180型復(fù)合管鏈條式脫模機的設(shè)計【含4張CAD圖帶開題報告+外文翻譯-獨家】.zip
180型復(fù)合管鏈條式脫模機的設(shè)計【含4張CAD圖帶開題報告+外文翻譯-獨家】.zip,含4張CAD圖帶開題報告+外文翻譯-獨家,180,復(fù)合管,鏈條,脫模,設(shè)計,CAD,開題,報告,外文,翻譯,獨家
資料來源：
文章名：Design and thermal analysis of plastic injection mould
書刊名：《Journal of Materials Processing Technology 171 (2006)》
作 者：S.H.Tang?,Y.M.Kong,
頁 碼：P2~P6
文 章 譯 名： 塑料注射模設(shè)計與熱分析
Abstract
This paper presents the design of a plastic injection mould for producing warpage testing specimen and performing thermal analysis for the mould to accesson the effect of thermal residual stress in the mould. The technique, theory, methods as well as consideration needed in designing of plastic injection mould are presented. Design of mould was carried out using commercial computer aided design software Unigraphics, Version13.0. The model for thermal residual stress analysis due to uneven cooling of the specimen was developed and solved using a commercial ?nite element analysis software called LUSASAnalyst, Version13.5. The software provides contour plot of temperature distribution for the model and also temperature variation through the plastic injection molding cycle by plotting time response curves. The results show that shrinkage is likely to occur in the region near the cooling channels as compared to other regions. This uneven cooling effect at different regions of mould contributed to warpage.
Introduction:
The plastic industry is one of the fastest growing industries in the world and is listed as an industry with a number of billions of dollars. Almost every product used in daily life involves the use of plastic, most of which can be produced by injection molding . The injection molding process is known for its manufacturing process as a product that produces various forms and complex geometries at a lower cost . Injection molding process is a cycle process, the whole process is divided into four important stages, that is, mold filling, pressure protection, cooling and injection. In the injection molding process, the resin and appropriate additives are injected into the injection molding machine from the funnel to the heating / injection system of the injection molding machine . This is the "mold filling stage" in which the mold cavity fills the hot polymer melt that reaches the injection temperature. During the "packing stage" after mold cavity filling, more polymer melt is loaded into the cavity at higher pressure to compensate for the anticipated shrinkage due to polymer curing. The next is the cooling stage, in which the mold will cool down until enough rigid parts are popped out. The last stage is the ejection stage. At this stage, the mold is opened and the molding part is ejected. After that, the mold will be closed again and start the next cycle . Because the experience is mainly based on experience, including the repeated modification of the actual tools, so the process of designing and manufacturing the injection molded polymer components with high performance is very expensive. In the mold design task, due to the factors of injection and air pressure, usually, the special geometric structure in the core area for mold design is quite complicated.
in order to design a mold, many important design factors must be taken into consideration. These factors are the size of the mold, the number and layout of the cavity, the heat flow system, the gate control system, the contraction and ejection system . In the thermal analysis of the mold, the main purpose is to analyze the effect of thermal residual stress or mould pressure on the size of the product. The thermal induced stress mainly occurs in the cooling stage of the injection molding parts, mainly due to the lower thermal conductivity and the temperature difference between the melt resin and the mold. The temperature of the cavity of the product in the process of cooling is unbalanced . In the cooling process, the closer to the cooling channel, the cooler can be cooled to a greater degree. The difference in temperature causes the hetero - contraction of the material, which leads to the thermal stress. Obvious thermal stress may cause deformation problems. Therefore, it is very important to simulate the thermal residual stress field in the cooling stage of the injection molding process. By understanding the distribution of the thermal residual stress, we can predict the deformation caused by the thermal residual stress. In this paper, an injection mold design is put forward for the production warpage test sample design: it can achieve the thermal analysis of the mold to achieve the effect of thermal residual stress on it.
Methodology：
2.1. Design of warpage testing specimen
This section illustrates the design of the warpage testing specimen to be used in plastic injection mould. It is clear that warpage is the main problem that exists in product with thin shell feature. Therefore, the main purpose of the product development is to design a plastic part for determining the effective factors in the warpage problem of an injectionmoulded part with a thin shell.
The warpage testing specimen is developed from thin shell plastics. The overall dimensions of the specimen were 120mmin length, 50mmin width and 1mmin thickness. The material used for producing the warpage testing specimen was acrylonitrile butadiene stylene (ABS) and the injection temperature, time and pressure were 210 ?C, 3 s and 60MPa, respectively. Fig. 1 shows the warpage testing specimen produced.
