注射器筒体模具设计-针筒注塑模【三维Creo】【含CAD图纸】
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大连交通大学2017届本科生毕业设计(论文)外文翻译Optimization of Conformal Cooling Channels with Array of Baffles for Plastic Injection MoldNOMENCLATURE = Thermal diffusivity of polymer (m2/s)T = Standard deviation of temperature distributiond = Diameter of baffle (mm)hc = Heat transfer coefficient (W/m2C)km = Thermal conductivity of mold material (W/mC)kp = Thermal conductivity of polymer (W/mC)q = Instantaneous heat flux (W/m2) s = Thickness of molded part (mm) tc = Cooling time (s)Tavg = verage temperature through parts thickness (C)Te = Ejection temperature (C) Ti = Injection temperature (C) Tm = Mold temperature (C)Tmax= Maximum temperature at center line of thickness (C)Tps = Molded part surface temperature (C)Tw = Coolant temperature (C)x = The pitch of baffles in x direction (mm)y = The pitch of baffles in y direction (mm)z = Distance from baffles tip to cavity surface (mm) KSPE and Springer 20101. IntroductionInjection molding has been the most popular method for making plastic product due to high efficiency and manufacturability. The injection molding process includes three significant stages: filling and packing stage, cooling stage and ejection stage. Among these stages, cooling stage is very important one because it mainly affects the productivity and molding quality. It is well known that more than two thirds of the molding cycle is taken up by cooling process. An appropriate design of cooling channel reduces cooling time, increases the productivity and minimizes undesired defects such as sink marks, differential shrinkage, thermal residual stress and warpage.For many years, the importance of cooling stage in injection molding has drawn a great attention from researchers and mold designers. They have been struggling for the improvement of the cooling system in the plastic injection mold. This field of study can be divided into two groups: optimizing conventional cooling channels (straight-drilled cooling lines) and finding new(a) straight-drilled channel(b) SFF conformal channel(c) channels with the array of baffles Fig. 1 Kinds of cooling channelsarchitecture for injection mold cooling channels (conformal cooling channels). The first group focuses on how to optimize the configuration of the cooling system in terms of shape, size and location of cooling lines.1-15 The second group investigates the wayto build the cooling layout namely conformal cooling channels that conform to the mold cavity surface and examines the effectiveness of this cooling system. Solid free-from fabrication (SFF) or rapid prototype (RP) techniques have been proposed to build this complex cooling system. It was reported