Dynamic mold temperature control technology is a new green injection molding technology. Implementation of dynamic control of mold temperature, the surface of products can effectively eliminate weld, residual stress reduction products, get a good surface quality. This article focuses on mold temperature combination to achieve the fast changing dynamic mold temperature control technology, principle, introduced steam heating, electromagnetic heating, infrared heating and other new heating methods, and prospects of fast changing technology, the development prospects of mold temperature.
Mold temperature and product accuracy, production efficiency is closely related to the current research focus within the industry. Fast changing technology, mold temperature through dynamic control of mold temperature, melt filling can improve mobility and reduce the injection pressure, improving products molding process; reduce the injection rate and melt filling process by the shear force, reducing the final products, residual stress and warpage, improved structural performance products. Mold temperature of the melt dynamics effectively avoid the formation of condensation in type at the parietal layer, the surface of the weld to eliminate products, fiber defects such as floating, the surface of the products show high-light effect. Quick change mold temperature technology is very promising with the development of green manufacturing technology.
Abstract...Articles section Fast changing technical principles and characteristics of mold temperature
Injection molding process the mold temperature is affecting the product quality in the important process parameters. Shrinkage affect the final dimensional accuracy of injection molding products, one of the key factors.
Affect the shrinkage deformation of factors, including the molding process of residual stress from the cavity after removing the crystallization behavior of molecules and materials continue to stress relaxation. When the injection molding products, by increasing the mold temperature can effectively reduce the residual stress generation products. Meanwhile, high mold temperature also allows the products to fully crystalline, and thus significantly reduce the amount of shrinkage after ejection. In addition, high mold temperature can reduce the products of the cooling rate, the polymer chains to fully relax, restore, this time products, internal stress, after shrinkage is also small. Rapidly varying mold temperature control technology and traditional mold temperature control technology compared to the fundamental difference lies in the dynamic mold temperature control. Quick change mold temperature technology has the following characteristics:
(1) to improve the quality of product appearance, effectively eliminate the weld surface of the product, crazing, fiber and other floating surface defects in injection molding.
The use of fast changing technology, mold temperature, cavity surface temperature was quickly raised to the heat distortion temperature of resin than plastic, thereby increasing the molten plastic in the mold cavity flow, reducing the cavity with molten plastic between the friction surface, significantly eliminate product surface weld, crazing and other cosmetic defects. Also, by controlling the cavity surface heating and cooling time can change the plastic surface of the crystalline state, effectively eliminate the impact of glass exposed to the product surface appearance problems.
(2) to improve the molding conditions, shorter cycle times, improve product structure and properties.
Fast changing technology of mold temperature in addition to the high mold temperature can increase the melt flow, reduce the injection pressure, and may reduce the injection rate and melt filling process by the shear force, to reduce the final pieces into the shaping of the residual stress and warpage, improved structural performance products.
(3) no secondary processing of green manufacturing technology.
Quick change mold temperature technology to improve product surface finish, surface finish can be achieved mirror requirements; without polluting the environment and other follow-up spray paint processing, reduce costs, shorten product cycle times.
Fast changing technology, mold temperature
Steam heating
Steam heating is the use of mold temperature control device to turn heat into steam and condensing water circulation pipe inside the mold, the mold in order to achieve the rapid heating and cooling of the molding process. Steam heating system can make the mold surface temperature reaches up to 160 ℃. However, due to the heat capacity of water vapor relative to the smaller temperature longer.
The relatively mature technology Ono Sangyo Co., Ltd. of Japan developed the steam heating system. Hisense Research Institute in Shandong University high marks green light without melting injection technology and new technology and complete sets of equipment, the study also made important progress, to achieve a high light LCD flat panel TV's continuous injection molding.
Advantages and disadvantages: the use of steam heating, mold temperature control, high precision, large range of heating and cooling, available surface light, no weld, no flow marks, no spray processing, plastics performance, low cost of production of plastic parts. However, due to increased external steam heat and steam to open pores inside the mold, the system more complex, higher operating costs.
