【正文】 these methods allow for little control and typically yield large voids and a nonuniform cell structure. This article reports on our use of an advanced structural foam molding machine to achieve a uniform cell structure with a high void fraction. We studied the following processing parameters: injection flow rate, blowing agent content, and melt temperature. The pressure profile inside the mold cavity under various processing conditions was also investigated to elucidate cell nucleation and growth behaviors. By optimizing all processing conditions, we achieved a uniform cell structure and a very high void fraction (over 40%).IntroductionStructural foams are plastic foams manufactured using ，conventional preplasticatingtype injectionmolding machines. A physical blowing agent (PBA), chemical blowing agent，(CBA), or both are employed in the process to produce a cellular (foam) structure. The advantages of structural foam molding，include the absence of sink marks on the final part’s surface, a reduced weight, a low back pressure, a faster production cycle ，time, and a high stiffnesstoweight Because of this unique set of advantages, a lowpressure preplasticatingtype，structural foam molding technology has been used widely for manufacturing large products that require geometric accuracy. Achieving a suitable void fraction in structural foams using conventional structural foam molding has not proven to be successful, however, as these molding methods allow for little control and yield large voids and a nonuniform cell obtain a uniform cell structure with a high void fraction, the machine must be capable of first producing a pletely dissolved and uniform gas/polymer mixture without any gas pockets. If a uniform singlephase polymer/gas solution is not achieved before foaming, it would be very difficult to attain a uniform cell structure in the final foam products. To meet this requirement, an advanced structural foam molding technology with continuous polymer/gas mixture formation was developed at the University of ,5 This technology facilitates the uniform dispersion and dissolution of gas in the polymer melt during the structural foam molding process, thereby safe guarding against the creation of large, undissolved gas pockets. In a previous work,5 we demonstrated the feasibility of using a customized small injection molding system consisting of a miniinjection unit and a foaming extruder based on this new technology. However, in addition to improved hardware technology, it is also