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In this study, an injection molding machine with a mixing mechanism of nitrogen (N2) and melt was designed, and the melt-fill/porous-foaming behavior is observed under the novel barrel design (plasticizing stage) of the gas/melt mixing for the porous injection molded thermoplastic. The thermoplastic employed in this study was polypropylene (PP), and the gas for forming the porous structure is N2. In addition, a thickness of 5 mm and a width of 10 mm paper-clip shape and the mold were constructed for studying the melt-fill-length and fill-length ratio through an experiment. The experimental results showed that the use of an injection molding machine with a mixing mechanism of N2 and melt decreased the melt-fill-length when the N2-output pressure was increased. The reason is that when the gas output, the speed of the screw will be affected. Therefore, during the gas/melt mixing and the plasticization rate will also affect the volume of the foam and the melt. But during plasticizing setting back pressure, can improve its melt volume reduction. When passing through the mixing mechanism and the injected melt, the melt is filled into the mold cavity, and the pressure in the melt is released/porous-foaming grows. At the same time, when the output pressure increases, the amount of melt in the injection barrel will decrease, and its relative porous structure/density distribution will increase. In addition, the mixing/flow direction of the melt impacted the density distribution and dispersion of porous foaming, thus the sample weight/shrinkage of melt-fill-length test sample (Mfl-ts) was improved.

In this study, an injection molding machine with a low-fracture-fiber mechanism was designed with three stages: a plasticizing stage, an injection stage, and a packing stage. The fiber-fracture behavior is observed under the screw (plasticizing stage) of low-compression/shear ratio for the ultra-long fiber during the molding process. The molding material employed in this study was 25-mm-ultra-long-glass-fiber-reinforced polypropylene (PP/U-LGF). In addition, a thickness of 3 mm and a width of 12 mm spiral-flow-mold were constructed for studying the melt flow length and flow-length ratio through an experiment. The experimental results showed that the use of an injection molding machine with a three-stage mechanism decreased the fiber length when the screw speed was increased. On average, each fiber was shortened by 50% (>15 mm on average) from its original length of 25 mm. Longer glass fibers were more resistant to melt filling, and as the fiber length was reduced, the mixing between the melt and glass fibers was improved. Thus, the melt fluidity and fiber ratios were increased. In addition, the mixing/flow direction of the melt had an impact on the dispersion and arrangement of glass fibers, thus the tensile strength of PP/U-LGF increased.

This research developed an adaptive control system for injection molding process. The purpose of this control system is to adaptively maintain the consistency of product quality by minimize the mass variation of injection molded parts. The adaptive control system works with the information collected through two sensors installed in the machine only—the injection nozzle pressure sensor and the temperature sensor. In this research, preliminary experiments are purposed to find master pressure curve that relates to product quality. Viscosity index, peak pressure, and timing of the peak pressure are used to characterize the pressure curve. The correlation between product quality and parameters such as switchover position and injection speed were used to produce a training data for back propagation neural network (BPNN) to compute weight and bias which are applied on the adaptive control system. By using this system, the variation of part weight is maintained to be as low as 0.14%.

Plastic foam molding methods include thermoforming, extrusion and injection molding. Injection foam molding is a one-time molding method with high production efficiency and good product quality. It is suitable for foamed plastic products with complex shapes and strict size requirements. It is also the main method for producing structural bubbles. In this investigation, we developed a structural foam injection molding technology using the gas supply equipment connected to the unique plasticizing mechanism of the injection machine and studied its influence on the specimens’ melt rheology quality and foam structures. In the experiment, the forming material was polypropylene (PP), and the gas for mixing/forming foaming characteristics was nitrogen (N2). Additionally, in order to observe the rheological properties of N2/melt mixing, a melt flow specimen mold cavity was designed and the change in the melt viscosity index was observed using a melt pressure sensing element installed at the nozzle position. With the nitrogen supply equipment connected to a unique plasticizing mechanism, the mixing of gas and molten plastic can be achieved at the screw plasticizing stage, where the foaming effect is realized during the melt-filling process due to the thermodynamic instability of the gas. It was also found that an increase in N2 fill content increased melt fluidity, and the trend of melt pressure and melt viscosity index showed that the higher the gas content, the lower the trend. The foaming characteristic depends on the gas thermodynamic instability and the pressure release, so it can be seen from the melt fill path that, the greater the pressure near the gate, the lower the foaming amount and the internal structure (SEM) after molding; the farther from the gate, the greater the relative increase in the foaming growth/amount. This phenomenon will be more obvious when the N2 fill content is increased.