that cooling quality isbetter than that of conventional cooling channels.16-24 Along withSFF technique, milled groove conformal cooling channels made by CNC milling machine has also been proposed by Sun Y. F. et al.25,26 Although these kinds of cooling channels offer an even cooling performance, there are still high manufacturing costs for mediumand large-sized mold.In order to improve the performance of the cooling system and to reduce mold making cost, this paper presents a kind of conformal cooling channel in the plastic injection mold by using an array of baffles. The difference between this cooling channels layout and the others is depicted in Fig. 1. Baffles are alternative cooling devicesthat are used to cool some small regions in the molds core which normally lack cooling.27 A series of baffles in cooling circuit for core of a box mold was suggested.28 For medium and large-sized molds with free-form cavitys surfaces, if a constant distance from the tip of the baffles to mold cavitys surface is maintained, this kind of cooling circuits can be considered as conformal cooling channels. Unfortunately, it still lacks of study of how well this conformal cooling system performs and how to optimize itsconfiguration in order to obtain minimum cooling time, even cooling and reasonable mold making cost. In addition, cooling design is often based on designers experience and tuition. When molding geometry becomes more complex, experience-based and trial-and-error approaches would be time-consuming and lessfeasible.3,5,11,13 Therefore, our study focuses on a systematic method(a) Real construction of the array of baffles cooling channels(b) Modeling of array of baffles cooling channels in CAE softwareFig. 2 Deployment and configuration of the cooling channels with array of bafflesfor optimizing the configuration of the proposed cooling channel including coolant temperature, the pitch (x and y), the distance z and the diameter d of the baffle. The combination of analytical method, design of experiment (DOE), finite difference method and CAE tool was used to derive approximate equations showing the relation among cooling channels design variables, mold material and process parameters for a given polymer. Cooling time and optimum cooling channels configuration of a given injection molding part can be determined easily at early design stage.The remainder of the paper is organized as follows. Section 2 introduces the deployment and configuration of the array of baffles in cooling channels. Section 3 describes the physical and mathematical model of heat transfer within the polymer and the mold. Mathematical solution in Section 3 is validated in Section 4. Section 5 proposes optimization