壁面內(nèi)嵌式開關(guān)按鈕注塑模具設(shè)計
壁面內(nèi)嵌式開關(guān)按鈕注塑模具設(shè)計,壁面內(nèi)嵌式,開關(guān),按鈕,注塑,模具設(shè)計
英文文獻翻譯
學(xué) 生 姓 名：
學(xué) 院： 機電工程學(xué)院
專業(yè)及班級： 機械設(shè)計制造及其自動化
學(xué) 號：
指導(dǎo)教師：
Research on Key Technologies of Rapid Heat Cycle Molding Injection Mold and Process
Injection molding technology is an important molding method of plastics, now it has been widely used in almost all fields of the national economy, such as household appliances, automobiles, electronics, aerospace, commodities and so on. However, as the complexity of the injection molding process, there are always many problems on the parts produced by conventional injection method, such as weld mark, flow mark, fiber exposure and so on. As a result, the appearance of the parts is seriously affected. The mechanical properties are decreased as well, leading to a hidden danger for the application of the parts. Therefore, spraying and coating have to be employed after injection molding process so as to improve the part’s performance or appearance. These subsequent re-processing operations increase the part manufacturing processes, waste raw material and energy. Especially, they also increase the production cost and cause environment pollution inevitably. How to reduce the defects of the injected polymer parts, improving the product quality and canceling the spraying or coating process is one of important research subjects of the injection molding technology.
In order to meet the requirements of the customers on the appearance, performance cost and environment of the plastic parts, rapid heat cycle molding (RHCM) technology is developed in recent years. Using this technology, high-quality plastic parts with excellent appearance and no weld marks can be produced and fiber exposure on the part surface can be avoided as well. Especially, the subsequent processing processes, such as spraying and coating which seriously pollute the environment can be eliminated. Thus, the whole production process flowchart is shortened. The energy, material and production cost are decreased. RHCM is a kind of potential green manufacturing technology and has a broad application prospect in plastic injection molding industry.
Based on the principles of the rapid heat cycle molding technology, firstly, the compositions of this new injection method are researched and the requirements of the production line established in the enterprise are discussed. Compared with the conventional injection molding process, the differences between the RHCM injection process and the conventional one are studied. The design rules of the products and molds for RHCM technology are established and the processing method of the mold is also discussed. Secondly, considering the working conditions of the mold in practical production process, the temperature and stress field during the injection process are studied. The service lifetime of the mold is estimated. Thirdly, in order to improving the production efficiency and the part quality, optimization models for different layouts of heating channels in the mold are proposed, the structures of the mold are then optimized according to the models. According to the characteristics of the RHCM technology, a mold temperature control equipment and a cooling system for the electrical experiment mold are developed. By using them, the mechanical properties and appearance of the glass-fiber reinforced parts which are injected by RHCM injection method are researched.
Different from the conventional injection molding process, the mold must be rapidly heated and cooled down to designated temperatures in RHCM injection molding cycle. In heating stage, the cavity surface of the mold should be heated up to the heat distortion temperature of polymer for ensuring good filling state of the plastic melt. In cooling stage, the mold and the polymer melt must be cooled down to ejected temperature of the polymer part rapidly in order to reduce the molding cycle. According to this characteristic, the structures of the products and mold for the technology are analyzed, and the principles that are needed to follow in structure design of RHCM products and the mold are presented. By researching on the mold material, machine method and polishing techniques, the precision machining of the mold cavity plate is achieved. Aiming at reducing the warpage and sink marks that are usually appeared on the RHCM injected parts, the mechanisms of the two defects are analyzed. The influence of the injection parameters on the warpage and the sink marks are also studied. Based on the researches above, the Steam-assisted Rapid Heat Cycle Molding (SRHCM) and electrical Rapid Heat Cycle Molding (ERHCM) are discussed respectively. The compositions of the two systems in which the molds are heated in different ways are analyzed. The requirements of both the two systems for the vapor source or heating rods, cooling water, mold temperature control equipments, process monitoring supervisory system and mold structures are proposed, and the key technologies for the application of the two different systems are studied.As the temperature distribution of the mold has significant effect on the part quality, the heat transfer process among the mold, heating system, plastic part, cooling system and ambience are all analyzed according to the heat transfer theory. The temperature field models for both the SRHCM mold and the ERHCM mold are established based on the above analysis and the finite element simulation theory. The instantaneous temperature of the cavity plate are obtained through the finite element simulation and the factors that influence the heating efficiency and temperature distribution on the mold cavity, including the spaces between channels, the diameters and numbers of channels and the distances from the cavity surface to the channels are all discussed.By using death-to-birth element technique, the temperature of the ERHCM mold during the whole injection molding cycle are obtained which is of great help to grasp the mold temperature and set the parameters values of the injection process.
