塑料密封圈注塑模具設計,塑料,密封圈,注塑,模具設計 廣東石油化工學院 課程設計說明書 題 目 塑 料 成 型 工 藝 及 模 具 設 計 專 業(yè)： 機 電 工 程 學 院 班 級： 材控11-1 學 生： 余明競 學 號： 40 指導教師： 陶筱梅 完成時間：2014年 9 月17日至2014 年9 月 24日 設計題目: 塑料密封圈2模具設計 材料：PE 技術要求： 1） 制品表面光滑美觀； 2） 脫模斜度：0.5°～1°； 3）未注圓角為R0.5～R1。 PE的特性： 聚乙烯塑料的產(chǎn)量為塑料工業(yè)之冠，其中以高壓聚乙烯的產(chǎn)量最大。聚乙烯樹脂為無毒、無味，呈白色或乳白色，柔軟、半透明的大理石狀粒料，密度為0.91~0.96g/cm3 ，為結晶型塑料。 聚乙烯按聚合時所采用壓力的不同，可分為高壓、中壓和低壓聚乙烯。高壓聚乙烯的分子結構不是單純的線型，而是帶有許多支鏈的樹枝狀分子。因此它的結晶度不高(結晶度僅60%~70%)，密度較低，相對分子質量較小，常稱為低密度聚乙烯。它的耐熱性、硬度、機械強度等都較低。但是它的介電性能好，具有較好的柔軟性、耐沖擊性及透明性，成形加工性能也較好。中、低壓聚乙烯的分子結構是支鏈很少的線型分子，其相對分子質量、結晶度較高(高達87%~95%)，密度大，相對分子質量大，常稱為高密度聚乙烯。它的耐熱性、硬度、機械強度等都較高，但柔軟性、耐沖擊性及透明性、成形加工性能都較差。 聚乙烯的吸水性極小，且介電性能與溫度、濕度無關。因此，聚乙烯是最理想的高頻電絕緣材料，在介電性能上只有聚苯乙烯、聚異丁烯及聚四氟乙烯可與之相比。 型腔數(shù)量及排列方式 對于精度要求不高的小型塑件（沒有配合精度要求），形狀簡單，又是大批量生產(chǎn)時，則采用多型腔模具可提供獨特的優(yōu)越條件，使生產(chǎn)效率大為提高。型腔的數(shù)目可根據(jù)模型的大小情況而定。該塑件對精度要求不高，為低精度塑件，再依據(jù)塑件的大小，采用一模四型的模具結構。 確定分型面 分開模具能取出塑件的面，稱作分型面，注射模只有一個分型面。塑件的分型面應位于截面尺寸最大的部位，并且保證塑件順利脫模和精度要求。 塑件外觀質量要求不高，尺寸精度要求一般的小型塑件，可采用多型腔單分型面模具。 最常用的澆口形式是側澆口，這種澆口形式注射工藝在制造上加工比較方便，由于塑件的形狀小，澆道流程短，熱量損耗少，澆口采用側澆口，且開設在分型面上。 塑件的體積和質量 利用proe對塑件進行分析可得到以下數(shù)據(jù)： 體積 = 5.6172432e+03 毫米^3 曲面面積 = 5.8898801e+03 毫米^2 平均密度 = 1.0000000e+00 公噸 / 毫米^3 質量 = 5.6172432e+03 公噸 根據(jù) PRT_CSYS_DEF 坐標邊框確定重心: X Y Z 2.0000000e+01 2.0000000e+01 -2.9568217e+00 毫米 相對于PRT_CSYS_DEF坐標系邊框之慣性. (公噸 * 毫米^2) 慣性張量 Ixx Ixy Ixz 4.7329438e+06 -2.2468971e+06 3.3218373e+05 Iyx Iyy Iyz -2.2468971e+06 4.7329440e+06 3.3218373e+05 Izx Izy Izz 3.3218373e+05 3.3218373e+05 9.3010438e+06 重心的慣性 (相對 PRT_CSYS_DEF 坐標系邊框): (公噸 * 毫米^2) 慣性張量 Ixx Ixy Ixz 2.4369362e+06 0.0000000e+00 0.0000000e+00 Iyx Iyy Iyz 0.0000000e+00 2.4369363e+06 0.0000000e+00 Izx Izy Izz 0.0000000e+00 0.0000000e+00 4.8072492e+06 主慣性力矩 (公噸 * 毫米^2) I1 I2 I3 2.4369360e+06 2.4369365e+06 4.8072492e+06 從PRT_CSYS_DEF 定位至主軸的旋轉矩陣: 1.00000 0.00000 0.00000 0.00000 1.00000 0.00000 0.00000 0.00000 1.00000 從PRT_CSYS_DEF 定位至主軸的旋轉角(度): 相對 x y z 的夾角 0.000 0.000 0.000 得到： 塑件體積 V = cm3 曲面面積 S = cm2 密度 = g/ cm3 塑件質量 m= g 選擇注射機： 澆注系統(tǒng)凝料體積的初步按照塑件的0.6倍來估算 cm3 注塑機的公稱注射量 cm3 選擇注射機 根據(jù)以上的計算，初步選定公稱注射量為30 cm3，注塑機型號為XS-Z-30型注塑機。 XS-Z-30型注射機的主要參數(shù)如下表所示： 注射量/ cm3 30 最大開模行程/mm 160 螺桿（柱塞）直徑/mm 28 動、定模固定板尺寸/mm 250*280 注射壓力/Mpa 119 最大成型面積/C㎡ 90 注射行程/mm 130 合模方式 液壓-機械 注射時間/s 0.7 電動力功率/kW 5.5 注射方式 柱塞式 噴嘴球半徑/mm 12 鎖模力/KN 250 噴嘴孔直徑/mm Φ4mm 1）注射壓力的校核 根據(jù)公式： 查表可知，PE在注射壓力為70～100MPa 時取得最大流動比，取P0=85MPa， 滿足要求 2）鎖模力的校核 塑件在分型面上的投影面積： 澆注系統(tǒng)的投影面積： ， ?。? 因為前面計算的A塑是4腔的總面積，所以 所以， 澆注系統(tǒng) 1） 主流道長度 主流道長度L，應盡量小于60mm，上標準模架及該模具結構， 取L = 45（mm） 2） 主流道小端直徑 d = 注射機噴嘴直徑 +（0.5～1）mm = 4 +（0.5～1）mm取 d = 5（mm）。 3） 主流道大端直徑 D = d+2Ltan（α/2）（α=4°） =5+ ≈8（mm） 4） 主流道球面半徑 SR=注射機噴嘴球頭半徑+（1～2）mm =12+（1～2）mm 取SR = 14（mm）。 5） 球面配合高度 配合高度為 3 ～ 5 mm 取 h=3（mm）。 6） 主流道錐度 主流道錐角一般應在2°6°，取α = 4°，所以流道錐度為 主流道的凝料體積 V主=L主（++R主） 式（3-11） =(3.14/3)32(4+2.5+42.5) =1080.16mm≈1.08cm 主流道當量半徑 R=mm =3.05mm 分流道的截面形狀 選用效率較高的圓形截面。 分流道的尺寸 一般采用下面的經(jīng)驗公式來確定截面尺寸。這里單邊分流道長度取L=30mm =0.2654 ＝0.92mm PE常用的分流道直徑為4.8～9.5mm，取D＝5mm 分流道凝料體積 分流道長度 L＝304＝120mm 分流道截面積 A＝/4＝3.145/4=19.625mm 凝料體積 V＝LA=120 19.625＝2355mm≈2.4cm 校核剪切速率 查表注射時間可取t=0.7s 計算分流道體積流量： q=cm3/s=15.817cm3/s≈1.58210mm/s 剪切速率 側澆口尺寸的確定 1.澆口的深度：， 2.ABS側澆口的厚度為1.2 ～1.4mm ,這里取1.4mm 3.澆口的寬度：,B取1.6mm； 4.澆口的長度：側澆口的長度L一般選用0.7～2.5mm ,取L=1.5mm n=0.7 校核澆口的剪切速率 確定注射時間：查表,可取t=0.7s 澆口的體積流量: q=cm3/s=3.1cm3/s=3.1mm/s 計算澆口的剪切速率： 校核主流道的剪切速率 （1） 計算主流道的體積流量 q=cm3/s=17.36cm3/s (2)計算主流道的剪切速率 處于澆口與分流道的最佳剪切速率（=5×102～5×103s-1）的范圍之內，故主流道的剪切速率校核合格。 凹模尺寸的計算 1)凹模徑向尺寸計算 ——凹模徑向尺寸（mm）； ——塑件的平均收縮率（PE收縮率為0.4%～0.7％，均0.55%）； ——塑件徑向公稱尺寸（mm）； ——塑件公差值(mm) x——隨塑件精度和尺寸變化，一般在0.5～0.8之間，取0.6）； ——凹模制造公差（mm）制造公差取塑件公公差的1/3. ——凹模徑向尺寸（mm）； ——塑件的平均收縮率（ABS收縮率為0.4%～0.7％，平均收縮率為0.55%）； ——塑件徑向公稱尺寸（mm）； ——塑件公差值(mm) x——隨塑件精度和尺寸變化，一般在0.5～0.8之間，取0.6）； ——凹模制造公差（mm）制造公差取塑件公公差的1/3. 