (PBT) composites; Processing parameters; B. Mechanical properties; Crystallinity; A. Polymer matrix composites; 1. Introduction Water-assisted injection molding technology [1] has proved itself a breakthrough in the manufacture of plastic parts due to its light weight, faster cycle time, and relatively lower resin cost per part. In the water-assisted injection molding process, the mold cavity is partially filled with the polymer melt followed by the injection of water into the core of the polymer melt. A schematic diagram of the water-assisted injection molding process is illustrated in Fig. 1.Water-assisted injection molding can produce parts incorporating both thick and thin sections with less shrink-age and warpage and with a better surface finish, but with a shorter cycle time. The water-assisted injection molding process can also enable greater freedom of design, material savings, weight reduction, and cost savings in terms of tooling and press capacity requirements [2–4]. Typical applications include rods and tubes, and large sheet-like structural parts with a built-in water channel network. On the other hand, despite the advantages associated with the process,the molding window and process control are more critical and difficult since additional processing parameters are involved. Water may also corrode the steel mold, and some materials including thermoplastic composites are difficult to mold successfully. The removal of water after molding is also a challenge for this novel technology. Table 1 lists the advantages and limitations of water-assisted injection molding technology. Fig. 1. Schematic diagram of water-assisted injection molding process. Water assisted injection molding has advantages over its better known competitor process, gas assisted injection molding [5], because it incorporates a shorter cycle time to successfully mold a part due to the higher cooling capacity of water during the molding process. The incompressibility, low cost, and ease of recycling the water makes it an ideal medium for the process. Since water does not dissolve and diffuse into the polymer melts during the molding process, the internal foaming phenomenon [6] that usually occurs in gas-assisted injection molded parts can be eliminated.In addition, water assisted injection molding provides a better capability of molding larger parts with a small residual wall thickness. Table 2 lists a comparison of water and gas assisted injection molding.With increasing demands for materials with improved performance, which may be characterized by the criteria of lower weight, higher strength, and a faster and cheaper production cycle time, the engineering of plastics is a process that cannot be ignored. These plastics include thermoplastic and thermoset polymers. In general, thermoplastic polymers have an advantage over thermoset polymers in popular materials in structural applications.Poly-butylene-terephthalate (PBT) is one of the most frequently used engineering thermoplastic materials, whichis formed by polymerizing 1.4 butylene glycol and DMT together. Fiber-reinforced composite materials have been adapted to improve the mechanical properties of neat plastic materials. Today, short glass fiber reinforced PBT is widely used in electronic, communication and automobile applications. Therefore, the investigation of the processing of fiber-reinforced PBT is becoming increasingly important[7–10].This report was made to experimentally study the waterassisted injection molding process of poly-butylene-terephthalate (PBT) materials. Experiments were carried out on an 80-ton injection-molding machine equipped with a lab scale water injection system, which included a water pump, a pressure accumulator, a water injection pin, a water tank equipped with a temperature regulator, and a control circuit. The materials included a virgin PBT and a 15% glass fiber filled PBT composite, and a plate cavity with a rib across center was used. Various processing variables were examined in terms of their influence on the length of water penetration in molded parts, which included melt temperature, mold temperature, melt filling speed, short-shot size, water pressure, water temperature,water hold and water injection delay time. Mechanical property tests were also performed on these molded parts,and XRD was used to identify the material and structural parameters. Finally, a comparison was made betweenwater-assisted and gas-assisted injection molded parts. Table 1 Advantages and disadvantages of water-assisted injection molding Advantages Disadvantages 1. Short cycle time 1. Corrosion of the steel mold due to water 2. Low assisting medium cost (water is much cheaper and can be easily recycled) 2. Larger orifices for the injection pin required (easier to get stuck by the polymer melt) 3. No internal foaming phenomenon in molded parts 3. Some materials are more difficult to mold (especially amorphous thermoplastics) 4. Removal of water after molding is required 2. Experimental procedure 2.1. Materials The materials used included a virgin PBT (Grade 1111FB, Nan-Ya Plastic, Taiwan) and a 15% glass fiber filled PBT composite (Grade 1210G3, Nan-Ya Plastic, Taiwan).Table 3 lists the characteristics of the composite materials. 2.2. Water injection unit A lab scale water injection unit, which included a water pump, a pressure accumulator, a water injection pin, a water tank equipped with a temperature regulator, and a control circuit, was used for all experiments [3]. An orifice-type water injection pin with two orifices (0.3 mm in diameter) on the sides was used to mold the parts. During the experiments, the control circuit of the water injection unit received a signal from the molding machine and controlled the time and pressure of the injected water. Before injection into the mold cavity, the water was stored in a tank with a temperature regulator for 30 min to sustain an isothermal water temperature. 