With the rapid development of information and multi me dia technologies, the demand for the optical plastic aspheric elements used in o pto-electronic devices, camera, optical disc and projector lens etc. has been i n...With the rapid development of information and multi me dia technologies, the demand for the optical plastic aspheric elements used in o pto-electronic devices, camera, optical disc and projector lens etc. has been i ncreased rapidly in the recent years. The key technologies of fabrication of asp heric plastic lens are the design and manufacturing moulds, selection of proper injection moulding equipment, and optimization of injection moulding parameters etc. In this paper, the effect of injection pressure, moulding temperature, cool ing time and injection speed on the surface profile of the lenses during injecti on and holding process is investigated. Surface quality of plastic lenses is mea sured by Talysurf Texture Measuring System. The experimental results showed that the injection pressure and moulding temperature are important parameters compar ing to cooling time and injection speed. A bit change of injection pressure or m oulding temperature will affect the property of the surface profile. Either incr easing injection pressure or mould temperature can achieve less shrinkage. Other wise, a lower injection pressure will produce more shrinkage, more air traps and a lower mould temperature results greater warp and higher shrinkage. The dynami c process of injection for optical plastic lenses is simulated by 3D Moldflow pl astic Insight software (MPI). The MPI will help us to optimize injection mouldin g parameters.展开更多
In an injection moulding process, the parallelism b et ween the tie bars of the injection moulding machine is very important as it will affect the mould closing and clamping system. In recent years, more and more ho t...In an injection moulding process, the parallelism b et ween the tie bars of the injection moulding machine is very important as it will affect the mould closing and clamping system. In recent years, more and more ho t runner systems are being applied in the moulding industry to save material and decrease the losses of injection pressure. Heat transfer from hot runner system from the fixed half which is secured in the fix machine platen could transmit s o much heat that it may cause high temperature differential between the machine fix platen and moving platen. This will cause the tie bar to become unparallel. Part quality will be compromised and the wear of the tie bar will be excessive. Overhaul of the tie bar may be necessary after a short period of time which is c ostly. This raises the need to analyze the heat transfer from the hot runner sys tem to the machine fix platen and the methods of isolating or minimizing the hea t transfer. In this case study, a photo lens article mould was used. The mould w as built with a direct hot runner nozzle system. Heat conduction from hot runner and machine screw to machine fix platen were studied based on either using high temperature heat insulating plate put in placed between the mould and the mould ing machine fix platen or drill cooling channels in the front mould clamping pla te. The high temperature insulator is very costly as it is made out of glass re inforced polymer composite material. Experimental results were obtained and anal yzed to find the best method to minimize the unwanted heat transfer using the ch eapest and most effective method.展开更多
Obtaining the optimal values of the parameters for th e design of a required mould and the operation of the moulding process are diffi cult, this is due to the complexity of product geometry and the variation of pla s...Obtaining the optimal values of the parameters for th e design of a required mould and the operation of the moulding process are diffi cult, this is due to the complexity of product geometry and the variation of pla stic material properties. The typical parameters for the mould design and mouldi ng process are melt flow length, injection pressure, holding pressure, back pres sure, injection speed, melt temperature, mould temperature, clamping force, inje ction time, holding time and cooling time. This paper discusses the difficulties of using the current computer aided optimization methods to acquire the values of the parameters. A method that is based on the concept of genetic algorithm is proposed to overcome the difficulties. The proposed method describes in details on how to attain the optimal values of the parameters form a given product geom etry.展开更多
In an injection moulding process, the mould cooling s ystem is very important as an efficient and uniform cooling effect can improve b oth the productivity and part quality. Due to the complexity of the process, muc h...In an injection moulding process, the mould cooling s ystem is very important as an efficient and uniform cooling effect can improve b oth the productivity and part quality. Due to the complexity of the process, muc h research on the mould cooling analysis and cooling design optimization has bee n focused on the core and the cavity, excluding other systems of injection mould s. However, the runner system introduces a considerable amount of heat into the mould. In recent years, more and more hot runner systems are being applied in th e moulding industry to save material and decrease losses of injection pressure. This raises the need to include the hot runner system in the cooling analysis. I n this paper, a photo frame part was studied. The mould was built with a hot run ner system. Two thermal sensors were installed: one measures the temperature of lateral surface of hot runner nozzle; the other measures the plastic temperature from the core side. A pressure sensor was also installed to measure the pressur e of the core impression. Cooling analysis was performed using ABAQUS, ananalysi s software based on the Finite Element Method (FEM). The assembly including core , cavity and plastic part was modeled. Heat conduction from hot runner to cavity and from polymer melt to the mould and force convection on the cooling channel surfaces were studied. The natural convection between the ambient air and the ex terior mould surface was ignored. The simulations were adjusted with the experim ental results to find out the heat input from hot runner and its influence on mo uld cooling. Finally, the optimal cooling design and optimal injection condition were obtained.展开更多
