外文翻译Concurrent Design of Plastics Injection Moulds_图文

1、Concurrent Design of Plastics Injection MouldsAbstractThe plastic product manufacturing industry has been growing rapidly in recent years. One of the most popular processes for making plastic parts is injection moulding. The design of injection mould is critically important to product quality and ef

2、ficient product processing. Mould-making companies, who wish to maintain the competitive edge, desire to shorten both design and manufacturing leading times of the by applying a systematic mould design process.The mould industry is an important support industry during the product development process

3、, serving as an important link between the product designer and manufacturer. Product development has changed from the traditional serial process of design, followed by manufacture, to a more organized concurrent process where design and manufacture are considered at a very early stage of design. Th

4、e concept of concurrent engineering (CE is no longer new and yet it is still applicable and relevant in todays manuf acturing environment. Team working spirit, management involvement, total design process and integration of IT tools are still the essence of CE. The application of The CE process to t

5、he design of an injection process involves the simultaneous consideration of plastic part design, mould design and injection moulding machine selection, production scheduling and cost as early as possible in the design stage.This paper presents the basic structure of an injection mould design. The b

6、asis of this system arises from an analysis of the injection mould design process for mould design companies. This injection mould design system covers both the mould design process and mould knowledge management. Finally the principle of concurrent engineering process is outlined and then its princ

7、iple is applied to the design of a plastic injection mould.Keywords : Plastic injection mould design, Concurrent engineering, Computer aidedengineering, Moulding conditions, Plastic injection moulding, Flow simulation1.IntroductionInjection moulds are always expensive to make, unfortunately without

8、a mould it can not be possible ho have a moulded product. Every mould maker has his/her own approach to design a mould and there are many different ways of designing and building a mould. Surely one of the most critical parameters to be considered in the design stage of the mould is the number of ca

9、vities, methods of injection, types of runners, methods of gating, methods of ejection, capacity and features of the injection moulding machines. Mould cost, mould quality and cost of mould product are inseparableIn todays completive environment, computer aided mould filling simulation packages can

10、accurately predict the fill patterns of any part. This allows for quick simulations of gate placements and helps finding the optimal location. Engineers can perform moulding trials on the computer before the part design is completed. Process engineers can systematically predict a design and process

11、window, and can obtain information about the cumulative effect of the process variables that influence part performance, cost, and appearance.2.Injection MouldingInjection moulding is one of the most effective ways to bring out the best in plastics. It is universally used to make complex, finished p

12、arts, often in a single step, economically, precisely and with little waste. Mass production of plastic parts mostly utilizes moulds. The manufacturing process and involving moulds must be designed after passing through the appearance evaluation and the structure optimization of the product design.

13、Designers face a huge number of options when they create injection-moulded components. Concurrent engineering requires an engineer to consider the manufacturing process of the designed product in the development phase. A good design of the product is unable to go to the market if its manufacturing p

14、rocess is impossible or too expensive. Integration of processsimulation, rapid prototyping and manufacturing can reduce the risk associated with moving from CAD to CAM and further enhance the validity of the product development.The plastics industry is one of the world's fastest growing industry

15、, belongs to a small number of hundreds of millions of dollars in industry. Almost all the supplies in their daily lives are inseparable from the plastic and most can use plastic injection mold production. Injection molding injection molding process to take advantage of low-cost production of a vari

16、ety of shapes and complex geometric patterns known . Injection molding injection molding process is a cyclic process. Can be divided into four key stages of packing, injection, cooling, demoulding. Plastic injection molding process begins to fill in the resin and the amount of additives to the hoppe

17、r into the heating of the injection molding machine or injection system. Grain filling stage in injection temperature, the hot plastic melt into the mold cavity. The cavity is filled, the amount of molten plastic in the plastic solidification shrinkage caused by a higher compensation under the press

18、ure of added. Followed by a cooling phase, the mold was cooled to a sufficient rigidity extrusion mold. Finally, the stripping stage, that is, open the mold and then the top part, and then together on the mold start the next cycle.The design and manufacture of injection molded plastic products with

19、the expected performance is to rely on the experience of control of an expensive process, including the actual modification of the cover embossed. In mold design, design mold supplementary geometry, usually in the side of the core, including the complex projection and groove.Mold design must take in

20、to account many important design factor. These factors are the number and layout of the size of the mold cavity, runner system, gate systems, mold release systems, and shrinkage.Thermal analysis of the mold, the main objective is to analyze the role of the residual thermal stress or pressure injecti

