Dual-Scale Modeling and Simulation of Skin Layer Thickness in Injection Molding with Variable Mold Temperatures

2016 ◽  
Vol 13 (10) ◽  
pp. 7125-7136
Author(s):  
Bei Su ◽  
Ying-Guo Zhou ◽  
Lih-Sheng Turng
Keyword(s):  
Injection Molding ◽  
Layer Thickness ◽  
Mold Temperature ◽  
Optical Microscope ◽  
Skin Layer ◽  
Injection Flow ◽  
Scale Modeling ◽  
Molded Parts ◽  
Dual Scale ◽  
Conventional Injection Molding

Compared with the constant mold temperature in conventional injection molding (CIM), injection molded parts with variable mold temperatures undergo a different thermomechanical history. As a result, the microstructure—for example, the skin–core structure found often in CIM—can be changed. However, unlike conventional injection molding, there have been few studies on the microstructure of injection molding with variable mold temperatures (IMVMT), possibly because the experimental control of variable mold temperatures remains difficult. In this paper, the skin layer thickness of CIM and IMVMT under different mold temperatures was carefully investigated by optical microscope. The higher mold temperatures and longer holding times during the injection flow stage caused a thinning of the highly oriented skin layer, and vice-versa. A dual-scale modeling was then proposed based on the prediction of crystal dimensions, and it was further used to predict the thickness of the skin layer. The predicted results were in agreement with the experimental observations under the different mold temperatures during IMVMT processing, and the proposed model proved to be effective.

Comparative study of crystallization and lamellae orientation of isotactic polypropylene by rapid heat cycle molding and conventional injection molding

e-Polymers ◽  
2017 ◽  
Vol 17 (1) ◽  
pp. 71-81 ◽  
Author(s):  
Jiquan Li ◽  
Shaoguang Yang ◽  
Lih-Sheng Turng ◽  
Wei Zheng ◽  
Shaofei Jiang
Keyword(s):  
Injection Molding ◽  
Isotactic Polypropylene ◽  
Heated Surface ◽  
Skin Layer ◽  
Multilayered Structure ◽  
X Ray Diffraction ◽  
Heat Cycle ◽  
Molded Parts ◽  
Part Thickness ◽  
Conventional Injection Molding

AbstractThe crystallization and orientation of isotactic polypropylene (iPP) molded by rapid heat cycle molding (RHCM) and conventional injection molding (CIM) were studied. Due to the varying cooling rates and shearing, the molded parts exhibited a multilayered structure (skin, shear and core) across the part thickness, reflecting different degrees of crystallization and lamellae orientation of iPP. The morphology evolution of RHCM products was discussed based on the comparative research of morphology and structure at multiple sites on the RHCM and CIM specimens. Scanning electron microscopy (SEM) and wide angle X-ray diffraction (WAXD) were used to analyze the thickness, crystallinity and lamellae orientation of these three distinct layers. The crystallization and lamellae orientation of iPP correlated strongly with the multilayered structure. In the RHCM process, one side of the mold is equipped with the rapid heat cycle function. The thickness and lamellae orientation next to the heated surface were less than that of the opposite skin layer without heating. Meanwhile, the crystallinity was greater than that of the opposite skin layer.

Effect of Processing Conditions on the Shrinkage and Warpage of Glass Fiber Reinforced PP Using Microcellular Injection Molding

2012 ◽  
Vol 501 ◽  
pp. 294-299 ◽  
Author(s):  
Zhi Bian ◽  
Peng Cheng Xie ◽  
Yu Mei Ding ◽  
Wei Min Yang
Keyword(s):  
Injection Molding ◽  
Glass Fiber ◽  
Injection Pressure ◽  
Mold Temperature ◽  
Process Conditions ◽  
Fiber Reinforced ◽  
Injection Speed ◽  
Glass Fiber Reinforced ◽  
Microcellular Injection Molding ◽  
Molded Parts

This study was aimed at understanding how the process conditions affected the dimensional stability of glass fiber reinforced PP by microcellular injection molding. A design of experiments (DOE) was performed and plane test specimens were produced for the shrinkage and warpage analysis. Injection molding trials were performed by systematically adjusting six process parameters (i.e., Injection speed, Injection pressure, Shot temperature, SCF level, Mold temperature, and Cooling time). By analyzing the statistically significant main and two-factor interaction effects, the results showed that the supercritical fluid (SCF) level and the injection speed affected the shrinkage and warpage of microcellular injection molded parts the most.

Study on Improving the Life of Stereolithography Injection Mold

2012 ◽  
Vol 468-471 ◽  
pp. 1013-1016 ◽  
Author(s):  
Hua Qing Lai
Keyword(s):  
Injection Molding ◽  
Injection Molding Process ◽  
Injection Mold ◽  
Molding Process ◽  
Molded Parts ◽  
Injection Molded ◽  
Plastic Parts ◽  
Assembly Operations ◽  
Conventional Injection Molding ◽  
Shape And Size

Molding is one of the most versatile and important processes for manufacturing complex plastic parts. It is a method of fabricating plastic parts by utilizing a mold or cavity that has a shape and size similar to the part being produced. Molten polymer is injected into the cavity, resulting in the desired part upon solidification. The injection-molded parts typically have excellent dimensional tolerance and require almost no finishing and assembly operations. But new variations and emerging innovations of conventional injection molding have been continuously developed to offer special features and benefits that cannot be accomplished by the conventional injection molding process. This study aims to improving the life of stereolithography injection mold.