凹模型腔的徑向尺寸計算為： 式（3-27） 型腔深度尺寸 = =9.935 H==1.915 式（3-30） 凸模部分的結構設計 （1）凸模尺寸的計算公式如下： ——凹模徑向尺寸（mm）； ——塑件的平均收縮率（ABS收縮率為0.4%～0.7％，平均收縮率為0.55%）； ——塑件徑向公稱尺寸（mm）； ——塑件公差值(mm) x——隨塑件精度和尺寸變化，一般在0.5～0.8之間，取0.6）； ——凹模制造公差（mm）制造公差取塑件公公差的1/3. （2）.型芯徑向尺寸 =20.266 （3）.型芯高度尺寸 = =12.186 式（3-33） （4）.型腔側壁厚度計算 按整體式圓形型腔計算： r—型腔內半徑，r＝24mm；[σ]碳鋼取160MPa； p—型腔內壓力，p＝Kp=0.4×117=46.8MPa. 因此，型腔側壁厚 取S＝50mm. （5）型腔底板厚度的計算： 型腔底板厚度取32mm 成型零件的結構 凹模結構 主要參考資料 1..機械制造工藝師手冊. 機械工業(yè)出版社 2..李秦蕊主編. 塑料模具設計. 西北工業(yè)大學出版社. 1988年 3..典型注射模具結構圖冊. 中南工業(yè)大學出版社。 4..實用塑料注射模設計與制造. 陳萬林等編. 機械工業(yè)出版社. 2000年。 5..塑料模設計手冊.《手冊》編寫組編. 機械工業(yè)出版社. 1985年。 Journal of Materials Processing Technology 171 (2006) 259–267 Design and thermal analysis of plastic injection mould S.H. Tang ? , Y .M. Kong, S.M. Sapuan, R. Samin, S. Sulaiman Department of Mechanical and Manufacturing Engineering, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia Received 3 September 2004; accepted 21 June 2005 Abstract This paper presents the design of a plastic injection mould for producing warpage testing specimen and performing thermal analysis for the mould to access on 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, Version 13.0. 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 LUSAS Analyst, Version 13.5. 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. ? 2005 Elsevier B.V . All rights reserved. Keywords: Plastic Injection mould; Design; Thermal analysis 1. Introduction Plastic industry is one of the world’s fastest growing industries, ranked as one of the few billion-dollar industries. Almost every product that is used in daily life involves the usage of plastic and most of these products can be produced by plastic injection molding method [1]. Plastic injection molding process is well known as the manufacturing process to create products with various shapes and complex geometry at low cost [2]. The plastic injection molding process is a cyclic process. There are four signicant stages in the process. These stages are lling, packing, cooling and ejection. The plastic injec- tion molding process begins with feeding the resin and the appropriate additives from the hopper to the heating/injection system of the injection plastic injection molding machine [3]. This is the “lling stage” in which the mould cavity is lled with hot polymer melt at injection temperature. After the cav- ity is lled, in the “packing stage”, additional polymer melt is packed into the cavity at a higher pressure to compensate the expected shrinkage as the polymer solidies. This is followed ? Corresponding author. E-mail address: saihong@eng.upm.edu.my (S.H. Tang). by “cooling stage” where the mould is cooled until the part is sufciently rigid to be ejected. The last step is the “ejection stage” in which the mould is opened and the part is ejected, after which the mould is closed again to begin the next cycle [4]. The design and manufacture of injection molded poly- meric parts with desired properties is a costly process domi- nated by empiricism, including the repeated modication of actual tooling. Among the task of mould design, designing the mould specic supplementary geometry, usually on the core side, is quite complicated by the inclusion of projection and depression [5]. In order to design a mould, many important designing factors must be taken into consideration. These factors are mould size, number of cavity, cavity layouts, runner systems, gating systems, shrinkage and ejection system [6]. In thermal analysis of the mould, the main objective is to analyze the effect of thermal residual stress or molded-in stresses on product dimension. Thermally induced stresses develop principally during the cooling stage of an injection molded part, mainly as a consequence of its low thermal conductivity and the difference in temperature between the molten resin and the mould. An uneven temperature eld exists around product cavity during cooling [7]. 