Nghiên cứu ảnh hưởng của nhiệt độ khuôn đến độ điền đầy của vật liệu composite trong quy trình phun ép TT TIENG ANH

MINISTRY OF EDUCATION AND TRAINING HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY AND EDUCATION PHAN THE NHAN EFFECT OF MOLD TEMPERATURE ON THE FILLING OF COMPOSITE MATERIALS IN INJECTION MOLDING PROCESS DISSERTATION SUMMARY Major: Mechanical Engineering Major Code: 62520103 Ho Chi Minh City - 2022 The dissertation is completed at Ho Chi Minh city University of Technology and Education Scientific Supervisors: Assoc Prof Dr Do Thanh Trung Assoc Prof Dr Pham Son Minh The dissertation will be defensed in front of the Council for Ph.D evaluation of the Ho Chi Minh City University of Technology and Education on ……… /2022 The dissertation can be found at: -The National Library of Vietnam -The Library of Ho Chi Minh City University of Technology and Education OVERVIEW Reasons for choosing the dissertation Thermoplastic composite products shaped by injection molding technology are widely applied in many fields with increasingly complex structures and shapes Along with this development, the defects of the product also appear more and more, due to the rapid freezing phenomenon when composite materials come into contact with molding wall, the viscosity of composite materials is higher than other common plastic materials Therefore, the process of flowing the material into the mold will bedifficult To increase mold filling capacity during injection pressing with composite materials, the mold temperature control is one of solutions studied to limit rapid freezing and increase the flow of the material in the mold Therefore, the dissertation "Effect of mold temperature on the filling of composite materials in injection molding process" is very necessary The results of this dissertation are scientific basis, references for training and scientific research at technical universities, especially in the field of injection In addition, the results also aim to transfer technology in the field of production of thermoplastic composite products with injection molding technology, especially for the products with small size and thin structure such as circuit boards, jacks in the field of electronics, fiber optic connectors for increasing heat resistance, insulation, significantly improve product durability In addition, it is also used to manufacture machine parts such as gears, washers with small size and high precision with a total weight of a few grams Research purposes Studying the effect of mold temperature on the filling of thin-walled composite products by using simulation and experimental methods with the water heating model with the mold temperature from 30 oC to 110 oC and the hot gas heating model with the mold temperature from 45 °C to 140 °C Research contents: - Overview and theoretical basis of issues related to mold temperature, filling process of composite materials in the injection molding products - Set up a research model and manufacture the water heating equipment with mold temperature from 30 °C to 110 °C and the hot gas heating equipment with mold temperature from 45 °C to 140 °C - Studying the effect of mold temperature on the flow length of composite materials by both simulation and experiment methods with basic model as the spiral flow, the glass fiber ratios varying from % to 30 % and the mold temperatures varying from 30 oC to 110 °C Thereby evaluating the effectiveness of mold temperature control through improving the flow capacity of thermoplastic composite materials At the same time, determine the regression equation on the relationship between flow length, mold temperature and product thickness - Studying the effect of mold temperature on the filling ability with thin-walled, thin-ribbed composite products by simulation and experiment with the fiber volume varying from % to 30 % and the mold temperature changed from 45 oC to 140 oC, in order to effectively apply the method of controlling mold temperature to improve the fillability for thin-walled and thin ribbed products Research scope and topic limitation - Evaluating the flowability of composite materials with thick spiral flowshaped models: 0.5 mm, 0.75 mm and mm; thin products with thickness: 0.2 mm, 0.4 mm, 0.6 mm; and thin rib products - Mold temperature: from 30 °C to 110 °C and high temperature to 140 °C - PA6 material and composite materials with PA6 base mixed with short glass fiber from % to 30 % Research methods In this dissertation, several research methods are used such as: Data collection and analysis, simulation of the heating process and the plastic filling process filled the mold, Experiment of the injection molding for analysis, evaluation of filling ability of materials Scientific significance - The relationship among flow length, mold temperature and product thickness is determined with the glass fiber ratio from % to 30 % of PA6 plastic composite materials - The injection molding method with high mold temperature area is one of the solutions to improve the flowability of composite materials in the mold cavity At the same time, controlling the surface temperature of the mold with hot gas can be applied to injection molding of thin-walled, thin-ribbed products to increase filling capacity - Increasing the mold temperature can proceed to the entire mold cavity or several locations before the material flows into locations with thin walls and thin ribs Practical values - The improvement of the flowability of composite materials has been carried