盖板零件注塑模具设计【一模两腔】【说明书+CAD+3D】
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盖板零件注塑模具设计【一模两腔】【说明书+CAD+3D】,一模两腔,盖板,零件,注塑,模具设计,说明书,CAD
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设 计（论 文）设计（论文）题目： 盖板模具设计 学 院 名 称： 专 业： 班 级： 姓 名： 学 号 指 导 教 师： 职 称 定稿日期： 年 月 日目 录目 录II第1章 产品的说明1第2章 塑件的工艺分析32.1塑件的结构和尺寸精度及表面质量分析32.1.1结构分析32.1.2尺寸精度分析32.1.3表面质量分析32.2计算塑件的体积和质量3第3章 注塑模设计43.1 注射模具分型面的选择43.1.1 分型面的基本形式43.1.2 分型面选择的基本原则43.1.3 分型面的选择43.2 浇注系统的设计43.2.1 浇注系统的组成43.2.2 注射模具主流道的设计43.2.3 分流道的设计63.2.4 浇口的设计73.2.5 冷料穴和钩料脱模装置103.3 型腔数目的确定及型腔的排列103.3.1 型腔数目的确定103.3.2 型腔的排列12第4章 成型零件和模体的设计124.1 模具型腔的结构设计124.2 型芯的结构设计134.3 成型零件的尺寸确定14第5章 推出机构的设计15第6章 温度调节系统的设计17第7章 排气系统18第8章 注射机有关参数校核18第9章 模具的动作过程19总结20参考文献2121第1章 产品的说明该塑件是盖板产品，其零件图如图所示。本塑件的材料采用PS，生产类型为大批量生产。图1 盖板正面图图2 盖板背面图概述PS（聚苯乙烯系塑料）是指大分子链中包括苯乙烯基的一类塑料，包括苯乙烯及其共聚物，具体品种包括普通聚苯乙烯（GPPS）、高抗冲聚苯乙烯（HIPS）、可发性聚苯乙烯（EPS）和茂金属聚苯乙烯（SPS）等。参数PS塑料（聚苯乙烯）英文名称:Polystyrene 比重：1.05克/立方厘米 成型收缩率：0.6-0.8% 成型温度：170-250 干燥条件：-物料性能电绝缘性（尤其高频绝缘性）优良，无色透明，透光率仅次于有机玻璃，着色性耐水性，化学稳定性良好，强度一般，但质脆，易产生应力脆裂，不耐苯.汽油等有机溶剂.适于制作绝缘透明件.装饰件及化学仪器.光学仪器等零件.成型性能 无定形料，吸湿小，不须充分干燥，不易分解，但热膨胀系数大，易产生内应力.流动性较好，可用螺杆或柱塞式注射机成型.宜用高料温，高模温，低注射压力，延长注射时间有利于降低内应力，防止缩孔.变形.可用各种形式浇口，浇口与塑件圆弧连接，以免去处浇口时损坏塑件.脱模斜度大，推出均匀.塑件壁厚均匀，最好不带镶件，如有镶件应预热.第2章 塑件的工艺分析2.1塑件的结构和尺寸精度及表面质量分析2.1.1结构分析从零件图上分析，该零件总体形状为板型。在一个带有28mm的孔对称分布,因此,模具设计,该零件属于中等复杂程度.2.1.2尺寸精度分析从塑件的壁厚上来看,壁厚最大处为3mm,壁厚均匀,，在制件的转角处设计圆角，防止在此处出现缺陷，由于制件的尺尺寸中等。2.1.3表面质量分析该零件的表面除要求没有缺陷毛刺，内部不得有杂质外，没有什么特别的表面质量要求，故比较容易实现。综上分析可以看出,注塑时在工艺控制得较好的情况下,零件的成型要求可以得到保证.2.2计算塑件的体积和质量计算塑件的质量是为了选用注塑机及确定模具型腔数。计算塑件的体积：V=46.87cm计算塑件的质量：根据设计手册可查得ABS的密度为=1.06kg/dm塑件质量：M=V50g(通过3D软件测量得到)采用一模两件的模具结构，考虑其外形尺寸，注塑时所需压力和工厂现有设备等情况，初步选用注塑机XSZY125型。第3章 注塑模设计3.1 注射模具分型面的选择3.1.1 分型面的基本形式分型面的形式由塑料的具体情况而定，但大体上有平面式分型面、阶梯式分型面、斜面式分型面、曲面式分型面、综合式分型面。3.1.2 分型面选择的基本原则选择分型面的基本原则：（1）保持塑料外观整洁；（2）分型面应有利于排气；（3）应考虑开模是塑料留在动模一侧；（4）应容易保证塑件的精度要求；（5）分型面应力求简单适用并易于加工；（6）考虑侧向分型面与主分型面的协调；（7）分型面应与注射机的参数相适应；（8）考虑脱模斜度的影响11。3.1.3 分型面的选择根据对工件模型的观察和分型面选择的基本原则。3.2 浇注系统的设计3.2.1 浇注系统的组成浇注系统是将熔融的塑料从注射机喷嘴进入模具型腔所经的通道，它包括主流道、分流道、浇口及冷料。在设计注射模具的浇注系统应注意以下几项原则12。（1）根据所确定的塑件型腔数设计合理的浇注系统布局。（2）根据塑件的形状和大小以及壁厚等诸多因素，并结合选择分型面的形式选择浇注系统的形式及位置。（3）应尽量的缩短物料的流程和便于清除料把，以节省原料，提升注射效率。（4）应根据所选用塑件的成型性能，特别是它的流动性能，选择浇注系统的截面积和长度，并使其圆滑过渡以利于物流的流动。3.2.2 注射模具主流道的设计主流道是熔融塑料由注射机喷嘴先经过的部位，它与注射机喷嘴在同一轴心线上。由于主流道与熔融注射机喷嘴反复接触、碰撞，一般浇口不直接开设在定模上，为了制造方便，都制成可拆卸的浇口套，用螺钉或迫合形式在定模板上13。（1）主流道的设计主流道是指浇注系统中从注射机喷嘴与模具接触处开始到分流道为止的塑料熔体的流动通道。主流道的形状与尺寸对塑料熔体的流动速度和充模时间有较大的影响，因此，必须使熔体的温度降和压力损失最小。（2）主流道尺寸在卧式或立式注射机上使用的模具中，主流道垂直于分型面。为了让主流道凝料能从浇口套中顺利拔出，主流道设计成圆锥形，其锥角 为26。小端直径d比注射机喷嘴直径大0.5mm1 mm。由于小端的前面是球面，其深度为3mm5 mm，注射机喷嘴的球面在该位置与模具接触并且贴合，因此要求主流道球面半径比喷嘴球面半径大1mm2mm。流道的表面粗糙度值Ra为0.08 。（3）主流道浇口套主流道浇口套一般采用碳素工具钢如T8A、T10A等材料制造，热处理淬火硬度53HRC57HRC。浇口套的材料应选用优质钢T8A，并应进行淬火处理，为了防止注射机喷嘴不被碰撞而损坏，浇口套的硬度应低于注射机喷嘴的硬度。为了便于浇注凝料从主流道中取出，主流道采用为36左右的圆锥孔。浇口套于注射机的喷嘴头的接触球面必须吻合，由于注射机喷嘴是球面，半径是固定的，所以为使熔融塑料从喷嘴完全进入主流道而不溢出，应使浇口套端面的凹球面与注射机喷嘴端的凸面接触良好，圆锥孔的小端直径则大于喷嘴的内孔直径，球面与主流道孔应以清角连接，不应有倒拔痕迹。为了便于浇注凝料从主流道中取出，主流道采用为36度左右的圆锥孔，对流动性较差的塑料也可取得稍大一些，但过于大则容易引起注射速度缓慢，并容易形成涡流。浇口套与塑料注射区直接接触时，其出料端端面直径应尽量选得小些。浇口套于注射机的喷嘴头的接触球面必须吻合，由于注射机喷嘴是球面，所以为使熔融塑料从喷嘴完全进入主流道而不溢出，应使浇口套端面的凹球面与注射机喷嘴端的凸面接触良好，圆锥孔的小端直径则大于喷嘴的内孔直径，球面与主流道孔应以清角连接，不应有倒拔痕迹，以保证主流道凝料顺利脱模14。定位环是模体与注射机的定位装置，它保证浇口套与注射机的喷嘴对中定位，定位环的外径应与注射机的定位孔间隙配合。浇口套端面应与定模相配合部分的平面高度一致。注射机XS-Z-30的喷嘴球半径为12 mm，喷嘴孔径为2 mm。所以要使浇口套端面的凹球面与注射机喷嘴的端凸球面接触良好，凹球面半径取13 mm，圆锥孔的小端直径则应大于喷嘴口内径，取3 mm，如图3.2。图3.2 浇口套3.2.3 分流道的设计分流道是将熔融塑料从主流道截面及其方向的变化，平稳进入单腔中的进料浇口或主流道进入多腔的浇口的通道，它是主流道与浇口的中间连接部分，起分流和转换方向的作用，通常分流道设置在分型面的成型区域内。在注射过程中，熔融的塑料在流经分流道时，应是它的压力损失以及热量损失最小，而以分流道中产生的凝料最少为原则，分流道的设计要点总体归纳如下：分流道的形状要考虑分流道的截面积与其周边长度的比最大为好，这样可以减少熔料的散热面积和摩擦阻力，减少压力损失。 在可能情况下，分流道的长度应尽量的短，以减少压力损失，避免模体过大影响成本，在多型腔模具中和型腔的分流道长度尽量相等，以达到注射大时压力传递的平衡，保证塑料尽可能同时均匀的充满各个型腔。在有些情况下分流道长度不能相等时，则应在浇口处作必要的补救措施，如果分流道较长时，应在其末端设置冷料穴，放置冷料和空气进入模腔15。在满足注射成型工艺的前提下，分流道的截面积应尽量的小，但分流道的截面积过小会降低注射速度，使填充时间延长，同时可能出现缺料、焦烧、皱纹、缩孔等塑件缺陷，而分流道过大则增大温度调节时间应比型腔中塑件的温度调节时间要短，才不影响注射时的效率。因此在设计时应采用较小的截面积，以便于在试模是为不要的修正留有余地。分流道和型腔的分布是排列紧凑，距离合理，应采用轴对称或中心对称，使其平衡，尽量缩小成型区域的总面积。最好使型腔和分流道在分型面上的总投影面积的几何中心和锁紧力的中心相重合。在分流道上的转向次数尽量少，在转向处应圆滑过渡，不能有尖角，这些都是为了减小压力损失，有利于物料的流动。当分流道设在定模一侧或分流道延伸较长时，应在浇口附近或分流道的交叉处设置钩料杆，以便于在开模时在钩料杆的作用下首先从定模中拉出分流道的凝料，并与塑料一起推出。分流道的内表面不必要求很光，一般表面粗糙度取1.6m即可，这样可以在分流道的摩擦阻力下使料流外层的流动小些，使其分流道的温度调节皮层固定，有利于熔融塑料的保温。在总体分布中，应综合考虑温度调节系统的方式和布局，并留出温度调节水路的空间。盖板注射模要求一模两腔，在布局上选择平衡式分流道。平衡式分流道的特点是：从主流道到各个型腔的分流道，其长度、截面尺寸及其形状完全相同，以保证各个型腔同时均匀进料，同时注射完毕。分流道的截面形状选择半圆形截面，它的效率比圆形稍差，但加工起来比圆形截面要简单。3.2.4 浇口的设计（1）浇口的概念浇口亦称进料口，是连接分流道与型腔的熔体通道。浇口的设计与位置的选择恰当与否，直接关系到塑件能否被完好、高质量地注射成形。（2）浇口的作用浇口可分成限制性浇口和非限制性浇口两类。非限制性浇口是整个浇注系统中截面尺寸最大的部位，它主要是对中大型筒类、壳类塑件型腔起引料和进料后的施压作用。限制性浇口是整个浇注系统中截面尺寸最小的部位，其作用如下：浇口通过截面积突然变化，使塑料熔体通过挠口的流速有突变性增加，提高塑料熔体的剪切速率，降低黏度，使其成为理想的流动状态，从而迅速均衡地充满型腔。对于多型腔模具，调节浇口的尺寸，还可以使非平衡布置的型腔达到同时进料的目的。浇口还起着较早固化、防止型腔中熔体倒流的作用。浇口通常是浇注系统最小截面部分，这有利于在塑件的后加丁中塑件与浇口凝料的分离16。（3）注射模浇口的类型单分型面注射模的浇口可以采用直接浇口、中心浇口、侧浇口、环形浇口、轮辐式浇口和爪形浇口。（a）直接浇口直接浇口叉称为主流道型浇口，它属于非限制性浇口。这种形式的浇口只适于单型腔模具。特点是：流动阻力小，流动路程短及补缩时间长等；有利于消除深型腔处气体不易排出的缺点；塑件和浇注系统在分型面上的投影面积最小，模具结构紧凑，注射机受力均匀；塑件翘曲变形、浇口截面大，去除浇口困难，去除后会留有较大的浇口痕迹，影响塑件的美观。 （b）中心浇口当筒类或壳类塑件的底部中心或接近于中心部位有通孔时，内浇口开设在该孔处，同时在中心处设置分流锥，该浇口称为中心浇口，是直接浇口的一种特殊形式。它具有直接浇口的优点，而克服了直接浇口易产生的缩孔、变形等缺陷。（c）侧浇口侧浇口一般开设在分型面上，塑料熔体从内侧或外侧充填模具型腔，其截面形状多为(扁槽)，是限制性浇口。侧浇口广泛使用在多型腔单分型面注射模上。特点是由于浇口截面小，减少了浇注系统塑料的消耗量，同时去除浇口容易，不留明显痕迹。侧浇口的两种变异形式为扇形浇口和平缝浇口。扇形浇口是一种沿浇口方向宽度逐渐增加、厚度逐渐减少的呈扇形的侧浇口， 平缝浇口又称薄片浇口，浇口宽度很大，厚度很小。主要用来成形面积较小、尺寸较大的扁平塑件，可减小平板塑件的翘曲变形，但浇口的去除比扇形浇口更困难，浇口在塑件上痕迹也更明显。（d）环形浇口对型腔填充采用圆环形进料形式的浇口称环形浇口。环形浇口的特点是进料均匀。圆周上各处流速大致相等，熔体流动状态好型腔中的空气容易排出，熔接痕可基本避免，但浇注系统耗料较多，浇口去除较难。（e）轮辐式浇口轮辐式浇口是在环形浇口基础上改进而成。这种形式的浇口耗料比环形浇口少得多。这类浇口在生产中比环形浇口应用广泛。多用于底部有大孔的圆筒形或壳形塑件。轮辐浇口的缺点是增加了熔接痕，会影响塑件的强度。（f）潜伏式浇口潜伏式浇口加工较困难，通常用电火花成形。型芯可用做分流锥，从而避免了塑件弯曲变形或同轴度差等成形缺陷。爪形浇口的缺点与轮辐式浇口类似，主要适用于成形内孔较小且同轴度要求较高的细长管状塑件。浇口位置的选择原则：尽量缩短流动距离；避免熔体破裂现象引起塑件的缺陷；浇口应开设在塑件厚壁处；考虑分子定向的影响；减少熔接痕。（4）浇注系统平衡设计（a）浇注系统的平衡概念为了提高生产效率，降低成本，小型(包括部分中型)塑件往往采取一模多腔的结构豫应尽量采用型腔平衡式布置的形式。若根据某种需要浇注系统被设计成型腔非平衡式布置形式，则需要通过调节浇口尺寸，使浇口的流量及成形工艺条件达到一致，这就是浇注系的平衡，亦称浇口的平衡。（b）浇注系统的平衡计算方法浇注平衡计算的思路是通过计算多型腔模具各个浇口的BGV(Balanced Gate Value)值来判断或计算。浇口平衡时，BGV值应符合下列要求：相同塑件的多型腔模具，各浇口计算出的BGV值必须相等；不同塑件的多型腔模具，各浇口计算出的BGV值必须与其塑件型腔的充填量成正比。（5）浇口的选择本模具为一模两腔，浇口为扁平形状，可以大大的缩短温度调节时间，缩短成型周期。易于去除浇注系统的凝料而不影响塑件的外观。浇口设置在塑件表面，浇口截面形状简单，容易加工，且注射效率高。若采用潜伏式浇口，不但避免塑件侧壁因修剪浇口而损伤，而且浇口能自动切断，模具结构也不算太复杂，提高了经济效益。因此确定采用潜伏式浇口。