Today, the time-to-market for plastic products ar e getting shorter, thus the lead-time for making the injection mould is decreasin g. There is potential in timesavings in the mould design stage because the design pro...Today, the time-to-market for plastic products ar e getting shorter, thus the lead-time for making the injection mould is decreasin g. There is potential in timesavings in the mould design stage because the design process that is repeatable for every mould design can be standardized. T he preliminary work of any final plastic injection mould design is to always pro vide an initial design of the mould assembly for product designers (customers) p rior to receiving the final product CAD data. Traditionally and even up till no w, this initial design is always created using 2D CAD packages. The information used for the initial design is based on the technical discussion checklist, in which most mould makers have their own standards. This checklist is also being used as a quotation since the most basic information of the mould in the particu lar project is being recorded in it. The basic information in this checklist in cludes the number of cavities, the type of mould base to be used, the moulding m achine to be used for the moulding, the type of gating system, the type of resin material used and its shrinkage value etc. Information on special requirements such as the number of sliders or lifters to be used is also listed in the check list. At this stage, there is still no information on the cooling and ejection design since they are greatly dependent on the final product CAD data. This res earch focuses on the methodology of providing the initial design in 3D solid bas ed on the technical discussion checklist, which takes the role of the overall st andard template since every sub-design has its own standard template. An examp le of a sub-design that has its own standard template is the cavity layout desi gn. The cavity layout for plastic injection moulds can be designed by controlli ng the geometrical parameters using a standardization template. The standardiza tion template for the cavity layout design consists of configurations for the po ssible layouts. Each configuration of the layout design has its own layout desi gn table of all the geometrical parameters. This standardization template is pr e-defined in the layout design level of the mould assembly design. This ensure s that the required configuration can be loaded into the mould assembly design v ery quickly without having the need to redesign the layout. This makes it usefu l for technical discussions between the product designers and mould designers pr ior to the manufacture of the mould. Changes can be made to the 3D cavity layou t design immediately during the discussions thus the savings in time and avo idance of miscommunications.展开更多
To evaluate the bioeompatibility of MIM 316L stainless steel,the percentage of S-period cells were detected by flow cytometry after L929 incubated with extraction of MIM 316L stainless steel,using titanium implant mat...To evaluate the bioeompatibility of MIM 316L stainless steel,the percentage of S-period cells were detected by flow cytometry after L929 incubated with extraction of MIM 316L stainless steel,using titanium implant materials of clinical application as the contrast.Both materials were implanted in animal and the histopathological evaluations were carried out.The statistical analyses show that there are no significant differences between two groups(P>0.05),which demonstrates that MIM 316L stainless steel has a good biocompatibility.展开更多
文摘With the rapid development of information and multi me dia technologies, the demand for the optical plastic aspheric elements used in o pto-electronic devices, camera, optical disc and projector lens etc. has been i ncreased rapidly in the recent years. The key technologies of fabrication of asp heric plastic lens are the design and manufacturing moulds, selection of proper injection moulding equipment, and optimization of injection moulding parameters etc. In this paper, the effect of injection pressure, moulding temperature, cool ing time and injection speed on the surface profile of the lenses during injecti on and holding process is investigated. Surface quality of plastic lenses is mea sured by Talysurf Texture Measuring System. The experimental results showed that the injection pressure and moulding temperature are important parameters compar ing to cooling time and injection speed. A bit change of injection pressure or m oulding temperature will affect the property of the surface profile. Either incr easing injection pressure or mould temperature can achieve less shrinkage. Other wise, a lower injection pressure will produce more shrinkage, more air traps and a lower mould temperature results greater warp and higher shrinkage. The dynami c process of injection for optical plastic lenses is simulated by 3D Moldflow pl astic Insight software (MPI). The MPI will help us to optimize injection mouldin g parameters.
文摘In an injection moulding process, the parallelism b et ween the tie bars of the injection moulding machine is very important as it will affect the mould closing and clamping system. In recent years, more and more ho t runner systems are being applied in the moulding industry to save material and decrease the losses of injection pressure. Heat transfer from hot runner system from the fixed half which is secured in the fix machine platen could transmit s o much heat that it may cause high temperature differential between the machine fix platen and moving platen. This will cause the tie bar to become unparallel. Part quality will be compromised and the wear of the tie bar will be excessive. Overhaul of the tie bar may be necessary after a short period of time which is c ostly. This raises the need to analyze the heat transfer from the hot runner sys tem to the machine fix platen and the methods of isolating or minimizing the hea t transfer. In this case study, a photo lens article mould was used. The mould w as built with a direct hot runner nozzle system. Heat conduction from hot runner and machine screw to machine fix platen were studied based on either using high temperature heat insulating plate put in placed between the mould and the mould ing machine fix platen or drill cooling channels in the front mould clamping pla te. The high temperature insulator is very costly as it is made out of glass re inforced polymer composite material. Experimental results were obtained and anal yzed to find the best method to minimize the unwanted heat transfer using the ch eapest and most effective method.