Processing equipment and parameters will highly influence the properties of long-fiber-reinforced injection-molded thermoplastic composites, leading to different fiber lengths and orientations. Thus, maintaining fiber length during the injection molding process is always a big challenge for engineers. This study uses long-glass-fiber-reinforced polypropylene with 25 mm fiber length and a special-built novel injection molding machine with a three-barrel injection unit, including a plasticizing screw, an injection plunger, and a packing plunger, to fabricate injection molding parts while retaining long fiber length. This study also discusses the influence of process parameters, such as back pressure, screw speed, melt temperature, and different flow paths, on the properties of long-glass-fiber-reinforced composites. The experiment results show that a higher screw speed and back pressure will reduce the fiber length in the injection-molded parts. However, using appropriate parameter settings can maintain the fiber length to more than 10 mm. It was found that by increasing the back pressure, the cross direction of the fiber orientation can be increased by up to 15% and the air trap volume fraction can be decreased by up to 86%. Setting appropriate back pressure under a low screw speed will increase the tensile strength. Finally, it was found that the single-edge-gate path results in a higher tensile strength than that of the single-sprue-gate path due to the retainment of longer fiber length in the injection-molded part.

The injection-molding process is a non-linear process, and the product quality and long-term production stability are affected by several factors. To stabilize the product quality effected by these factors, this research establishes a standard process parameter setup procedure and an adaptive process control system based on the data collected by a nozzle pressure sensor and a tie-bar strain gauge to achieve this goal. In this research, process parameters such as the V/P switchover point, injection speed, packing pressure, and clamping force are sequentially optimized based on the characteristics of the pressure profile. After the optimization process, this research defines the standard quality characteristics through the optimized process parameters and combines it with the adaptive process control system in order to achieve the purpose of automatic adjustment of the machine and maintain high-quality production. Finally, three different viscosity materials are used to verify the effectiveness of the optimization procedure and the adaptive process control system. With the system, the variation of product weight was reduced to 0.106%, 0.092%, and 0.079%, respectively.

Glass fiber composites are prevalent molded materials used in various fields, including aviation engineering, automobile manufacturing, and medical equipment production. The length of a glass fiber affects the mechanical properties of a glass fiber composite. Studies have reported that breakage occurs in long fibers subjected to screw plasticization, injection processes, and geometrical changes in injection molding. Moreover, multigate injection molding can result in weldlines on the final product, consequently reducing its strength. Further exploration is required to determine how product strength is affected by weldlines generated through injection molding with glass fiber composites and how product tensile properties associated with weldlines can be improved. Therefore, this study designed a mold with a vent area and a plug-in mold-surface-heating device to examine changes in the weldlines and tensile properties of long-glass-fiber composite specimens fabricated through injection molding using two melts. The results revealed that fiber length decreased with increasing screw speed; such declines in fiber length affected the tensile strength of the long-glass-fiber-reinforced polyamide-66 composites. In addition, because the arrangement and distribution of the glass fibers were affected by the melt flow rate, melt flow direction, and changes in mold cavity volume, the weldline tensile strength varied with the depth of the vent area. Mold surface heating improved the specimen surface roughness by 5.79% and effectively improved the interfacial adhesion between the fibers and melts, thereby resulting in more favorable weldline tensile strength. This also notably reduced the depth of weldlines produced by the adhesion of two melts.

In this study, fiber breaking behavior, fiber orientation, length variation, and changes in melt flow ability of long glass fiber reinforced polypropylene (L-FRP) composites under different mold cavity geometry, melt fill path, and plasticization parameters were investigated. The matrix material used was polypropylene and the reinforcement fibers were 25 mm long. An ultra-long-fiber composite injection molding machine (with a three-stage plunger and injection mechanism design) was used with different mold cavity geometry and plasticization parameters. Different screw speeds were used to explore the changes in fiber length and to provide a reference for setting fiber length and parameter combinations. Flow-length specimen molds with different specimen thickness, melt fill path, and gate design were used to observe the effect of plasticizing properties on the flow ability of the L-FRP composite materials. The experimental results showed that the use of an injection molding machine with a mechanism that reduced the amount of fiber breakage was advantageous. It was also found that an increase in screw speed increased fiber breakage, and 25 mm long fibers were shortened by an average of 50% (to 10 mm). Long fibers were more resistant to melt filling than short fibers. In addition, the thickness of the specimen and the gate design were also found to affect the filling process. The rounded angle gate and thick wall product decreased the flow resistance and assisted the flow ability and fiber distribution of the L-FRP injection molding.