method, and Section 6 illustrates two case studies to test the facility and feasibility of the proposed method for a plastic cover and an automotive plastic part. Finally, some conclusions and discussions of future work are given in Section 7.2. Deployment and configuration of array of baffles in cooling channelsA baffle is a cooling channel drilled perpendicular to a main cooling line with a thin plate separating the drilled hole into two semicircular channels. The plate forces the coolant to flow down in one side and up in the other side (see Fig. 1(c) and Fig. 2(a). Bychanging the direction of the coolant flow in cooling channels, the baffle creates turbulence around the bend and increases the heat transfer coefficient. Nevertheless, pressure drop increases, and more pump power is required in comparison to straight or smooth cooling channels. There are two kinds of baffles: normal baffle and spiral baffle (Fig. 2(a). The first one is simple, but it is difficult to mount the thin plate (divider) exactly in the center of the channels and the temperature distributions in both sides of the baffle are different. The other one is a bit more complex, but it is easy to place the divider at the center of cooling channels; the turbulent effect and temperature distribution are improved. In this study, it is assumed that the flow rate of coolant is large enough to achieve effective turbulent flow, and an increase in flow rate makes little difference to the rate of heat extraction. For this reason, both types of baffles are treated the same in terms of heat extraction.Baffles are arranged as a two-dimensional array including rows and columns. The configuration of the proposed cooling channels includes the pitch (x and y) between the baffles, the distance from a baffles tip to the cavity surface (z) and the diameter of the baffle (d) (Fig. 2). The diameter of the main cooling line is proportional to d. The baffles tip conforms to the cavity surface in order to remove heat from hot polymer evenly. The baffle channels are machined by drilling method which reduces the manufacturing cost.3. Physical-mathematical model and numerical solutionThis section addresses the mathematical relation among cooling channels configuration, temperature distribution in the mold and molded part, cooling time and process parameters. Without losing the generality, a cooling cell (see Fig. 3) is extracted and examined instead of considering the whole mold. Four lateral faces of the cooling cell are treated as adiabatic. With this physical model, the simulation time is reduced significantly since the number of elements decreases. Assuming that the cavity surface of the cooling(a) (b)Fig. 3 Physical