文摘Obtaining the optimal values of the parameters for th e design of a required mould and the operation of the moulding process are diffi cult, this is due to the complexity of product geometry and the variation of pla stic material properties. The typical parameters for the mould design and mouldi ng process are melt flow length, injection pressure, holding pressure, back pres sure, injection speed, melt temperature, mould temperature, clamping force, inje ction time, holding time and cooling time. This paper discusses the difficulties of using the current computer aided optimization methods to acquire the values of the parameters. A method that is based on the concept of genetic algorithm is proposed to overcome the difficulties. The proposed method describes in details on how to attain the optimal values of the parameters form a given product geom etry.
文摘In an injection moulding process, the mould cooling s ystem is very important as an efficient and uniform cooling effect can improve b oth the productivity and part quality. Due to the complexity of the process, muc h research on the mould cooling analysis and cooling design optimization has bee n focused on the core and the cavity, excluding other systems of injection mould s. However, the runner system introduces a considerable amount of heat into the mould. In recent years, more and more hot runner systems are being applied in th e moulding industry to save material and decrease losses of injection pressure. This raises the need to include the hot runner system in the cooling analysis. I n this paper, a photo frame part was studied. The mould was built with a hot run ner system. Two thermal sensors were installed: one measures the temperature of lateral surface of hot runner nozzle; the other measures the plastic temperature from the core side. A pressure sensor was also installed to measure the pressur e of the core impression. Cooling analysis was performed using ABAQUS, ananalysi s software based on the Finite Element Method (FEM). The assembly including core , cavity and plastic part was modeled. Heat conduction from hot runner to cavity and from polymer melt to the mould and force convection on the cooling channel surfaces were studied. The natural convection between the ambient air and the ex terior mould surface was ignored. The simulations were adjusted with the experim ental results to find out the heat input from hot runner and its influence on mo uld cooling. Finally, the optimal cooling design and optimal injection condition were obtained.
文摘Today, the time-to-market for plastic products ar e getting shorter, thus the lead-time for making the injection mould is decreasin g. There is potential in timesavings in the mould design stage because the design process that is repeatable for every mould design can be standardized. T he preliminary work of any final plastic injection mould design is to always pro vide an initial design of the mould assembly for product designers (customers) p rior to receiving the final product CAD data. Traditionally and even up till no w, this initial design is always created using 2D CAD packages. The information used for the initial design is based on the technical discussion checklist, in which most mould makers have their own standards. This checklist is also being used as a quotation since the most basic information of the mould in the particu lar project is being recorded in it. The basic information in this checklist in cludes the number of cavities, the type of mould base to be used, the moulding m achine to be used for the moulding, the type of gating system, the type of resin material used and its shrinkage value etc. Information on special requirements such as the number of sliders or lifters to be used is also listed in the check list. At this stage, there is still no information on the cooling and ejection design since they are greatly dependent on the final product CAD data. This res earch focuses on the methodology of providing the initial design in 3D solid bas ed on the technical discussion checklist, which takes the role of the overall st andard template since every sub-design has its own standard template. An examp le of a sub-design that has its own standard template is the cavity layout desi gn. The cavity layout for plastic injection moulds can be designed by controlli ng the geometrical parameters using a standardization template. The standardiza tion template for the cavity layout design consists of configurations for the po ssible layouts. Each configuration of the layout design has its own layout desi gn table of all the geometrical parameters. This standardization template is pr e-defined in the layout design level of the mould assembly design. This ensure s that the required configuration can be loaded into the mould assembly design v ery quickly without having the need to redesign the layout. This makes it usefu l for technical discussions between the product designers and mould designers pr ior to the manufacture of the mould. Changes can be made to the 3D cavity layou t design immediately during the discussions thus the savings in time and avo idance of miscommunications.
基金Project(2003AA302210)supported by the National Hi-tech Research Prograrm of Chinap.
文摘To evaluate the bioeompatibility of MIM 316L stainless steel,the percentage of S-period cells were detected by flow cytometry after L929 incubated with extraction of MIM 316L stainless steel,using titanium implant materials of clinical application as the contrast.Both materials were implanted in animal and the histopathological evaluations were carried out.The statistical analyses show that there are no significant differences between two groups(P>0.05),which demonstrates that MIM 316L stainless steel has a good biocompatibility.