To increase the productivity of injection molding machines, we developed a smart injection part weight stability control system based on C++ programming and domain knowledge. The proposed system is meant to eliminate variability in the quality of injected parts by adjusting the changeover position. We developed a viscosity index based on melt pressure data related to guide the adjustment to the changeover position in accordance with material properties. This was achieved by mounting a pressure sensor on the nozzle of the injection molding machine to enable the on-line monitoring of pressure throughout the injection molding process. A series of experiments was conducted to characterize the relationship between viscosity index and injection-molded samples in order to validate the efficacy of the proposed injection stability system. Single-factor experiments were conducted with the changeover position and melt temperature as parameters. The quality of the molded samples obtained under different process parameters was evaluated in terms of weight. Experiment results revealed a correlation between changes in viscosity index and changes in the weight of the samples. The injection stability system can also be operated in self-adjusting mode, in which the changeover position is varied according to viscosity index. In experiments, abnormal machine operations prompted the adjustment of changeover position. Variation in the weight of parts was used to define an index to validate the efficacy of the proposed system.

Long-fiber polymers offer the advantage of a lower production cost because specific tool designs are required for conventional injection molding equipment to produce long-fiber polymer parts. The use of long fibers allows relatively high fiber aspect ratios to be obtained, thereby enhancing composite stiffness, strength, creep endurance, and fatigue endurance. However, the multigate design of the injection-molded part can result in weldline formation during the molding process, which reduces the structural strength of the molded part. Therefore, in this study, the surface quality, fiber compatibility, and structural strength of long-glass-fiber-reinforced polypropylene (PP/LGF) injection-molded samples were compared in the use versus nonuse of a mold-cavity overflow-well area and the mold-face infrared heating method. The experimental results indicate that the mold-cavity overflow-well area more greatly improved the surface roughness of the PP/LGF molded samples. Moreover, the infrared heating of the mold-face decreased the weldline depth of the samples. Optical-microscopy images and mold-cavity pressure distributions indicated that the weldline tensile strength and the interface compatibility between fibers and melts at the weldline region during the molding stage were higher in the use than in the nonuse of the mold-cavity overflow-well and mold-face infrared heating method.

This study investigates the effects of the vent-area on bubble-microstructure and shrinkage variation of gas-assisted foam-injection molding (GAFIM). The molding material is polystyrene (PS), and the gas foaming agent is nitrogen (N 2 ). This study carried out the injection experiment with and without GAFIM to observe the molding characteristics of gas-filling pressure variation. In addition, the integration of vent-area volumes and cavity pressure measurement was developed to achieve foam growth and microstructure inside the sample to observe the effect of with and without vent-area on shrinkage variation and correlated pressure distribution near gate position during the filling process. The experimental results revealed that with the vent-area, the sample dimension shrinkage was relatively improved and the sample weight was reduced. On the other hand, the bubble-distribution increased with the changes in the volume of the vent-area and gas-filling pressure as the foam growth space increased.

The ease with which modern plastics can be injection molded makes them very suitable for the production of many different products and, today, plastics are often used as substitutes for metal. Polypropylene (PP) is one of the most widely used thermoplastics globally since it is very useful, cost-effective and flexible for molding. However, the amount of harm to the environment caused by plastic waste has become phenomenal and the recycling of plastics has become a serious aspect of environmental protection. PP, as the most commonly used plastic material, was selected for use in this study. It has a melt flow index of 15 g/min and its recyclability, fluidity, and physical properties, as well as manufacturing conditions, were explored in relation to the number of times the material could be recycled (TR). A cavity pressure sensor was used to measure the viscosity index of the recycled plastic after multiple cycles of plasticizing and injection, part molding, scrap-recycling, and crushing. A paperclip-shaped test specimen was used to determine PP fluidity and crystallinity of specimens with different TRs. Tensile tests were used to detect differences in the tensile strength between specimens made from Raw-PP and recycled PP. The results showed that PP that had been recycled several times had a higher melt flow index, material fluidity, melting peak area, crystallinity, crystallization rate, and crystallization temperature. Repeated injection and recycling of the material had reduced the length of the molecular chains and broadened the molecular weight distribution. This improved the fluidity and increased crystallinity. The increase in fluidity made cavity filling easier, reducing the cavity pressure as well as the viscosity index. The results of this study showed that the recycling of the PP could improve the physical properties of the products to a degree and also went some way to further the benefits of a circular economy. The recycling of injection-molded PP material can be added to renewable energy technologies and used in environmental impact assessment.