model of a cooling cell (a), and typical temperature distribution (b) The minimum Reynolds number in cooling channels should be more than 10,000. The thermal effect derived from the crystallization process is ignored.In this study, the coupling of cycle-averaged and one- dimensional transient approach was applied since it is computationally efficient and sufficiently accurate for mold design purpose.11,35 Heat transfer in the mold is treated as cycle-averagedsteady state, and 3D FEM simulation was used for analyzing the temperature distribution. The cycle-averaged approach is applied because after a certain transition period from the beginning of the molding operation, the steady-state cyclic heat transfer within the mold is achieved. The fluctuating component of the mold temperature is small compared to the cycle-averaged component so that cycle-averaged temperature approach is computationally moreefficient than periodic transition analysis.37 Heat transfer in polymer(molding) is considered as transient process, and finite difference method was applied.The temperature distribution in the molding is modeled by following equation:cell has a small curvature, this surface can be considered as a planar face.T = t 2Tz(1)In physical aspect, heat transfer in cooling process is complicated. To simplify the mathematical model, the following assumptions are made in this study: Physical properties of mold material are constant. The heat flux in mold-polymer interface is constant on each element of mold cavity surface.1 Constant cycle-averaged mold temperature is used. Only packing and cooling phases are considered because the filling phase is short.29,30The partial difference equation (1) can be solved conveniently by finite difference method. Laasonen method,38 unconditionally stable scheme, was used to solve Eq.(1). Due to the nature of thermal contact resistance between polymer and mold, a convective boundary condition39 was applied instead of isothermal boundary condition. This boundary condition expresses the nature of heat transfer in mold-polymer interface better than isothermal boundary condition. Thermal analysis for polymer is performed in one dimensionh T T = k T(2)because the thickness of the molding is small in comparison tocpsmp zplanar dimension.31-36 Natural convection between ambient air and exterior mold faces is ignored because it takes less than 5% of overall heat loss.7 Cooling effect of main cooling lines is ignored because most of the heat is removed by the baffles.The inversion of the heat transfer coefficient (HTC) is called thermal contact resistance (TCR). It is reported that TCR between the polymer and the mold is not negligible. TCR is the function