Ti-Mo getters have been fabricated via metal injection molding (MIM) using three kinds of Ti powders with different mean particle sizes of 46 μm,35 μm and 26 μm,respectively. The surface morphology,porosity,and hyd...Ti-Mo getters have been fabricated via metal injection molding (MIM) using three kinds of Ti powders with different mean particle sizes of 46 μm,35 μm and 26 μm,respectively. The surface morphology,porosity,and hydrogen sorption properties of Ti-Mo getters formed by MIM using paraffin wax as a principal binder constituent were examined. It has been proven that the powder injection molding is a viable forming technique for porous Ti-Mo getters. The particle size of Ti powders and the powder loading influence the porosity of getters,and this affects the sorption capacity of Ti-Mo getters. Ti-Mo getters produced with the Ti powders possessing a mean particle size of 35 μm using a powder loading of 40 vol.% have a high porosity,resulting in a good sorption capacity.展开更多
The quality of injection plastic molded parts relates to precise geometry,smooth surface,strength,durability,and other indicators that are associated with the mold,materials,injection process,and service environment.T...The quality of injection plastic molded parts relates to precise geometry,smooth surface,strength,durability,and other indicators that are associated with the mold,materials,injection process,and service environment.The warpage is one of main defects of injection products,which cost much time and materials.In order to minimize warpage to ensure the precise shape of molded parts,it needs to combine design,service conditions,process parameters,material properties,and other factors in the design and manufacturing.Finite element tools and material database are used to analyze the occurrence of warpage,and analysis results contribute to the improvement and optimization of injection molding process of typical parts.To find the optimal process parameters in the solution space,experimental data are used to establish backpropagation(BP)network for predicting warpage of a bearing stand based on analysis with Moldflow.With a proper transfer function and the BP network architecture,results from the BP network method satisfiy the criteria of accuracy.The optimal solutions are searched in the BP network by the genetic algorithm with the finding that the optimization method based on the BP network is efficient.展开更多
Poly(3-hydroxy butyrate)-co-(3-hydroxy valerate)(PHBV)is a biobased and biodegradable polyester.This semicrystalline bioplastic could be a good candidate for the replacement of some commodity plastics derived from oil...Poly(3-hydroxy butyrate)-co-(3-hydroxy valerate)(PHBV)is a biobased and biodegradable polyester.This semicrystalline bioplastic could be a good candidate for the replacement of some commodity plastics derived from oil.However,the control of the conditions of its processing in order to obtain optimal properties of the finished products remains a current research subject.The objective of this work is to better understand the crystallization under injection molding conditions by inline measurements during the process.We focused on the influence of two key processing parameters,namely,mold temperature and packing pressure.The modeling of inline temperature measurements allowed an inverse estimation of the thermodynamic melting temperature of PHBV and of the heat of crystallization’s variations with processing parameters.展开更多
Residual stresses can reduce the reliability of plastic injection molding parts. This work is an attempt to model the residual stresses as a function of injection molding parameters. More stress is placed on reducing ...Residual stresses can reduce the reliability of plastic injection molding parts. This work is an attempt to model the residual stresses as a function of injection molding parameters. More stress is placed on reducing the number of input factors and to include all possible interactions. For this purpose, two-stage experimentation is suggested: a factor screening stage and Response Surface optimization stage. In screening stage Taguchi 3 level experimental design is used to classify the input parameters as significant and non-significant factors. Eight input variables were classified into 3 non-significant and 5 significant factors using this screening stage. Thus for the Response Surface optimization stage: instead of doing 160 experiments in Central Composite, 56 are only needed after the screening stage in half Central Composite Design. The best subset and regression model fitting tools in addition to model verification using randomly selected input setting were used to select a model for predicting residual stresses with a verified Root Mean Square Error (RSME) of nearly 0.93 MPa.展开更多
Plastic injection molding is a very complex process and its process planning has a direct influence on product quality and production efficiency. This paper studied the optimization of injection molding process by com...Plastic injection molding is a very complex process and its process planning has a direct influence on product quality and production efficiency. This paper studied the optimization of injection molding process by combining the numerical simulation with back-propagation(BP) networks. The BP networks are trained by the results of numerical simulation. The trained BP networks may:(1) shorten time for process planning;(2) optimize process parameters;(3) be employed in on-line quality control;(4) be integrated with knowledge-based system(KBS) and case-based reasoning(CBR) to make intelligent process planning of injection molding.展开更多
Quick material change is often encountered for the different colors or kinds of polymer in hot runner injecting molding process. Time costing and incompleteness of material change process often affects the quality and...Quick material change is often encountered for the different colors or kinds of polymer in hot runner injecting molding process. Time costing and incompleteness of material change process often affects the quality and productivity of products. In the practical production, multi injection or white material as the transition material is often adopted for quick material change. Based on the rheological behavior of the new and the previous plastic melt, the researches on the related problems were carried out. The concept of drag material change was originally presented. The physical and mathematical model on the simultaneous flow process of the new and the previous plastic melt in hot runner were built up, which can well explain the influence of the injection speed, pressure, viscosity difference, temperature and mold structure on the drag material change efficiency. When temperature in different position in the mold was increased and adjusted, the viscosity difference between the two kinds of melt can be controlled. Therefore the material change ability can be greatly improved during the whole material change process, getting rid of more and more difficult changing in the late stage.展开更多