0924-0136/$ – see front matter ? 2005 Elsevier B.V . All rights reserved. doi:10.1016/j.jmatprotec.2005.06.075260 S.H. Tang et al. / Journal of Materials Processing Technology 171 (2006) 259–267 During cooling, location near the cooling channel experi- ences more cooling than location far away from the cooling channel. This different temperature causes the material to experience differential shrinkage causing thermal stresses. Signicant thermal stress can cause warpage problem. There- fore, it is important to simulate the thermal residual stress eld of the injection-molded part during the cooling stage [8].By understanding the characteristics of thermal stress distribu- tion, deformation caused by the thermal residual stress can be predicted. In this paper the design of a plastic injection mould for producing warpage testing specimen and for performing ther- mal analysis for the mould to access on the effect of thermal residual stress in the mould is presented. 2. 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 prod- uct development is to design a plastic part for determining the effective factors in the warpage problem of an injection- moulded part with a thin shell. The warpage testing specimen is developed from thin shell plastics. The overall dimensions of the specimen were 120 mm in length, 50 mm in width and 1 mm in 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 60 MPa, respectively. Fig. 1 shows the warpage testing specimen pro- duced. 2.2. Design of plastic injection mould for warpage testing specimen This section describes the design aspects and other consid- erations involved in designing the mould to produce warpage testing specimen. The material used for producing the plastic Fig. 1. Warpage testing specimen produced. injection mould for warpage testing specimen was AISI 1050 carbon steel. 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 spec- imen, the fourth design concept had been applied. Various design considerations had been applied in the design. Firstly, the mould was designed based on the platen dimen- sion 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, 4 mm space had been reserved between the two tie bars and the mould for mould setting-up and handling purposes. This gives the nal max- imum width of the mould as 250 mm. The standard mould base with 250 mm × 250 mm is employed. The mould base is tted to the machine using Matex clamp at the upper right and lower left corner of the mould base or mould platen. Dimen- sions of other related mould plates are shown in Table 1. The mould had been designed with clamping pressure having clamping force higher than the internal cavity force (reaction force) to avoid ashing from happening. 