3.2.5 冷料穴和钩料脱模装置冷料穴设置在主流道的末端，即主流道正对面的动模板上。它的作用是用来储存注射间歇期间，喷嘴前端由散热造成温度降低而产生的冷料。在注射时，如果它们进入流道，将堵塞流道并减缓料流速度。进入型腔，将在塑件上出现冷疤或冷斑。球形拉料装置由冷料穴、拉料杆组成，拉料杆安装在型芯固定板上，不与推出系统联动。3.3 型腔数目的确定及型腔的排列3.3.1 型腔数目的确定根据塑件生产批量及经济性，通过注射量及锁模力计算，可确定尽可能多的型腔数，以提高生产率。其型腔在一模中的数目确定方法见表三：序号确定依据确定方法说明1按塑件的经济性确定型腔数按总成型加工费用最小的原则，并忽略准备时间和试生产时的原材料费用，仅考虑模具费和成型加工费。其型腔数量，可用下式计算：N=式中 N每副模具型腔数； P计划生产总件数； Y单位小时模具加工费用（元h）；T成型周期（min）；c每个型腔模具加工费用（元）；单型腔模具比多型腔模具制造成本低、周期短，所以批量较少的塑件，不宜采用多型腔特别是形状复杂、尺寸较大的、精度要求较高、小批量试生产的塑件应选用单型腔模具比较经济。2按注射机的最大注射量确定型腔数塑件的每次注射量总和不能超过注射机最大额定注射量的80，其计算方法是：N式中 N每台模具允许型腔数； V注射机最大注射量； Vj浇注系统凝料量； Vs单个塑件的容积；或质量（cm 或g） 若每次注射量总和大于注射机额定注射量，则型腔数应减小或采用单型腔；3按注射机额定锁模力确定型腔数按注射机额定锁模力确定所需设型腔数，可以按下式核算：N式中 F注射机额定锁模力（KN）； P塑料对型腔平均压力（MPa）；A浇注系统在分型面上的投影面积（cm）；AZ单个塑件在分型面上的投影面积（cm）；所确定的型腔个数总锁模力不应超过注射机额定锁模力，否则合模时，模具难以合严，有溢料产生，应减小型腔个数。4按制品精度要求确定型腔数型腔数越多精度越低，从满足精度要求出发型腔数可按下式确定：N2500-24式中 L塑件基本尺寸（mm）； 塑件尺寸公差（mm）； 单腔时，塑件可能达到尺寸公差（mm），其中聚甲醛为0.2、PE、PP、PC、PVC为0.05 ；1.根据经验，每增加一个型腔，其尺寸精度可降低4。2.一模一腔时，塑料公差聚甲醛为0.2，尼龙66为0。3，聚碳酸酯ABS，聚乙烯为0.05。3.对于高精度塑件，一模不能超过四腔。表三此塑件采用第二种方法确定型腔数目；按注射机的最大注射量确定型腔数；根据公式：NN5（取整）最终确定采用一模二腔的结构形式；3.3.2 型腔的排列型腔的布置采用对称分布，以防模具承受偏载而产生溢料。平衡性好，加工容易，使用比较广泛。第4章 成型零件和模体的设计4.1 模具型腔的结构设计型腔大体有以下几种结构形式：整体式、整体组合式、局部组合式和完全组合式。型腔由整块材料制成，用台肩或螺栓固定在模板上。它的主要优点是便于加工，特别是在多型腔模具中，型腔单个加工后，在分别装入模板，这样容易保证各型腔的同心度以及尺寸精度要求，并且便于部分成型件进行处理等。型腔由整块材料制成，但局部镶有成型嵌件的局部组合式型腔。局部组合式型腔多于型腔较深或形状较为复杂，整体加工比较困难或局部需要淬硬的模具。完全组合式是由多个螺栓拼块组合而成的型腔。它的特点是，便于机加工，便于抛光研磨和局部热处理。节约优质钢材。这种形式多用于不容易加工的型腔或成型大面积塑件的大型型腔上。这里选择整体式型腔。在塑料注射模具的注射过程中，型腔从合模到注射保证过程中受到高压的冲击力，因此模具型腔应该有足够的硬度和刚度，总的来说，型腔所承受的力大体有合模时的压应力、注射过程中塑料流动的注射压力、浇口封闭前一瞬间的压力保证和开模时的压应力，但型腔所承受的力主要是注射压力和保证压力，并在注射过程中总是在变化。在这些压力作用下，当型腔的刚度不足时，往往会产生弹性变形，导致型腔向外膨胀，它将直接影响塑件的质量和尺寸精度。所以在模具设计时要首先考虑使型腔的壁厚和底板厚度都有足够的强度和刚度，以保证型腔在注射过程中产生超过规定限度的弹性变形。因此型腔壁厚和底板的计算和选择是十分重要的。（1）型腔侧壁厚度的计算按强度计算其壁厚S按下列公式计算 式中 型腔材料的许用应力，=156.8MPa p型腔内单位平均压力，P=38.4MPar型腔内半径，r=10mm代入公式得：S=4mm（2）底板厚度的计算按强度计算其壁厚H按下面公式计算 式中 型腔材料的许用应力，=156.8MPa p型腔内单位平均压力，P=38.4MPar型腔内半径，r=10mm代入公式得：H=5.5mm4.2 型芯的结构设计型芯的结构形式大体有：整体式、整体复合式、局部组合式、完全组合式。4.3 成型零件的尺寸确定（1）型腔尺寸计算型腔的各部分尺寸一般都是趋于增大尺寸，因此应选择塑件公差的1/2，取负偏差，再加上-1/4的磨损量，而型芯深度则再加上-1/6的磨损量，这样的型芯的计算尺寸的表述如下。（a）型腔的径向尺寸的计算式： 式中 D0型芯的最小基本尺寸； 塑件的最大基本尺寸；S塑件的平均收缩率，S=0.02；塑件的公差，取八级精度；模具制造公差，按1/4选取；根据公式计算得型腔的径向尺寸： （b）型腔的深度根据尺寸的计算公式 式中 型腔深度的最小尺寸； 塑件的最大基本小尺寸；S塑件的平均收缩率；塑件的公差，取八级精度；模具制造公差，按1/4选取；根据公式计算得型腔的深度尺寸： （2）型芯尺寸的计算型芯的各部尺寸除特殊情况外都是趋于缩小尺寸,因此应选择塑件公差的1/2,取正偏差,再加上+1/4的磨损量,而型芯高度则加上+1/6的磨损量.型芯的计算尺寸表达如下。（a）型芯的径向尺寸的计算式： 式中 型芯的最大基本尺寸； 塑件的最小基本尺寸；S塑件的平均收缩率；塑件的公差，取八级精度；模具制造公差，按1/4选取；根据公式计算得型芯的径向尺寸： （b）型芯的高度尺寸的计算： 式中 型芯高度的最大尺寸； 塑件内形深度的最小尺寸；S塑件的平均收缩率；塑件的公差，取八级精度；模具制造公差，按1/4选取；根据公式计算得型芯的高度尺寸： 第5章 推出机构的设计推出机构的分类：按驱动方式分类可分为：手动推出、机动推出、启动推出。按模具结构分类可分为：一次推出、二次推出、螺纹推出、特殊推出。（1）推出机构的结构组成 在注射成形的每个周期中，将塑料制品及浇注系统凝料从模具巾脱出的机构称为推出机构，也叫推出机构或脱模机构。推出机构的动作通常是由安装在注射机上的机械顶杆或液压缸的活塞杆来完成的。结构组成：由推出、复位和导向零件组成。（2）结构分类手动推出、机动推出、液压或气动推出。（3）结构设计要求塑件留在动模,塑件在推出过程中不变形、不损坏,不损坏塑件的外观质量,合模时应使推出机构正确复位,动作可靠。（4）结构设计（a）推杆推出机构推杆推出机构是整个推出机构中最简单、最常见的一种形式。由于设置推杆的自由度较大，而且推杆截面大部分为圆形，容易达到推杆与模板或型芯上推杆孔的配合精度推杆推出时运动阻力小，推出动作灵活可靠，因此在生产中广泛应用。 但是因为推杆的推出面积一般比较小，易引起较大局部应力而顶穿塑件或使塑件变形，所以很少用于脱模斜度小和脱模阻力大的管类或箱类塑件。（b）推管推出机构推管推出机构是用来推出圆筒形、环形塑件或带有孔的塑件的一种特殊结构形式，其脱模运动方式和推杆相同。由于推管是一种空心推杆，故整个周边接触塑件，推出塑件的力量均匀，塑件不易变形，也不会留下明显的推出痕迹。（c）推件板的推出机构凡是薄壁容器、壳形塑件以及表面不允许有推出痕迹的塑料制品，可采用推件板推出推件板推出机构义称顶板推出机构，它由一块与型芯按一定配合精度相配合的模板和推杆组成。 特点：推件板推出的特点是推出力均匀，运动平稳，且推出力大。但是对于截面为非圆形的塑件，其配合部分加工比较困难。 （d）活动嵌件及凹模推出机构有一些塑件由于结构形状和所用材料的关系，不能采用推杆、推管、推件板等简单推出机构脱模时，可用成形嵌件或型腔带出塑件。（5）推出机构的设计原则： 塑件在成型推出后，一般都留有推出痕迹，但应尽量使推出的残留痕迹不影响塑件的外观，这是在选择推出形式和推出位置时必须考虑到的问题。一般推出机构应设在塑件的内表面以及不显眼的位置。注射设备的推出装置都设计在动模一侧，因此，在一般情况下开模时，尽量设计使塑件留在动模一侧，以便于推出塑件。这在分型面的选择时就应充分考虑。在实践中如果出现塑件并没有留在动模侧的情况时，可设法增加动默一侧的阻力，一是将型芯的脱模斜度变小，或增加型芯的表面粗糙度，或者在不影响塑件使用的前提下，在型芯侧面人为的开设横凹槽、凹窝等脱模障碍，以增大动模的阻力。在特殊情况下必须使塑件留在定模时可采用定模推出机构。 塑件在成型推出后，一般都留有推出痕迹，但应尽量使推出的残留痕迹不影响塑件的外观，这是在选择推出形式和推出位置时必须考虑到的问题。一般推出机构应设在塑件的内表面以及不显眼的位置。推出零件应有足够的机械强度和耐磨性能，使其在相当长的运作周期内平稳顺畅，无卡滞现象，并力求制造方便，容易维修。 推出装置力求均匀分布，推出力作用点应在塑件承受推出力最大的部件，尽量避免推出力作用于最薄的部位，防止塑件在推出过程中的变形和损伤。推出零件应有足够的机械强度和耐磨性能，使其在相当长的运作周期内平稳顺畅，无卡滞现象，并力求制造方便，容易维修。第6章 温度调节系统的设计塑料在生产过程中由于需要对熔融的塑料流体进行温度调节，塑料制件不能有太高的温度（防止出模后制件发生翘曲，变形）温度调节系统设计可按下式进行计算：设该模具平均工作温度为60，用20的常温水作为模具的温度调节介质，其出口温度为30，产量为（1分钟2模）1000g/h。求塑件在硬化时每小时释放的热量为Q3，查有关文献得尼龙1010的单位热流量为Q2=314.3398.1J/g ,取Q2=350J/g：Q3=WQ2=1008g/h350J/h=352800J求温度调节水的体积流量VV=WQ1/Pc1(T1T2)=140cm3温度调节对塑件的质量影响主要表现在以下几个方面：变形尺寸精度 力学性能 表面质量在选择模具温度时，应根据使用情况着重满足制件的质量要求。在注射模具中溶体从200 C,左右降低到60C左右，所释放的能量5以辐射，对流的方式散发到大气中，其余95由温度调节介质带走，因此注射模的温度调节时间只要取决与温度调节系统的温度调节效果。模具的温度调节时间约占整个循环周期的2/3。缩短循环周期的温度调节时间是提高是提高生产效率的关键。在温度调节水温度调节过程中，在湍流下的热传递是层流的1020倍。在此我选择湍流。 如表五：温度调节水道直径 d/（mm） 最低流量v /（m/s）流量 qv/（m/min） 12 1.10 7.410表五第7章 排气系统在注塑模具的设计过程中，必须考虑排气结构的设计，否则，熔融的塑料流体进入模具型腔内，在填充模具的型腔过程中同时要排出型强及流道原有的空气，气体如不能及时排出会使制件的内部有气泡， 除此以外，塑料熔体会产生微量的分解气体。这些气体必须及时排出。否则，被压缩的空气产生高温，会引起塑件局部碳化烧焦，或塑件产生气泡，或使塑件熔接不良引起强度下降，甚至充模不满甚至会产生很高的温度使塑料烧焦，从而出现废品。排气方式有两种：开排气槽排气和利用合模间隙排气。由于盖板注塑模是小型镶拼式模具，可直接利用分型面和镶拼间隙进行排气，而不需在模具上开设排气槽。第8章 注射机有关参数校核1、模具闭合高度的确定根据支承与固定零件中提供的数据确定：定模座板H1=25mm ，上固定板H2=20mm 下固定板H3=25mm支承板H4=32mm动模座板H5=25mm，垫块H6=50mmH=H1+H2+H3H+H4+H5+H6+H7=25+20+25+32+25+50=177mm2、 注射机有关参数的校核本模具的外形尺寸为340255，XSZ125型注射机模板最大安装尺寸为500500；故能满足模具的安装要求。经验证，XSZ250型注射机能够满足使用要求，故可以采用总结总结在设计期间，我学习并运用CAD对推出机构的注射模的所有零件进行了造型设计和对所有零件进行装配设计。提高了我对CAD的运用能力和计算机的应用能力，为以后我的工作奠定了基础。总之，通过本次毕业设计，加强了我对各项知识的学习深度，更培养了分析问题和解决问题的能力，教会我怎样才能按步骤有条不紊地进行工作。这些为我走上工作岗位奠定了坚实的基础。参考文献参考文献1 申长雨，陈静波等. 塑料型材挤初模具 CAE 技术M. 模具工业出版社，2001(7). 2 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Pro/ENGINEER Wildfire 模具设计与数控加工M. 北京：清华大学出版社，2004.3. 3 李迎春，杜栓丽，申开智. 聚丙烯(PP)塑料注塑模具点浇口大小的研究J. 华北工学院学报，1998 年第 19 卷第 1 期(总第 61 期)：3034.4 付永刚. 注塑模 CAD 系统开发的理论研究及应用J. 西安理工大学硕士论文，2000.3.5 陈志刚. 塑料模具设计M. 北京：机械工业出版社，2002.1.6 刘法谦，燕立唐，胡海青，等. CAE 在彩电后壳浇注系统中的应用，现代塑料加工应用J，2002.6，第 14 卷第 3 期：1922.7 李德群，肖祥芷. 模具 CAD/CAE/CAM 的发展概况及趋势J. 模具工业，2005（07).8 张祥杰. Pro/ENGINEER Wildfire模具设计M. 中国铁道出版社，2004：35188.9 田福祥. 现代模具技术的特点及其发展趋势J热加工工艺，2004（08）10 王文广等.塑料注射模具设计技巧与实力M.北京:化工工业出版社,2003.11 日村上宗雄.最新塑料模具手册M.上海:上海科学文献出版社,1985.13 王广文.塑料材料的选用M.北京:化工工业出版社,2001.14 成都科技大学.塑料成型工艺M.北京:中国轻工业出版社,1993.15 欧阳国思.实用塑料材料学M.长沙:国防科技出版社,1991.16 唐志玉.大型注塑模设计基础M.成都:成都科技大学出版社,1987.17 马金俊.塑料模具设计M.北京:中国科学科技出版社,1994. 