【外翻原文】Moldflow Software in a Complex Plastic Shell Injection Mold Design.pdf

1、 Moldflow software in a complex plastic shell injection mold design Zhenyu ZHAO1, a, Long LIAO1, b, Fei TANG1, c, Bai LIU1, d 1Shenzhen Institute of Information Technology, Shenzhen, China , , , Keywords: Injection mold, Moldflow, mold design, MPI Abstract. The paper describes the important role of

2、Moldflow technology and status. Through the application of Moldflow / MPI (Moldflow Plastics Insight) software for CAE under a comprehensive analysis of the shell molds, injection molding parameters such as mold temperature, melt temperature, injection time and injection pressure are used to simulat

3、e the actual production process. This shows the Moldflow technology plays a significant role in the mold development process for optimizing plastic products design, plastic mold design and injection process parameters, etc. Introduction At present, most injection mold designers are based mainly on t

4、heir years of experience in mold design. Due to the diversity, complexity of plastic workpieces and the limited experience of designers, it is difficult to accurately design a low-cost, short cycle, good quality products, qualified high rate of mold and craft programs, and designers often requires r

5、epeated continuously in order to tryout with the revised model formally put into production, some beyond repair due to the precision die scrap. Moldflow technology1 has a great advantage to improving productivity, ensure product quality, or reduce costs, reduce labor intensity and so on. Moldflow te

6、chnology can be used in mold processing prior to use computers to simulate the entire injection molding process analysis, to predict the melt filling, packing, air traps, weld lines, temperature at flow front and warpage, etc. 2-6, so that designers can early detection of problems, revise plastic pa

7、rts and mold design, reduce and even avoid mold rework scrap, improve quality and reduce the cost of plastic parts and so on. Moldflow technology has significant technical and economic significance. In the paper, a plastic shell injection mold is selected as an flow analysis example, Moldflow softwa

8、re to optimize the design of molds for plastic injection products, mold filling, cooling, warpage and other behavior of the dynamic simulation for the products, mold design and determination of injection molding process parameters provides a theoretical basis in order to improve the quality of moldi

9、ng products. Molding process analysis The product for the plastic shell parts is shown in Fig.1, using ABS plastic, and the outer surface has the higher quality requirements. In the paper, MPI module is used to process the product flow analysis. In the analysis, through the process flow simulation a

10、nalysis is determined the gate location, quantity and process conditions, and the process flow simulation is predicted the cavity pressure distribution, temperature distribution, clamping force size, etc., for the actual molding to provide molding process parameters. After completing the above analy

11、sis, the injection molding material is selected. In the software, there are many large companies of products to choose from. In the case material select ABS type, Parameter setting is in Tab.1. Tab.1 Moldflow analysis parameter settings injection molding temperature 230 Forming control Filling contr

12、ol Pressure 90MPa Mold temperature Punch 55 speed/ pressure conversion automatic Die 80 packing pressure control 80% injection pressure 6s Applied Mechanics and Materials Vols. 29-32 (2010) pp 646-650 Online available since 2010/Aug/13 at (2010) Trans Tech Publications, Switzerland doi:10.4028/ All

13、rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, . (ID: 58.17.52.14, The University of Manchester, Manchester, United Kingdom-11/01/14,03:19:49) MPI will automatically generate the best gate locatio

14、n of relevant information and to graphically display the best gate region, the deeper the color the more suitable area selected as a gate. According to Fig.1 the plastic model shows a symmetrical structure, and the best location is the middle region in the paper. Fig.1 plastic shell model Fig.2 Fill

15、 time Moldflow analysis In the paper MPI software is used to analysis the fill time and filling pressure, weld lines, air traps, maximum clamping force and warpage. Through the analysis of these parameters, the best injection programs are selected. Fill time. Gating system design directly affects th

16、e melt filling behavior, while the filling analysis of their ultimate goal is to get the best gating system design. Fill analysis is from the beginning to the cavity that is filled with injection of the entire process of analysis of the flow front location. The analysis used to predict the filling b