out in order to increase the ability to manufacture plastic products in general and especially thin-walled composite products in particular The new feature in this study is the mold temperature control to improve the ability to fill the mold - By applying injection molding with high mold temperature, helping companies improve technology capabilities, without spending too much on investment, still meet the requirements of thin-walled products and lowviscosity materials such as composite materials Chapter 1: OVERVIEW 1.1 Introduction of injection molding technology Injection is a forming technology in the mold with the support of the heating system that melts the material from the outside and is injected into the mold through screw to form the corresponding product when the mold cools down Currently, there are many types of materials used in injection technology, including thermoplastic composite materials The injection method shows the advantages of the process of making products with composite materials such as increasing the uniformity of shape in a wide range of products and being less defects 1.2 The situation of overseas research Injection technology is used quite commonly and applied in many fields In fact, composite injection also appears a number of issues affecting productivity, processing costs, product durability compared to conventional plastic material injection So many recent studies have been conducted with research directions such as figure 1.2 Figure 1.2: Research directions in the field of composite material injection - Additive effect on injection molding capacity and composite product durability These research directions show that additives are used as one of the solutions to increase the flow capacity of the material, especially for thermoplastic composite materials in the mold, while reducing the phenomenon of shrinkage, warping of the product at the end of the injection process - The injection mold structure increases the flowing capacity of composite materials in the mold Adjusting the mold structure to adapt to the requirements of heating methods, as well as a new process has been considered to improve the filling capacity of the flow, reduce the injection cycle, eliminate product defects, improve the productivity of the product shaping process - Injection molding conditions increase the productivity and durability of thermoplastic composite materials Studies on injection molding conditions have been conducted in recent years such as: press pressure, shaping pressure, plastic temperature and mold temperature are the main factors affecting the injection process In particular, mold temperature parameters are mentioned by many studies as one of the parameters that greatly affect the quality of the product surface and the injection productivity - Effect of glass fiber ratio on product durability composite material in injectionpress Studies have shown that material hardness increases gradually as fiberglass increases, while durability also improves and the trend increases as the ratio of glass fiber increases to 30 % Thereby showing that the mechanical and physical properties of composite plastic depend on the ratio of fibers - The effect of the heating method on mold temperature and composite product quality in injection molding With heating methods somewhat improve the flow of composite materials during filling However, with each method there are still some limitations that need to be improved (Figure 1.4) In particular, the method of heating with water is used very effectively and popularly in the field of injection molding, this is a method that can raise the mold temperature up to near the boiling temperature of the water, which is the right temperature to maintain the flow capacity for turpendiated products However, in cases where high mold temperature is required, to improve the efficiency of the injection process, the method of heating with hot gas from the outside will be considered, especially for composite thin products Figure 1.4: Some methods of heating injection mold With the research directions to improve productivity and product quality with thermoplastic composite materials in recent years, ingeneral, the method of controlling mold temperature during injection is one of the effective solutions to improve productivity, product quality, as well as reducing production costs for products that are composite materials Therefore, studying the effects of mold temperature in the injection molding process to improve the quality of composite products is essential and is of interest to research 1.3 The state of research in the country Many studies involving composite materials and injection technology have been carried out, such as: - Author Dao Le Chung with colleagues reporting at the 12th Science and Technology Conference, Ho Chi Minh City University of Technology shows the ability to localize Kia-Thaco light ruck machine parts with composite materials - Author Tran Minh Ho conducted the study "Surveying the proportional effect of reinforcing materials on the properties of composite materials hybrid on polymer resin" The results show that composite materials created with 35 % glass fiber + 60 % epoxy resin + % TiO2 have higher mechanical properties than composites containing %, 10 % and 20 % TiO2 - Author Tran Minh The Uyen conducted "Studying the effect of heating hot gas injection molds on the durability of plastic products in thin form" In this study, the author focused on heating methods for the mold