2.3. Molding machine and molds Water-assisted injection molding experiments were conducted on an 80-ton conventional injection-molding machine with a highest injection rate of 109 cm3/s. A plate cavity with a trapezoidal water channel across the center was used in this study. Fig. 2 shows the dimensions of the cavity. The temperature of the mold was regulated by a water-circulating mold temperature control unit. Various processing variables were examined in terms of their influence on the length of water penetration in water channels of molded parts: melt temperature, mold temperature, melt fill pressure, water temperature and pressure, water injection delay time and hold time, and short shot size of the polymer melt. Table 4 lists these processing variables as well as the values used in the experiments. 2.4. Gas injection unit In order to make a comparison of water and gas-assisted injection molded parts, a commercially available gas injection unit (Gas Injection PPC-1000) was used for the gas assisted injection molding experiments. Details of the gas injection unit setup can be found in the Refs. [11–15].The processing conditions used for gas-assisted injection molding were the same as that of water-assisted injection molding (terms in bold in Table 4), with the exception of gas temperature which was set at 25 C. 2.5. XRD In order to analyze the crystal structure within the water-assisted injection-molded parts, wide-angle X-ray diffraction (XRD) with 2D detector analyses in transmission mode were performed with Cu Ka radiation at 40 kV and 40 mA. More specifically, the measurements were performed on the mold-side and water-side layers of the water-assisted injection-molded parts, with the 2h angle ranging from 7 to 40. The samples required for these analyses were taken from the center portion of these molded parts. To obtain the desired thickness for the XRD samples, the excess was removed by polishing the Table 3 Characteristics of the glass–fiber reinforced PBT composite Property ASTM PBT 15% G.F. PBT Yield strength (kg/cm2) D-638 600 1000 Bending stress (kg/cm2) D-570 900 1500 Hardness (R-scale) D-785 119 120 Heat distortion temperature(C) (18.6 kg/cm2) D-648 60 200 Melt flow index (MFI) D-1238 40 25 1238 Impact strength (Kg-cm/cm) D-256 5 5 Melting temperature (C) DSC 224 224 samples on a rotating wheel on a rotating wheel, first with wet silicon carbide papers, then with 300-grade silicon carbide paper, followed by 600- and 1200-grade paper for a better surface smoothness. 2.6. Mechanical properties Tensile strength and bending strength were measured on a tensile tester. Tensile tests were performed on specimens obtained from the water-assisted injection molded parts (see Fig. 3) to evaluate the effect of water temperature on the tensile properties. The dimensions of specimens for the experiments were 30 mm · 10 mm · 1 mm. Tensile tests were performed in a LLOYD tensiometer according to the ASTM D638M test. A 2.5 kN load cell was used and the crosshead speed was 50 mm/min. Bending tests were also performed at room temperature on water-assisted injection molded parts. The bending specimens were obtained with a die cutter from parts (Fig. 3) subjected to various water temperatures.The dimensions of the specimens were 20 mm · 10 mm · 1 mm. Bending tests were performed in a micro tensile tester according to the ASTM D256 test. A 200 N load cell was used and the crosshead speed was 50 mm/min. 2.7. Microscopic observation The fiber orientation in molded specimens was observed under a scanning electron microscope (Jeol Model 5410).Specimens for observation were cut from parts molded by water-assisted injection molding across the thickness (Fig. 3). They were observed on the cross-section perpendicular to the flow direction. All specimen surfaces were gold sputtered before observation. 3. Results and discussion All experiments were conducted on an 80-ton conventional injection-molding machine, with a highest injection rate of 109 cm3/s. A plate cavity with a trapezoidal water channel across the center was used for all experiments Table 4 The processing variables as well as the values used in the experiments A B C D E F Melt pressure (Mpa) Melt temperature (C) Short shot size (%) Water pressure (Mpa) Water temperature (C) Mold temperature (C) 140 280（270） 76 8 80 80 126 275（265） 77 9 75 75 114 270 (260) 78 10 70 70 98 265 (255) 80 11 65 65 84 260 (250) 81 12 60 60 Fig. 3. Schematically, the positioning of the samples cut from the molded parts for tensile and bending tests and microscopic observations. 3.1. Fingerings in molded parts All molded parts exhibited the water fingering phenomenon at the channel to plate transition areas. In addition,molded glass fiber filled composites showed more severe water fingerings than those of non-filled materials, as shown photographically in Fig. 4. Fingerings usually form when a less dense, less viscous fluid penetrates a denser,more viscous fluid immiscible with it. Consider a sharp two phase interface or zone where density and viscosity change rapidly. The pressure force (P2P1) on the displaced fluid as a result of a virtual displacement dx of the interface can be described by [16], where U is the characteristic velocity and K is the permeability.If the net pressure force is positive, then any small displacement will be amplified and lead to an instability and part fingerings. For the displacement of a dense, viscous fluid (the polymer melt) by a lighter, less viscous one (water), we can have Dl = l1l2 > 0, and U > 0 [16].In this case, instability and the relevant fingering result when a more viscous fluid is displaced by a less viscous one, since the less viscous fluid has the greater mobility.The results in this study suggest that glass fiber filled composites exhibit a higher tendency for part fingerings. This might be due to the fact that the viscosity difference Dl between water and the filled composites is larger than the difference between water and the non-filled materials. Waterassisted injection molded composites thus exhibit more severe part