Glass positioning and holding is difficult in the process of injection molding encapsulation of automobile glass. A suction cup or soft resin is always introduced in this process. However,these materials cannot hold g...Glass positioning and holding is difficult in the process of injection molding encapsulation of automobile glass. A suction cup or soft resin is always introduced in this process. However,these materials cannot hold glass tightly,thus resulting in the unsteady quality of toughened glass and encapsulated plastic. To solve this problem,a novel holding method called magnetic high-pressure holding with twin bags is proposed to address the features of toughened glass and the encapsulation injection process. Firstly,a pair of permanent magnets is introduced as energy source,followed by the magnetization of a couple of magnetic particle bags. Contact between the single bag and the glass surface will enable the couple of magnetic particle bags to hold glass tightly and to self-adapt the freeform of the glass. Secondly, an experimental system with mechanical and control systems is designed. This system is controlled by the opening and closing force of the mold,which turns the magnetic field on or off to hold or loosen the glass. The magnetic field distributions are measured at important positions of the permanent magnets and in the magnetized particles in the experiments to determine the holding performance. Finally, the process of determining the parameters of the magnet and its attenuation is analyzed, including the minimum friction force between the glass and the particle bag during injection molding,the magnetic energy product and the magnetized filed distributions,and the re-checking method for these parameters. The theoretical analysis and the experimental result show that this flexible holding system may produce sufficient holding force,which not only protects glass but self-adapts the glass freeform as well. The production practice meets the technical requirements of injection molding with a defect-free surface,with no scratches and cracks on the glass and no slight glass movements in the mold cavity.展开更多
This paper presents simulation study on Milled Grooved conformal cooling channels(MGCCC)in injection molding.MGCCC has a more effective cooling surface area which helps to provide efficient cooling as compared to conv...This paper presents simulation study on Milled Grooved conformal cooling channels(MGCCC)in injection molding.MGCCC has a more effective cooling surface area which helps to provide efficient cooling as compared to conventional cooling.A case study of Encloser part is investigated for cycle time reduction and quality improvement.The performance designs of straight drilled are compared with MGCCC by using Autodesk Moldflow Insight(AMI)2016.The results show total 32.1% reduction of cooling time and 9.86% reduction of warpage in case of MGCCC as compared to conventional cooling.展开更多
Cooling system improvement is important in injection molding to get betterquality and productivity. The aim of this paper was to compare the different shapes of theconformal cooling channels (CCC) with constant surfac...Cooling system improvement is important in injection molding to get betterquality and productivity. The aim of this paper was to compare the different shapes of theconformal cooling channels (CCC) with constant surface area and CCC with constantvolume in injection molding using Mold-flow Insight 2016 software. Also the CCC resultswere compared with conventional cooling channels. Four different shapes of the CCC suchas circular, elliptical, rectangular and semi-circular were proposed. The locations of thecooling channels were also kept constant. The results in terms of cooling time, cycle timereduction and improvement in quality of the product shows that no significant effect ofCCC’s shapes when surface area of CCC kept constant. On the other hand, the rectangularCCC shows better result as compared to other shapes of CCC when volume of CCC werekept constant.展开更多
In view of the high energy consumption and low response speed of the traditional hydraulic system for an injection molding machine,a servo motor driven constant pump hydraulic system is designed for a precision inject...In view of the high energy consumption and low response speed of the traditional hydraulic system for an injection molding machine,a servo motor driven constant pump hydraulic system is designed for a precision injection molding process,which uses a servo motor,a constant pump,and a pressure sensor,instead of a common motor,a constant pump,a pressure proportion valve,and a flow proportion valve.A model predictive control strategy based on neurodynamic optimization is proposed to control this new hydraulic system in the injection molding process.Simulation results showed that this control method has good control precision and quick response.展开更多
This paper deals with a multi-objective parameter optimization framework for energy saving in injection molding process.It combines an experimental design by Taguchi's method,a process analysis by analysis of vari...This paper deals with a multi-objective parameter optimization framework for energy saving in injection molding process.It combines an experimental design by Taguchi's method,a process analysis by analysis of variance(ANOVA),a process modeling algorithm by artificial neural network(ANN),and a multi-objective parameter optimization algorithm by genetic algorithm(GA)-based lexicographic method.Local and global Pareto analyses show the trade-off between product quality and energy consumption.The implementation of the proposed framework can reduce the energy consumption significantly in laboratory scale tests,and at the same time,the product quality can meet the pre-determined requirements.展开更多