编号： 毕业设计(论文)外文翻译（原文）院 （系）： 国防生学院 专 业：机械设计制造及其自动化 学生姓名： 蔡秀滨 学 号： 1001020105 指导教师单位： 机电工程学院 姓 名： 郭中玲 职 称： 高级工程师 2014年 3 月 9 日Contents1.The Injection Molding12.Automated surface nishing of plastic injection mold steel with spherical grinding and ball burnishing processes14第 22 页 共 23 页 桂林电子科技大学毕业（论文）报告专用纸 The Injection Molding Alp Tekin Ergenc , Deniz Ozde KocaYildiz Tecnical University, Mechanical Engineering Department, IC Engines Laboratory, TurkeyThe Introduction of MoldsThe mold is at the core of a plastic manufacturing process because its cavity gives a part its shape. This makes the mold at least as critical-and many cases more so-for the quality of the end product as, for example, the plasticiting unit or other components of the processing equipment.Mold MaterialDepending on the processing parameters for the various processing methods as well as the length of the production run, the number of finished products to be produced, molds for plastics processing must satisfy a great variety of requirements. It is therefore not surprising that molds can be made from a very broad spectrum of materials, including-from a technical standpoint-such exotic materials as paper matched and plaster. However, because most processes require high pressures, often combined with high temperatures, metals still represent by far the most important material group, with steel being the predominant metal. It is interesting in this regard that, in many cases, the selection of the mold material is not only a question of material properties and an optimum price-to-performance ratio but also that the methods used to produce the mold, and thus the entire design, can be influenced.A typical example can be seen in the choice between cast metal molds, with their very different cooling systems, compared to machined molds. In addition, the production technique can also have an effect; for instance, it is often reported that, for the sake of simplicity, a prototype mold is frequently machined from solid stock with the aid of the latest technology such as computer-aided (CAD) and computer-integrated manufacturing (CIMS). In contrast to the previously used methods based on the use of patterns, the use of CAD and CAM often represents the more economical solution today, not only because this production capability is available pin-house but also because with any other technique an order would have to be placed with an outside supplier.Overall, although high-grade materials are often used, as a rule standard materials are used in mold making. New, state-of-the art (high-performance) materials, such as ceramics, for instance, are almost completely absent. This may be related to the fact that their desirable characteristics, such as constant properties up to very high temperatures, are not required on molds, whereas their negative characteristics, e. g. low tensile strength and poor thermal conductivity, have a clearly related to ceramics, such as sintered material, is found in mild making only to a limited degree. This refers less to the modern materials and components produced by powder metallurgy, and possibly by hot isocratic pressing, than to sintered metals in the sense of porous, air-permeable materials.Removal of air from the cavity of a mold is necessary with many different processing methods, and it has been proposed many times that this can be accomplished using porous metallic materials. The advantages over specially fabricated venting devices, particularly in areas where melt flow fronts meet, I, e, at weld lines, are as obvious as the potential problem areas: on one hand, preventing the texture of such surfaces from becoming visible on the finished product, and on the other hand, preventing the microspores from quickly becoming clogged with residues (broken off flash, deposits from the molding material, so-called plate out, etc.). It is also interesting in this case that completely new possibilities with regard to mold design and processing technique result from the use of such materials. A. Design rules There are many rules for designing molds. These rules and standard practices are based on logic, past experience, convenience, and economy. For designing, mold making, and molding, it is usually of advantage to follow the rules. But occasionally, it may work out better if a rule is ignored and an alternative way is selected. In this text, the most common rules are noted, but the designer will learn only from experience which way to go. The designer must ever be open to new ideas and methods, to new molding and mold materials that may affect these rules.B. The basic mold1. Mold cavity space The mold cavity space is a shape inside the mold, “excavated” in such a manner that when the molding material is forced into this space it will take on the shape of the cavity space and, therefore, the desired product. The principle of a mold is almost as old as human civilization. Molds have metals into sand forms. Such molds, which are still used today in foundries, can be used only once because the mold is destroyed to release the product after it has solidified. Today, we are looking for permanent molds that can be used over and over. Now molds are made from strong, durable materials, such as steel, or from softer aluminum or metal alloys and even from certain plastics where a long mold life is not required because the planned production is small. In injection molding the plastic is injected into the cavity space with high pressure, so the mold must be strong enough to resist the injection pressure without deforming.2. Number of cavities Many molds, particularly molds for larger products, are built for only cavity space, but many molds, especially large production molds, are built with 2 or more cavities. The reason for this is purely economical. It takes only little more time to inject several cavities than to inject one. For example, a 4-cavity mold requires only one-fourth of the machine time of a single-cavity mold. Conversely, the production increases in proportion to the number of cavities. A mold with more cavities is more expensive to build than a single-cavity mold, but not necessarily 4 times as much as a single-cavity