Filling-to-Packing Switchover Mode Based on Cavity Pressure for Injection Molding

2012 ◽  
Vol 501 ◽  
pp. 168-173 ◽  
Author(s):  
Jian Wang
Keyword(s):  
Injection Molding ◽  
Crucial Role ◽  
Mold Temperature ◽  
The Other ◽  
Injection Time ◽  
Cavity Pressure ◽  
Part Quality ◽  
Molded Parts ◽  
Screw Position

Filling-to-packing switchover control during injection molding plays a crucial role in ensuring the quality of the molded parts. In this study, a filling-to-packing switchover mode based on cavity pressure was presented, and it was compared with other two switchover modes by injection time and screw position. The objective of this study was to validate the accuracy of the switchover mode based on cavity pressure, and examine its consistency. Weight of the molded parts served as the main measure to probe the process capabilities. In this study, the change in mold temperature was monitored; variation of mold temperature affecting the process was examined. The results of the verification experiments revealed that the switchover mode based on cavity pressure could yield a better part quality and consistent part weight compared with the other two traditional switchover modes. It was proved that the switchover mode by cavity pressure can be used to improve the precision of the injection molding. However, a suitable switchover pressure must be used for achieving such high process capability, and the position to get the pressure signal and mold temperature should also be considered.

scholarly journals Optimization and application of temperature field in rapid heat cycling molding

2021 ◽  
pp. 291-291
Author(s):  
Mingliang Hao ◽  
Haimei Li
Keyword(s):  
Injection Molding ◽  
Electric Heating ◽  
Heating System ◽  
Mold Temperature ◽  
Temperature Control System ◽  
Cavity Surface ◽  
Injection Mold ◽  
Molding Process ◽  
Molded Parts ◽  
Automotive Part

The rapid thermal cycle molding (RHCM) belongs to the injection mold temperature control system which is helpful to improve mold ability and enhance part quality. Despite many available literatures, RHCM does not represent a well-developed area of practice. The challenge is the uneven distribution of temperature in the cavity after heating, which mostly leads to defects on the surface of the products. In order to obtain uniform cavity surface temperature distribution of RHCM, the power of heating rods of the electric-heating system in an injection mold was optimized by the response surface method(RSM) in this work. The proposed optimization result was applied to design a complex RHCM injection mold with side core-pulling, holes and different thickness of an automotive part to verify its effectiveness by injection molding. Compared with initial design, the mold temperature uniformity was remarkably improvedby79%. Based on the optimization and injection molding numerical simulation results, the workable molding process to weaken the weld-lines effects on the quality was suggested and the practical injection molded parts were well produced.

scholarly journals Reducing the Burn Marks on Injection-Molded Parts by External Gas-Assisted Injection Molding

Polymers ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 4087
Author(s):  
Jiquan Li ◽  
Wenyong Liu ◽  
Xinxin Xia ◽  
Hangchao Zhou ◽  
Liting Jing ◽  
...  
Keyword(s):  
Image Processing ◽  
Injection Molding ◽  
Delay Time ◽  
Quantitative Method ◽  
Surface Defect ◽  
Processing Method ◽  
Traditional Methods ◽  
Molded Parts ◽  
Injection Molded ◽  
Conventional Injection Molding

A burn mark is a sort of serious surface defect on injection-molded parts. In some cases, it can be difficult to reduce the burn marks by traditional methods. In this study, external gas-assisted injection molding (EGAIM) was introduced to reduce the burn marks, as EGAIM has been reported to reduce the holding pressure. The parts with different severities of burn marks were produced by EGAIM and conventional injection molding (CIM) with the same molding parameters but different gas parameters. The burn marks were quantified by an image processing method and the quantitative method was introduced to discuss the influence of the gas parameters on burn marks. The results show that the burn marks can be eliminated by EGAIM without changing the structure of the part or the mold, and the severity of the burn marks changed from 4.98% with CIM to 0% with EGAIM. Additionally, the gas delay time is the most important gas parameter affecting the burn marks.

Effects of Process Parameters on Shrinkage Uniformity and Birefringence of Injection-Compression Molded Parts

2008 ◽  
Author(s):  
Han-Xiong Huang ◽  
Can Yang ◽  
Kun Li
Keyword(s):  
Process Parameters ◽  
Delay Time ◽  
Mold Temperature ◽  
Compression Force ◽  
Melt Temperature ◽  
Compression Speed ◽  
Compression Time ◽  
Molded Parts ◽  
Injection Compression Molding ◽  
Conventional Injection Molding

Injection-compression molding (ICM) with greater flexibility than conventional injection molding (CIM) can produce parts with better quality. In this work, polystyrene (PS) parts were molded by ICM technology. The effects of seven dominating process parameters, including mold temperature, melt temperature, compression force, compression distance, compression speed, compression time, and delay time, on both shrinkage uniformity and birefringence of PS parts were investigated. The results showed that compression force is the most important parameter for part shrinkage uniformity. The position with a lowest shrinkage moved towards the gate with increased compression distance. There is a remarkable increase in birefringence with larger compression forces. There is certain relationship between shrinkage uniformity and birefringence results.