Different types of polymer films were used in the combined in-mold decoration and microcellular injection molding(IMD/MIM)process.The multiphase fluid-solid coupled heat transfer model was established to study the the...Different types of polymer films were used in the combined in-mold decoration and microcellular injection molding(IMD/MIM)process.The multiphase fluid-solid coupled heat transfer model was established to study the thermal response at the melt filling stage in the IMD/MIM process.It was found that the temperature distributed asymmetrically along the thickness direction due to the changed heat transfer coefficient of the melt on the film side.When polyethylene terephthalate(PET)films were applied,the temperature of the melt-film interface increased faster and to be higher at the end of melt filling stage in comparison with the application of polycarbonate(PC)and thermoplastic polyurethane(TPU)films.And the effects of film types on the cellular structure,forming defects and mechanical properties of IMD/MIM parts were also studied experimentally.The results showed that the film types had no obvious effect on the cells size in the transition layer and the mechanical properties of the parts.Under certain film thickness,the offset distance of core layer was the largest with PET film used,while the offset distance was the smallest with TPU film used.And similar results were found for the warpage of the parts.However,an exactly opposite change occurred for the thickness of film-side transition layer and the bubble marks on the surface of the parts.展开更多
A novel category of polyphenylene oxide/high-impact polystyrene(PPO/HIPS)alloy was used as the polymer matrix(abbreviated as mPPO)and loaded with different volume fractions(0,10,20,30,40,50 vol.%)of MgTiO_(3)-Ca_(0.7)...A novel category of polyphenylene oxide/high-impact polystyrene(PPO/HIPS)alloy was used as the polymer matrix(abbreviated as mPPO)and loaded with different volume fractions(0,10,20,30,40,50 vol.%)of MgTiO_(3)-Ca_(0.7)La_(0.2)TiO_(3)(abbreviated as MTCLT)ceramics to prepare composites by injection molding.Its micromorphology,density,dielectric,thermal and mechanical properties were analyzed in detail.The experimental results show that the composites possess a compact microstructure because HIPS increases the fluidity of PPO.Due to the excellent dielectric properties of both mPPO and MTCLT,the composites have an extremely low dielectric loss.The realization of the high ceramic filler fraction greatly limits the thermal expansion of the polymer chain by introducing the interphase,so that the coefficient of thermal expansion of the composite material could be as low as 21.8 ppm/°C.At the same time,the presence of ceramic particles could reinforce the mechanical property of the compos-ites.When the ceramic filler fraction is higher than 20 vol.%,the bending strength of the composite material is around 110 MPa.When the ceramic filler fraction is 40 vol.%,the composite possesses the best comprehensive performance.The dielectric constant is 6.81,the dielectric loss is 0.00104,the thermal expansion coefficient is as low as 25.3 ppm/°C,and the bending strength is 110.4 MPa.Due to its excellent properties,this material can be a good candidate in the field of microwave communication.展开更多
Sintering additives and micro-powder injection molding offer an effective method to densify boron carbide(B_(4)C)and make B_(4)C components with complex shapes.By adjusting the proportion of three kinds of powders(SiC...Sintering additives and micro-powder injection molding offer an effective method to densify boron carbide(B_(4)C)and make B_(4)C components with complex shapes.By adjusting the proportion of three kinds of powders(SiC,Al_(2)O_(3)and Y_(2)O_(3)),four kinds of sintering additives were prepared.The feedstock uniformity,debinding behavior,phase composition and microstructure of micro injection molded B_(4)C components with different sintering additives were studied.The results showed that the defects such as lattice distortion and vacancy were introduced into ball milling,which increase the surface energy and benefit subsequent sintering densification.The feedstock had good uniformity and rheology that met the requirements of micro powder injection molding.After debinding,B_(4)C components had enough strength and showed certain sintering characteristics.The addition of sintering additives was beneficial to densification and sintering temperature reduction.The addition of sintering additives formed a second phase in the B_(4)C crystal and at the grain boundary of B_(4)C crystal,which changed the fracture mode from transgranular fracture to mixed fracture mechanism with transgranular fracture.展开更多
Density variation during the injection molding process directly reflects the state of plastic melt and contains valuable information for process monitoring and optimization.Therefore,in-situ density measurement is of ...Density variation during the injection molding process directly reflects the state of plastic melt and contains valuable information for process monitoring and optimization.Therefore,in-situ density measurement is of great interest and has significant application value.The existing methods,such as pressure−volume−temperature(PVT)method,have the shortages of time-delay and high cost of sensors.This study is the first to propose an in-situ density measurement method using ultrasonic technology.The analyses of the time-domain and frequency-domain signals are combined in the proposed method.The ultrasonic velocity is obtained from the time-domain signals,and the acoustic impedance is computed through a full-spectral analysis of the frequency-domain signals.Experiments with different process conditions are conducted,including different melt temperature,injection speed,material,and mold structure.Results show that the proposed method has good agreement with the PVT method.The proposed method has the advantages of in-situ measurement,non-destructive,high accuracy,low cost,and is of great application value for the injection molding industry.展开更多