2.2. Design of plastic injection mould for warpage testing specimen
This section describes the design aspects and other considerations involved in designing the mould to produce warpage testing specimen. The material used for producing the plastic injection mould for warpage testing specimen was AISI 1050 carbon steel.
Fig. 1. Warpage testing specimen produced.
Four design concepts had been considered in designing of the mould including:
i. Three-plate mould (Concept 1) having two parting line with single cavity. Not applicable due to high cost.
ii. Two-plate mould (Concept 2) having one parting line with single cavity without gating system. Not applicable due to low production quantity per injection.
iii. Two-plate mould (Concept 3) having one parting line with double cavities with gating and ejection system. Not applicable as ejector pins might damage the product as the product is too thin.
iv. Two-plate mould (Concept 4) having one parting line with double cavities with gating system, only used sprue puller act as ejector to avoid product damage during ejection.
In designing of the mould for the warpage testing specimen, the fourth design concept had been applied. Various design considerations had been applied in the design.
Firstly, the mouldwas designed based on the platen dimension of the plastic injection machine used (BOY 22D). There is a limitation of the machine, which is the maximum area of machine platen is given by the distance between two tie bars. The distance between tie bars of the machine is 254 mm. Therefore, the maximum width of the mould plate should not exceed this distance. Furthermore, 4mm space had been reserved between the two tie bars and the mould for mould setting-up and handling purposes. This gives the final maximum width of the mould as 250 mm. The standard mould base with 250mm×250mmis employed. The mould base is fitted to the machine using Matex clamp at the upper right and lower left corner of the mould base or mould platen. Dimensions of other related mould plates are shown in Table 1.
Table 1：
Based on the dimensions provided by standard mould set, the width and the height of the core plate are 200 and 250 mm, respectively. These dimensions enabled design of two cavities on core plate to be placed horizontally as there is enough space while the cavity plate is left empty and it is only fixed with sprue bushing for the purpose of feeding molten plastics. Therefore, it is only one standard parting line was designed at the surface of the product. The product and the runner were released in a plane through the parting line during mould opening.
Standard or side gate was designed for this mould. The gate is located between the runner and the product. The bottom land of the gate was designed to have 20? slanting and has only 0.5mm thickness for easy de-gating purpose. The gate was also designed to have 4mm width and 0.5mm thickness for the entrance of molten plastic.
In the mould design, the parabolic cross section type of runner was selected as it has the advantage of simpler machining in one mould half only, which is the core plate in this case. However, this type of runner has disadvantages such as more heat loss and scrap compared with circular cross section type. This might cause the molten plastic to solidify faster.
This problem was reduced by designing in such a way that the
runner is short and has larger diameter, which is 6mm in diameter.
It is important that the runner designed 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 between 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 released 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 mould 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. The 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 the 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 the wire frame modeling of the mould developed using Unigraphics.
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 defects 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 be controlled by controlling various parameters such as the injection time, injection temperature and melting temperature.
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 process, 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 testing 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 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 the 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 different regions.
Modeling 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 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.
As a result, the cooling channel located at the center of the product cavity caused the temperature difference around the middle of the part higher than other locations. Compressive stress was developed at the middle area of the part due to more shrinkage and caused warpage due to uneven shrinkage that happened. However, the temperature differences after cooling for different nodes are small and the warpage effect is not very significant. It is important for a designer to design a mould that has less thermal residual stress effect with efficient cooling system.
For the product analysis, from the steps being carried out to analyze the plastic injection product, the stress distribution on product at different load factor is observed in the two dimensional analysis.
A critical point, Node 127, where the product experiences maximum tensile stress was selected for analysis.
From the load case versus stress curves at this point plotted in Fig. 23, it is clear that the product experiencing increased in tensile load until it reached the load factor of 23, which is 1150 N. This means that the product can withstand tensile load until 1150 N. Load higher than this value causes failure to the product. Based on Fig. 23, the failure is likely to occur at the region near to the fixed end of the product with maximum stress of 3.27×107 Pa.
The product stress analysis reveals very limited information since the product produced was for warpage testing purposes and had no relation with tensile loading analysis.
In future, however, it is suggested that the product service condition should be determined so that further analysis may be carried out for other behaviors under various other loading. that affect warpage. The testing specimen was produced at low cost and involves only little finishing that is de-gating.
The thermal analysis of plastic injection mould has provided an understanding of the effect of thermal residual stress on deformed shape of the specimen and the tensile stress analysis of product managed to predict the tensile load that the warpage testing specimen can withstand before experiencing failure.
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