required to develop appropriate processing strategies to control cell nucleation and growth inside the mold cavity. In this context, the current article discusses some processing strategies required to obtain a uniform cell structure with a high void fraction in an advanced structural foam molding process. We investigated the following critical parameters: blowing agent content, injection flow rate, and melt temperature. The structural foams obtained using our advanced molding technology were characterized in terms of void fraction, cell density, and cell size distribution。參考文獻(xiàn)(1) Hornsby, P. R. Thermoplastics Structural Foams: Part 2 Properties and Application. Mater. Eng. 1982, 3, 443.(2) Ahmadi, A. A.。當(dāng)?shù)獨(dú)夂刻?即,%),空腔壓降成核率會(huì)下降并導(dǎo)致制品的密度過(guò)低。因?yàn)樵诤畏N程度上的不同,熔體冷卻流量、更高注射注塑流動(dòng)速度下降冷卻速率在注射過(guò)程中,這導(dǎo)致熔融粘度較低,同時(shí),也增加了聚合物的力學(xué)性能。充填型腔的程度隨氮?dú)夂亢妥⑷肓髁慷黾?。圖4顯示了吹劑的影響(氮?dú)?和溫度對(duì)泡沫融化程度充滿了模具。此外,保持了足夠高的壓力后的油已經(jīng)完全溶解,防止形成第二階段在聚合物熔體在積累階段。,從以前所有的結(jié)構(gòu)發(fā)泡成型技術(shù)是基于低壓塑料注塑系統(tǒng)。聚合物/氣體混合物能夠控制的變轉(zhuǎn)速的齒輪泵。就需要有一個(gè)常數(shù)溶氣/重量配比提供理論依據(jù)。均勻分布和完全溶解吹塑過(guò)程保持一致的氣體充填的聚合物和替代或近乎溶解所有的氣體在聚合物熔體,螺桿必須保持相對(duì)穩(wěn)定的自轉(zhuǎn)時(shí)，在螺桿的優(yōu)點(diǎn)是恒轉(zhuǎn)速移動(dòng)一倍。在注塑業(yè)務(wù),橡膠壓片機(jī)壓出的螺桿轉(zhuǎn)動(dòng),而生成聚合物/氣體混合物收集在加時(shí)賽的蓄電池。但是它認(rèn)識(shí)到連續(xù)成型行為不可避免地引起不一致的氣體充填、這種結(jié)構(gòu)使得流動(dòng)但是聚合物熔體和天然氣是連續(xù)的(即不停止在注射時(shí)期)。換句話說(shuō),更新的設(shè)計(jì)完全解耦,氣體溶解步驟的注塑操作使用一個(gè)主驅(qū)動(dòng)泵。此外,它達(dá)到更好的分散性之氣, 靜態(tài)混合元素被安裝之間的氣體噴油嘴和關(guān)閉噴嘴。Trexel公司開(kāi)發(fā)了一種微往復(fù)式注射成型技術(shù)的基出上,對(duì)預(yù)塑式注塑機(jī)進(jìn)行了大量的工作。使用我們的結(jié)構(gòu)性泡沫獲得先進(jìn)的成型技術(shù)進(jìn)行表征方面的空隙率、細(xì)胞密度、細(xì)胞三維地形尺寸分布。在一個(gè)我們展示了以前的工作,用一個(gè)定制的可行性小注塑系統(tǒng)組成的一個(gè)微型注射單位和發(fā)泡擠出機(jī)，基于這種新技術(shù)。實(shí)現(xiàn)一個(gè)適當(dāng)?shù)目障堵试诮Y(jié)構(gòu)泡沫使用傳統(tǒng)的注塑機(jī)并沒(méi)有證明是非常成功的,但由于這些成型方法允許小的控制和產(chǎn)量大的孔洞及非均勻的細(xì)胞結(jié)構(gòu)。通過(guò)優(yōu)化工藝條件,所有我們?nèi)〉昧艘粋€(gè)統(tǒng)一的單元結(jié)構(gòu)和非常高的空隙率(40%)。這些方法允許小的控制和產(chǎn)量大的孔洞及非均勻的單元結(jié)構(gòu)。感謝這將近四年來(lái)在我身邊曾經(jīng)幫助和關(guān)心過(guò)我的人們。趙老師淵博的知識(shí)、嚴(yán)謹(jǐn)?shù)闹螌W(xué)態(tài)度、高度的責(zé)任心以及嚴(yán)于律己、待人誠(chéng)懇的思想品德深深影響著我，這不僅使我順利完成了此項(xiàng)設(shè)計(jì)，而且也將成為使我受益終生的寶貴財(cái)富。40:19–32.[11]Lin HH, Oswald FB, Townsend DP. 齒輪動(dòng)態(tài)加載與線性或拋物線齒廓修改. 機(jī)械理論1989。參考文獻(xiàn)[1]濮良貴，（第八版）.北京：高等教育出版社，2007. [2]孫恒,(第七版)。創(chuàng)新型國(guó)家、創(chuàng)新型社會(huì)、創(chuàng)新型企業(yè)需要的是不斷創(chuàng)新的精神和意識(shí)，設(shè)計(jì)中的創(chuàng)新需要高度和豐富的創(chuàng)造性思維，創(chuàng)造性的構(gòu)思才能制造產(chǎn)品的創(chuàng)新，那樣的創(chuàng)新型產(chǎn)品的競(jìng)爭(zhēng)力也是無(wú)與倫比的。