applied in injection technology to clarify the effect of the parameters on mold heating - The state-level scientific and technological research project (KC.03.22/11-15) is led by the author "Dang Van Nghin" Research on the design and fabrication of a technical thermoplastic injection mold system with a controlled hot channel" In this research, the team used the hot runner technique to limit the pressure reduction of the flow of molten plastic during the flow through the channel system - In addition, some related studies by the Ho Chi Minh City University of Technology and Education modeling research group such as: Le Quoc Viet Study the effect of technological parameters and additives on the durability of polymer and composite materials in injection technology, Phung Huy Dung Researching the effect of heating method with hot gas on the appearance of welding lines of thin plastic products, Vu Viet Chuyen - Study the effect of injection parameters on bending strength of PA6 plastic material Through the results of the study, the mold temperature control is understood only and carried out in the direction of cooling the mold or limiting the phenomenon of reducing the pressure of the plastic flow during the flow into the mold The possibility of limiting defects to the product has not yet been considered and applied In contrast, the problem of keeping the surface of the face at a high temperature during injection to improve product durability, especially with products with high accuracy requirements has begun to take care In general, the quality of the product in the injection molding process depends on many parameters, of which the mold temperature is one of the important parameters If the mold temperature is low, the plastic flow will be difficult to fill, especially with composite materials, due to the higher viscosity than conventional plastics With the research results as well as in the production process, the solution of heating for molds has not been paid enough attention 1.4 Practical needs of thermoplastic composite products Thermoplastic composite materials are also researched and applied in our country Products shaped by injection molding technology are increasingly in demand and are applied in a variety of fields: mechanical, electronic, medical, aviation and life Therefore, it can be said that thermoplastic composites have a lot of potential and prospects, which are being gradually replaced by metals and alloys in all fields 1.5 The problem needs to continue research - Clarify the effect of mold temperature on filling of materials, especially with thin-walled products using injection molding technology - Evaluation of simulation methods, experimental process of filling up composites - Evaluate the results of plastic composite product shaping through the effect of mold temperature when injecting products - Application of hot gas mold temperature control method improves filling capacity, especially with thin composite products Chapter 2: THEORETICAL BASIS 2.1 Thermoplastic composite material Composite materials are materials that are combined from two or more different types of materials and have many advantages over individual materials In particular: The core material plays a role in ensuring that composites have the necessary mechanical characteristics, so that the background has a role to ensure that the core componentof composites is linked together to create monolithic and uniformity for composites In this study, thematerial selected for the study was thermoplastic composite material with PA6 (Polyaminde 6) short glass fiber Glass fiber material is reinforced to increase the durability and toughness of the product and is used in many industries, has high insulation and durability properties 2.2 Fiber ratio of composite material The ratio of fibers is determined by the density of component materials: ρ -ρ Vf = ρc - ρ m (2.8) f m In there: ρc It's the density of composites, ρm is the density of the plastic component, ρf is the density of the fiber component The composite material used in this study is a material that is pre-blended by the manufacturer of glass fiber with PA6 substrate material in proportions: %GF, 10 %GF, 15 %GF, 20 %GF, 25 %GF, 30 %GF 2.3 Fiber orientation during injection pressing During the filling of the material into the mold, molten plastic at high temperatures comes into contact with the surface of the mold, forming the surface layer (figure 2.2) and solidating rapidly because of heat loss Reinforced fibers in this solid grade are not oriented for a short time, so the arrangement in the direction of flow is more irregular than the cutting layer The inner molten composite resin is the core layer and is less affected by friction and low sliding stresses so only a few fibers can be oriented towards the flow Figure 2.2: Description of fiber orientation 2.4 The relationship between viscosity and temperature The viscosity of thermoplastics depends heavily on temperature with the typical phenomenon for this properties: the viscosity of thermoplastics will decrease sharply when the temperature of that material increases as figure 2.5 Figure 2.5: Shear viscosity of various temperatures To describe the effect of temperature on viscosity, one uses a coefficientaT : μ (T) aT = μ0 (T0 ) In it, T0 is the original temperature, T is the temperature at the time of consideration, is the μ0 viscosity corresponding to the temperature T and T0 2.5 Characteristics of flow “Fountain” In the field of injection, the plastic flow