Replication processes for the manufacturing of micro/nano-structured components are characterized by a certain degree of precision and accuracy.The transcription loss,or replication fidelity,defines the geometrical an...Replication processes for the manufacturing of micro/nano-structured components are characterized by a certain degree of precision and accuracy.The transcription loss,or replication fidelity,defines the geometrical and dimensional correspondence of micro/nano-structure from metal tool inserts into plastic patterned products.The employment of a vast spectrum of micro/nano-structured geometries calls for methodologies that can be used for the estimation of replication fidelity.This study presents a number of product fingerprints,which propose multiple ways to characterize micro/nano structures in replication technologies.Replication fidelity yielded values above 80%and up to 96%depending on the considered product fingerprints and their definition.Thereafter,a correlation of the product fingerprint with the process parameters was found to optimize the replication process.Measurement uncertainty accompanies the analysis of the product fingerprints,enabling a standardized,robust,and quantitative methodology for process learning,modeling,and optimization.展开更多
The linear isothermo-viscoelastic constitutive equation is established according to the principle of viscoelastic mechanics. Given the boundary conditions of the temperature field, the linear thermo-viscoelastic const...The linear isothermo-viscoelastic constitutive equation is established according to the principle of viscoelastic mechanics. Given the boundary conditions of the temperature field, the linear thermo-viscoelastic constitutive equation is established acording to the analysis of the thermorheologically simple. The stress analysis model is constructed on the base of some reasonable hypotheses which consider the restraint conditions of mold and the characteristics of injection molding in the post-filling stage. The mathematical model is calculated by the finite difference method. The results can help to predict the warpage of plastic products.展开更多
To tackle the challenge of producing highly filled polymer composites using the traditional injection molding technique,which is characterized by the fairly high melt viscosity that makes mold filling difficult,the au...To tackle the challenge of producing highly filled polymer composites using the traditional injection molding technique,which is characterized by the fairly high melt viscosity that makes mold filling difficult,the authors propose a solution based on dynamic covalent chemistry.As demonstrated by the proof-of-concept experiments,the 4-arm starshaped polycaprolactone(PCL)oligomers and microcrystalline cel-lulose(MCC)are crosslinked by the reversible Diels-Alder(DA)bonds.The flowability of the compounds greatly decreases due to the dissociation of the intercomponent DA bonds at the retro-reaction tempera-ture,and the networked architecture is reconstructed during cooling as a result of the forward DA reaction.Consequently,the high-loading MCC fillers are well distributed in the matrix and covalently bonded to the nearby PCL,forming a striking contrast to the control in which linear PCL acts as the matrix.The DA bonds crosslinked biodegradable PCL composites exhibit decent mechanical strength(20.7 MPa)even at the MCC fraction of 65 wt%,which is superior to those(5-12.2 MPa)of the highly filled PCL composites(with filler contents of 50-63.8 wt%)reported so far.The proposed approach has sufficient expansibility for the fabrication of the highly filled polymer composites constructed by other types of matrix and fillers.展开更多
In this study, the relationship between skin structure and shear strength distribution of thin-wall injection molded polypropylene (PP) molded at different molecular weight and molecular distribution was investigated....In this study, the relationship between skin structure and shear strength distribution of thin-wall injection molded polypropylene (PP) molded at different molecular weight and molecular distribution was investigated. Skin-core structure, cross-sectional morphology, crystallinity, crystal orientation, crystal morphology and molecular orientation were evaluated by using polarized optical microscope, differential scanning calorimeter, X-ray spectroscopic analyzer and laser Raman spectroscopy, respectively, while the shear strength distribution was investigated using a micro cutting method called SAICAS (Surface And Interfacial Cutting Analysis System). The results indicated that the difference of molecular weight and molecular weight distribution showed own skin layer thickness. Especially, high molecular weight sample showed thicker layer of the lamellar orientation and molecular orientation than low molecular weight sample. In addition, wide molecular distribution sample showed large crystal orientation layer.展开更多
Thin-wall injection molded parts have been paid much attention to the lightweight saving from viewpoints of natural resources saving. In the injection molding, skin-core structure can be found in the parts. This skin-...Thin-wall injection molded parts have been paid much attention to the lightweight saving from viewpoints of natural resources saving. In the injection molding, skin-core structure can be found in the parts. This skin-core structure affects the property of completed injection molding parts (bulk property) even if in thin-wall injection molding. However, there is a few research about the relationship between bulk property and internal property distribution in the injection molding specimen. In this study, thin-wall injection molded parts of polypropylene (PP) were prepared by 4 different molecular weight and molecular weight distribution to reveal the relationship between bulk property and property distribution. These characteristics were investigated by using tensile test, fracture toughness characterized by Essential Work of Fracture (EWF) method for bulk property and film tensile test by sliced sample for tensile property distribution. The property distribution test results revealed that the highly bulk property sample had thicker highly mechanical property layer on its surface.展开更多
文摘Ti-Mo getters have been fabricated via metal injection molding (MIM) using three kinds of Ti powders with different mean particle sizes of 46 μm,35 μm and 26 μm,respectively. The surface morphology,porosity,and hydrogen sorption properties of Ti-Mo getters formed by MIM using paraffin wax as a principal binder constituent were examined. It has been proven that the powder injection molding is a viable forming technique for porous Ti-Mo getters. The particle size of Ti powders and the powder loading influence the porosity of getters,and this affects the sorption capacity of Ti-Mo getters. Ti-Mo getters produced with the Ti powders possessing a mean particle size of 35 μm using a powder loading of 40 vol.% have a high porosity,resulting in a good sorption capacity.