of a gap, roughness of contact surface, time and process parameters. The values of TCR are very different,29,34,40-45 and they are often obtained by experiment. In this study, HTC is set to 10,000 W/m2C1. Smith, A. G., Wrobel, L. C., McCalla, B. A., Allan, P. S. and Hornsby, P. R., “A computational model for the cooling phase of injection moulding,” Journal of Materials Processing Technology, Vol. 195, No. 1-3, pp. 305-313, 2008.2. Sridhar, L. and Narh, K. A., “Finite size gap effects on the modeling of thermal contact conductance at polymer-mold wall interface in injection molding,” Journal of Applied Polymer Science, Vol. 75, No. 14, pp. 1776-1782, 2000.摘 要模具属于精密机械的产品,它主要机械零件和机构组成。如成形工作零件、导向零件、定位零件、支撑零件及送料机构、抽芯机构、推出机构等。模具与相应的成形设备(如冲床、塑料注射机、压铸机等)配套使用时,可直接改变金属或非金属材料的形状、尺寸、相对位置和性能,使之成形为合格的制件。模具设计是模具制造的基础,合理正确的设计是正确制造模具的保证:模具制造技术的发展对提高模具质量、使用寿命、精度以及缩短制造模具周期具有重要的意义:模具的质量、使用寿命、制造精度及合格率在很大程度上取决于制造模具的材料及热处理工艺:模具成本直接关系到制件的成本以及模具生产企业的经济效益;模具工作零件的精度决定制件的精度;模具的寿命又与模具材料及热处理、模具结构以及所加工制作材料等诸多因素有关;模具的安装与使用直接关系到模具的使用性能及安全;而模具的标准化是模具设计与制造的基础,对大规模、专业化生产模具具有极重要的作用,模具标准化程度的高低是模具工业发展水平的标志。本次设计注射器筒体的模具,设计中建模采用Cero PTC 4.0软件,AutoCAD为计算机辅助制图工具,是一款专业机械平面制图软件,具有很强的图像处理功能。关键词:模具设计 注射器筒体 复合模AbstractMold products are precision machinery, it mainly consists of mechanical parts and bodies,such as forming working parts, parts orientation, positioning parts, supporting parts, positioning components and feed mechanism, core-pulling mechanism, introduced institutions. Mold and the corresponding forming equipment (such as punching, plastic injection machine, die-casting machine, etc. ) supporting the use of, may directly alter the shape of metal or non-metallic materials, size, relative position and performance, shaping the work piece for qualified.Mold manufacturing mold design is the basis for rational design of the right mold to ensure correct; mold manufacturing technology to improve the mold quality, service life, accuracy and shorten the manufacturing cycle is of great significance mold; mold quality, service life, manufacturing precision and the passing rate depends largely on the manufacture of mold materials and heat treatment; mold costs directly related to the work piece, the cost and economic efficiency of enterprises mold; determine the accuracy of the die components parts precision; dies life expectancy and the mold materials and heat treatment, mold structure and the production of materials processing, and many other factors; and mold die design and manufacturing and use of mold performance and safety; and mold die design and manufacturing standards are the basis of the same, large scale, specialized production mold is a very important role in standardization of the level of mold is a sign