in the heart of the mold complies with the characteristics of the "Fountain" with the characteristics: the plastic part at the center of the flow will flow faster than the plastic part close to themold wall In particular, at the location of contact with the mold wall, the plastic is considered non-flowing The plastic at the beginning of the flow is injected forward and swept towards the mold (Figure 2.8) Mold Skin Flow front Core Flow direction Mold Figure 2.8: Flow of plastic in mold 2.6 Heat exchange temperature ambient element flow Call q the heat vector that flows through the flow element with a general flow: - div (q) = div [k grad (T)] (2.19) With k is the thermal conductivity coefficient of the flow 2.7 Equation balancing material flow in the lap of injection mold press - Principle of mass preservation in the coordinate system Descartes: From equilibrium, we are given the equation of mass conservation.: ∂ρ + div (ρu) = (2.22) ∂t product (mm) Mold temperature Flow length (mm) (oC) 28.3 26.1 24.1 20.8 19.7 15.7 14.7 30 33.5 33.4 31.4 24.7 20.8 22.7 15.3 50 36.3 35.7 34.7 30.5 26.1 26.4 18.8 0.5 70 40.1 39.5 36.7 34.8 30.3 27.4 19.7 90 43.1 44.4 42.1 39.8 34.7 30.7 21.5 110 Table 4.2: Simulation results of flow length with a thickness of 0.75 mm Fiber ratio (%) Thickness Mold product temperature 10 15 20 25 30 (mm) (oC) Flow length (mm) 89.5 78.6 75.1 72.1 69.1 68.1 64.3 30 91.3 80.7 76.9 74.3 71.7 70.3 65.6 50 97.3 86.3 80.7 77.1 74.8 72.1 71.8 0.75 70 101.7 90,1 87.1 81.5 77.5 75.1 73.3 90 107.8 93.7 91.7 85.7 81.7 80.7 75.7 110 Table 4.3: Simulation results of flow length with a thickness of mm Fiber ratio (%) Thickness Mold product temperature 10 15 20 25 30 o (mm) ( C) Flow length (mm) 115.3 102.7 94.3 90.7 85.7 82.1 80.6 30 117.8 107.7 100.7 94.8 88.5 85.1 82.1 50 128.7 111.1 105.7 101.3 97.1 96.1 93.1 70 132.6 114.1 110.4 105.8 101.3 100.1 97.1 90 150.8 117.5 114.5 109.1 105.8 101.1 99.9 110 4.2 Experimental results of flow length with spiral model Experimental results as shown in Tables 4.4, 4.5 and 4.6 show that the smaller the product thickness and the larger the reinforcement ratio, the harder it is for the composite material to flow in the mold cavity Thereby, it is shown that the mold temperature parameter can be used as a solution to improve the flowability of composite materials, can choose the appropriate mold temperature for each product size for effective injection molding highest Table 4.4: Experimental results of flow length with a thickness of 0.5 mm Fiber ratio (%) Thickness 10 15 20 25 30 16 product (mm) Mold temperature Flow length (mm) (oC) 29.8 25.1 24.3 22.3 20.1 18.3 13.3 30 32.7 31.7 29.1 24.1 22.3 21.2 14.3 50 37.7 34.1 30.8 29.1 25.1 24.7 19.7 0.5 70 39.7 37.8 34.2 32.7 28.4 25.2 23.6 90 41.4 39.8 38.3 34.7 31.7 30.1 25.8 110 Table 4.5: Experimental results of flow length with a thickness of 0.75 mm Fiber ratio (%) Thickness Mold product temperature 10 15 20 25 30 (mm) (oC) Flow length (mm) 87.1 79.1 74.4 71.1 68.4 67.1 64.1 30 89.1 81.3 75.5 73.1 70.6 69.8 65.2 50 94.1 83.8 77.8 74.4 73.3 72.2 70.4 0.75 70 99.3 87.4 81.8 79.0 74.4 74.4 72.6 90 104.1 93.1 88.3 84.1 79.1 78.5 75.4 110 Table 4.6: Experimental results of flow length with a thickness of mm Fiber ratio (%) Thickness Mold product temperature 10 15 20 25 30 (mm) (oC) Flow length (mm) 114.8 101.1 95.1 91.3 87.6 83.2 79.9 30 118.1 109.1 101.5 97.6 91.1 87.2 84.6 50 125.3 111.4 105.8 100.1 97.5 95.2 93.6 70 135.8 114.8 108.4 104.3 100.2 98.1 96.1 90 145.8 115.3 113.5 110.2 106.4 102.3 100.3 110 4.3 Comparison of experimental and simulation results The results are compared through the difference between the experimental and simulated flow lengths with the average difference of 6.9 %, 2.1 % and 1.4 %, respectively product thickness 0.5 mm, 0.75 mm and mm The cause of the deviation is due to the influence of the experimental environment of injection molding and the measurement process, as well as the simulation results are approximate results In general, the experimental results are quite similar to the simulation results on Moldex3D software Therefore, one of these two results can be selected to analyze and evaluate the influence of mold temperature on the flow length At the same time, the mold temperature parameter can be used as a solution to improve the flowability of the material in the injection mold cavity 17 4.4 Effect of mold temperature on material flow length The effect of mold temperature on flow length with yarn ratio, product thickness changes is described as figure 4.1, 4.2, 4.3 Experimental results show that: when increasing the mold temperature from 30 °C to 110 °C, the plastic flow length increases for all cases of product thickness of 0.5 mm, 0.75 mm and mm However, the degree of increase is different as the product thickness changes Thereby, it shows that it is necessary to choose the right mold temperature for each product size in order for the injection molding process to achieve the highest efficiency With this research result, heating the mold temperature as a solution to improve the filling of the mold cavity, as well as improve the distribution of reinforcing fibers in the injection molding process of thermoplastic composite materials, thereby increasing the durability of the product 0% GF 5% GF 10% GF 15% GF 20% GF 25% GF 30% GF 100 Flow Length (mm) Flow Length (mm) 40 0% GF 5% GF 10% GF 15% GF 20% GF 25% GF 30% GF 110 30 160 0% GF 5% GF 10% GF 15% GF 20% GF 25% GF 30% GF 140 Flow Length (mm) 50 90 80 120 100 20 80 70 