Mold temperature and product accuracy, production efficiency is closely related to the current research focus within the industry. Fast changing technology, mold temperature through dynamic control of mold temperature, melt filling can improve mobility and reduce the injection pressure, improving products molding process; reduce the injection rate and melt filling process by the shear force, reducing the final products, residual stress and warpage, improved structural performance products. Mold temperature of the melt dynamics effectively avoid the formation of condensation in type at the parietal layer, the surface of the weld to eliminate products, fiber defects such as floating, the surface of the products show high-light effect. Quick change mold temperature technology is very promising with the development of green manufacturing technology.
Abstract...Articles section Fast changing technical principles and characteristics of mold temperature
Injection molding process the mold temperature is affecting the product quality in the important process parameters. Shrinkage affect the final dimensional accuracy of injection molding products, one of the key factors.
Affect the shrinkage deformation of factors, including the molding process of residual stress from the cavity after removing the crystallization behavior of molecules and materials continue to stress relaxation. When the injection molding products, by increasing the mold temperature can effectively reduce the residual stress generation products. Meanwhile, high mold temperature also allows the products to fully crystalline, and thus significantly reduce the amount of shrinkage after ejection. In addition, high mold temperature can reduce the products of the cooling rate, the polymer chains to fully relax, restore, this time products, internal stress, after shrinkage is also small. Rapidly varying mold temperature control technology and traditional mold temperature control technology compared to the fundamental difference lies in the dynamic mold temperature control. Quick change mold temperature technology has the following characteristics:
(1) to improve the quality of product appearance, effectively eliminate the weld surface of the product, crazing, fiber and other floating surface defects in injection molding.
The use of fast changing technology, mold temperature, cavity surface temperature was quickly raised to the heat distortion temperature of resin than plastic, thereby increasing the molten plastic in the mold cavity flow, reducing the cavity with molten plastic between the friction surface, significantly eliminate product surface weld, crazing and other cosmetic defects. Also, by controlling the cavity surface heating and cooling time can change the plastic surface of the crystalline state, effectively eliminate the impact of glass exposed to the product surface appearance problems.
(2) to improve the molding conditions, shorter cycle times, improve product structure and properties.
Fast changing technology of mold temperature in addition to the high mold temperature can increase the melt flow, reduce the injection pressure, and may reduce the injection rate and melt filling process by the shear force, to reduce the final pieces into the shaping of the residual stress and warpage, improved structural performance products.
(3) no secondary processing of green manufacturing technology.
Quick change mold temperature technology to improve product surface finish, surface finish can be achieved mirror requirements; without polluting the environment and other follow-up spray paint processing, reduce costs, shorten product cycle times.
Fast changing technology, mold temperature
Steam heating
Steam heating is the use of mold temperature control device to turn heat into steam and condensing water circulation pipe inside the mold, the mold in order to achieve the rapid heating and cooling of the molding process. Steam heating system can make the mold surface temperature reaches up to 160 ℃. However, due to the heat capacity of water vapor relative to the smaller temperature longer.
The relatively mature technology Ono Sangyo Co., Ltd. of Japan developed the steam heating system. Hisense Research Institute in Shandong University high marks green light without melting injection technology and new technology and complete sets of equipment, the study also made important progress, to achieve a high light LCD flat panel TV's continuous injection molding.
Advantages and disadvantages: the use of steam heating, mold temperature control, high precision, large range of heating and cooling, available surface light, no weld, no flow marks, no spray processing, plastics performance, low cost of production of plastic parts. However, due to increased external steam heat and steam to open pores inside the mold, the system more complex, higher operating costs.
Electromagnetic induction heating
Faraday's electromagnetic induction heating is based on the principle of electromagnetic induction heating the mold surface temperature. Alternating magnetic field induced current with skin effect, eddy current distribution of the mold surface and the core is close to zero. Therefore, the electromagnetic induction heating only the skin in the mold surface to the depth range of heating, heating, small size, heating speed, Taiwan Chung Yuan Christian University system, the heating rate can be developed to 40 ℃ / s or more.