mold. But it may also require a larger machine with larger platen area and more clamping capacity, and because it will use 4 times the amount of plastic, it may need a large injection unit, so the machine hour cost will be higher than for a machine large enough for the smaller mold.3. Cavity shape and shrinkage The shape of the cavity is essentially the “negative” of the shape of the desired product, with dimensional allowance added to allow for shrinking of the plastic. The shape of the cavity is usually created with chip-removing machine tools, or with electric discharge machining, with chemical etching, or by any new method that may be available to remove metal or build it up, such as galvanic processes. It may also be created by casting certain metals in plaster molds created from models of the product to be made, or by casting some suitable hard plastics. The cavity shape can be either cut directly into the mold plates or formed by putting inserts into the plates.C. Cavity and core By convention, the hollow portion of the cavity space is called the cavity. The matching, often raised portion of the cavity space is called the core. Most plastic products are cup-shaped. This does not mean that they look like a cup, but they do have an inside and an outside. The outside of the product is formed by the cavity, the inside by the core. The alternative to the cup shape is the flat shape. In this case, there is no specific convex portion, and sometimes, the core looks like a mirror image of the cavity. Typical examples for this are plastic knives, game chips, or round disks such as records. While these items are simple in appearance, they often present serious molding problems for ejection of the product. The reason for this is that all injection molding machines provide an ejection mechanism on the moving platen and the products tend to shrink onto and cling to the core, from where they are then ejected. Most injection molding machines do not provide ejection mechanisms on the injection side.Polymer Processing Polymer processing, in its most general context, involves the transformation of a solid (sometimes liquid) polymeric resin, which is in a random form (e.g., powder, pellets, beads), to a solid plastics product of specified shape, dimensions, and properties. This is achieved by means of a transformation process: extrusion, molding, calendaring, coating, thermoforming, etc. The process, in order to achieve the above objective, usually involves the following operations: solid transport, compression, heating, melting, mixing, shaping, cooling, solidification, and finishing. Obviously, these operations do not necessarily occur in sequence, and many of them take place simultaneously. Shaping is required in order to impart to the material the desired geometry and dimensions. It involves combinations of viscoelastic deformations and heat transfer, which are generally associated with solidification of the product from the melt. Shaping includes: two-dimensional operations, e.g. die forming, calendaring and coating; three-dimensional molding and forming operations. Two-dimensional processes are either of the continuous, steady state type (e.g. film and sheet extrusion, wire coating, paper and sheet coating, calendaring, fiber spinning, pipe and profile extrusion, etc.) or intermittent as in the case of extrusions associated with intermittent extrusion blow molding. Generally, molding operations are intermittent, and, thus, they tend to involve unsteady state conditions. Thermoforming, vacuum forming, and similar processes may be considered as secondary shaping operations, since they usually involve the reshaping of an already shaped form. In some cases, like blow molding, the process involves primary shaping (pair-son formation) and secondary shaping (pair son inflation). Shaping operations involve simultaneous or staggered fluid flow and heat transfer. In two-dimensional processes, solidification usually follows the shaping process, whereas solidification and shaping tend to take place simultaneously inside the mold in three dimensional processes. Flow regimes, depending on the nature of the material, the equipment, and the processing conditions, usually involve combinations of shear, extensional, and squeezing flows in conjunction with enclosed (contained) or free surface flows. The thermo-mechanical history experienced by the polymer during flow and solidification results in the development of microstructure (morphology, crystallinity, and orientation distributions) in the manufactured article. The ultimate properties of the article are closely related to the microstructure. Therefore, the control of the process and product quality must be based on an understanding of the interactions between resin properties, equipment design, operating conditions, thermo-mechanical history, microstructure, and ultimate product properties. Mathematical modeling and computer simulation have been employed to obtain an understanding of these interactions. Such an approach has gained more importance in view of the expanding utilization of computer design/computer assisted manufacturing/computer aided engineering (CAD/CAM/CAE) systems in conjunction with plastics processing. It will emphasize recent developments relating to the analysis and simulation of some important commercial process, with due consideration to elucidation of both thermo-mechanical history and microstructure development. As mentioned above, shaping operations involve combinations of fluid flow and heat transfer, with phase change, of a visco-elastic polymer melt. Both steady and unsteady state processes are encountered. A scientific analysis of operations of this type requires solving the relevant equations of continuity, motion, and energy (I. e. conservation equations).Injection Molding Many different processes are used to transform plastic granules, powders, and liquids into final product. The plastic material is in moldable form, and is adaptable to various forming methods. In most cases thermoplastic materials are suitable for certain