10 60 60 20 30 40 50 60 70 80 90 100 110 Mold Temperature (0C) Figure 4.1: Flow length with thickness of 0.5 mm 120 20 40 60 80 100 Mold Temperture (0C) Figure 4.2: Flow length with thickness of 0.75 mm 120 20 40 60 80 100 120 Mold Temperature (0 C) Figure 4.3: Flow length with thickness of mm 4.5 Effect of fiber ratio on flow length The flow length does not depend solely on the mold temperature (figure 1, 4.2 and 4.3), which also depends on the ratio of fibers Figure 4.4, 4.6, 4.8 shows the result describing the effect of the fiber ratio on the flow length of composite material to i mold temperature 30 oC, 70 oC and 110 oC Experimental results showed that theproportion offibers (Vf) increased in the survey range from % to 30 %, the flow length decreased significantly Therefore, when using reinforced short fibers for injection products, it is necessary to choose the right mold temperature to increase quality as well as ensure economic efficiency In general, in the process of spraying products with thermoplastic composite, the mold temperature, fiber ratio have a great influence on the orientation of the fiber, filling, surface gloss 18 Depth of flow 160 Depth of flow 120 100 Depth of flow 140 1mm 0.75mm 0.5mm 1mm 0.75mm 0.5mm 140 1mm 0.75mm 0.5mm 120 Flow Length (mm) 120 Flow Length (mm) Flow Length (mm) 100 80 60 40 80 60 40 20 20 0 10 15 20 25 30 Glass Fiber Volume (%) Figure 4.4: Flow length with mold temperature 30 oC 80 60 40 20 100 10 15 20 25 30 Glass fiber volume (%) Figure 4.6: Flow length with mold temperature 70 oC 10 15 20 25 30 Glass fiber volume (%) Figure 4.8: Flow length with mold temperature 110 oC 4.6 Effect of mold temperature on fiberglass bonding SEM imaging method was used with composite material PA6 + 30 %GF, thickness mm and mold temperature varied from 30 °C to 110 °C The results of SEM images with a magnification of 3000 times are depicted as shown in figure 4.10 Thereby, it is shown that when the mold temperature is low, the viscosity of the plastic flow is also low, leading to the plastic components (PA6) and short glass fibers (GF) being difficult to bond together, forming many internal voids greatly affect the filling quality When the mold temperature is large enough (>70 °C), the flow viscosity increases, the bond between the component materials is significantly improved and the filling quality is better Figure 4.10: The fiber bond corresponds to the mold temperature change: 30 oC, 50 oC, 70 oC, 90 oC, 110 oC respectively 4.7 Effect of fiber ratio on glass fiber distribution SEM imaging with 800 magnification was used for product samples with a mold temperature of 70 °C, a thickness of mm and a fiber ratio varying from % to 30 % The results show that the fiber ratio significantly affects the distribution and bonding between the composite material components In the absence of fiber reinforcement, PA6 resin is uniformly distributed and has a ripple-like structure (Vf = %) When the fiber is reinforced, the fiber distribution in injection molding changes significantly With Vf = 30 %, the glass short fibers tend to cluster together, leading to a significant influence on the filling of the composite material in the mold cavity (figure 4.11) 19 Vf = 30 % Vf = % Vf = 10 % Vf = 20 % Figure 4.11: The distribution of glass fibers with different fiber ratios 4.8 Building a regression equation to determine the flow length of composite materials in the injection molding process Regression equation for relationship of flow length of plastic material with mold temperature, product thickness and percentage of fibers varying from % to 30 % was established based on experimental results (table 4.1, 4.2, 4.3) and Minitab software with R2 reliability in the range of 93.5 % to 98.4 % and presented in table 4.11 The result of the general regression equation is of the form: L = aT + bh – c (4.1) o Inside: L: flow length (mm), T: mold temperature ( C), h: product thickness (mm), a, b and c are the dependent coefficients into the T, Vf and h Table 4.11: The regression equation determines the flow length Vf (%) Regression equation Vf (%) Regression equation L = 0.170T + 142h – 53.0 L = 0.265T + 185h – 70.4 20 L = 0.175T + 138h – 52.7 L = 0.179T + 152h – 49.9 25 L = 0.187T + 143h – 60.0 10 L = 0.176T + 147h – 50.0 30 15 L = 0.171T + 143h – 48.8 4.9 Relationship between flow length ratio and product thickness for composite materials The relationship between the ratio of flow length and product thickness with the change of temperature, the fiber ratio is determined with the results as shown in Table 4.12 Table 4.12: Relationship between flow length ratio and product thickness for composite materials Mold temperature (oC) Yarn Thickness ratio 30 50 70 90 110 (mm) (%) Ratio of flow length and product thickness 26.6-59.6 28.6-65.4 39.4-75.5 47.2-79.4 51.6-82.8 0.5 0.75 - 30 85.7-116.1 86.9-118.8 93.8-125.4 96.8-132.4 100.5-138.8 79.9-114.8 84.6-118.1 93.6-125.3 96.1-135.8 100.3-145.8 20 Based on this relationship will determine the limit of filling capacity corresponding to each thickness size, reinforcement fiber ratio Thereby, it is more convenient in the process of designing and manufacturing the mold cavity to apply production practices Chapter 5: APPLICATION METHOD OF TEMPERATURE CONTROL TEMPERATURE ADVANCED FILLING 5.1 Flow model of thin-walled product mold 5.1.1 Simulation results of heating the inside of a thin-walled product mold The simulation results of the mold cavity heating are shown in figure 5.1 and the temperature measured