外文翻译塑料注射模具设计及其热分析.docx

1、外文翻译塑料注射模具设计及其热分析 毕业设计(论文)外文资料翻译系部： 机械工程系 专 业： 机械工程及自动化 姓 名： 学 号： (用外文写)外文出处： Manufacturing Engineering and TechnologyMachining 附 件： 1.外文资料翻译译文；2.外文原文。 指导教师评语：该外文翻译语言流畅通顺，较准确完整地翻译了原文，所翻译的文章模具设计原理及成型工艺与夹具设计原理及加工工艺设计相类似，与毕业设计课题相关联。达到了本科毕业外文翻译的要求。 签名： 年 月 日注：请将该封面与附件装订成册。附件1：外文资料翻译译文塑料注射模具设计及其热分析材料或熔融塑

2、料在同一温度同一压力下同时被送到个模腔对于流道设计来说是很重要的一点。基于这点，模腔的布局一般都是对称的。 另外，气孔的设计也是模具设计中一个重要的方面。公模板和母模板的配合表面有很高的加工精度以防止注塑时泄露的发生。但是，这会使空气被封闭在闭合模腔内从而导致短射或使零件不完整。合适起气孔设计可以使空气释放出来不会出现零件不完整的现象。 冷却系统是沿模腔长度方向在模具上打出的水平孔，只起冷却作用。在湍流情况下，水线可以充分冷却模具。图2显示了在公模板上气孔、水线以及模腔的布局。 图2 在公模板上气孔、水线以及模腔的布局 在这个设计中，脱模系统只有推杆固定板、浇口套和推板。交口套的位于公模的中心

3、，它的作用不仅是将产品固定在合适位置，在开模是还起到将产品拉出模腔的作用。因为产品非常薄，通常为1mm，所以不需要设计其附加的推杆。模腔里的推杆反而有可能在脱模的时候在零件上推出破孔。 最后，还要根据材料的收缩率留出足够的公差补偿。 图3所示的是用Unigraphics设计的模具三维模型以及线框模型。 图3 模具的三维实体模型和线框模型 3. 结果与讨论 3.1. 产品的生产及改良 模具的设计和制造完成后，试模注塑出来的翘曲试样会存在很多缺陷。包括短射、喷溅和翘曲。短射的解决可以通过在模腔的角落里铣出附加的气孔来排出被困的空气。同时，减小注射压力可以减小喷溅的发生。对于翘曲的控制可以通过控制很

4、多因素，例如注射时间、注射温度和溶料温度。 经过这些修整之后，模具可以生产出低成本高质量的翘曲试样，这些试样需要经过简单的抛光处理。图4显示的是修整后的模具，加工出附加的排气孔可避免短射现象的发生。 图4 附加气孔以避免短射 3.2. 模具及产品的详细分析 模具和试样都准备好之后，就可以对其进行分析了。在注塑的过程中，210熔融的ABS通过母模上的浇口套直接注入模腔，经过冷却，制件就成型了。制件的生产周期为35s，包括20s的冷却时间。用来制造模具的材料是AISI 1050碳钢。表2列出了ABS以及AISI 1050碳钢的性能。 表2 ABS以及AISI 1050碳钢的性能 模具，AISI 1

5、050碳钢 试样，ABS 密度 7860 kg/m3 弹性模量 208 GPa 泊松比 0.297 屈服强度 365.4MPa 抗拉强度 636MPa 热膨胀率 65106 K1 电导率 0.135 W/(m K) 比热 1250 J/(kg K) 1050 kg/m3 2.519 GPa 0.4 65MPa 11.65106 K1 49.4 W/(m K) 477 J/(kg K) 由于对称，在注塑过程中只需对公模和母模垂直截面的上半部分进行热分析。图5所示的是多层模板闭合的热分析模型。 建模包括分配各部分的性能以及模型的循环周期。这样可以用有限元分析软件用造型模拟模具模型进行分析，还可以绘

6、制时间响应曲线显示再某段时间内特定区域的温差变化。 对试样的分析可以用LUSAS分析员13.5.版本分析双向拉伸应力。一般只需在试样的一端施加拉力另一端则固定住，然后慢慢增加拉力一直到达塑性极限。图6所示的示分析的加载模型。 图5 热分析模型 图6 试样分析的加载模型 3.3. 模具及试样分析的结果及讨论 模具分析过程对不同时间段的热量分布作了观测。图7所示是在一个完整的注塑周期中不同时间段的二维等高线热量分布图。 对模具进行二维分析后，可绘制出时间响应曲线以分析残余热应力对制件的影响。图8所示是绘制时间响应曲线所选的节点。 图917所示的是图8中各节点的温度分布曲线。 图7 不同时间段的热量

