Simulation of Internal Stress in Injection Molded Parts

The development of internal stress in injection molded parts is analyzed. Different from other researches, this study uses a new modified Maxwell model to calculate the internal stress. On the basis of the creep experiments of injection molded parts, a non-linear constitutive equation is proposed. Non-linear finite element equation to calculate the internal stress is derived. By means of this model, the internal stress of an injection molded polystyrene plate is simulated. The effects of mold wall temperature, cooling time and packing pressure on the development of internal stress are investigated. The predicting results are in good agreement with experimental data.

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Effects of Process Conditions on Shrinkage and Warpage: Experiments and Simulations

10.1115/imece2000-1232 ◽

2000 ◽

Author(s):

James T. Wang ◽

C. K. Yoon

Keyword(s):

Residual Stress ◽

Mold Wall ◽

Polymer Melt ◽

Process Conditions ◽

Cooling Channels ◽

Part Quality ◽

Molded Part ◽

Packing Pressure ◽

Molded Parts ◽

Injection Molded

Abstract In the injection mold process, a pressure gradient exists from the polymer entrance to the last-fill location. At different planar locations of a part, when the polymer melt cools down to the transition temperature and freezes (changes from liquid to solid) at different pressures, shrinkage at the various locations will be different. If cooling channels are not arranged properly, the mold wall temperatures on the cavity and core sides can be different. This unbalanced cooling can also cause the melt at the upper and lower halves of the cavity to shrink differently, because they freeze at different times and different pressures. These two types of non-uniform shrinkage will cause parts to warp. Reducing shrinkage and warpage is one of the top priorities for improving the quality of injection molded parts. In addition to part design and material properties, process conditions are the most important determinants of part quality. In this paper, the relationship between process conditions and in-cavity residual stress will be studied. In-cavity residual stress is the driving force that causes parts to deform after they are taken out of the mold. The effects of process conditions on injection-molded part quality (in terms of shrinkage and warpage) will be discussed. Different packing pressure levels, together with unbalanced cooling from mold wall temperatures, will be examined. Deformation of injection molded parts will be measured. Comparisons between experimental and numerical simulation results will be reported.

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Geometry-Based Index for Predicting Sink Mark in Plastic Parts

3rd International Conference on Design Theory and Methodology ◽

10.1115/detc1991-0037 ◽

1991 ◽

Author(s):

Kurt Beiter ◽

Kosuke Ishii ◽

Lee Hornberger

Keyword(s):

Process Conditions ◽

Plastic Part ◽

Design Rules ◽

Packing Pressure ◽

Molded Parts ◽

Injection Molded ◽

Form Features ◽

Plastic Parts ◽

Sink Mark

Abstract This paper describes the development of geometry-based indices that predict sink mark depth in injection molded parts. Plastic part designers need such indices to incorporate manufacturability concerns at the conceptual stage of design. These indices apply to several form features so engineers do not have to check different design rules for each geometry element. First, we propose a geometry-based sink index that can be used to predict sink mark depth as a function of process conditions such as packing pressure. Next, we explain how this relationship is identified through experiments. We also describe HyperDesign/Plastics, a Macintosh-based design aid that incorporates the sink index.

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Integrated simulations of structural performance, molding process, and warpage for gas-assisted injection-molded parts. III. Simulation of cyclic, transient variations in mold wall temperatures

Journal of Applied Polymer Science ◽

10.1002/(sici)1097-4628(19990110)71:2<339::aid-app18>3.0.co;2-h ◽

1999 ◽

Vol 71 (2) ◽

pp. 339-351

Author(s):

Shia-Chung Chen ◽

Sheng-Yan Hu ◽

Wen-Ren Jong

Keyword(s):

Mold Wall ◽

Structural Performance ◽

Molding Process ◽

Molded Parts ◽

Injection Molded ◽

Transient Variations

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Analysis of Effect of Process Parameters on Warpage of a Automobile Bumper Injection Molded Parts

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.652-654.2062 ◽

2013 ◽

Vol 652-654 ◽

pp. 2062-2066 ◽

Cited By ~ 1

Author(s):

Shu Ting Wu ◽

Hong Bin Liu ◽

Hai Tao Wu

Keyword(s):

Process Parameters ◽

Cooling Time ◽

Injection Time ◽

Melt Temperature ◽

Packing Pressure ◽

Molded Parts ◽

Injection Molded

Take a automobile bumper for example, analysis of effect of process parameters on warpage of a automobile bumper, including melt temperature, injection time, cooling time and packing pressure, on the warpage of the automobile bumper were analyzed by means of Moldflow software. The results show the warpage decrease of the increase of the injection time, the cooling time and the packing pressure, but when the packing pressure reached 45MPa, the warpage slightly increased; the melt temperature should be picked out by the characteristics of the plastics material.