at four points as shown in Table 5.1 The results show the difference in temperature at the beginning of the heating period On the contrary, when the heating temperature is increased, the difference in temperature is also evident at the end of the heating period At the same time, the results also show that the heating efficiency only increases at the beginning of the heating process, and after 20 s, the temperature rise slows down Therefore, with four hot-air injection ports, the heating system is highly efficient in the first 20 s, with a maximum heating rate of 6.4 °C/s with 400 °Cb Nhiệt gas b Nhiệt độ khí: độ khí: 250250 C C a Nhiệt a Nhiệt độ độ khí:khí: 200200 C C c Nhiệt c Nhiệt độ khí: độ khí: 300 300 C C 30 s30 s 30 s 30 s 30 s 30 s 25 s25 s 25 s 25 s 25 s 25 s 20 s20 s 20 s 20 s 20 s 20 s 15 s15 s 15 s 15 s 15 s 15 s 10 s10 s 10 s 10 s 10 s 10 s 5s 5s 5s 5s 5s Nhiệt Nhiệt độ độ Nhiệt Nhiệt độ độ o NhiệtNhiệt độ độ o o 30 s 30 s 30 s 30 s 30 s 30 s 30 s 25 s 25 s 25 s 25 s 25 s 25 s 25 s 20 s 20 s 20 s 20 s 20 s 20 s 20 s 15 s 15 s 15 s 15 s 15 s 15 s 15 s 10 s 10 s 10 s 10 s 10 s 10 s 10 s 5s 5s 5s 5s 5s Temperature Temperature Gas temperatures: 200 oC Temperature b Gas temperatures: 250 oC 30 s 30 s 25 s 25 s 20 s 20 s 15 s 15 s 10 s 10 s 5s 5s c Gas temperatures: 300 oC Temperature Temperature oC o C d Nhiệt d Nhiệt độ khí: độ khí: 350350 5s 5s o 5s Temperature Temperature oC oC e Nhiệt e Nhiệt độ khí: độ khí: 400 400 Figure 5.1: Simulation results of surface temperature distribution of mold cavity after 30 s of heating with different gas temperatures Table 5.1: Simulation results of the temperature at the mold cavity with the heating time by hot air from s to 30 s Gas temperature (°C) d Gas temperatures: 350 C e Gas temperatures: 400 C Heating 200 250 300 350 400 Location time (s) Mold temperature (°C) P1 62.3 73.2 83.3 92.5 102.8 P2 58.1 69.3 81.4 84.5 95.4 P3 56.6 67.2 79.8 82.4 91.3 P4 57.8 66 78.9 76.6 88.4 P1 76 91.6 109.1 115.8 125.6 10 P2 78.3 92.6 109.5 115.5 126.8 P3 74.5 84.4 105.6 104.3 115.7 Nhiệt độ Nhiệt độ o o 21 o o P4 74.4 86.8 104.4 105.1 115.6 P1 90.8 105.7 119 131.8 148.4 P2 87.2 102.7 117.5 123.7 144.2 15 P3 86.6 101.5 116.3 124.2 142.1 P4 85.5 101.3 115.4 131 141.6 P1 92.2 114 125.6 147.8 154.8 P2 90.2 110.9 122.9 146.6 153.7 20 P3 88.3 108.1 119.7 145.9 151.1 P4 84.8 105.3 117.1 145.9 150.5 P1 95.6 116.2 129.8 147.4 160.1 P2 92.1 112.4 125.5 144 158.6 25 P3 91.2 112.6 123.3 142.1 157.8 P4 86.6 96.8 117.4 143.8 155.7 P1 96.5 119.6 132.9 151.7 161.3 P2 94.4 117.7 128 147.9 159.4 30 P3 94.3 116.9 127.4 145.3 158.1 P4 84 106.2 119.6 140.7 152.5 5.1.2 Experimental results of temperature distribution and flow length 5.1.2.1 Mold temperature distribution results The temperature distribution of the mold is determined as shown in Figure 5.3 The results show that with heating time of s, 10 s, 15 s and 20 s, the temperature of the mold surface remains at 62.8 °C, 94.9 °C, 121.2 °C and 130, °C respectively The results also show that with a reasonable arrangement of the air injection ports, the method of controlling the mold temperature by hot air heating outside the mold (Ex-GMTC) can be applied to the complex shape of the mold cavity The comparison results have the difference in temperature between simulation and experiment but lower than 12 °C The difference is due to the delay of the thermal camera In general, the simulation and experimental results are consistent and relatively accurate 22 170 170 65.4 95.6 92.6 60.4 138 138 68.8 99.5 62.5 105 95.7 105 70.1 100.1 63.1 72 96.0 72 65.1 66.2 95.4 96.2 40 40 Simulation Experiment (a) Heating time: s Simulation 170 170 125.8 Experiment (b) Heating time: 10 s 135.4 128.9 118.5 138 138 128.5 135.8 119.8 105 130.5 105 130.4 136.7 120.1 72 130.8 72 126.5 127.0 133.7 138.0 40 40 Simulation Experiment (c) Heating time: 15 s Simulation Experiment (d) Heating time: 20 s Unit: °C Figure 5.3: Experimental results of temperature distribution at the surface of the mold cavity with different heating times 5.1.2.2 Result of determining flow length The experimental results of the flow length are as shown in Figures 5.4 and 5.5 At the same time, the percentage improvement of flow length with heating time, product thickness varies as shown in figure 5.6 Experimental results show that with PA6 and PA6 + 30 %GF materials, the flowability improvement rate of the material is significantly improved Specifically, with material PA6 and a flow thickness of 0.6 mm, the flow length is increased by about 90.6 % upon heating for 20 s With PA6 + 30 %GF composite, the flow thickness is 0.6 mm when heating for 20 s, length is improved by 108.6 % Thereby, showing the effectiveness of Ex-GMTC method Without heating 20.1 mm 28.9 mm 38.9 mm 22.5 mm 31.2 mm 42.6 mm 26.7 mm 37.3 mm 54.7 mm 30.5 mm 48.8 mm 67.9 mm Heating time: s Heating time: 10 s Heating time: 15 s Heating time: 20 s 36.4 mm 0.2 mm thickness 53.6 mm 0.4 mm thickness 74.3 mm 0.6 mm thickness Figure 5.4: Experimental flow length results for PA6 material 23 Without heating 18.5 mm 22.9 mm 28.5 mm 24.1 mm 31.5 mm 40.3 mm Heating time: s Heating time: 10 s 28.4 mm 37.6 mm 49.3 mm 31.6 mm 39.9 mm 56.9 mm Heating time: 15 s Heating time: 20 s 33.1 mm 44.9 mm 0.2 mm thickness 58.9 mm 0.4 mm thickness 0.6 mm thickness % improvement % improvement Figure 5.5: Experimental flow length results for PA6 + 30 %GF material 5s Without Heating 10 s 15 s Without Heating 20 s 5s 10 s 15 s 20 s Heating time (s) Heating time (s) (d) PA6 + 30%GF (c) PA6 