Fabrication of Supports for Solid Oxide Fuel Cells by Powder Injection Molding

2011 ◽  
Author(s):  
Ali Keshavarz Panahi ◽  
Hadi Miyanaji ◽  
Moein Taheri ◽  
Milad Janbakhsh
Keyword(s):  
Injection Molding ◽  
Weld Line ◽  
Injection Pressure ◽  
Mold Temperature ◽  
Injection Rate ◽  
Powder Injection ◽  
Pressure Injection ◽  
Packing Pressure ◽  
Molded Parts ◽  
Short Shot

In this paper the processing steps for producing SOFC (Solid Oxide Fuel Cell) supports by means of PIM (Powder Injection Molding) technique were investigated. Injection molding parameters in this study were divided into pressure-related (injection pressure and packing pressure), temperature-related (nozzle temperature and mold temperature), and time-related (injection rate and holding time) parameters. Keeping the other parameters (pressure-related, temperature-related and time-related parameters) constant at an optimized value, the effects of each of the molding parameters above were investigated. The results show that the short shot, warpage, weld line and void are the most common defects in molded parts. According to the results the short shot could be seen in low values of injection pressure, injection rate, nozzle and mold temperature. Also, warpage could be seen in high values of mold temperature, injection and packing pressure. Poor weld line was another defect that could be seen in low values of injection pressure, injection rate, nozzle and mold temperature. Also the void was one of the most common defects that could be seen in high values of injection rate and nozzle temperatures. Finally, using optimized molding parameters, the molded parts underwent debinding and sintering processes. Based on the results of thermal shock tests and the porosity measurements of the sintered parts, these molded parts possessed relatively desirable characteristics.

Study on the End-Point Control of Holding Phase during Injection Molding

2009 ◽  
Vol 87-88 ◽  
pp. 222-227 ◽  
Author(s):  
Jian Wang ◽  
Peng Cheng Xie ◽  
Yu Mei Ding ◽  
Wei Min Yang
Keyword(s):  
Injection Molding ◽  
Mold Temperature ◽  
Control Methods ◽  
Cavity Pressure ◽  
Precise Control ◽  
End Point ◽  
Control Change ◽  
Molded Parts ◽  
Point Control ◽  
Product Weight

While the transfer from filling to packing is particularly crucial during injection molding, the transfers from packing to holding and holding to screw recovery also significantly affect part quality. In this study, the control of the transfer from holding to screw recovery, that is the control of the end-point of the holding phase, was examined. The holding end-point control by time, cavity pressure and cavity temperature were presented. The purpose of this study was to validate the feasibility of the control methods of holding end-point by cavity pressure and cavity temperature. The qualities of injection-molded parts, weight, will serve as measures to probe their process capabilities. Recently found to be a good indicator of product quality, both cavity pressure and temperature profiles are applied here to obtain more precise control. Change of mold temperature was specially considered. After the experimental verification is conducted, the results reveal that the innovative holding end-point control by cavity temperature yields a more uniform product weight with mold temperature. It proved that the holding end-point control by cavity temperature can be used to obtain the optimum holding time and accommodate the product weight to the change of mold temperature, which is the other holding control methods cannot obtain.

scholarly journals The use of IR thermography to show the mold and part temperature evolution in injection molding

2016 ◽  
Vol 36 (1) ◽  
pp. 40-43 ◽  
Author(s):  
Karol Bula ◽  
Leszek Różański ◽  
Lidia Marciniak-Podsadna ◽  
Dawid Wróbel
Keyword(s):  
Injection Molding ◽  
Isotactic Polypropylene ◽  
Infrared Camera ◽  
Mold Temperature ◽  
Temperature Evolution ◽  
Injection Mold ◽  
Ir Thermography ◽  
Molded Parts ◽  
Injection Molded

Abstract This study concerns the application of infrared camera for injection molding analysis by measuring temperatures of both injection molded parts and injection mold cavities in a function of injection cycles. The mold with two cavities, differing in thickness (1 and 3 mm), and a cold direct runner was used. Isotactic polypropylene homopolymer was utilized to produce parts. Mold temperature was set at 22°C and controlled by a water chiller. Five measuring points were determined: SP1, SP2 (placed in the 3 mm cavity), SP3, SP4 (located in the 1 mm cavity) and SP5 around an injection molding gate. Our investigations showed that the highest temperature is localized around SP2 point and the lowest at SP4. Also, it was proved that even after 62 injection molding cycles, temperatures of cavities were not stable, revealing their further increase with each cycle.

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