基金supported by a grant from the Ningbo Furja Industrial Corporation Limited
文摘The quality of injection plastic molded parts relates to precise geometry,smooth surface,strength,durability,and other indicators that are associated with the mold,materials,injection process,and service environment.The warpage is one of main defects of injection products,which cost much time and materials.In order to minimize warpage to ensure the precise shape of molded parts,it needs to combine design,service conditions,process parameters,material properties,and other factors in the design and manufacturing.Finite element tools and material database are used to analyze the occurrence of warpage,and analysis results contribute to the improvement and optimization of injection molding process of typical parts.To find the optimal process parameters in the solution space,experimental data are used to establish backpropagation(BP)network for predicting warpage of a bearing stand based on analysis with Moldflow.With a proper transfer function and the BP network architecture,results from the BP network method satisfiy the criteria of accuracy.The optimal solutions are searched in the BP network by the genetic algorithm with the finding that the optimization method based on the BP network is efficient.
文摘Poly(3-hydroxy butyrate)-co-(3-hydroxy valerate)(PHBV)is a biobased and biodegradable polyester.This semicrystalline bioplastic could be a good candidate for the replacement of some commodity plastics derived from oil.However,the control of the conditions of its processing in order to obtain optimal properties of the finished products remains a current research subject.The objective of this work is to better understand the crystallization under injection molding conditions by inline measurements during the process.We focused on the influence of two key processing parameters,namely,mold temperature and packing pressure.The modeling of inline temperature measurements allowed an inverse estimation of the thermodynamic melting temperature of PHBV and of the heat of crystallization’s variations with processing parameters.
文摘Residual stresses can reduce the reliability of plastic injection molding parts. This work is an attempt to model the residual stresses as a function of injection molding parameters. More stress is placed on reducing the number of input factors and to include all possible interactions. For this purpose, two-stage experimentation is suggested: a factor screening stage and Response Surface optimization stage. In screening stage Taguchi 3 level experimental design is used to classify the input parameters as significant and non-significant factors. Eight input variables were classified into 3 non-significant and 5 significant factors using this screening stage. Thus for the Response Surface optimization stage: instead of doing 160 experiments in Central Composite, 56 are only needed after the screening stage in half Central Composite Design. The best subset and regression model fitting tools in addition to model verification using randomly selected input setting were used to select a model for predicting residual stresses with a verified Root Mean Square Error (RSME) of nearly 0.93 MPa.
文摘Plastic injection molding is a very complex process and its process planning has a direct influence on product quality and production efficiency. This paper studied the optimization of injection molding process by combining the numerical simulation with back-propagation(BP) networks. The BP networks are trained by the results of numerical simulation. The trained BP networks may:(1) shorten time for process planning;(2) optimize process parameters;(3) be employed in on-line quality control;(4) be integrated with knowledge-based system(KBS) and case-based reasoning(CBR) to make intelligent process planning of injection molding.
文摘Quick material change is often encountered for the different colors or kinds of polymer in hot runner injecting molding process. Time costing and incompleteness of material change process often affects the quality and productivity of products. In the practical production, multi injection or white material as the transition material is often adopted for quick material change. Based on the rheological behavior of the new and the previous plastic melt, the researches on the related problems were carried out. The concept of drag material change was originally presented. The physical and mathematical model on the simultaneous flow process of the new and the previous plastic melt in hot runner were built up, which can well explain the influence of the injection speed, pressure, viscosity difference, temperature and mold structure on the drag material change efficiency. When temperature in different position in the mold was increased and adjusted, the viscosity difference between the two kinds of melt can be controlled. Therefore the material change ability can be greatly improved during the whole material change process, getting rid of more and more difficult changing in the late stage.