This study used the cavity-surface infrared rapid-heating method and tensile specimens (ASTM-D638) to test the fiber compatibility and tensile characteristics of long glass fiber reinforced PA66 (LGF-PA66) composites. The weldline molding experiment on the injected specimen was conducted using a double-gate. In addition, the integration of infrared heating and cavity pressure measurement were developed to achieve cavity-surface heating and observe the effect of with/without cavity-surf ace heating on weldline tensile strength variation and correlated pressure distribution near the weldline region. On the other hand, a vent -well was designed in the center position of the specimen (vent-well depths are 0.9 mm, 1.8 mm, and 3.6 mm), in order to discuss the effect of the two-melts on fiber and melt compatibility in the compatible process. The experimental results show that vent-well provides better weldline tensile strength; moreover, infrared heating cavity -surface also provides the better weldline tensile strength of LGF-PA66 composites molded parts. In addition, from SEM images and cavity pressure distributions, considering in presence or absence of vent-well design and cavity-surface heating, it provides better weldline tensile strength and interfaces compatibility between fiber and resin at weldline region during molding stage.

Injection molding is a popular process for the mass production of polymer products, but due to the characteristics of the injection process, there are many factors that will affect the product quality during the long fabrication processes. In this study, an adaptive adjustment system was developed by C++ programming to adjust the V/P switchover point and injection speed during the injection molding process in order to minimize the variation of the product weight. Based on a series of preliminary experiments, it was found that the viscosity index and peak pressure had a strong correlation with the weight of the injection-molded parts. Therefore, the viscosity index and peak pressure are used to guide the adjustment in the presented control system, and only one nozzle pressure sensor is used in the system. The results of the preliminary experiments indicate that the reduction of the packing time and setting enough clamping force can decrease the variation of the injected weight without turning on the adaptive control system, meanwhile, the master pressure curve obtained from the preliminary experiment was used as the control target of the system. With this system, the variation of the product weight and coefficient of variation (CV) of the product weight can be decreased to 0.21 and 0.05%, respectively.

PET bottle is an excellent packaging material, is widely used in the food & beverage industry which has further given impetus to the market. With an increasing demand for production capability of PET bottle, the rapid cooling efficiency and uniform temperature distribution are important issue on cooling channel design of blow mold. Due to the insufficient cooling time and non-uniform mold temperature distribution that cause bottle stress cracking or broken. In this study, the conformal cooling channel design is developed to achieve a rapid cooling efficiency and uniform temperature distribution of blow mold. The cooling efficiency and temperature distribution during cooling process was measured using infrared thermal image system and thermocouple sensor. Simulation technology was also developed by integration of thermal and fluid flow analysis modules of ANSYS-FLUENT. For cooling efficiency comparison, the shape and size of the conformal cooling channels, fluid temperature and flow rate were varied for both experiments and simulations. The capability and accuracy of simulation on conformal cooling channel design and analysis were verified via experiments. The simulated cooling efficiency and temperature distribution show reasonable agreement with measured results. A reduction in cooling time from the initial 2.9 seconds to 1 second; moreover, conformal cooling channel provides uniform temperature distribution and less temperature difference of 4°C.

In recent years, due to the raising of green manufacturing and environmental consciousness, the industrial equipment and molded product request toward energy saving, reducing cycle time and secondary process procedure. With high strength, high stiffness, high design possibility, better fatigue life and better corrosion resistance capability, PA66 polymer composite materials are gaining more and more attention in functional products. In this study, PA66 polymer composites material used in slide components molding to replace the original metal material. The results indicated that PA66 polymer composites add 2%wt MoS2 result higher tensile strength and flexural strength than the original polymer material. The value of increased strength of tensile strength is 8% and flexural strength is 27%. In addition, the CAE simulated results are successful to predictive molding characteristics and improve structural strength of molded parts.