21、on of product diameter direction. Heat flux density enhancements in the cooling phase of the molded parts, mainly because of its low thermal conductivity and the temperature difference between the melting resin and mold. During cooling near the mold cavity will be non-uniform temperature region.Duri

22、ng cooling, coolingchannels near the area than the area far from the cooling channels to cool faster. This temperature difference will cause uneven shrinkage of the material to heat stress. The strong thermal stresses can cause warping problem. Therefore, it is an imitation of the important stage in

23、 the molded parts during the cooling area of the thermal residual stress. Understand the characteristics of the thermal stress, causing deformation of pre-simulation.In this article, the injection mold is designed to produce warping of test samples and perform the thermal analysis presented in the m

24、old on the role of the residual thermal stress. After the completion of the mold design and manufacture of, tryout injection warp specimens there are many defects. Including a short shot, splash and warping. The solution of a short shot by milling out the additional pores to drain the trapped air in

25、 the corner of the cavity. At the same time, reducing the injection pressure can reduce the occurrence of splashing. Warpage control can be controlled by many factors, such as injection time, injection temperature and dissolved material temperature.After these trimming, mold can produce low-cost hig

26、h-quality warp specimens, these specimens need to go through a simple polishing.3.Importance of Computer Aided Injection Mould DesignThe injection moulding design task can be highly complex. Computer Aided Engineering (CAE analysis tools provide enormous advantages of enabling design engineers to co

27、nsider virtually and part, mould and injection parameters without the real use of any manufacturing and time. The possibility of trying alternative designs or concepts on the computer screen gives the engineers the opportunity to eliminate potential problems before beginning the real production. Mor

28、eover, in virtual environment, designers can quickly and easily asses the sensitivity of specific moulding parameters on the quality and manufacturability of the final product. All theseCAE tools enable all these analysis to be completed in a meter of days or even hours, rather than weeks or months

29、needed for the real experimental trial and error cycles. As CAE is used in the early design of part, mould and moulding parameters, the cost savings are substantial not only because of best functioning part and timesavings but also the shortens the time needed to launch the product to the market.The

30、 need to meet set tolerances of plastic part ties in to all aspects of the moulding process, including part size and shape, resin chemical structure, the fillers used, mould cavity layout, gating, mould cooling and the release mechanisms used. Given this complexity, designers often use computer desi

31、gn tools, such as finite element analysis (FEA and mould filling analysis (MFA, to reduce development time and cost. FEA determines strain, stress and deflection in a part by dividing the structure into small elements where these parameters can be well defined. MFA evaluates gate position and size t

32、o optimize resin flow. It also defines placement of weld lines, areas of excessive stress, and how wall and rib thickness affect flow. Other finite element design tools include mould cooling analysis for temperature distribution, and cycle time and shrinkage analysis for dimensional control and pred

33、iction of frozen stress and warpage.The CAE analysis of compression moulded parts is shown in Figure 1. The analysis cycle starts with the creation of a CAD model and a finite element mesh of the mould cavity. After the injection conditions are specified, mould filling, fiber orientation, curing and

34、 thermal history, shrinkage and warpage can be simulated. The material properties calculated by the simulation can be used to model the structural behaviour of the part. If required, part design, gate location and processing conditions can be modified in the computer until an acceptable part is obta

35、ined. After the analysis is finished an optimized part can be produced with reduced weldline (known also knitline, optimized strength, controlled temperatures and curing, minimized shrinkage and warpage.Machining of the moulds was formerly done manually, with a toolmaker checking each cut. This proc

36、ess became more automated with the growth and widespread use of computer numerically controlled or CNC machining centres. Setup time has also been significantly reduced through the use of special software capable of generating cutter paths directly from a CAD data file. Spindle speeds as high as 100

37、,000 rpm provide further advances in high speed machining. Cutting materialshave demonstrated phenomenal performance without the use of any cutting/coolant fluid whatsoever. As a result, the process of machining complex cores and cavities has been accelerated.It is good news that the time it takes t

38、o generate a mould is constantly being reduced. The bad news, on the other hand, is that even with all these advances, designing and manufacturing of the mould can still take a long time and can be extremely expensive. Figure 1 CAE analysis of injection moulded partsMany company executives now reali

39、ze how vital it is to deploy new products to market rapidly. New products are the key to corporate prosperity. They drive corporate revenues, market shares, bottom lines and share prices. A company able to launch good quality products with reasonable prices ahead of their competition not only realiz

40、es 100% of the market before rival products arrive but also tends tomaintain a dominant position for a few years even after competitive products have finally been announced (Smith, 1991. For most products, these two advantages are dramatic. Rapid product development is now a key aspect of competitiv