of mold level of industrial development.The design of the syringe cylinder mold, the design of modeling using Cero PTC 4.0 software, AutoCAD for the computer-aided drawing tool, is a professional mechanical plane mapping software, has a strong image processing functions. Key words: mold design syringe cylinder composite mold目 录第一章 设计任务书11.1塑件及其尺寸11.2 设计内容及其要求1第二章 塑件成型工艺分析32.1塑件的分析32.2PP聚丙烯的性能分析3第三章 拟定模具的结构形式53.1分型面位置确定53.2型腔数量和排列方式的确定53.3注射机的型号确定6第四章 浇注系统的设计84.1主流道的设计84.2分流到的设计94.3浇口的设计124.4校核主流道的剪切速率13第五章 模具零件的结构设计及计算145.1成型零件的结构设计145.2成型零件钢材的选用155.3成型零件工作尺寸的计算155.4模架的确定165.5排气槽的设计175.7冷却系统的设计185.8导向与定位结构205.9总装图和零件图的绘制20谢辞21参考文献2223大连交通大学2017届本科生毕业设计(论文)第一章 设计任务书1.1塑件及其尺寸零件名称:注射器筒体零件材料:聚丙烯 零件图:图1-1图 1-1 零件图1.2 设计内容及其要求在设汁之前,学生已具备机械制图、公差与技术测量、机械原理及零件、模具材料及热处理、模具制造工艺、塑料成型工艺及模具设计等方面必要的基础知识和专业知识,并已通过金工和生产实习。做过注射成型实验:韧步了解塑料的成型工艺和生产过程,熟悉多种塑料模具的典型结构。课程设计的内容包括: 1.独立拟定塑件的成型工艺,正确选用成型设备。 2.合理地选择模具结构。根据塑件图的技术要求,提出模具结构方案,并使之结构合理,质量可靠,操作方便。必要时可根据模具设计和制造的要求提出修改塑件图纸的意见,但必须征得设计者或用户同意后方可实施。3正确地确定模具成型零件的结构形状、尺寸及其技术要求。4.所设计的模具应当制造工艺性良好,造价便宜。5.充分利用塑料成型优良的特点,尽量减少后加工。6.设计的模具应当能高效、优质、安全可靠地生产,且模具使用寿命长。第二章 塑件成型工艺分析2.1塑件的分析2.1.1外形尺寸 该塑件壁厚最大为2mm塑件外观尺寸不大,塑料熔体流程不长,适合于注射成型。2.1.2精度等级 未标注采用MT6。2.1.3脱模斜度 塑件材料采用PP(聚丙烯) 因塑件尺寸较小成型收缩率较小,差参考文献,选择塑件上型芯和凹模的统一脱模斜度1。2.2PP聚丙烯的性能分析产品质轻,韧性好,耐化学性好,耐磨性好,高温冲击性好软化温度为150C,由于结晶温度较高,这种材料的表面刚度和抗划痕特性很好。不存在环境应力开裂问题。流动性好,成型性能好。PP是通用塑料中耐热性能最好的,具有突出的延展性和抗疲劳性能,屈服强度高,有很高的疲劳寿命。2.2.1 PP的主要性能指标表2-2 聚丙烯(PP)的成型条件塑料名称聚丙烯缩写PP堆密度/0.9-0.91计算收缩率/%1.8-2.5注射成型机类型螺杆式料筒温度/前端200-220中段180-200后端160-180预热温度/80-100时间/h1-2模具温度/80-90注射压力/MPa70-100成型时间/s注射时间20-60高压时间0-3冷却时间20-90总周期50-160螺杆转速r/min48使用注射机类型螺杆、柱塞均可第三章 拟定模具的结构形式3.1分型面位置确定通过对塑件的分析,塑件开模分为三次 三次分模的位置如图3-1。图3-1 分型面位置3.2型腔数量和排列方式的确定3.2.1型腔数量的确定 该塑件的精度一般在23级之间,且为大批量生产,可采用一模多腔的结构形式。同时考虑到塑件的尺寸较小,以及制造费用等因素,初步定为一模二十腔设计。3.2.2型腔排列方式的确定 多腔模具尽可能的采用平衡式排列布置,且要求紧凑并于交口开设的部位对称。由于该模具采用一模二十腔,采用5X4的矩形排列,如图3-2。3-2 型腔分布图3.3注射机的型号确定3.3.1注射量的计算 通过三维建模软件分析计算的塑件体积: V塑=9.52cm3塑件质量: m塑=V塑=9.520.9g=8.568g式中取0.9g/cm33.3.2注射系统凝料体积初步估算 浇注系统的凝料在设计之前是不能确定的,但可以根据经验公式塑件体积的0.21倍来估算。本次注射由于多型腔,系数选为0.8来估算,因此:V总=V塑(1+0.5)20=9.521.820=285.5cm33.3.3选择注射机根据计算一次注入模具型腔V总=285.5cm3,预估注射用量V总/0.8=285.50.8=356.875cm3。注射机型号选用为J54-S 200/400,主要技术要求见表3-3:表3-3 J54-S 200/400参数额定注射量(cm)200400螺杆直径(mm)55注射压力(MPa)109注射行程(mm) 160注射方式螺杆式螺杆驱动功率(kw)18.5锁模力(KN)25.4102模板尺寸(mm)532634最大开合模行程(mm)160模具最大厚度(mm)406模具最小厚度(mm)165合模方式液压-机械喷嘴口孔径(mm)7.5喷嘴球半径(mm)183.3.4注射机的相关参数校核1.注射机的压力校核 查表3-3可知,PP材料所需的注射压力为70100MPa,这里去80MPa,该注射机注射压力为109MPa,安全压力系数为k1=1.251.4,这里取1.3,则:K1p0=1.380=104109所以压力合格。2.锁模力校核塑件在分型面上的投影面积A塑,有三维软件计算得7cm2。浇注系统在分型面面积的投影A浇,按多腔模的统计分析确定为A塑的0.20.5倍,这里取0.3。则总面积为:A=A塑(1+0.3)20=71.320=182cm2磨具型腔的型胀力F涨=AP模。即F涨=AP模=18241.6=757.12KN,该注射机公称锁模力为3500KN,符合要求。对于其他安装尺寸校核等选定模架后计算。第四章 浇注系统的设计4.1主流道的设计浇注系统是指模具中由注射剂喷嘴到型腔之间的进料通道。