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 xed with sprue bushing for the purpose of feeding molten plastics. Therefore, it is only one standard parting line was designed at Table 1 Mould plates dimensions. Components Size (mm) ? width × height × thickness Top clamping plate 250 × 250 × 25 Cavity plate 200 × 250 × 40 Core plate 200 × 250 × 40 Side plate/support plate 37 × 250 × 70 Ejector-retainer plate 120 × 250 × 15 Ejector plate 120 × 250 × 20 Bottom clamping plate 250 × 250 × 25S.H. Tang et al. / Journal of Materials Processing Technology 171 (2006) 259–267 261 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 0.5 mm thickness for easy de-gating purpose. The gate was also designed to have 4 mm width and 0.5 mm 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 machin- ing 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 6 mm 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 ne nishing in order to prevent ashing 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. Sufcient 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 suf- cient cooling of the mould in the case of turbulent ow. Fig. 2 shows cavity layout with air vents and cooling channels on core plate. In this mould design, the ejection system only consists of the ejector retainer plate, sprue puller and also the ejector Fig. 2. Cavity layout with air vents and cooling channels. 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 addi- tional ejector is used or located at product cavities because the product produced is very thin, i.e. 1 mm. Additional ejec- tor in the product cavity area might create hole and damage to the product during ejection. Finally, enough tolerance of dimensions is given consid- eration to compensate for shrinkage of materials. Fig. 3 shows 3D solid modeling as well as the wireframe modeling of the mould developed using Unigraphics. 3. Results and discussion 3.1. Results of product production and modi?cation From the mould designed and fabricated, the warpage testing specimens produced have some defects during trial run. The defects are short shot, ashing and warpage. The short shot is subsequently eliminated by milling of additional air vents at corners of the cavities to allow air trapped to Fig. 3. 3D solid modeling and wireframe modeling of the mould.262 S.H. Tang et al. / Journal of Materials Processing Technology 171 (2006) 259–267 Fig. 4. Extra air vents to avoid short shot. escape. Meanwhile, ashing 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. After these modications, the mould produced high qual- ity warpage testing specimen with low cost and required little nishing by de-gating. Fig. 4 shows modications of the mould, which is machining of extra air vents that can eliminate 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 injec- tion 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 speci- men was ABS and the injection temperature, time and pres- sure were 210 ? C, 3 s and 60 MPa respectively. The material selected for the mould was AISI 1050 carbon steel. Properties of these materials were important in determin- ing temperature distribution in the mould carried out using nite element analysis. Table 2 shows the properties for ABS and AISI 1050 carbon steel. 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 Fig. 5. Model for thermal analysis. distribution and temperature at through different times are performed using commercial nite 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. 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 for the model also involves assigning properties and process or cycle time to the model. This allowed the nite 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. 