41、e success. Figure 2 shows that only 37% of the product mix from the average industrial or electronics company is less than 5 years old. For companies in the top quartile, the number increases to 1525%. For world-class firms, it is 6080% (Thompson, 1996. The best companies continuously develop new pr

42、oducts. AtHewlett-Packard, over 80% of the profits result from products less than 2 years old! (Neel, 1997 Figure 2. Importance of new product (Jacobs, 2000 With the advances in computer technology and artificial intelligence, efforts have been directed to reduce the cost and lead time in the design

43、 and manufacture of an injection mould. Injection mould design has been the main area of interest since it is a complex process involving several sub-designs related to various components of the mould, each requiring expert knowledge and experience. Lee et. al. (1997 proposed a systematic methodolog

44、y and knowledge base for injection mould design in a concurrent engineering environment.4.Concurrent Engineering in Mould DesignConcurrent Engineering (CE is a systematic approach to integrated product development process. It represents team values of co-operation, trust and sharing in such a manner

45、 that decision making is by consensus, involving all per spectives in parallel, from the very beginning of the product life-cycle (Evans, 1998. Essentially, CE provides a collaborative, co-operative, collective and simultaneous engineering working environment. A concurrent engineering approach is ba

46、sed on five key elements:1. process2. multidisciplinary team3. integrated design model4. facility5. software infrastructure Figure 3 Methodologies in plastic injection mould design, a Serial engineering b Concurrent engineeringIn the plastics and mould industry, CE is very important due to the high

47、cost tooling and long lead times. Typically, CE is utilized by manufacturing prototype tooling early in the design phase to analyze and adjust the design. Production tooling is manufactured as the final step. The manufacturing process and involving moulds must be designed after passing through the a

48、ppearance evaluation and the structure optimization of the product design. CE requires an engineer to consider the manufacturing process of the designed product in the development phase. A good design of the product is unable to go to the market if its manufacturing process is impossible. Integratio

49、n of process simulation and rapid prototyping and manufacturing can reduce the risk associated with moving from CAD to CAM and further enhance the validity of the product development.For years, designers have been restricted in what they can produce as they generally have to design for manufacture (

50、DFM that is, adjust their design intent to enable the component (or assembly to be manufactured using a particular process or processes. In addition, if a mould is used to produce an item, there are therefore automatically inherent restrictions to the design imposed at the very beginning. Taking inj

51、ection moulding as an example, in order to process a component successfully, at a minimum, the following design elements need to be taken into account:1. . geometry;. draft angles,. Non re-entrants shapes,. near constant wall thickness,. complexity,. split line location, and. surface finish,2. mater

52、ial choice;3. rationalisation of components (reducing assemblies;4. cost.In injection moulding, the manufacture of the mould to produce theinjection-moulded components is usually the longest part of the product development process. When utilising rapid modelling, the CAD takes the longer time and th

53、erefore becomes the bottleneck.The process design and injection moulding of plastics involves rather complicated and time consuming activities including part design, mould design, injection moulding machine selection, production scheduling, tooling and cost estimation. Traditionally all these activi

54、ties are done by part designers and mould making personnel in a sequential manner after completing injection moulded plastic part design. Obviously these sequential stages could lead to long product development time. However with the implementation of concurrent engineering process in the all parame

55、ters effecting product design, mould design, machine selection, production scheduling, tooling and processing cost are considered as early as possible in the design of the plastic part.When used effectively, CAE methods provide enormous cost and time savings for the part design and manufacturing. Th

56、ese tools allow engineers to virtually test how the part will be processed and how it performs during its normal operating life. The material supplier, designer, moulder and manufacturer should apply these tools concurrently early in the design stage of the plastic parts in order to exploit the cost

57、 benefit of CAE. CAE makes it possible to replace traditional, sequentialdecision-making procedures with a concurrent design process, in which all parties can interact and share information, Figure 3. For plastic injection moulding, CAE and related design data provide an integrated environment that

58、facilitates concurrent engineering for the design and manufacture of the part and mould, as well as material selection and simulation of optimal process control parameters.Qualitative expense comparison associated with the part design changes is shownin Figure 4 , showing the fact that when design c

59、hanges are done at an early stages on the computer screen, the cost associated with is an order of 10.000 times lower than that if the part is in production. These modifications in plastic parts could arise fr om mould modifications, such as gate location, thickness changes, production delays, quality costs, machine setup times, or design change in plastic parts. Figure 4 Cost of design changes during part product development cycle (Rios et.al, 2001 At the early design stage, part d