17、ehavior of workpiece is reasonable, whether the balance of filling, whether to complete the whole workpiece fill. Filling the purpose of the analysis is to obtain the best gate location, gate number and the best casting system layout. Fig.2 shows the results of the analysis of filling time. Through

18、the different shades of color, the change of state as well as the melt flow during filling is reflected, from which can see whether the cavity is filled, and whether the process of filling is balance. As can be see from Fig.2, Filling time is 2.825s, and the color shade is softer transition. The ind

19、icates that the filling process is relatively flat, and that the entire injection molded parts can be filled within a short period of time, liquidity balance of good and filling and reasonable situation. Thus the analysis can be proved that gating system design shown in Figure 2 is feasible. Air tra

20、ps. The circle shown in Fig.3 is air trap. Air trap location map is shown in the figure. Melt front bubbles gathered in injection parts within or cavity surface are basically around the lateral side of the injection parts, and concentrated in the parting surface. In the case air traps mainly in the

21、inner surface of plastic shell, and most appear in the parting surface, as shown in Fig.3. So air in the melt filling will automatically discharge, the air traps does not affect the appearance of the quality of the product. Therefore, the case of gas very easily through the mold parting surface gap

22、discharge, there is no trapped air phenomenon, which can effectively prevent the formation of air traps injection molded parts, and scorch the surface defects such as defective. Fig.3 Air traps Fig.4 Weld lines Applied Mechanics and Materials Vols. 29-32647 Weld lines. When two or more of the flow f

23、ront integration, it will form a weld line. In the weld-line position the molecules are tend to change strongly, so that the mechanical strength significantly weakened in the position, and weld line is not visually obvious. In this case, increasing the mold temperature and melt temperature make two

24、melt encounters merge better. It is advisable to increase the screw speed or improve the design of gating system to reduce the friction generated heat, while maintaining melt flow rate to reduce flow channel dimensions. If weld lines can not eliminated, then they should be located the place that it

25、is less sensitive on the workpiece area to prevent the impact of the mechanical properties and appearance of workpiece quality. By changing the gate location, or to change the workpiece thickness can change the location of weld lines. The weld lines position is shown on the plastic pieces in Fig.4.

26、After a Moldflow optimization analysis, improving the die temperature, increasing adequate the gate and reducing appropriately clamping force, opening of the exhaust system in the welding seam, the product weld lines will become Obvious, reduced scrap rates, to meet actual production needs. The resu

27、lts from Fig.4 can be seen that there is no large area and continuous weld lines, so workpiece surface quality will not be affected. Sink index. Shrinkage lines refer to the phenomenon of surface depressions in the moldings. Although these depressions are small, but as long as viewing from different

28、 angles, but it is visible. Shrinkage lines visibility and its surface texture is the role of the color components, so deep is the distinguishing criteria. The main reason of lines appearance is that in the cooling process heat is contracted. Figure 5 shows the depth of shrinkage lines. In the case

29、lines depth is very small, shrink lines very clearly does not affect the products appearance. Fig.5 Sink index Fig.6 Clamp force Clamp force. In the injection process, due to expansion force of melt within the mold, mold parting surface may separate, resulting in the flying side, it is necessary for

30、 the injection mold machine to provide a locking force, and the force known as the clamping force. With the force can offset the cavity expansion force generated by melt. Usually clamp force should be as small as possible. The smaller clamping force can not only save energy, reduce costs, but also t

31、o extend the service life of injection molding machines and mold, while the mold is also an exhaust can be carried out smoothly, so that the mold filling state is more easily controlled. In injection molding the clamping force distribution is shown in Fig.6. The maximum clamping force is 86kN, the r

32、esults of the analysis can be used to help designers to choose different types of injection molding machine. As can be seen from Fig.5, the machinery can meet the requirements and is capable of normal production. Recommended ram speed. Fig.7 is the recommended ram of the program graph, and its role

33、in the regulation of ram into the cavity of the injection speed, speed of injection mold filling process to ensure consistent, will help to improve the surface quality of workpieces and to avoid excessive shear stress. The injection speed is recommended to make a more uniform rate of flow front, whi