During the practical injection process, as the rising of the mold temperature and the restriction between the mold plates, the thermal distortion and stress are brought inevitably. Meantime, the mold also suffers great clamping pressure, injection pressure and other mechanical stress during the injection cycle. As a result, a much larger deformation of the mold is induced. The precision, cost and the surface quality of the part are affected. With the continuous production, fatigue cracks are much easier to generate on the RHCM mold due to the great stresses, and the mold lifetime becomes shorter.
快速熱循環(huán)注塑模具及工藝關(guān)鍵技術(shù)研究
注塑成型是塑料加工中重要的成型方法之一,在家用電器、汽車、電子、航空航天、日用品等國民經(jīng)濟的各個領(lǐng)域都有廣泛的應(yīng)用。但由于注塑成型過程的復(fù)雜性,成型產(chǎn)品表面易產(chǎn)生熔接痕、流痕、浮纖等各種缺陷,既影響產(chǎn)品的外觀質(zhì)量,又減弱了產(chǎn)品的力學(xué)性能,給產(chǎn)品的正常使用帶來隱患。為提高成型產(chǎn)品表面質(zhì)量,目前生產(chǎn)中主要通過塑料噴涂技術(shù)使其表面質(zhì)量得到提高,但噴涂是對塑料產(chǎn)品的二次加工,既浪費生產(chǎn)原料和能源,增加塑料制品的生產(chǎn)成本,又造成了嚴重的環(huán)境污染,并危害操作人員的身體健康。如何減少注塑產(chǎn)品的成型缺陷,全面提高產(chǎn)品質(zhì)量,取消或減少產(chǎn)品表面噴涂量,是注塑成型加工及模具設(shè)計與制造領(lǐng)域的重要研究課題。
近年來,為滿足人們對塑料產(chǎn)品的外觀、性能、成本以及環(huán)保等方面的要求,快速熱循環(huán)注塑成型(Rapid Heat Cycle Molding, RHCM)技術(shù)應(yīng)運而生。利用該技術(shù)能獲得表面無熔接痕、無纖維暴露等表面缺陷的高光澤度塑料產(chǎn)品,顯著提升產(chǎn)品的質(zhì)量。使用該技術(shù)既可以取消污染嚴重且成本昂貴的噴涂工藝,直接降低塑料產(chǎn)品的生產(chǎn)成本,又滿足了社會的環(huán)保要求,使注塑成型實現(xiàn)真正的綠色化生產(chǎn)。因此,該技術(shù)市場競爭力強大,應(yīng)用前景十分廣闊。
本文根據(jù)快速熱循環(huán)注塑成型工藝原理,研究了該新型注塑工藝的系統(tǒng)組成,探討了在實際生產(chǎn)中建立穩(wěn)定生產(chǎn)線的原則和要求。通過與常規(guī)注塑工藝進行對比,研究了RHCM產(chǎn)品及其模具結(jié)構(gòu)與常規(guī)注塑產(chǎn)品及其模具結(jié)構(gòu)的異同,建立了RHCM產(chǎn)品和模具設(shè)計及模具加工的原則與方法。結(jié)合生產(chǎn)實際,討論了模具溫度對RHCM成型產(chǎn)品質(zhì)量的影響,研究了注塑周期內(nèi)RHCM模具的溫度變化過程。為提高RHCM模具的使用壽命,研究了模具工作過程中的應(yīng)力應(yīng)變狀態(tài),提出了能有效提高模具使用壽命的方法。