fingerings. Fig. 4. Photograph of water-assisted injection molded PBT composite part. 3.2. Effects of processing parameters on water penetration Various processing variables were studied in terms of their influence on the water penetration behavior. Table 4 lists these processing variables as well as the values used in the experiments. To mold the parts, one central processing condition was chosen as a reference (bold term in Table By changing one of the parameters in each test, we were able to better understand the effect of each parameter on the water penetration behavior of water assisted injection molded composites. After molding, the length of water penetration was measured. Figs. 5–10 show the effects of these processing parameters on the length of water penetration in molded parts, including melt fill pressure, melt temperature, mold temperature, short shot size, water temperature, and water pressure.The experimental results in this study suggest that water penetrates further in virgin PBT than in glass fiber filled PBT composites. This is due to the fact that with the reinforcing glass fibers the composite materials have less volumetric shrinkage during the cooling process. Therefore,they mold parts with a shorter water penetration length.The length of water penetration decreases with the melt fill pressure (Fig. 5). This can be explained by the fact that increasing the melt fill pressure increases the flow resistance inside the mold cavity. It is then more difficult for the water to penetrate into the core of the materials. The length of water penetration decreases accordingly [3].The melt temperature was also found to reduce the water penetration in molded PBT composite parts (Fig. 6). This might be due to the fact that increasing the melt temperature decreases viscosity of the polymer melt.A lower viscosity of the materials helps the water to pack the water channel and increase its void area, instead of penetrating further into the parts [4]. The hollow core ratio at the beginning of the water channel increases and the length of water penetration may thus decrease.Increasing the mold temperature decreases somewhat the length of water penetration in molded parts (Fig. 7).This is due to the fact that increasing the mold temperature decreases the cooling rate as well as the viscosity of the materials. The water then packs the channel and increases its void area near the beginning of the water channel,instead of penetrating further into the parts [3]. Molded parts thus have a shorter water penetration length.Increasing the short shot size decreases the length of water penetration (Fig. 8). In water-assisted injection molding, the mold cavity is partially filled with the polymer melt followed by the injection of water into the core of the polymer melt [4]. Increasing the short shot size of the polymer melt will therefore decrease the length of water penetration in molded parts.For the processing parameters used in the experiments,increasing the water temperature (Fig. 9) or the water pressure(Fig. 10) increases the length of water penetration in molded parts. Increasing the water temperature decreases the cooling rate of the materials and keeps the polymer melt hot for a longer time; the viscosity of the materials decreases accordingly. This will help the water penetrate further into the core of the parts [3]. Increasing the water pressure also helps the water penetrate into the materials.The length of water penetration thus increases.Finally, the deflection of molded parts, subjected to various processing parameters, was also measured by a profilemeter.The maximum measured deflection is considered as the part warpage. The result in Fig. 11 suggests that the part warpage decreases with the length of water penetration.This is due to the fact that the longer the water penetration,the more the water pressure can pack the polymeric materials against the mold wall. The shrinkage as well as the relevant part warpage decreases accordingly. Fig. 5. Effects of melt fill pressure on the length of water penetration in molded parts. Fig. 6. Effects of melt temperature on the length of water penetration in molded parts. Fig. 9. Effects of water temperature on the length of water penetration in molded parts. Fig. 7. Effects of mold temperature on the length of water penetration in molded parts. Fig. 8. Effects of short shot size on the length of water penetration inmolded parts. Fig. 10. Effects of water pressure on the length of water penetration inmolded parts. 3.3. Crystallinity of molded parts PBT is a semi-crystalline thermoplastic polyester with a high crystallization rate. In the water-assisted injection molding process, crystallization occurs under non-isothermal conditions in which the cooling rate varies with cooling time. Here the effects of various processing parameters (including melt temperature, mold temperature, and water temperature) on the level of crystallinity in molded parts were studied. Measurements were conducted on a wideangle X-ray diffraction (XRD) with 2D detector analyses(as described in Section 2). The measured results in Fig. 12 showed that all materials at the mold-side lay erexhibited a higher degree of crystallinity than those at the water-side layer. The result indicates that the water has a better cooling capacity than the mold during the cooling process. This matches our earlier finding [17] by measuring the in-mold temperature distribution. In addition, the experimental result in Fig. 12c also suggests that the crystallinity of the molded materials generally increases with the water temperature. This is due to the fact that increasing the water temperature decreases the cooling rate of the materials during the cooling process. Molded parts thus exhibited a higher level of crystallinity.On the other hand, to make a comparison of the crysallinity of parts molded by gas and water, gas-assisted injection molding experiments were carried out on the same injection molding machine as that used with water