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Effects of Polymer-Filler Properties on the Warpage of Injection Molded Automobile Door

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.239-242.2511 ◽

2011 ◽

Vol 239-242 ◽

pp. 2511-2514

Author(s):

Qiu Hui Liao ◽

Xiao Xun Zhang ◽

Qin Chao Ruan

Keyword(s):

Numerical Simulation ◽

Experimental Investigation ◽

Major Axis ◽

Mold Design ◽

Experimental Measurements ◽

Thermal Displacement ◽

Polymer Filler ◽

Molded Parts ◽

Injection Molded ◽

Good Agreement

The accurate prediction of warpage of injection molded parts is important to achieve successful mold design with high precision. In this study, effects of polymer-filler properties, such as filler aspect ratio (L/D), filler modulus parallel to major axis (E1) and filler modulus perpendicular to major axis (E2), on warpage displacement of automobile door were studied quantitatively by experimental investigation and numerical simulation. The numerical results are in good agreement with the experimental measurements. It is also found that: (1) the thermal displacement decreases as E1 and E2 decrease, (2) the PVT displacement is not influenced by change of L/D, E1 and E2, (3) the orientation effect displacement is neglected small when L/D=1 and E1= E2, and it also increases as L/D and E1/E2 increase.

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A Study on the Birefringence Measurement in Injection Molded Parts Using Two Different Laser Sources and R-G-B Separation of White Light

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.326-328.187 ◽

2006 ◽

Vol 326-328 ◽

pp. 187-190

Author(s):

Jong Sun Kim ◽

Chul Jin Hwang ◽

Kyung Hwan Yoon

Keyword(s):

White Light ◽

Low Cost ◽

Main Idea ◽

Injection Molding Process ◽

Molding Process ◽

Laser Method ◽

High Productivity ◽

Molded Parts ◽

Injection Molded ◽

Plastic Parts

Recently, injection molded plastic optical products are widely used in many fields, because injection molding process has advantages of low cost and high productivity. However, there remains residual birefringence and residual stresses originated from flow history and differential cooling. The present study focused on developing a technique to measure the birefringence in transparent injection-molded optical plastic parts using two methods as follows: (i) the two colored laser method, (ii) the R-G-B separation method of white light. The main idea of both methods came from the fact that more information can be obtained from the distribution of retardation caused by different wavelengths. The comparison between two methods is demonstrated for the same sample of which retardation is up to 850 nm.

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A Practical Numerical Approach to Characterizing Non-Linear Shrinkage and Optimizing Dimensional Deviation of Injection-Molded Small Module Plastic Gears

Polymers ◽

10.3390/polym13132092 ◽

2021 ◽

Vol 13 (13) ◽

pp. 2092

Author(s):

Xiansong He ◽

Wangqing Wu

Keyword(s):

Injection Molding ◽

High Speed ◽

Numerical Approach ◽

Linear Shrinkage ◽

Influential Factor ◽

Dimensional Deviation ◽

Non Linear ◽

Injection Molded ◽

Plastic Gears ◽

Circle Diameter

This paper was aimed at finding out the solution to the problem of insufficient dimensional accuracy caused by non-linear shrinkage deformation during injection molding of small module plastic gears. A practical numerical approach was proposed to characterize the non-linear shrinkage and optimize the dimensional deviation of the small module plastic gears. Specifically, Moldflow analysis was applied to visually simulate the shrinkage process of small module plastic gears during injection molding. A 3D shrinkage gear model was obtained and exported to compare with the designed gear model. After analyzing the non-linear shrinkage characteristics, the dimensional deviation of the addendum circle diameter and root circle diameter was investigated by orthogonal experiments. In the end, a high-speed cooling concept for the mold plate and the gear cavity was proposed to optimize the dimensional deviation. It was confirmed that the cooling rate is the most influential factor on the non-linear shrinkage of the injection-molded small module plastic gears. The dimensional deviation of the addendum circle diameter and the root circle diameter can be reduced by 22.79% and 22.99% with the proposed high-speed cooling concept, respectively.

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Silane-Functionalized Sheep Wool Fibers from Dairy Industry Waste for the Development of Plasticized PLA Composites with Maleinized Linseed Oil for Injection-Molded Parts

Polymers ◽

10.3390/polym12112523 ◽

2020 ◽

Vol 12 (11) ◽

pp. 2523

Author(s):

Franciszek Pawlak ◽

Miguel Aldas ◽

Francisco Parres ◽

Juan López-Martínez ◽

Marina Patricia Arrieta

Keyword(s):

Linseed Oil ◽

Microstructural Analysis ◽

Dairy Industry ◽

Poly Lactic Acid ◽

Industry Waste ◽

Wool Fibers ◽

Molded Parts ◽

Silane Modification ◽

Injection Molded ◽

Sheep Wool

Poly(lactic acid) (PLA) was plasticized with maleinized linseed oil (MLO) and further reinforced with sheep wool fibers recovered from the dairy industry. The wool fibers were firstly functionalized with 1 and 2.5 phr of tris(2-methoxyethoxy)(vinyl) (TVS) silane coupling agent and were further used in 1, 5, and 10 phr to reinforce the PLA/MLO matrix. Then, the composite materials were processed by extrusion, followed by injection-molding processes. The mechanical, thermal, microstructural, and surface properties were assessed. While the addition of untreated wool fibers to the plasticized PLA/MLO matrix caused a general decrease in the mechanical properties, the TVS treatment was able to slightly compensate for such mechanical losses. Additionally, a shift in cold crystallization and a decrease in the degree of crystallization were observed due to the fiber silane modification. The microstructural analysis confirmed enhanced interaction between silane-modified fibers and the polymeric matrix. The inclusion of the fiber into the PLA/MLO matrix made the obtained material more hydrophobic, while the yellowish color of the material increased with the fiber content.

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