processes while thermosetting materials require other methods of forming. This is recognized by the fact that thermoplastics are usually heated to a soft state and then reshaped before cooling. Theromosets, on the other hand have not yet been polymerized before processing, and the chemical reaction takes place during the process, usually through heat, a catalyst, or pressure. It is important to remember this concept while studying the plastics manufacturing processes and the polymers used. Injection molding is by far the most widely used process of forming thermoplastic materials. It is also one of the oldest. Currently injection molding accounts for 30% of all plastics resin consumption. Since raw material can be converted by a single procedure, injection molding is suitable for mass production of plastics articles and automated one-step production of complex geometries. In most cases, finishing is not necessary. Typical products include toys, automotive parts, household articles, and consumer electronics goods, Since injection molding has a number of interdependent variables, it is a process of considerable complexity. The success of the injection molding operation is dependent not only in the proper setup of the machine variables, but also on eliminating shot-to-shot variations that are caused by the machine hydraulics, barrel temperature variations, and changes in material viscosity. Increasing shot-to-shot repeatability of machine variables helps produce parts with tighter tolerance, lowers the level of rejects, and increases product quality ( i.e., appearance and serviceability). The principal objective of any molding operation is the manufacture of products: to a specific quality level, in the shortest time, and using a repeatable and fully automatic cycle. Molders strive to reduce or eliminate rejected parts, or parts with a high added value such as appliance cases, the payoff of reduced rejects is high. A typical injection molding cycle or sequence consists of five phases:1 Injection or mold filling2 Packing or compression3 Holding4 Cooling5 Part ejectionInjection Molding OverviewProcessInjection molding is a cyclic process of forming plastic into a desired shape by forcingthe material under pressure into a cavity. The shaping is achieved by cooling(thermoplastics) or by a chemical reaction (thermosets). It is one of the most commonand versatile operations for mass production of complex plastics parts with excellentdimensional tolerance. It requires minimal or no finishing or assembly operations. Inaddition to thermoplastics and thermosets, the process is being extended to suchmaterials as fibers, ceramics, and powdered metals, with polymers as binders.ApplicationsApproximately 32 percent by weight of all plastics processed go through injection moldingmachines. Historically, the major milestones of injection molding include the invention of thereciprocating screw machine and various new alternative processes, and the application of computersimulation to the design and manufacture of plastics parts.Development of the injection molding machineSince its introduction in the early 1870s, the injection molding machine has undergone significantmodifications and improvements. In particular, the invention of the reciprocating screw machine hasrevolutionized the versatility and productivity of the thermoplastic injection molding process.Benefits of the reciprocating screwApart from obvious improvements in machine control and machine functions, the majordevelopment for the injection molding machine is the change from a plunger mechanism to areciprocating screw. Although the plunger-type machine is inherently simple, its popularity waslimited due to the slow heating rate through pure conduction only. The reciprocating screw canplasticize the material more quickly and uniformly with its rotating motion, as shown in Figure 1. Inaddition, it is able to inject the molten polymer in a forward direction, as a plunger.Development of the injection molding processThe injection molding process was first used only with thermoplastic polymers. Advances in theunderstanding of materials, improvements in molding equipment, and the needs of specific industrysegments have expanded the use of the process to areas beyond its original scope.Alternative injection molding processesDuring the past two decades, numerous attempts have been made to develop injection moldingprocesses to produce parts with special design features and properties. Alternative processes derivedfrom conventional injection molding have created a new era for additional applications, more designfreedom, and special structural features. These efforts have resulted in a number of processes,including: Co-injection (sandwich) molding Fusible core injection molding) Gas-assisted injection molding Injection-compression molding Lamellar (microlayer) injection moldin Live-feed injection molding Low-pressure injection molding Push-pull injection molding Reactive molding Structural foam injection molding Thin-wall moldingComputer simulation of injection molding processesBecause of these extensions and their promising future, computer simulation of the process has alsoexpanded beyond the early lay-flat, empirical cavity-filling estimates. Now, complex programs simulate post-filling behavior, reaction kinetics, and the use of two materials with different properties, or two distinct phases, during the process.The Simulation section provides information on using C-MOLD products.Among the Design topicsare several examples that illustrate how you can use CAE tools to improve your part and molddesign and optimize processing conditions.Co-injection (sandwich) moldingOverviewCo-injection molding involves sequential or concurrent injection of two different butcompatible polymer melts into a cavity. The materials laminate and solidify. This processproduces parts that have a laminated structure, with the core material embedded betweenthe layers of the skin material. This innovative process offers the inherent flexibility ofusing the optimal properties of each material