In this study, a gas-assisted heating system for mold surface temperature control was established. Two gap size control modes (A and B) of the gas channel and the heating results of both cavity and core sides were investigated, moreover, the effective heating area for gas heating expansion angle were determined as well by using gas flow rate 300 l/min. The results show that the mold temperature difference on the gas inlet of core and cavity surface can be reduced from 39.8 oC with A mode to 1.4 oC with B mode under the gap size of 5mm. For the hot gas heating expansion angle, it directly affected heating area, and being relative with the entrance of gas channel. A case study of micro-molding for double sides 0.4mm thin wall plat with micro-dot arrays shows that replication accuracies reach higher than 90% when molding at a mold temperature of 150 oC, an improvement of 25.3% over injection molding at the regular mold temperature of 90 oC.

This study explores how ultra high-speed processing parameters affect the melt flow length and tensile strength of thin-wall injection molded parts. A spiral shaped mold with a specimen thickness of 0.4 mm and a width of 6 mm was first constructed to test the melt flow length as an index of process capability for ultra high-speed injection molding. It was observed that the flow length increases with increasing injection speed. High-density polyethylene (HDPE) tensile test specimens with different thicknesses (0.6 mm and 2 mm) were also molded for tensile tests. Both single gate and double gates were used to form parts without and with weldlines. Injection molding trials were executed by systematically adjusting related parameters setting including mold temperature, melt temperature, and injection speed. The parts’ tensile strengths were measured experimentally. It was found that tensile strengths of 0.6 mm thick parts both with and without weldlines were higher than those of 2 mm thick parts. The tensile ...

It is known that the weldline reduces the mechanical strength of the conventional injection molded parts. Systematic studies on the weldline strength of thin-wall molded parts were not yet reported. This study investigates the effect of processing conditions including melt temperature, mold temperature, injection speed and packing pressure on the weldline strength of thin-wall parts. Tensile test specimen of 2.5, 1 and 0.8 mm thick were injection molded under specified conditions. Both single gate and double gates were used to form parts with and without weldlines. Part tensile strengths were measured experimentally. From the experimental results, it was found that higher melt temperature and mold temperature as well as faster injection speed will increase weldline strength whereas higher packing pressure would decrease weldline strength. Melt temperature and mold temperature are two parameters that affect weldline strength most significantly within the current molding window. Higher melt and mold temperatures not only lower the residual stress but also help the diffusion of molecular chains leading to a higher degree of bonding at the weldline interface. On the other hand, high packing pressure leads to higher residual stress formation and reduces the molecular bonding rate. Part thickness also exhibits significant effect on weldline strength reduction. Thinner parts resulting in higher percentage of frozen layer in filling process thus limit the bonding rate at weldline interface. From the regression analysis, the KIM model with corrected terms in the fitting coefficient was found to correlate process conditions and weldline strength reduction quite well.

Effect of processing conditions including injection speed, melt temperature, mold temperature and packing pressure on tensile properties of polycarbonate (PC) thin-wall parts were investigated. Tensile test specimen with thickness of 2.5, 1.0 and 0.8 mm were injection molded under specified conditions. Tensile properties and residual stresses were measured experimentally. It was found that the residual stress plays a more significant role in influencing part tensile properties than flow-induced molecular orientation. Part thickness and injection speed are two key factors that affect residual stress most significantly within the current molding window. As part thickness decreases, residual stress increases resulting in the greater influence in reduction of part tensile strength, yield stress as well as Young’s modulus. Higher melt temperature and higher mold temperature would reduce residual stress whereas higher injection speed and higher packing pressure would increase residual stress. Associated with the decrease of residual stress, part’s tensile strength, yield strength and Young’s modulus increase with increased melt temperature, mold temperature and injection speed. On the other hand, higher packing pressure results in a decrease of part mechanical strength.

Manufacturing of 3C (Computer, Communication, and Consumer Electronics) products toward weight reduction, thin-wall, and minified-size is an inescapable trend for the future 3C industries. However, the induced damage information from drop impact, including exterior housing fracture, liquid crystal display (LCD) cracking, solder-joint breaking, or interior component failure, is still derived experimentally and involves very complicated parametric analyses, such as a dynamic impact process, drop orientation, contact behavior, and large deformation during the impact instance. In the present study, numerical simulations for the drop test and bending strength were applied to a thin-wall computer dictionary (Model CD-66) housing to understand the key factors that affect the part drop test performance. The appropriate modeling that would affect simulation accuracy as well as the associated nodal degree of freedom and computer time were also investigated. A housing of CD-66 was redesigned to be 1 mm thick and structurally verified with two different plastics: polycarbonate (PC) and acrylonitrile butadiene styrene (ABS). The simplification of the PC board and LCD backlight circuit in finite element modeling (FEM) only causes about a 10% difference, while saving many modeling costs. The numerical simulations also indicate that both its bending strength and drop-impact strength were decreased only about 5%, whereas the product quality still met its strength requirement if only the top housing plate thickness was reduced while the remaining sidewall thickness was kept unchanged. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3064–3071, 2002