34、ch will help to eliminate the pressure peak, and at the same time can improve workpiece surface finish in Fig.7. XY position by injection pressure map can easily show the changes in pressure. Temperature. Temperature mainly includes temperature at flow front and bulk temperature at the end of fillin

35、g. The integrated use of temperature at flow front and the weld line graph can be analyzed 648Applied Mechanics And Mechanical Engineering whether weld-line quality is good or bad. The narrower the size range of temperature distribution is at the end of filling, the better mold quality is. Two kinds

36、 of thermal analysis results are shown in Fig.8 and Fig.9. Thermoplastic polymer flow analysis is usually used to predict the flow behavior inside the die. Moldflow simulation begins to melt from the injection site spread to the adjacent point of the flow front, until the flow front to spread and fi

37、ll workpiece and the last point to complete the flow analysis and calculation. The objective is to obtain the best packing stage set time, thereby reducing as much as possible cause of the workpiece by the holding pressure contraction, warping and other quality defects. A reasonable temperature dist

38、ribution at flow front should be uniform, and the model can not be much difference in temperature. As can be seen from Fig.8, the model is more uniform temperature distribution model shows that the melt temperature in the flow of slow decline, which will help fill, and a smaller drop in the temperat

39、ure of the product, which means that the surface quality of plastic parts will be guaranteed. Figure 8 Simulation results for the flow front temperature. As can be seen from Fig.8, material flow analysis can be seen that the maximum temperature the forefront is 230.6 , the lowest temperature is 223.

40、8 , injection molded parts of the temperature difference is 6.8 , the recommended values of the control value (20 ) within indicated that a smaller temperature difference, which means the quality of the surface of injection molded parts are guaranteed, workpieces can be filled.Fig.8 shows that when

41、the material fusion temperature is 228.9 230.6 , the lowest melt temperature is only lower than the injection temperature of 223.8 . So materials can be a very good fusion, and does not appear Weld. Cavitations are seen in the fusion line and parting surface, and exhaust ducts are set at the opening

42、 of weld line. This is not only convenient to exhaust, but also increase the fusion line of fastness. From the Fig.8 flow front temperature graph and Fig.4 weld line graph, we can see the formation of weld lines when the melt temperature is about 230 . The weld line is not obvious, and the results a

43、re best. Bulk temperature has reflected the shear heat produced inside the workpiece. If the workpiece has a strong shear within the role, workpiece temperature will rise. In the mold filling stage, the volume can be seen from Fig.9 that the temperature diagram (speed-weighted average temperature) s

44、hould be very uniform. The minimum temperature is 177.3 C, and the maximum temperature is 234.3 C. The changes meet the bulk temperature controlled range. Fig.7 Recommended ram speed Fig.8 Temperature at flow front Fig.9 Bulk temperature Fig.10 Pressure at the end of filling Applied Mechanics and Ma

45、terials Vols. 29-32649 Pressure. As can be seen from Fig.10, the pressure distribution is obtained at the end of filling, and analysis of filling pressure distribution is balanced. In the final filling pressure on the lower part of the blue, the entire plastic pressure difference is below 35MPa. Vol

46、ume / pressure conversion data and filling pressure data at the end of filling mold are the same effect. Usually, the volume and pressure conversion throughout the injection molding cycle is the highest. At this time the size and distribution of pressure through the pressure profile can be observed,

47、 and workpiece fill basically reach 100% at the conversion. As can be seen from Fig.11, the largest injection pressure is 53.37MPa in molding process, and it is the red in the diagram position. The grey part in the figure indicates that the workpiece 100% filled with good effect. Pressure at the inj

48、ection location. Packing process based on the filling process is simulated by optimizing the injection of reasonable force and packing pressure for production preparation. Fig.12 shows the packing process of simulation results. Injection pressure flow is also key parameters, a direct impact on mold

49、filling good or bad. As can be seen from Fig.12, the end of injection molding pressure reaches the maximum 55MPa, less than the maximum injection molding machine, packing pressure curve and set the basic line. Fig.11 Volume / pressure conversion Fig.12 Injection force and packing process Conclusion In the paper, Moldflow software through the flow behavior is used in the simulation, prediction, and display the foref