or modifying the properties of the moldedpart.FIGURE 1. Four stages of co-injection molding. (a) Short shot of skin polymer melt (shown in dark green)is injected into the mold. (b) Injection of core polymer melt until cavity is nearly filled, as shown in (c). (d)Skin polymer is injected again, to purge the core polymer away from the sprue.Fusible core injection moldingOverviewThe fusible (lost, soluble) core injection molding process illustrated below producessingle-piece, hollow parts with complex internal geometry. This process molds a coreinside the plastic part. After the molding, the core will be physically melted or chemicallydissolved, leaving its outer geometry as the internal shape of the plastic part.FIGURE 1. Fusible (lost, soluble) core injection moldingGas-assisted injection moldingGas-assisted processThe gas-assisted injection molding process begins with a partial or full injection ofpolymer melt into the mold cavity. Compressed gas is then injected into the core of thepolymer melt to help fill and pack the mold. This process is illustrated below.FIGURE 1. Gas-assisted injection molding: (a) the electrical system, (b) the hydraulic system, (c) the control panel, and (d) the gas cylinder.Injection-compression moldingOverviewThe injection-compression molding process is an extension of conventional injectionmolding. After a pre-set amount of polymer melt is fed into an open cavity, it iscompressed, as shown below. The compression can also take place when the polymer isto be injected. The primary advantage of this process is the ability to producedimensionally stable, relatively stress-free parts, at a low clamp tonnage (typically 20 to50 percent lower).Lamellar (microlayer) injection moldingOverviewThis process uses a feedblock and layer multipliers to combine melt streams from dualinjection cylinders. It produces parts from multiple resins in distinct microlayers, asshown in Figure 1 below. Combining different resins in a layered structure enhances anumber of properties, such as the gas barrier property, dimensional stability, heatresistance, and optical clarity.Live-feed injection moldingOverviewThe live-feed injection molding process applies oscillating pressure at multiple polymerentrances to cause the melt to oscillate, as shown in the illustration below. The action ofthe pistons keeps the material in the gates molten while different layers of molecular orfiber orientation are being built up in the mold due to solidification. This process providesa means of making simple or complex parts that are free from voids, cracks, sink marks,and weld-line defects.Low-pressure injection moldingOverviewLow-pressure injection molding is essentially an optimized extension of conventionalinjection molding (see Figure 1). Low pressure can be achieved by properly programmingthe screw revolutions per minute, hydraulic back pressure, and screw speed to controlthe melt temperature and the injection speed. It also makes use of a generous gate size ora n reduce umber of valve gates that open and close sequentially to reduce the flow length. Thepacking stage is eliminated with a generally slow and controlled injection speed. Thebenefits of low-pressure injection molding include a reduction of the clamp force tonnagerequirement, less costly molds and presses, and lower stress in the molded parts.Push-pull injection moldingOverviewThe push-pull injection molding process uses a conventional twin-component injectionsystem and a two-gate mold to force material to flow back and forth between a masterinjection unit and a secondary injection unit, as shown below. This process eliminatesweld lines, voids, and cracks, and controls the fiber orientation.Reactive molding ProcessingMajor reactive molding processes include reactive injection molding (RIM), and compositesprocessing, such as resin transfer molding (RTM) and structural reactive injection molding (SRIM).The typically low viscosity of the reactive materials permits large and complex parts to be moldedwith relatively lower pressure and clamp tonnage than required for thermoplastics molding.relatively For example, to make high-strength and low-volume large parts, RTM and SRIM can be used to include a preform made of long fibers. Another area that is receiving more attention than ever before is the encapsulation of microelectronic IC chips.The adaptation of injection molding to these materials includes only a small increase in temperature in the feed mechanism (barrel) to avoid pre-curing. The cavity, however, is usually hot enough to initiate chemical cross-linking. As the warm pre-polymer is forced into the cavity, heat is added from the cavity wall, from viscous (frictional) heating of the flow, and from the heat released by the reacting components. The temperature of the part often exceeds the temperature of the mold. When the reaction is sufficiently advanced for the part to be rigid (even at a high temperature) the cycle is complete and the part is ejected.Design considerationsThe mold and process design for injection molding of reactive materials is much more complexbecause of the chemical reaction that takes place during the filling and post-filling stages. Forinstance, slow filling often causes premature gelling and a resultant short shot, while fast fillingcould induce turbulent flow that creates internal porosity. Improper control of mold-walltemperature and/or inadequate part thickness will either give rise to moldability problems duringinjection, or cause scorching of the materials. Computer simulation is generally recognized as amore cost-effective tool than the conventional, time-consuming trial-and-error method for tool andprocess debugging.Structural foam injection moldingOverviewStructural foam molding produces parts consisting of solid external skin surfacessurrounding an inner cellular (or foam) core, as illustrated in Figure 1 below. This processis suitable for large, thick parts that are subject to bending loads in their end-use application. Structural foam parts can be produced with both low and high pressure, withnitrogen