7、等高线分布图 图8 在制件上为绘制时间响应曲线选择的节点 图9 节点284的温度分布曲线 从图917中的温度分布曲线可以清楚的看出每个节为曲线图选择计画翻译经历温度的增加, 也就是从那对特定的温度周围超过温度比较高的周围温度然后在这保持持续一段特定时间的温度。这些增加温度是由溶化塑料的注入产品的型腔所引起的。 在一段特定时间之后, 温度更进一步增加达成最高的温度，然后保持该温度。这里的温度增加是由于包装阶段相关的高压导致的。这个温度一直持续到冷却阶段的开始。计画翻译的曲线图不是平滑适当的到那输入溶化人的充填物率的缺少功能塑料和冷冻剂的冷却比率。绘制的曲线是不平滑的，因为注入熔融塑料的速率和冷却

8、速率是相应的。这条曲线仅反应了一个周期里可以达到的最高温度。 热残余应力的分析中最关键的阶段在冷却阶段。这是因为冷却阶段导致材料冷却从高温到玻璃态转变温度的低温。物质的不均匀收缩可能产生热应力从而引起翘曲。 图10 节点213的温度分布曲线 图11 节点302的温度分布曲线 图12 节点290的温度分布曲线 如图9-17中所示冷却阶段后的温度显示，离水线越近的地方冷却效果越好，相反则越差。冷却越快收缩也越大。虽然，节点284离水线最远，却冷却得很快，那是因为热量被释放到周围的环境中了。 图13 节点278的温度分布曲线 图14 节点1838的温度分布曲线 图15 节点1904的温度分布曲线 图

9、16 节点1853的温度分布曲线 图17 节点1866的温度分布曲线 根据以上所述，水线位于产品型腔的中心引起了中心周围的温度高于其他区域。因此，中心区域会由于受到收缩力的作用产生更大的收缩从而产生翘曲。然而, 冷却温度在不同的节点处的不同很小，翘曲效果不非常明显。设计一个有比较小的残余热应力作用和一个有效率的冷却系统的模具对于一个设计者来说是很重要的。注塑注射成型工艺是一个循环过程。可分为填料、注射、冷却、脱模四个重要阶段。塑料注射成型过程开始于往料斗到注塑机的加热或注射系统中填入树脂和适量的添加剂。灌浆阶段就是在注射温度下用融解的热塑料注入模腔。模腔被填满之后，适量的熔融塑料在一个较高的补

10、偿压力下补充塑料凝固引起的收缩。跟着是冷却阶段，将模具冷却至有足够的刚度脱出模具。最后是脱模阶段，即打开模具然后顶出零件，再合上模具开始下一个循环。 需要注塑成型的塑料产品的设计和制造与预期性能是要靠经验控制的一个昂贵的过程，包括实际对封面压花的修改。在模具设计之中，设计模具具体补充几何，通常在核心边，包括相当复杂的投射和凹槽。 对于产品分析, 从被实行开始到分析塑料产品,在产品上不同负荷因素的状态下的应力分配情况可以通过观察生成的二维曲进行线分析。 分析的时候选择了一个临界节点，即节点127，这是拉应力最大的时候。此时参考负载应力曲线如图23,它很清楚表明产品在增加拉力负荷，直到它达到了23

11、的负载因数,这意谓产品能抵抗的1150 N的拉力。由图23可知,对产品的固定端以施加最大应力3.27 107 Pa时损坏可能发生在其附近区域。 4. 结论 经过翘曲测试试样的分析确定影响翘曲的参数来设计的模具已经使产品质量达到最高。生产测试试样所需的成本很低而且只需经过很少的表面处理。 通过注塑模的热分析得出残余热应力对试样的影响，对加载拉应力的分析也可以预测到翘曲测试试样所能承受的最大拉力。 附件2：外文原文（复印件）Design and thermal analysis of plastic injection mouldIt is important that the runner de

12、signed distributes material or molten plastic into cavities at the same time under the same pressure and with the same temperature. Due to this, the cavity layout had been designed in symmetrical form. Another design aspect that is taken into consideration was air vent design. The mating surface bet

13、ween the core plate and the cavity plate has very fine finishing in order to prevent flashing from taking place. However, this can cause air to trap in the cavity when the mould is closed and cause short shot or incomplete part. Sufficient air vent was designed to ensure that air trap can be release

14、d to avoid incomplete part from occurring. The cooling system was drilled along the length of the cavities and was located horizontally to the mould to allow even cooling. These cooling channels were drilled on both cavity and core plates. The cooling channels provided sufficient cooling of the moul