Precision injection moulding of thin walled parts has become an important concern in the computer, communication, and consumer electronics plastics industry. Previous studies in precision injection moulding control focus on the injection screw and the associated operations. In the present study, the influence of relevant parameters including injection speed, melt temperature, mould temperature, filling-packing switchover, and packing pressure on the mould plate separation under different clamping pressure were investigated as part of precision moulding control. A two cavity tensile test specimen mould equipped with four linear variable displacement transducers across the parting surfaces of the mould was used. A computer based monitoring system was built to detect the mould separation signals. Mould separation can also be identified from part weight and thickness variation and exhibits relevant correspondence with them. It was found that owing to the high injection speed required for thin wall mo...

Simulations of the injection-compression molding (ICM) process based on a Leonov viscoelastic fluid model has been employed to study the effects of processing conditions on the birefringence development and distribution in injection-compression molded parts. A numerical algorithm combined with a modified control-volume/finite-element method is developed to predict the melt front advancement and the distributions of pressure, temperature, and flow velocity dynamically during the injection melt-filling, compression melt-filling, and postfilling stages of the entire process. Part birefringence was then calculated from residual stresses following the thermal-mechanical history of the entire molding process. Simulations of a disk part under different process conditions including compression speed, switch time from injection to compression, compression stroke, packing pressure, and postfilling time were performed to understand their effects on birefringence variation. The simulated results were also compared with those required by conventional injection molding (CIM). It has been found that an ICM part shows a significant reduction of part birefringence near the gate area as compared with CIM parts. However, ICM parts exhibit higher birefringence values near the rim of the disk. The minimum birefringence occurs around the location where injection is switched over to compression. Although longer postfilling time and higher packing pressure result in higher birefringence values, their effects are not very significant. On the other hand, higher compression speed, larger compression stroke, and shorter switch time exhibit greater effects on the increase of part birefringence. Flow-induced residual stress is the major origin of birefringence formation in the present case. The simulated birefringence for both ICM and CIM parts show good coincidence with those obtained from measurements by using a digital photoelasticity technique. © 2002 Wiley Periodicals, Inc. Adv Polym Techn 21: 177–187, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/adv.10024

A numerical algorithm is developed to simulate the injection–compression molding (ICM) process. A Hele–Shaw fluid-flow model combined with a modified control-volume/finite-element method is implemented to predict the melt-front advancement and the distributions of pressure, temperature, and flow velocity dynamically during the injection melt filling, compression melt filling, and postfilling stages of the entire process. Part volumetric shrinkage was then investigated by tracing the thermal–mechanical history of the polymer melt via a path display in the pressure–volume–temperature (PVT) diagram during the entire process. Influence of the process parameters including compression speed, switch time from injection to compression, compression stroke, and part thickness on part shrinkage were understood through simulations of a disk part. The simulated results were also compared with those required by conventional injection molding (CIM). It was found that ICM not only shows a significant effect on reducing part shrinkage but also provides much more uniform shrinkage within the whole part as compared with CIM. Although using a higher switch time, lower compression speed, and higher compression stroke may result in a lower molding pressure, however, they do not show an apparent effect on part shrinkage once the compression pressure is the same in the compression-holding stage. However, using a lower switch time, higher compression speed, and lower compression stroke under the same compression pressure in the postfilling stage will result in an improvement in shrinkage reduction due to the melt-temperature effect introduced in the end of the filling stage. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1640–1654, 2000

Dynamic mold surface temperature control (DMTC) has the advantage of improving molded part qualities without significant increases in cycle time. A gas-assisted heating system combined with water cooling was developed to achieve DMTC for injection molding. With gas-assisted heating, it takes 2s for the mold surface temperature to vary from 60 °C to 120 °C whereas it requires 186s using water heating. Further, it takes 21s and 84s for the mold surface to cool to 60 °C under gas heating and water heating, respectively. The gas-assisted heating system also shows excellent efficiency for micro injection molding of biochips to achieve high replication accuracy of the micro channels.Copyright © 2008 by ASME