基金National Natural Science Foundation of China(No.51303027)Program for New Century Excellent Talents in Fujian Province University,China(No.NCETFJ-2010)+1 种基金Research Fund for Fujian Provincial University,China(No.JK2010038)Research Fund of Fujian Education Department,China(No.JA11189)
文摘Glass positioning and holding is difficult in the process of injection molding encapsulation of automobile glass. A suction cup or soft resin is always introduced in this process. However,these materials cannot hold glass tightly,thus resulting in the unsteady quality of toughened glass and encapsulated plastic. To solve this problem,a novel holding method called magnetic high-pressure holding with twin bags is proposed to address the features of toughened glass and the encapsulation injection process. Firstly,a pair of permanent magnets is introduced as energy source,followed by the magnetization of a couple of magnetic particle bags. Contact between the single bag and the glass surface will enable the couple of magnetic particle bags to hold glass tightly and to self-adapt the freeform of the glass. Secondly, an experimental system with mechanical and control systems is designed. This system is controlled by the opening and closing force of the mold,which turns the magnetic field on or off to hold or loosen the glass. The magnetic field distributions are measured at important positions of the permanent magnets and in the magnetized particles in the experiments to determine the holding performance. Finally, the process of determining the parameters of the magnet and its attenuation is analyzed, including the minimum friction force between the glass and the particle bag during injection molding,the magnetic energy product and the magnetized filed distributions,and the re-checking method for these parameters. The theoretical analysis and the experimental result show that this flexible holding system may produce sufficient holding force,which not only protects glass but self-adapts the glass freeform as well. The production practice meets the technical requirements of injection molding with a defect-free surface,with no scratches and cracks on the glass and no slight glass movements in the mold cavity.
文摘This paper presents simulation study on Milled Grooved conformal cooling channels(MGCCC)in injection molding.MGCCC has a more effective cooling surface area which helps to provide efficient cooling as compared to conventional cooling.A case study of Encloser part is investigated for cycle time reduction and quality improvement.The performance designs of straight drilled are compared with MGCCC by using Autodesk Moldflow Insight(AMI)2016.The results show total 32.1% reduction of cooling time and 9.86% reduction of warpage in case of MGCCC as compared to conventional cooling.
文摘Cooling system improvement is important in injection molding to get betterquality and productivity. The aim of this paper was to compare the different shapes of theconformal cooling channels (CCC) with constant surface area and CCC with constantvolume in injection molding using Mold-flow Insight 2016 software. Also the CCC resultswere compared with conventional cooling channels. Four different shapes of the CCC suchas circular, elliptical, rectangular and semi-circular were proposed. The locations of thecooling channels were also kept constant. The results in terms of cooling time, cycle timereduction and improvement in quality of the product shows that no significant effect ofCCC’s shapes when surface area of CCC kept constant. On the other hand, the rectangularCCC shows better result as compared to other shapes of CCC when volume of CCC werekept constant.
基金Project supported by the National Natural Science Foundation of China(No.61203299)the Fundamental Research Funds for the Central Universities(No.2013QNA4021)+1 种基金the Natural Science Foundation of Zhejiang Province(Nos.Y1110135 and LY12F03018)the Qianjiang Talents Program of Zhejiang Province,China(No.2013R10047)
文摘In view of the high energy consumption and low response speed of the traditional hydraulic system for an injection molding machine,a servo motor driven constant pump hydraulic system is designed for a precision injection molding process,which uses a servo motor,a constant pump,and a pressure sensor,instead of a common motor,a constant pump,a pressure proportion valve,and a flow proportion valve.A model predictive control strategy based on neurodynamic optimization is proposed to control this new hydraulic system in the injection molding process.Simulation results showed that this control method has good control precision and quick response.
基金(Nos. 20806040,61073059 and 61034005) supported by the National Natural Science Foundation of China
文摘This paper deals with a multi-objective parameter optimization framework for energy saving in injection molding process.It combines an experimental design by Taguchi's method,a process analysis by analysis of variance(ANOVA),a process modeling algorithm by artificial neural network(ANN),and a multi-objective parameter optimization algorithm by genetic algorithm(GA)-based lexicographic method.Local and global Pareto analyses show the trade-off between product quality and energy consumption.The implementation of the proposed framework can reduce the energy consumption significantly in laboratory scale tests,and at the same time,the product quality can meet the pre-determined requirements.