普通浇注系统一般由主流道、分流道、浇口和冷料穴等四部分组成。浇注系统的设计师模具设计的一个重要环节,设计合理与否对塑件的性能、尺寸、内在质量、外在质量及模具的结构、塑料的利用率等有较大影响。对浇注系统进行设计时应遵循以下原则:了解塑件的成型性能;尽量避免或减少产生熔接痕;有利于型腔中气体的排出;防止型芯的变形和嵌件的位移;尽量采用较短的流程充满型腔;流动距离比的校核。1. 主流道的尺寸(1) 主流道的长度:本次设计初选取60mm进行设计。(2) 主流道的小端直径:d=注射机喷嘴尺寸+(0.51)mm=7.5+0.5=8mm(3) 主流的道大端直径:d=d+2L主tana15,a=4(4) 主流道球面半径:SR0=注射机喷嘴半径+(12)mm=20mm(5) 球面配合高度:h=3mm2. 主流道的凝料体积三维软件计算为V主=8.5cm33. 主流道当量半径: Rn=(4+10)/4=4.5mm4. 主流道浇口套的形式主流道在注射过程中反复与注射机喷嘴接触,易磨损。故设计为可便于拆卸替换的零件。 主流道的定位与固定需定位圈。定位圈设计如图4-2。图4-1 浇口套图4-2 定位圈4.2分流到的设计4.2.1分流道的布置形式在设置的时候应尽量考虑减少在流道内的压力损失和尽可能避免熔体温度降低,同时还要考虑减小分流道的容积和压力平衡,因此采用综合型分流道。4.2.2分流道的长度 由于采用多型腔设计,流道较长,流道形状如图,总长度为1988mm。见图4-3。图4-3 分流道分布4.2.3分流道的当量直径根据当量直径经验公式D=0.2654m4L分别确定各位置分流道的当量直径D1分=0.2654108.56842209.5mmD2分=0.26548.5684643mmD3分= D2分=3mm4.2.4分流道的截面形状U型截面的加工难度较小,且对流体的热量损失较小,所以本设计L1、L2段分流道采用U形截面,L3采用圆形分流道,方便加工与开模拔模。4.2.5分流道的截面尺寸根据书上表4-51,L1:r1=0.4599.54.5mmH1=0.9189.59mmL2: r2=0.4593=1.5mmH2=0.9183=3mmL3:D=3mm4. 凝料体积根据三位软件计算得出V1=125213mm3V2=5106.5mm3V3=4880.5mm35. 校核剪切速率(1) 确定注射时间t=2.2s(2) 计算分流道体积流量q分1=V1t=1252132.2mm3/s=56915 mm3/sq分2=V2t=5106.52.2mm3/s=2321 mm3/sq分3=V3t=4880.52.2mm3/s=2218 mm3/s(3) 由式(4-20)1可得剪切速率分1=3.3q分1R分13=3.3569153.144.753=558s-1分2=3.3q分2R分23=3.323213.141.53=722s-1分3=3.3q分3R分33=3.322183.141.53=691s-1该分流道的表面剪切速率处于浇口主流道的最佳剪切速率500 s-15000 s-1之间,所以,分流道内剪切速率合格。6. 分流道的表面粗糙度和脱模斜度分流道的表面粗糙度要求不是很低,一般取Ra1.252.5m即可,此处取Ra1.6m。其脱模斜度一般在510之间,这里去脱模斜度8。图4-4 分流道截面4.3浇口的设计该塑件要求不允许有裂纹和变形缺陷,表面质量要求较高,采用一模20腔注射,为了便于调整冲模时的剪切速率和封闭时间,因此采用点浇口。截面形状简单,易于加工。4.4校核主流道的剪切速率计算主流道的体积流量q总=V1t=2589262.2mm3/s=117693 mm3/s计算主流道的剪切速率总=3.3q总R总3=3.31176933.144.53=1357s-1该主流道的表面剪切速率处于浇口主流道的最佳剪切速率500 s-15000 s-1之间,所以,分流道内剪切速率合格。第五章 模具零件的结构设计及计算5.1成型零件的结构设计5.1.1凹模的结构设计 凹模是成型制品的外表面的成型零件。按凹模结构的不同可将其分为整体式、整体嵌入式、组合式和镶拼式四种。根据对塑件的结构分析,本设计中采用镶拼式式凹模,如图5-1所示。图5-1 凹模结构图5-2 型芯5.1.2凸模的结构设计(型芯) 凸模是成型塑件内表面的成型零件,通常可以分为整体式和组合式两种类型。通过对塑件的结构分析可知,该塑件的型芯有一个,如图5-2所示, 设计采用单型芯设计。5.2成型零件钢材的选用 根据对成型塑件的综合分析,该塑件的成型零件要有足够的刚度、强度、耐磨性及良好的抗疲劳性能,同时考虑它的机械性能和抛光性能。又因为该塑件为大批量生产,所以构成型腔的嵌入式凹模钢材选用40Cr。对于成型塑件的型芯来说,由于脱模时与塑件的磨损严重,因此钢材选用Q235。5.3成型零件工作尺寸的计算 采用表4-151的平均尺寸法计算成型零件尺寸,塑件尺寸公差按照塑件零件图中给定的公差计算。5.3.1型腔的计算因为本制品的不是精密器具,对制品的尺寸精度的要求比较低,所以,尽管PP的收缩率比较大,也可按平均收缩率计算。查1P表1-7知PP的平均收缩率为S=0.0180.025 ,取S=0.02。由7P式15-21和式15-22有:制品工件辟厚为:H=1mm,长度为:L=96mm所以,成型腔即型腔套的内半径为:r=8+H(1+0.02)=9.02 (mm)L=96(1+0.02) =97.92 (mm)而此次设计的注射器筒体只要容积大于10ml,约为12ml,产品的长度没有要求,考虑到设计方便和设计成本,取型腔套内径r=9mm,长度L=96mm,生产出来的产品也满足容积的要求,所以取此值型腔套只要满足强度要求就可以了。故取r=6.5mm,L=95mm。5.3.2型芯主要尺寸的计算1)径向尺寸DD= D(1+ S)=8(1+0.02)=8.16 (mm)2)被塑件包容部分的深度hh= h(1+ S)=96(1+0.02)= 97.92 (mm) 因为,型销的半径小1mm,包容长度短,制品的厚度小,可以不考虑制品其尺寸在型销上的收缩变化。5.4模架的确定由于本次设计应用的模架为非标准模架,模架尺寸可参考标准模架并有一定改动。根据模具型腔布局的中心距和凹模嵌件的尺寸可以算出凹模嵌件所占的平面尺寸为230mm200mm,又考虑凹模最小厚壁,导柱、导套的布置等,可确定选用的模架为330mm400mm。