針對RHCM模具加熱管道優(yōu)化設(shè)計理論缺乏,產(chǎn)品質(zhì)量不穩(wěn)定的現(xiàn)狀,建立了模具加熱管道的優(yōu)化設(shè)計模型,實現(xiàn)了模具結(jié)構(gòu)的優(yōu)化,提高了產(chǎn)品質(zhì)量并保證了生產(chǎn)效率。從RHCM注塑成型工藝特點出發(fā),開發(fā)了電熱式模具溫度控制系統(tǒng),建立了快速熱循環(huán)注塑工藝實驗線,利用該實驗線研究了纖維增強聚合物在RHCM注塑工藝下的性能特點,為該工藝的推廣應(yīng)用提供了技術(shù)指導(dǎo)。
RHCM注塑工藝過程與常規(guī)注塑工藝過程不同,生產(chǎn)中增加了模具的快速加熱與快速冷卻兩個階段。在模具加熱階段,需將模具型腔成型面溫度升高到塑料的熱變形溫度以上,以保證塑料熔體具有良好的充模狀態(tài)；而在冷卻階段,需要使熔體溫度迅速降低到塑料的頂出溫度以下,減少注塑成型周期。根據(jù)該技術(shù)特點,通過與常規(guī)注塑技術(shù)進行比較,分析了RHCM注塑工藝對其產(chǎn)品和模具結(jié)構(gòu)設(shè)計的獨特要求,提出了RHCM產(chǎn)品和模具關(guān)鍵部位的設(shè)計準(zhǔn)則,為生產(chǎn)中產(chǎn)品和模具設(shè)計提供了重要的依據(jù)。從模具材料、磨具磨料和拋光方法等方面對模具的拋光技術(shù)進行研究,實現(xiàn)了RHCM模具型腔表面的精密拋光。針對RHCM產(chǎn)品產(chǎn)生翹曲變形和表面縮痕的現(xiàn)象,分析了其產(chǎn)生變形和表面縮痕的機理,研究獲得了注塑工藝參數(shù)對上述兩種缺陷的影響程度,保證了注塑生產(chǎn)的順利進行。根據(jù)以上研究,分析了利用蒸汽加熱和電加熱兩種不同模具加熱方式下的快速熱循環(huán)注塑工藝的系統(tǒng)組成,詳細研究了兩種方式對蒸汽源或加熱棒、冷卻水源、模溫控制系統(tǒng)、工藝監(jiān)控系統(tǒng)和模具結(jié)構(gòu)的要求,并探討了兩種方式在實際生產(chǎn)實施中的關(guān)鍵技術(shù)。模具溫度對成型塑料產(chǎn)品的質(zhì)量具有至關(guān)重要的作用。結(jié)合實際RHCM注塑工藝的生產(chǎn)流程,詳細研究了模具溫度對RHCM成型產(chǎn)品質(zhì)量的影響。根據(jù)傳熱學(xué)的基本理論,研究了RHCM注塑周期內(nèi)模具與加熱系統(tǒng)、塑件、冷卻系統(tǒng)和周圍環(huán)境的熱量傳遞過程,建立了RHCM模具加熱和冷卻階段的溫度場分析模型,研究獲得了模具型腔板在注塑過程中溫度瞬時變化規(guī)律,并討論了加熱管道間距、管道直徑和數(shù)目、管道到型腔壁面距離等因素對蒸汽加熱RHCM模具型腔板的加熱效率和其溫度分布的影響規(guī)律和程度。利用生死單元技術(shù),模擬了電加熱RHCM注塑周期內(nèi)模具型腔板溫度變化的全過程,對有效控制模具溫度,提高模具設(shè)計精度和工藝調(diào)整的準(zhǔn)確性提供重要依據(jù)。
生產(chǎn)過程中,由于模具溫度的升高及模板之間的相互約束,模具內(nèi)部不可避免地會產(chǎn)生熱變形和熱應(yīng)力,同時,工作過程中,模具還要承受合模壓力、注射壓力等各種機械應(yīng)力的影響,當(dāng)模具內(nèi)部產(chǎn)生的應(yīng)力較大時,模具將會產(chǎn)生過量變形,從而影響產(chǎn)品的精度、生產(chǎn)成本及其表面質(zhì)量。隨著生產(chǎn)的連續(xù)進行,模具的變形將會發(fā)生周期性的變化,易造成模具表面產(chǎn)生疲勞裂紋,使模具失效
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