最終讓自己的設(shè)計(jì)設(shè)計(jì)符合工程標(biāo)準(zhǔn)。后附有三維仿真視頻。圖85 凸輪定位座3. 凸輪桿的主要結(jié)構(gòu)特點(diǎn)是上端連接有一個(gè)止動(dòng)帽，下端穿過(guò)固定座后安裝上減磨得小型滾子，再與凸輪進(jìn)行配合，完成機(jī)械的凸輪配合設(shè)置后即可與凸輪進(jìn)行配合運(yùn)動(dòng)。圖75 L型連桿三維外形圖，左端連接的是小連桿的連接端，右側(cè)是一個(gè)錐形的漏料腔體，方便干粉料在內(nèi)部左右晃動(dòng)時(shí)均勻進(jìn)入到壓制模型內(nèi)部。 曲柄滑塊機(jī)構(gòu)的主要零部件有曲線凸輪、L形連桿、小連桿、中支座、右支座、送料桿，以及滾子、滾輪等其他附件。＜。 基圓半徑rb=30mm ： 將凸輪基圓以每份9176。~38176。首先要按下“自動(dòng)鍵碼”（這個(gè)很重要,因?yàn)樗鼤?huì)在時(shí)間軸上自動(dòng)放置一個(gè)鍵碼），馬達(dá)命令的添加如圖所示，為了方便觀看效果，這里初步設(shè)定轉(zhuǎn)速為20rpm。如想關(guān)閉運(yùn)動(dòng)算例窗口點(diǎn)擊模型；如欲放下, 點(diǎn)擊界面右下方的雙ν箭頭；如欲撤消, 右擊“運(yùn)動(dòng)算例”或“動(dòng)畫(huà)”彈出的界面的生成新的運(yùn)動(dòng)算例項(xiàng)；如果出現(xiàn)“運(yùn)動(dòng)算例1”或“動(dòng)畫(huà)1”或“運(yùn)動(dòng)算例2”或“動(dòng)畫(huà)2”，可以把不要的給它刪除。：CD=260mm，AB=50mm，BC=162mm，AD=335mm滿足桿長(zhǎng)之和定理，即AD+AB＜CD+BC，確保了曲柄的存在。因?yàn)轭}設(shè)要求擺角小于60176。圖63 上連桿4. 整個(gè)六桿機(jī)構(gòu)建模完成后新建裝配總圖，對(duì)各個(gè)添加進(jìn)入的零部件進(jìn)行配合約束，以及尺寸進(jìn)行約束定位，讓整個(gè)裝配體在軸向進(jìn)行全部約束。直觀地修剪、延伸、圖化、縫織曲面、縮放和復(fù)制排列曲面。讓3D CAD系統(tǒng)使用者透過(guò)市場(chǎng)上領(lǐng)先的線上目錄使用現(xiàn)在的零組件。測(cè)試零件設(shè)計(jì)，分析設(shè)計(jì)的完整性。其余部分為鎖止圓弧。由《機(jī)械設(shè)計(jì)》（文獻(xiàn)[1]）圖1018取彎曲壽命系數(shù)；計(jì)算彎曲疲勞許用應(yīng)力取彎曲疲勞安全系數(shù)，得 計(jì)算載荷系數(shù)：查取齒形系數(shù)：由《機(jī)械設(shè)計(jì)》（文獻(xiàn)[1]）表105查得計(jì)算大、小齒輪并加以比較 大齒輪的數(shù)值大。選擇一級(jí)小齒輪牙數(shù)，二級(jí)大齒輪齒數(shù)。查《機(jī)械設(shè)計(jì)》（文獻(xiàn)[1]）表85得，查表82得，故有計(jì)算V型帶的根數(shù)Z： 故取4根⑦計(jì)算單根V型帶得初拉力的最小值：由表83得Z型帶的單位長(zhǎng)度，所以：F0=應(yīng)使帶得實(shí)際初拉力。120176。(dd2dd1)/a176。由《機(jī)械設(shè)計(jì)》（文獻(xiàn)[1]）圖811選擇A型V帶。故可采用兩級(jí)減速箱。故其中：V帶傳動(dòng)效率； 直齒輪傳動(dòng)8級(jí)效率（油潤(rùn)滑）； 滾子軸承效率（脂潤(rùn)滑正常）； 彈性聯(lián)軸器；由于該機(jī)械為制藥機(jī)械，主要針對(duì)工廠設(shè)計(jì)，故采用380V額定電壓，異步電機(jī)較直流電機(jī)實(shí)用方便，價(jià)格低廉，故采用三相電容啟動(dòng)異步電動(dòng)機(jī)作為動(dòng)力源。將列出的三種方案經(jīng)過(guò)分析和比較后擇優(yōu)進(jìn)行選用，綜合考慮傳動(dòng)的動(dòng)作要求以及實(shí)際的工作工況，從節(jié)約成本和環(huán)保的要素進(jìn)行考慮后發(fā)現(xiàn)方案一在三個(gè)方案中對(duì)比后，發(fā)現(xiàn)其可以實(shí)現(xiàn)干粉壓片及設(shè)計(jì)功能的情況下兼顧了成本因素，有效的做好了噪音低，傳動(dòng)比可靠，環(huán)境污染小，工作平穩(wěn)等要素，所以選擇方案一作為本次設(shè)計(jì)方案。通過(guò)傳動(dòng)桿帶動(dòng)渦輪蝸桿j帶動(dòng)D凹槽凸輪機(jī)構(gòu)使上沖頭向下壓同時(shí)下沖頭向上壓并保持一段時(shí)間。兩凸輪又分別控制振動(dòng)篩和凸輪機(jī)構(gòu)，凸輪通過(guò)皮帶傳動(dòng)帶動(dòng)曲柄滑塊機(jī)構(gòu)，最終帶動(dòng)上沖頭、振動(dòng)篩、下沖頭運(yùn)動(dòng)起來(lái)，從而使整個(gè)機(jī)構(gòu)工作起來(lái)。2. 兩渦輪蝸桿分別帶動(dòng)曲柄連桿機(jī)構(gòu)、凸輪機(jī)構(gòu)運(yùn)動(dòng)。相比之下雙凸輪聯(lián)動(dòng)機(jī)構(gòu)加工成本高，故備選；而單凸輪機(jī)構(gòu)可優(yōu)先。對(duì)于二次減速功能元：齒輪和蝸桿傳動(dòng)穩(wěn)定，屬于定速比傳動(dòng)同時(shí)精度較高可以較好滿