Figure 5.6: Flow length improvement with PA6 and PA6 + 30 %GF 5.2 Flow model of thin ribbed products 5.2.1 Simulation results of mold heating of thin ribbed products Simulation of heating with hot air temperature of 400 °C for thin ribbed model (figure 3.25) and temperature distribution in B-B section is shown in figure 5.7 The simulation results show that the temperature difference between the three points is less than 10 °C The temperature difference between point and point (figure 3.27) is less than 3.2 °C The more suitable the temperature between points and 3, the more balanced the filling of the two veins 120.8 120.8 123.7 123.7 118.9 118.9 Heating time: s 125.6 127.5 123.8 Heating time: s 125.6 127.5 123.8 Heating time: s 120.8 123.7 118.9 134.5 136.7 132.9 Heating time: s 134.5 136.7 132.9 Heating time: s Heating time: s Heating time: s 125.6 127.5 144.1 144.1 123.8 147.8 55 134.5 136.790 143.2 Heating time: 10 s Heating s s Heatingtime: time:610 20 147.8 143.2 132.9 Temperature 125 160 [C] 20 Temperature 55 90 125 160 [C] Figure 5.7: Temperature distribution at B-B section of thin ribbed product 24 Heating time: s 144.1 147.8 143.2 5.2.2 Experimental results of heating and filling 5.2.2.1 Result of the heating process To determine the temperature distribution in the thin ribbed die at the end of the heating step, an infrared thermal camera was used with the results shown in figure 5.8 The results show that the temperature is uniformly distributed, the heating process only affects the heating position Simultaneously, to study the heating step for thin ribbed molds, the surface temperature of the mold cavity was measured at three points (figure 3.26) with the number of repetitions of each experiment being 10 times, the average temperature at different locations The measurements are summarized in table 5.2 and the comparison results are shown in figure 5.9 With the colored values in table 5.2 representing the mold temperature during heating, the unshaded positions represent the mold temperature value after the heating has finished (this is the time the device takes to the heating element is moved out of the heating zone and the two halves of the mold are closed) Normally, the mold closing time is less than 6s Therefore, in this study, the total travel time of the heating and closing devices was chosen to be s The temperature in figure 5.9 shows that at the end of the heating step, the mold temperature reached 120.6 °C, 125.5 °C, 134.7 °C and 140.8 °C at heating times of 4, respectively s, s, s and 10 s Also, after s to close the mold, the temperature of the heating surface decreases by about 10 °C with the thin rib The temperature value at the mold surface decreases because the hot air has stopped spraying into the heating zone, in addition, the heat energy at the mold surface is transferred to the mold plate volume and the air a Heating time: s Max Temperature: 120.6 °C b Heating time: s Max Temperature: 125.5 °C c Heating time: s Max Temperature: 134.7 °C d Heating time: 10 s Max Temperature: 140.8 °C Figure 5.8: Temperature distribution at the end of the heating step for thin ribbed molds with different heating times 25 Table 5.2: Experimental results of measuring the heating temperature of the thin rib mold cavity with different heating times Heating time (s) Measurement Measurement 10 position time (s) Mold temperature (oC) 30 30 30 30 99.2 100.2 101.2 102.2 118.6 119.9 120.1 121.1 116.4 123.4 124.2 125.6 111.1 121.5 132.6 133.5 10 107 118 129.5 142.3 12 115.5 126.7 140.8 14 122 137.2 16 133 30 30 30 30 101.2 102.1 103.3 104.2 120.6 121.9 122.2 123.6 118.5 125.5 126.6 127.2 116.7 124.4 134.7 135.1 10 112.0 121.3 132.5 140.8 12 118.4 130.2 144.2 14 125.1 141.6 16 138.1 30 30 30 30 99.2 100.3 101.2 102.3 116.2 117.5 118.3 119.9 114.1 122.4 123.4 124.8 110.4 120.1 130.5 131.1 10 105.6 117.2 128.9 141.4 12 113.2 125.7 138.3 14 121.1 134.5 16 131.1 Mold temperature when heating mold temperature whenatheating Mold temperature the end of heating and closing of the mold 26 Time for mold closing Temperature (°C) Temperature (°C) Time for mold closing End of heating step Melt fills into the cavity Point Point Point (*) Heating time: s End of heating step Melt fills into the cavity Point Point Point (*) Heating time: s Time (s) (a) Time (s) (b) Time for mold closing End of heating step Melt fills into the cavity Point Point Point (*) Heating time: s End of heating step Temperature (°C) Temperature (°C) Time for mold closing Melt fills into the cavity Point Point Point (*) Heating time: 10 s Time (s) Time (s) (c) (d) Figure 5.9: Comparison of thin ribbed mold surface temperature values at three measurement locations 5.2.2.2 Thin ribbed height filling results At each die temperature, the injection molding cycle was performed 20 times to achieve system stability, before the next 10 cycles were used to compare the tendon heights After the injection molding step, product samples were collected and ribbed height measured and the results are shown in Figures 5.10 and 5.11 When the mold temperature increases from 45 °C to 75 °C, the tendon height increases from 2.8 mm to 4.2 mm However, when Ex-GMTC is used with a 400 °C gas source, the mold temperature varies from 120.6 °C to 140.8 °C and the thin ribbed height reaches a maximum of mm This improvement is due to the ability to limit the thickness of the solid layer as the flow flows through the insert plate in the mold cavity, which increases the filling pressure at the thin ribbed position The