gas or chemical blowing agents.Thin-wall moldingOverviewThe term thin-wall is relative. Conventional plastic parts are typically 2 to 4 mm thick.Thin-wall designs are called advanced when thicknesses range from 1.2 to 2 mm, andleading-edge when the dimension is below 1.2 mm. Another definition of thin-wallmolding is based on the flow-length-to-wall-thickness ratios. Typical ratios for thesethin-wall applications range from 100:1 to 150:1 or more.Typical applicationsThin-wall molding is more popular in portable communication and computing equipment, whichdemand plastic shells that are much thinner yet still provide the same mechanical strength asconventional parts.ProcessingBecause thin-wall parts freeze off quickly, they require high melt temperatures, high injectiospeeds, and very high injection pressures if multiple gates or sequential valve gating are not an optimized ram-speed profile helps to reduce the pressure requirement.Due to the high velocity and shear rate in thin-wall molding, orientation occurs more readilyhelp minimize anisotropic shrinkage in thin-wall parts, it is important to pack the part adequately while the core is still molten.Injection molding machineComponentsFor thermoplastics, the injection molding machine converts granular or pelleted rawplastic into final molded parts via a melt, inject, pack, and cool cycle. A typical injectionmolding machine consists of the following major components, as illustrated in Figure 1below.Machine functionInjection molding machines can be generally classified into three categories, based on machinefunction:General-purpose machinesPrecision, tight-tolerance machinesHigh-speed, thin-wall machinesAuxiliary equipmentThe major equipment auxiliary to an injection molding machine includes resin dryers,materials-handling equipment, granulators, mold-temperature controllers and chillers, part-removal robots, and part-handling equipment.Automated surface nishing of plastic injection mold steel with spherical grinding and ball burnishing processesC. Apreaa, R. Mastrullob, C. Rennoa,*Department of Mechanical Engineering, University of Salerno, Via Ponte Don Melillo 1, 84084 Fisciano (Salerno), ItalybDETEC, University of Naples Federico II, P.le Tecchio 80, 80125 Naples, ItalyReceived 8 August 2002; received in revised form 18 December 2003; accepted 18 February 2004AbstractThis study investigates the possibilities of automated spherical grinding and ball burnishing surface nishing processes in a freeform surface plastic injection mold steel PDS5 on a CNC machining center. The design and manufacture of a grinding tool holder has been accomplished in this study.The optimal surface grinding parameters were determined usingTaguchis orthogonal array method for plastic injection moldingsteel PDS5 on a machining center. The optimal surface grinding parameters for the plastic injection mold steel PDS5 werethe combination of an abrasive material of PA Al2O3, a grinding speed of 18 000 rpm, a grinding depth of 20 m, and a feed of 50 mm/min. The surface roughness Raof the specimen can be improved from about 1.60 m to 0.35 m by using the optimal parameters for surface grinding. Surface roughness Ra can befurther improved from about 0.343 m to 0.06 m by using the ball burnishing process with the optimal burnishing parameters.Applying the optimal surface grinding and burnishing parame-ters sequentially to a ne-milled freeform surface mold insert,the surface roughness Raof freeform surface region on the tested part can be improved from about 2.15 m to 0.07 m.Keywords:Automated surface nishing；Ball burnishing process；Grinding process；Surface roughness；Taguchis method1 IntroductionPlastics are important engineering materials due to their specic characteristics, such as corrosion resistance, resistance to chemicals, low density, and ease of manufacture, and have increasingly replaced metallic components in industrial applications. Injection molding is one of the important forming processes for plastic products. The surface nish quality of the plastic injection mold is an essential requirement due to its direct effects on the appearance of the plastic product. Finishing processes such as grinding, polishing and lapping are commonly used to improve the surface nish. The mounted grinding tools (wheels) have been widely used in conventional mold and die nishing industries. The geometric model of mounted grinding tools for automated surface nishing processes was introduced in 1. A nishing process model of spherical grinding tools for automated surface nishing systems was developed in 2. Grinding speed, depth of cut, feed rate, and wheel properties such as abrasive material and abrasive grain size, are the dominant parameters for the spherical grinding process, as shown in Fig. 1. The optimal spherical grinding parameters for the injection mold steel have not yet been investigated based in the literature.In recent years, some research has been carried out in determining the optimal parameters of the ball burnishing process (Fig. 2). For instance, it has been found that plastic deformation on the workpiece surface can be reduced by using a tungsten carbide ball or a roller, thus improving the surface roughness, surface hardness, and fatigue resistance 36. The burnishing process is accomplished by machining centers 3, 4 and lathes 5, 6. The main burnishing parameters having signicant effects on the surface roughness are ball or roller material,burnishing force, feed rate, burnishing speed, lubrication, and number of burnishing passes, among others 3. The optimal surface burnishing parameters for the plastic injection mold steel PDS5 were a combination of grease lubricant, the tungsten carbide ball, a burnishing speed of 200 mm/min, a burnishing force of 300 N, and a feed of 40 m 7. The depth of penetration of the burnished surface using the optimal ball burnishing parameters was about 2.5 microns. The improvement of the surface roughness through burnishing process generally ranged between 40% and 90% 37.The aim of this study was to develop spherical grinding and ball