基金financially supported by the National Natural Science Foundation of China(Nos.51801141 and 51605356)the 111 Project(No.B17034)+1 种基金the Innovative Research Team Development Program of Ministry of Education of China(No.IRT17R83)the Fundamental Research Funds for the Central Universities(No.WUT:2017IVB035)。
文摘Different types of polymer films were used in the combined in-mold decoration and microcellular injection molding(IMD/MIM)process.The multiphase fluid-solid coupled heat transfer model was established to study the thermal response at the melt filling stage in the IMD/MIM process.It was found that the temperature distributed asymmetrically along the thickness direction due to the changed heat transfer coefficient of the melt on the film side.When polyethylene terephthalate(PET)films were applied,the temperature of the melt-film interface increased faster and to be higher at the end of melt filling stage in comparison with the application of polycarbonate(PC)and thermoplastic polyurethane(TPU)films.And the effects of film types on the cellular structure,forming defects and mechanical properties of IMD/MIM parts were also studied experimentally.The results showed that the film types had no obvious effect on the cells size in the transition layer and the mechanical properties of the parts.Under certain film thickness,the offset distance of core layer was the largest with PET film used,while the offset distance was the smallest with TPU film used.And similar results were found for the warpage of the parts.However,an exactly opposite change occurred for the thickness of film-side transition layer and the bubble marks on the surface of the parts.
文摘A novel category of polyphenylene oxide/high-impact polystyrene(PPO/HIPS)alloy was used as the polymer matrix(abbreviated as mPPO)and loaded with different volume fractions(0,10,20,30,40,50 vol.%)of MgTiO_(3)-Ca_(0.7)La_(0.2)TiO_(3)(abbreviated as MTCLT)ceramics to prepare composites by injection molding.Its micromorphology,density,dielectric,thermal and mechanical properties were analyzed in detail.The experimental results show that the composites possess a compact microstructure because HIPS increases the fluidity of PPO.Due to the excellent dielectric properties of both mPPO and MTCLT,the composites have an extremely low dielectric loss.The realization of the high ceramic filler fraction greatly limits the thermal expansion of the polymer chain by introducing the interphase,so that the coefficient of thermal expansion of the composite material could be as low as 21.8 ppm/°C.At the same time,the presence of ceramic particles could reinforce the mechanical property of the compos-ites.When the ceramic filler fraction is higher than 20 vol.%,the bending strength of the composite material is around 110 MPa.When the ceramic filler fraction is 40 vol.%,the composite possesses the best comprehensive performance.The dielectric constant is 6.81,the dielectric loss is 0.00104,the thermal expansion coefficient is as low as 25.3 ppm/°C,and the bending strength is 110.4 MPa.Due to its excellent properties,this material can be a good candidate in the field of microwave communication.
基金supported by the National Natural Science Foundation of China(Grant No.52075250)the China Postdoctoral Science Foundation(No.2020M683376)the National Key Laboratory of Science and Technology on Helicopter Transmission(No.HTL-O-19G09)。
文摘Sintering additives and micro-powder injection molding offer an effective method to densify boron carbide(B_(4)C)and make B_(4)C components with complex shapes.By adjusting the proportion of three kinds of powders(SiC,Al_(2)O_(3)and Y_(2)O_(3)),four kinds of sintering additives were prepared.The feedstock uniformity,debinding behavior,phase composition and microstructure of micro injection molded B_(4)C components with different sintering additives were studied.The results showed that the defects such as lattice distortion and vacancy were introduced into ball milling,which increase the surface energy and benefit subsequent sintering densification.The feedstock had good uniformity and rheology that met the requirements of micro powder injection molding.After debinding,B_(4)C components had enough strength and showed certain sintering characteristics.The addition of sintering additives was beneficial to densification and sintering temperature reduction.The addition of sintering additives formed a second phase in the B_(4)C crystal and at the grain boundary of B_(4)C crystal,which changed the fracture mode from transgranular fracture to mixed fracture mechanism with transgranular fracture.
基金supported by the“Pioneer”and“Leading Goose”R&D Program of Zhejiang,China(Grant No.2022C01069)the National Natural Science Foundation of China(Grant No.51875519)+1 种基金the Key Project of Science and Technology Innovation 2025 of Ningbo City,China(Grant No.2021Z044)the Project of Innovation Enterprises Union of Ningbo City,China(Grant No.2021H002).
文摘Density variation during the injection molding process directly reflects the state of plastic melt and contains valuable information for process monitoring and optimization.Therefore,in-situ density measurement is of great interest and has significant application value.The existing methods,such as pressure−volume−temperature(PVT)method,have the shortages of time-delay and high cost of sensors.This study is the first to propose an in-situ density measurement method using ultrasonic technology.The analyses of the time-domain and frequency-domain signals are combined in the proposed method.The ultrasonic velocity is obtained from the time-domain signals,and the acoustic impedance is computed through a full-spectral analysis of the frequency-domain signals.Experiments with different process conditions are conducted,including different melt temperature,injection speed,material,and mold structure.Results show that the proposed method has good agreement with the PVT method.The proposed method has the advantages of in-situ measurement,non-destructive,high accuracy,low cost,and is of great application value for the injection molding industry.