15、d in the case of turbulent flow. Fig. 2 shows cavity layout with air vents and cooling channels on core plate. Fig. 2. Cavity layout with air vents and cooling channels. In this mould design, the ejection system only consists of the ejector retainer plate, sprue puller and also the ejector plate. Th

16、e sprue puller located at the center of core plate not only functions as the puller to hold the product in position when the mould is opened but it also acts as ejector to push the product out of the mould during ejection stage. No additional ejector is used or located at product cavities because th

17、e product produced is very thin, i.e. 1 mm. Additional ejector in the product cavity area might create hole and damage to the product during ejection. Finally, enough tolerance of dimensions is given consideration to compensate for shrinkage of materials. Fig. 3 shows 3D solid modeling as well as th

18、e wire frame modeling of the mould developed using Unigraphics. Fig. 3. 3D solid modeling and wireframe modeling of the mould. 3. Results and discussion 3.1. Results of product production and modification From the mould designed and fabricated, the warpage testing specimens produced have some defect

19、s during trial run. The defects are short shot, flashing and warpage. The short shot is subsequently eliminated by milling of additional air vents at corners of the cavities to allow air trapped to escape. Meanwhile, flashing was reduced by reducing the packing pressure of the machine. Warpage can b

20、e controlled by controlling various parameters such as the injection time, injection temperature and melting temperature. After these modifications, the mould produced high quality warpage testing specimen with low cost and required little finishing by de-gating. Fig. 4 shows modifications of the mo

21、uld, which is machining of extra air vents that can eliminate short shot. Fig. 4. Extra air vents to avoid short shot. 3.2. Detail analysis of mould and product After the mould and products were developed, the analysis of mould and the product was carried out. In the plastic injection moulding proce

22、ss, molten ABS at 210 C is injected into the mould through the sprue bushing on the cavity plate and directed into the product cavity. After cooling takes place, the product is formed. One cycle of the product takes about 35 s including 20 s of cooling time. The material used for producing warpage t

23、esting specimen was ABS and the injection temperature, time and pressure were 210 C, 3 s and 60MPa respectively. The material selected for the mould was AISI 1050 carbon steel. Properties of these materials were important in determining temperature distribution in the mould carried out using finite

24、element analysis. Table 2 shows the properties for ABS and AISI 1050 carbon steel. Table 2 Material properties for mould and product The critical part of analysis for mould is on the cavity and core plate because these are the place where the product is formed. Therefore, thermal analysis to study t

25、he temperature distribution and temperature at through different times are performed using commercial finite element analysis software called LUSAS Analyst, Version 13.5. A two-dimensional (2D) thermal analysis is carried out for to study the effect of thermal residual stress on the mould at differe

26、nt regions. Due to symmetry, the thermal analysis was performed by modeling only the top half of the vertical cross section or side view of both the cavity and core plate that were clamped together during injection. Fig. 5 shows the model of thermal analysis analyzed with irregular meshing. Modeling

27、 for the model also involves assigning properties and process or cycle time to the model. This allowed the finite element solver to analyze the mould modeled and plot time response graphs to show temperature variation over a certain duration and at different regions. For the product analysis, a two

28、dimensional tensile stress analysis was carried using LUSAS Analyst, Version 13.5. Basically the product was loaded in tension on one end while the other end is clamped. Load increments were applied until the model reaches plasticity. Fig. 6 shows loaded model of the analysis. Fig. 5. Model for ther

29、mal analysis. Fig. 6. Loaded model for analysis of product. 3.3. Result and discussion for mould and product analysis For mould analysis, the thermal distribution at different time intervals was observed. Fig. 7 shows the 2D analysis contour plots of thermal or heat distribution at different timeint

30、ervals in one complete cycle of plastic injection molding. Fig. 7. Contour plots of heat distribution at different time intervals. For the 2D analysis of the mould, time response graphs are plotted to analyze the effect of thermal residual stress on the products. Fig. 8 shows nodes selected for plot

31、ting time response graphs. Figs. 917 show temperature distribution curves for different nodes as indicated in Fig. 8. From the temperature distribution graphs plotted in Figs. 917, it is clear that every node selected for the graph plotted experiencing increased in temperature, i.e. from the ambient

32、 temperature to a certain temperature higher than the ambient temperature and then remained constant at this temperature for a certain period of time. This increase in temperature was caused by the injection of molten plastic into the cavity of the product. After a certain period of time, the temperature is then further increased to achieve the highest temperature and remained constant at tha