burnishing surface nish processes of a freeform surface plastic injection mold on a machining center. The owchart of automated surface nish using spherical grinding and ball burnishing processes is shown in Fig. 3. We began by designing and manufacturing the spherical grinding tool and its alignment device for use on a machining center. The optimal surface spherical grinding parameters were determined by utilizing a Taguchis orthogonal array method. Four factors and three corresponding levels were then chosen for the Taguchis L18matrix experiment.The optimal mounted spherical grinding parameters for surface grinding were then applied to the surface nish of a freeform surface carrier. To improve the surface roughness, the ground surface was further burnished, using the optimal ball burnishing parameters.Fig. 1. Schematic diagram of the spherical grinding process Fig. 2. Schematic diagram of the ball-burnishing processFig. 3. Flowchart of automated surface nish using spherical grinding and ball burnishing processes2 Design of the spherical grinding tool and its alignment deviceTo carry out the possible spherical grinding process of a freeform surface, the center of the ball grinder should coincide with the z-axis of the machining center. The mounted spherical grinding tool and its adjustment device was designed, as shown in Fig. 4. The electric grinder was mounted in a tool holder with two adjustable pivot screws. The center of the grinder ball was well aligned with the help of the conic groove of the alignment components. Having aligned the grinder ball, two adjustable pivot screws were tightened; after which, the alignment components could be removed. The deviation between the center coordinates of the ball grinder and that of the shank was about 5 m, which was measured by a CNC coordinate measuring machine. The force induced by the vibration of the machine bed is absorbed by a helical spring. The manufactured spherical grinding tool and ball-burnishing tool were mounted, as shown in Fig. 5. The spindle was locked for both the spherical grinding process and the ball burnishing process by a spindle-locking mechanism.3 Planning of the matrix experiment3.1 Conguration of Taguchis orthogonal arrayThe effects of several parameters can be determined efciently by conducting matrix experiments using Taguchis orthogonal array 8. To match the aforementioned spherical grinding parameters, the abrasive material of the grinder ball (with the diameter of 10 mm), the feed rate, the depth of grinding, and the revolution of the electric grinder were selected as the four experimental factors (parameters) and designated as factor A to D (see Table 1) in this research. Three levels (settings) for each factor were congured to cover the range of interest, and were identied by the digits 1, 2, and 3. Three types of abrasive materials, namely silicon carbide (SiC), white aluminum oxide (Al2O3, WA), and pink aluminum oxide (Al2O3, PA), were selected and studied. Three numerical values of each factor were determined based on the pre-study results. The L18 orthogonal array was selected to conduct the matrix experiment for four 3-level factors of the spherical grinding process.Fig. 4. Schematic illustration of the spherical grinding tool and its adjustment deviceFig. 5. a Photo of the spherical grinding tool b Photo of the ball burnishing tool3.2 Denition of the data analysisEngineering design problems can be divided into smaller-the-better types, nominal-the-best types, larger-the-better types, signed-target types, among others 8. The signal-to-noise (S/N) ratio is used as the objective function for optimizing a product or process design. The surface roughness value of the ground surface via an adequate combination of grinding parameters should be smaller than that of the original surface. Consequently, the spherical grinding process is an example of a smaller-the-better type problem. The S/N ratio, is dened by the following equation 8: =10 log （mean square quality characteristic)=10 logwhere:yi: observations of the quality characteristic under different noise conditionsn: number of experimentAfter the S/N ratio from the experimental data of each L18 orthogonal array is calculated, the main effect of each factor was determined by using an analysis of variance (ANOVA) technique and an F-ratio test 8. The optimization strategy of the smaller-the better problem is to maximize , as dened by Eq. 1. Levels that maximize will be selected for the factors that have a signicant effect on. The optimal conditions for spherical grinding can then be determined.Table 1. The experimental factors and their levels4 Experimental work and resultsThe material used in this study was PDS5 tool steel (equivalent to AISI P20) 9, which is commonly used for the molds of large plastic injection products in the eld of automobile components and domestic appliances. The hardness of this material is about HRC33 (HS46) 9. One specic advantage of this material is that after machining, the mold can be directly used for further nishing processes without heat treatment due to its special pre-treatment. The specimens were designed and manufactured so that they could be mounted on a dynamometer to measure the reaction force. The PDS5 specimen was roughly machined and then mounted on the dynamometer to carry out the ne milling on a three-axis machining center made by YangIron Company (type MV-3A), equipped with a FUNUC Company NC-controller (type 0M) 10. The pre-machined surface roughness was measured, using Hommelwerke T4000 equipment, to be about 1.6 m. Figure 6 shows the experimental set-up of the spherical grinding process. A MP10 touch-trigger probe made by the Renishaw Company was also integrated with the machining center tool magazine to measure and determine the coordinated origin of the specimen to be ground. The NCcodes needed for the ball-burnishing path were generated by PowerMILL CAM software. These codes can be transmitted to the CNC controller of the machining center via RS232 serial inter
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