Electromagnetic induction heating induction heating can be divided into mold and outer mold induction heating. Mode outside the induction heating aid agencies will need to use an external surface coil placed in the cavity, heated to remove the coil set temperature mold injection mold; mold induction heating induction coil is placed inside the mold, the mold cavity when the surface heating, precise control of mold temperature.
Advantages and disadvantages: electromagnetic induction heating system and no heat transfer medium between the mold, heat transfer speed, short cycle times. As the skin effect, only the mold surface heating, saving energy, but also a special area for mold, such as possible micro-structure or weld the parts of local heating. The use of electromagnetic induction as a heating source than electric heating, steam heating have higher thermal efficiency, saving energy consumption in the heating process, with flexible, convenient, and safety. Due to the induction coil shape constraints, electromagnetic induction heating does not apply with complex structures or large size mold.
Infrared heatingInfrared heating technology is the use of mold thermal infrared radiation method of heating the mold cavity. Heating plate work surface coated with a layer thickness of 0.2-1000μm film to reflect infrared light, the mold cavity coated with a layer of absorption of infrared film. Form of infrared heat radiation heat transfer by electromagnetic waves transfer energy without heat transfer media, with some penetration.
Advantages and disadvantages: The method has the energy, safety, simple equipment, easy to promote and so on. However, due to the absorption of infrared light metal weak, heated slowly, the heating plate and the mold cavity coated with a thin film to reflect and absorb infrared light, increase the cost of the system unit, and by the infrared transmitter unit size and shape restrictions generally used in the field of micro-injection molding.
Flame heating
Flame heating is a gas flame using the instantaneous method of heating the mold. The use of gas flame heating, the 10s will be able to upgrade to the mold surface temperature above 400 ℃, and the ability to rapidly cool the mold surface temperature to below freezing temperatures the polymer, this heating method can not only greatly improve the quality of molding, and can make product strength than ordinary molding method increased by 40 percent.
Flame heating the cavity surface, fast heating, the mold surface temperature, help to improve the surface quality of plastic parts. But the need to open the fuel within the pores in the mold, the mold structure is relatively complex, and it is not forming the shape of complex plastic parts. The use of gas, on-site there are some security risks. Cavity surface temperature is not easy to control, resulting in the size of the cavity surface temperature and temperature distribution uniformity is difficult to control.
Compound die wall heating
Composite mold wall heating mold temperature change technology works in the mold surface coated with a layer of high thermal conductivity material such as metal materials, such as pyrolytic graphite mold cavity wall, then use the electric heating effect mold.
In order to improve the heating efficiency, but also in the mold is generally heated layer between the substrate and the layer of low thermal conductivity materials such as oxides, polymer materials.
Usually die wall by the combined three layers: the outer layer of high thermal conductivity material for the formation of the warm layer, middle layer of low thermal conductivity material to form the insulating layer, the bottom of the template matrix. After the compression mold casting system by injecting hot air preheated mold cavity wall, and out through the exhaust port, and then close the compressed hot air, vacuum, injection. The main compound die wall heating up a small compressed hot air heat capacity, heat transfer low efficiency.
Strengths and weaknesses: This method of temperature control heating convenient, responsive, and relatively simple structure. But for the complex structure of the products, plating production has yet to be resolved. In addition, due to frequent heating and cooling the mold, the thermal stress under the effect of coating prone to fatigue damage, reduce die life.
With the continuous development of precision processing technology, industrial quality requirements for products is also rising. Mold temperature is the product of molecular orientation, residual stress, shrinkage and warpage of one of the most important process parameters, mold temperature quickly changing technology is designed to dynamically control the surface temperature of the mold surface to improve product quality, optimize the internal structure of products. This technique can effectively eliminate the surface of weld products, crazing, floating fiber and other defects, such as reducing the coating or painting process, to protect the environment and operator health, energy and materials, is an advanced green injection molding process , has great potential for development.
In the next few years, both in technology development or the promotion of application, quick change mold temperature injection technique will gain greater development, but also will become the focus of the study area of injection molding and hot.
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Peter Huang
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