5.4.1各模板尺寸的确定定模底座:450mm355mm25mm导杆固定板:400mm355mm15mm刮料板:400mm355mm25mm点浇板:400mm355mm20mm型腔板:400mm355mm80mm推板:400mm355mm20mm动模板:400mm355mm40mm动模底座:450mm355mm32mm如图5-1。图5-1 模架尺寸5.4.2模架各尺寸的校核根据所选注射机来校核该模具的尺寸。模具平面尺寸400mm355mm448mm370mm(拉杆距离),校核合格。模具高度尺寸165mm257mm406mm(模具的最大厚度和最小厚度),校核合格。模具的开模行程S=H1+H2+H3+H4+(510)mm=265270mm500mm(开模行程),校核合格。5.5排气槽的设计该塑件由于采用点浇口进料,熔体经塑件上方的浇口充满型腔,气体通过分型面,其配合间隙可作为气体排出的方式,不会在底部产生憋气的现象,同时,气体会沿着推杆的配合间隙、分型面和型芯与脱模板之间的间隙向外排出。5.6 脱模推出机构的设计 5.6.1.推出方式的确定 本模具采用限位杆定位开模位置,无主动推出,工件依靠开模后各板的展开吧工件从型腔、型芯抽离。5.6.2脱模力的计算脱模力分为初始脱模力和相继脱模力两部分,但前者通常大于后者,故设计时以初始脱模力为设计依据,而略去相继抽拔力。由3P式8-71有: F=66.5968(0.2cos1-sin1)10.8 (KN)5.7冷却系统的设计冷却系统的计算很麻烦,在此只进行简单的计算,设计时忽略模具因空气对流、辐射以及与注射机接触散发的热量,按单位时间内塑料熔体凝固时所释放的热量应等于冷却水所带走的热量。5.7.1冷却介质 PP属中等粘度材料,其成型温度及模具温度分别为200C和50C80C,所以,模具温度初步选定为50C,用常温水对模具进行冷却。5.7.2冷却系统的简单计算单位时间内注入模具中的塑料熔体的总质量W塑件制品的体积V=258926mm3塑件制品的质量m=233g塑件厚度为1.5mm,可以查表4-341得tl冷=8s,取注射时间t=2.2s,脱模时间t脱=8s,则注射周期:T=18.2s。由此可以得到每小时注射次数190次。单位时间内注入模具中的塑料熔体的总质量为:Wh=44.27Kg/h确定单位质量的塑件在凝固时所放出的热量Q,查表4.351直接可知PP的单位热量590KJ/Kg。计算冷却水的体积流量qv设冷却水道入水口的水温为22C,出水口的水温为30C,取水的密度为1000Kg/m3,水的比热容4.187KJ/(Kg*C)。则根据公式可得:qv=WQS60c(1-2)=0.012m3/min确定冷却水路的直径d 当qv=0.012m3/min时,查表4.351可知,为了使冷却水处于湍流状态,取模具冷却水孔的直径0.008m。冷却水在管内的流速 vv=4qv60*d2=3.98m/s求冷却管壁与水交界面的膜传热系数h 因为平均水温为26C,因为平均水温为23.5,查表可得f=0.67,则有: 计算模具所需冷却水管的总长度L冷却水路的根数x 设每条冷却水道的长度位l=200mm,则冷却水路的跟数为根由上述计算可以看出,一条冷水道对于模具来说显然是不合适的,因此应根据具体情况加以修改。为了提高生产效率,凹模和型芯都应得到充分的冷却。采用4 根直通式冷水道。动模板冷却水道如图,顶模板冷却水道如图5-2图5-2 水道5.8导向与定位结构 注射模的导向机构用于动、定模之间的开合模导向和脱模机构的运动导向。按作用分为模外定位和模内定位。模外定位是通过定位圈使模具的浇口套能与注射机喷嘴精确定位;而模内定位机构则通过导柱导套进行合模定位。锥面定位则用于动、定模之间的精密定位。本模具所成型的塑件比较简单,模具定位精度要求不是很高,因此可采用模架本身所带的定位结构。5.9总装图和零件图的绘制 经过上述一系列计算和绘图,把设计结果用总装图来表示模具结构,如图5.3所示。图5-3 总装谢 辞我们即将毕业,告别大学,走向社会!在此,我很想对敬爱的老师们和可爱同学们说:感谢你们!特别是我的指导老师周智鹏老师,没有他的指导帮助,我的毕业设计很难独立完成,从设计项目的选择,再到对我的工艺过程和夹具的设计上都给出了针对性的参照和修改意见,使我的设计得以相对好的完成。在此,谨向周智鹏导师致以深深的敬意和由衷的感谢!大学四年的学习生涯匆匆而过,它给予我太多不可磨灭的记忆。在充满激情的青春岁月里,有机会认识杨老师这位不可多得的人生引路人,是我莫大的幸运。在毕业设计遇到困难障碍时,老师总是在思想上给予点津,在方法上给予指导,使我受益匪浅。老师治学严谨、态度谦和、思维开阔以及积极人生态度潜移默化的影响着我,成为不断向前奋进的不竭动力。从项目地选择到零件的详细工艺计划过程的部分,全部设计进程中体现出周智鹏导师的汗水和辛劳。在我完成的毕业设计的过程中,因自己自身的知识的缺陷,遇到了很多难题,但周智鹏导师可以给我带来很多最实用的建议和仔细地向我解释我遇到的问题。如果没有杨君悦导师关键的建议和指导,我不会那么顺利的完成毕业设计。我非常感谢同组的。要是没有周智鹏导师关键性建议和指点,我不会这么顺利的完成毕业设计。我也非常感谢同组的同窗,感激他们在繁忙之余还能对我的毕业设计提出他们本身的发起,以是此次顺利完成毕业设计也离不开同组的同学窗们。因为只有知识的积累和经验,才能设计出令人满意的机械产品,各科任老师所讲解的知识,我都能很好地运用到了此次的毕业设计中,也意识到了理论知识运用到实际原来如此简单。同时,在完成毕业设计的过程中,我也参考了许多有关的书籍和论文,在这里共同向有关的作者表示谢意,也对他们严谨的学术态度产生崇高的敬意。作为本科生的毕业设计,因知识的缺陷和缺乏,此次毕业设计肯定会出现许多毛病,如果没有周智鹏导师教好,和同学们的重要性建议,我一个人完成此次毕业设计是一个非常痛苦的过程。衷心的谢谢周智鹏导师,虽然有忙碌的事情,但仍抽出时间赐予我学术上的指点和帮忙,告知了我很多获得和这次毕业设计有关的文献的渠道,使我从中受益非浅。周智鹏导师对学生认真负责,尤其是在给我们讲授难点时特别耐心,直到我能彻底明白。 在此,我还要感激全部给我上过课的各科任老师,你们辛苦了,不论是刮风或者飘着大雪,都一如既往地教学,同时还要感激全部的同学们,恰是有了你们的建议和鼓励,这次毕业设计才能顺利完成。 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