experimental results comparing the height between two ribs on the same product also show that the height of the two ribs is different when controlling the mold temperature through the water channel integrated in the mold (Figure 3.25) This is because due to the asymmetry of the mold structure, the temperature distribution inside the mold is affected, especially in the case of lower mold temperatures In contrast, with Ex-GMTC, the heating affects only the injection mold surface, so the mold texture has almost no effect on the heating result Thus, the height of the two thin ribs is more uniform than the water heating control method In general, the Ex-GMTC method supports a better temperature distribution than the water heating method, resulting in a better temperature 27 balance in the flow that can be achieved, thereby improving the filling process full inside the mold 120,6 °C 125,5 °C 134,7 °C a Mold temperature control With the hot water b Mold temperature control With Ex - GMTC Figure 5.10: Rib height variation with different mold temperatures PA6 + 30 %GF - Gân PA6 + 30 %GF - Gân Chiều cao gân (mm) Chiều cao gân (mm) PA6 - Gân PA6 - Gân Nhiệt độ khuôn (oC) Nhiệt độ khuôn (oC) Figure 5.11: Comparison of thin ribbed height with different mold temperatures of PA6 and PA6 + 30 %GF 28 CONCLUSIONS Establishing a study model of thermoplastic composite material filling with different mold temperature regions Flow length of composite materials with thin-walled samples was determined by simulation and experiment with glass fiber ratio and variable mold temperature, especially with mold temperature region higher than 70 °C Through the experimental method of melt length, determine: - Regression equation for the relationship among flow length, mold temperature and product thickness - Ratio of flow length and product thickness for different mold temperatures, fiber ratios The method of heating the mold surface by hot air from outside is effective with thin-walled flow pattern and high mold temperature In which, with composite material PA6 + 30 %GF and flow thickness of 0.6 mm, when heated for 20 s, the mold surface temperature reaches 133.7 °C, the flow length is improved by 108.6 % Ex-GMTC mold temperature control can be performed on the entire mold cavity or at several locations before the composite material flows into the thin-walled and thin-rib site 29 LIST OF PUBLICATIONS Trần Minh Thế Uyên, Phan Thế Nhân, Phạm Sơn Minh, Thanh Trung Do Trần Văn Trọn, Ảnh hưởng áp suất phun đến chiều dài dòng chảy nhựa lỏng sản phẩm phun ép nhựa, Tạp chí Cơ khí Việt Nam, Số 7, 2014, trang 60-63 Pham Son Minh and Phan The Nhan, Effect of CaCO3 additive on the warpage of injection molding part, Universal Journal of Mechanical Engineering, Vol 2, Issue 9, 2014, p 280-286 Trần Minh Thế Uyên, Phan Thế Nhân, Phạm Sơn Minh Đỗ Thành Trung, Ảnh hưởng nhiệt độ đến chiều dài dịng chảy nhựa lỏng khn phun ép nhựa, Tạp chí Khoa học Giáo dục Kỹ thuật, Số 30, 2014, trang 15-20 Đỗ Thành Trung, Phạm Sơn Minh, Phan Thế Nhân Phùng Huy Dũng, Gia nhiệt cục cho lịng khn phun ép nhựa khí nóng, Tạp chí Cơ khí Việt Nam, Số 4, 2015, trang 15-20 Phạm Sơn Minh, Đỗ Thành Trung, Nguyễn Hộ Phan Thế Nhân, Đánh giá trình gia nhiệt cho lịng khn hình chữ nhật phương pháp phun khí nóng từ bên ngồi, Tạp chí Khoa học Giáo dục Kỹ thuật, Số 33, 2015, trang 9-15 Phạm Sơn Minh, Đỗ Thành Trung, Trần Minh Thế Uyên Phan Thế Nhân, Ảnh hưởng chiều dày sản phẩm nhiệt độ khuôn đến độ cong vênh sản phẩm nhựa polypropylene dạng tấm, Hội nghị Khoa học Cơng nghệ Tồn quốc Cơ khí lần thứ IV, Tp HCM, 2015, trang 536-543 Pham Son Minh, Thanh Trung Do, Tran Minh The Uyen and Phan The Nhan, A study on the welding line strength of composite parts with various venting systems in injection molding process, Key Engineering Materials, Vol 737, 2017, p 70-76 (SCOPUS Journal) Pham Son Minh and Phan The Nhan, Numerical study on the air heating for injection mold, International Journal of Research in Engineering and Science, Vol 6, Issue 8, 2018, p 31-35 Phan The Nhan, Thanh Trung Do, Tran Anh Son and Pham Son Minh, Study on external gas-assisted mold temperature control for improving the melt flow length of thin rib products in the injection molding process, Advances in Polymer Technology, 2019, p 1-17, doi.org/10.1155/2019/5973403 (SCIE Journal) 10 Phan The Nhan, Thanh Trung Do and Pham Son Minh, Numerical study on the melt flow length of the composite materials in the injection molding process, Materials Science Forum, Vol 971, 2019, p 15-20 (SCOPUS Journal) 11 Phan The Nhan, Nguyen Tinh and Nguyen Phuoc Thien, Study on the temperature distribution of the mold cavity with the air heating method, American Journal of Engineering Research (AJER), Vol 9, Issue 11, 2020, p 116-120 12 Phan Thế Nhân Nguyễn Tình, Nghiên cứu ảnh hưởng nhiệt độ khuôn đến áp suất định hình qui trình phun ép nhựa, Tạp chí Cơ khí Việt Nam, Số 11, 2020, trang 54-57 30 ... maximum heating rate of 6.4 °C/s with 400 °Cb Nhiệt gas b Nhiệt độ khí: độ khí: 250250 C C a Nhiệt a Nhiệt độ độ khí:khí: 200200 C C c Nhiệt c Nhiệt độ khí: độ khí: 300 300 C C 30 s30 s 30 s 30 s 30... s15 s 15 s 15 s 15 s 15 s 10 s10 s 10 s 10 s 10 s 10 s 5s 5s 5s 5s 5s Nhiệt Nhiệt độ độ Nhiệt Nhiệt độ độ o NhiệtNhiệt độ độ o o 30 s 30 s 30 s 30 s 30 s 30 s 30 s 25 s 25 s 25 s 25 s 25 s 25... Vol 9, Issue 11, 2020, p 116-120 12 Phan Thế Nhân Nguyễn Tình, Nghiên cứu ảnh hưởng nhiệt độ khn đến áp suất định hình qui trình phun ép nhựa, Tạp chí Cơ khí Việt Nam, Số 11, 2020, trang 54-57 30