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 Table 2 Material properties for mould and product Carbon Steel (AISI 1050), mould ABS Polymer, product Density,ρ 7860 kg/m 3 Density,ρ 1050 kg/m 3 Young’s modulus, E 208 GPa Young’s modulus, E 2.519 GPa Poisson’s ratio,ν 0.297 Poisson’s ratio,ν 0.4 Yield strength, S Y 365.4 MPa Yield strength, S Y 65 MPa Tensile strength, S UTS 636 MPa Thermal expansion,α 65 × 10 ?6 K ?1 Thermal expansion,α 11.65 × 10 ?6 K ?1 Conductivity, k 0.135 W/(m K) Conductivity, k 49.4 W/(m K) Specic heat, c 1250 J/(kg K) Specic heat, c 477 J/(kg K)S.H. Tang et al. / Journal of Materials Processing Technology 171 (2006) 259–267 263 Fig. 6. Loaded model for analysis of product. contour plots of thermal or heat distribution at different time intervals in one complete cycle of plastic injection molding. 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 plotting time response graphs. Figs. 9–17 show temperature distribution curves for dif- ferent nodes as indicated in Fig. 8. From the temperature distribution graphs plotted in Figs. 9–17, it is clear that every node selected for the graph plotted experiencing increased in temperature, i.e. from the ambient 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 tem- perature 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 that temperature. Increase in temper- ature was due to packing stages that involved high pressure, Fig. 7. Contour plots of heat distribution at different time intervals.264 S.H. Tang et al. / Journal of Materials Processing Technology 171 (2006) 259–267 Fig. 8. Selected nodals near product region for time response graph plots. Fig. 9. Temperature distribution graph for Node 284. Fig. 10. Temperature distribution graph for Node 213. Fig. 11. Temperature distribution graph for Node 302. Fig. 12. Temperature distribution graph for Node 290. which caused the temperature to increase. This temperature remains constant until the cooling stage starts, which causes reduction in mould temperature to a lower value and remains at this value. The graphs plotted were not smooth due to the absence of function of inputting lling rate of the molten plastic as well as the cooling rate of the coolant. The graphs plotted only show maximum value of temperature that can be achieved in the cycle. The most critical stage in the thermal residual stress anal- ysis is during the cooling stage. This is because the cooling Fig. 13. Temperature distribution graph for Node 278.S.H. Tang et al. / Journal of Materials Processing Technology 171 (2006) 259–267 265 Fig. 14. Temperature distribution graph for Node 1838. Fig. 15. Temperature distribution graph for Node 1904. stage causes the material to cool from above to below the glass transition temperature. The material experiences differ- ential shrinkage that causes thermal stress that might result in warpage. From the temperature after the cooling stage as shown in Figs. 9–17, it is clear that the area (node) located near the cooling channel experienced more cooling effect due to fur- Fig. 16. Temperature distribution graph for Node 1853. Fig. 17. Temperature distribution graph for Node 1866. ther decreasing in temperature and the region away from the cooling channel experienced less cooling effect. More cool- ing effect with quite fast cooling rate means more shrinkage is occurring at the region. However, the farthest region, Node 284 experience more cooling although far away from cooling channel due to heat loss to environment. 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 signicant. It is important for a designer to design a mould that has less thermal residual stress effect with efcient 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. Figs. 18–21 show the contour plots of equivalent stress at different load increments. A critical point, Node 127, where the product experiences maximum tensile stress w