基金The PROSURF project(“Surface Specifications and Process Chains for Functional Surfaces”,http://www.prosurf-project.eu/)is funded by the HORIZON 2020 program(Project ID:767589)the European Commission.MADE DIGITAL(Project ID:6151-00006B),Manufacturing Academy of Denmark(http://en.made.dk/),Work Package WP3“Digital manufacturing processes”,is funded by Innovation Fund Denmark(https://innovationsfonden.dk/en).
文摘Replication processes for the manufacturing of micro/nano-structured components are characterized by a certain degree of precision and accuracy.The transcription loss,or replication fidelity,defines the geometrical and dimensional correspondence of micro/nano-structure from metal tool inserts into plastic patterned products.The employment of a vast spectrum of micro/nano-structured geometries calls for methodologies that can be used for the estimation of replication fidelity.This study presents a number of product fingerprints,which propose multiple ways to characterize micro/nano structures in replication technologies.Replication fidelity yielded values above 80%and up to 96%depending on the considered product fingerprints and their definition.Thereafter,a correlation of the product fingerprint with the process parameters was found to optimize the replication process.Measurement uncertainty accompanies the analysis of the product fingerprints,enabling a standardized,robust,and quantitative methodology for process learning,modeling,and optimization.
文摘The linear isothermo-viscoelastic constitutive equation is established according to the principle of viscoelastic mechanics. Given the boundary conditions of the temperature field, the linear thermo-viscoelastic constitutive equation is established acording to the analysis of the thermorheologically simple. The stress analysis model is constructed on the base of some reasonable hypotheses which consider the restraint conditions of mold and the characteristics of injection molding in the post-filling stage. The mathematical model is calculated by the finite difference method. The results can help to predict the warpage of plastic products.
基金the support of the National Natural Science Foundation of China(Grants:52033011,51973237,and 52173092)Natural Science Foundation of Guangdong Province(Grants:2019B1515120038,2020A1515011276,2021A1515010417)+1 种基金Science and Technology Planning Project of Guangzhou City(Grant:202201011568)Fundamental Research Funds for the Central Universities,Sun Yatsen University(Grant:23yxqntd002).
文摘To tackle the challenge of producing highly filled polymer composites using the traditional injection molding technique,which is characterized by the fairly high melt viscosity that makes mold filling difficult,the authors propose a solution based on dynamic covalent chemistry.As demonstrated by the proof-of-concept experiments,the 4-arm starshaped polycaprolactone(PCL)oligomers and microcrystalline cel-lulose(MCC)are crosslinked by the reversible Diels-Alder(DA)bonds.The flowability of the compounds greatly decreases due to the dissociation of the intercomponent DA bonds at the retro-reaction tempera-ture,and the networked architecture is reconstructed during cooling as a result of the forward DA reaction.Consequently,the high-loading MCC fillers are well distributed in the matrix and covalently bonded to the nearby PCL,forming a striking contrast to the control in which linear PCL acts as the matrix.The DA bonds crosslinked biodegradable PCL composites exhibit decent mechanical strength(20.7 MPa)even at the MCC fraction of 65 wt%,which is superior to those(5-12.2 MPa)of the highly filled PCL composites(with filler contents of 50-63.8 wt%)reported so far.The proposed approach has sufficient expansibility for the fabrication of the highly filled polymer composites constructed by other types of matrix and fillers.
文摘In this study, the relationship between skin structure and shear strength distribution of thin-wall injection molded polypropylene (PP) molded at different molecular weight and molecular distribution was investigated. Skin-core structure, cross-sectional morphology, crystallinity, crystal orientation, crystal morphology and molecular orientation were evaluated by using polarized optical microscope, differential scanning calorimeter, X-ray spectroscopic analyzer and laser Raman spectroscopy, respectively, while the shear strength distribution was investigated using a micro cutting method called SAICAS (Surface And Interfacial Cutting Analysis System). The results indicated that the difference of molecular weight and molecular weight distribution showed own skin layer thickness. Especially, high molecular weight sample showed thicker layer of the lamellar orientation and molecular orientation than low molecular weight sample. In addition, wide molecular distribution sample showed large crystal orientation layer.
文摘Thin-wall injection molded parts have been paid much attention to the lightweight saving from viewpoints of natural resources saving. In the injection molding, skin-core structure can be found in the parts. This skin-core structure affects the property of completed injection molding parts (bulk property) even if in thin-wall injection molding. However, there is a few research about the relationship between bulk property and internal property distribution in the injection molding specimen. In this study, thin-wall injection molded parts of polypropylene (PP) were prepared by 4 different molecular weight and molecular weight distribution to reveal the relationship between bulk property and property distribution. These characteristics were investigated by using tensile test, fracture toughness characterized by Essential Work of Fracture (EWF) method for bulk property and film tensile test by sliced sample for tensile property distribution. The property distribution test results revealed that the highly bulk property sample had thicker highly mechanical property layer on its surface.
