Warpage Prediction of RHCM Crystalline Parts Based on Multi-Layers

Warpage is a typical defect for injection-molded parts, especially for crystalline parts molded by rapid heat cycle molding (RHCM). In this paper, a prediction method is proposed for predicting the warpage of crystalline parts molded by the RHCM process. Multi-layer models were established to predict warpage with the same thicknesses as the skin-core structures in the molded parts. Warpages were defined as the deformations calculated by the multi-layer models. The deformations were solved using the classical laminated plate theory by Abaqus. A model was introduced to describe the elastic modulus with the influence of temperature and crystallinity. The simulation process was divided into two procedures, before ejection and after ejection. Thermal stresses and thermal strains were simulated, respectively, in the procedure before ejection and after ejection. The prediction results were compared with the experimental results, which showed that the average errors between predicted warpage and average experimental warpage are, respectively, 7.0%, 3.5%, and 4.4% in conventional injection molding (CIM), in RHCM under a 60 °C heating mold (RHCM60), and in RHCM under a 90 °C heating mold (RHCM90).

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Study on Improving the Life of Stereolithography Injection Mold

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.468-471.1013 ◽

2012 ◽

Vol 468-471 ◽

pp. 1013-1016 ◽

Cited By ~ 1

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.

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Residual stresses determination in injection molded virgin and recycled HDPE blends: mechanical properties and morphology

e-Polymers ◽

10.1515/epoly.2008.8.1.1937 ◽

2008 ◽

Vol 8 (1) ◽

Cited By ~ 3

Author(s):

Mirigul Altan ◽

Mehmet Emin Yurci ◽

Nihan Nugay

Keyword(s):

Elastic Modulus ◽

Impact Strength ◽

Residual Stresses ◽

Thermal Stresses ◽

Mold Temperature ◽

Morphological Properties ◽

Time Layer ◽

Melt Temperature ◽

Injection Molded ◽

Recycled Hdpe

AbstractAn experimental study of residual thermal stresses has been carried out in injection molded virgin and recycled high density polyethylene (HDPE) blends. Effects of blend concentrations on residual stresses were investigated under different injection conditions such as melt temperature, mold temperature and cooling time. Layer removal technique was used for measuring residual stresses. In order to determine the relation between the residual stresses and material characteristic of HDPE blends, mechanical and morphological properties of the blends were also investigated. Elastic modulus and impact strength were important key factors for determining the blend characteristics. As a result, it was found that HDPE blends gave higher residual stresses but lower impact strength with higher elastic modulus when recycled concentration was increased. Furthermore, it was seen that shape and size of the crystallites were also effective on residual stresses. Small and spherulitic crystallite structured blends such as 30 % recycled HDPE induced reduction in residual stresses due to easier relaxation with lower elastic modulus and higher impact strength while lamellar crystallite structured blends such as 50 % recycled HDPE gave higher elastic modulus but lower impact strength with higher residual stresses.

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

Polymers ◽

10.3390/polym13234087 ◽

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.

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Thermal Stresses in Nonlinearly Viscoelastic Solids

Journal of Applied Mechanics ◽

10.1115/1.2899506 ◽

1992 ◽

Vol 59 (2S) ◽

pp. S43-S49 ◽

Cited By ~ 10

Author(s):

Giancarlo U. Losi ◽

Wolfgang G. Knauss

Keyword(s):

Glass Transition ◽

Residual Stresses ◽

Free Volume ◽

Thermal Stresses ◽

Morphological Changes ◽

Polymer Chains ◽

Transition Range ◽

Rheological Models ◽

Molded Parts ◽

Injection Molded

Three different rheological models are applied to the study of transient and residual thermal stresses in amorphous polymers cooled across the glass transition. The models differ mainly in their treatments of the nonequilibrium (time-dependent) portion of the morphological changes in the polymer and their influence on the relaxation process. The interstitial volume between polymer chains (free volume) is found to play an important role in the residual stresses; they are affected by the relative time scale of thermal diffusion and thermoviscoelastic relaxation/creep. This result has implications for injection molded parts of different section dimensions and for extrusion products. This fact must also be accounted for in determining the thermomechanicalproperties in the glass transition range. The step cooling ofPVAc spheres (1 and 20 mm dia.) and a cylinder (20 mm dia.) have been considered; most of the results presented apply to the sphere(s). Residual stresses can vary by as much as 100percent depending on whether the interstitial molecular (free) volume is counted or not. It is also demonstrated that residual stresses can be higher than an elastic analysis based on the glassy properties would suggest; thus the “stressfree temperature” is found to be significantly above the glass transition.

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Correlation Between Mechanical Properties in Standard Test Specimens and Injection Molded Thin-Wall Parts

Volume 1: Processing ◽

10.1115/msec2013-1032 ◽

2013 ◽

Author(s):

Laurentiu I. Sandu ◽

Felicia Stan ◽

Catalin Fetecau

Keyword(s):

Mechanical Properties ◽

Elastic Modulus ◽

Yield Strength ◽

Injection Molding ◽

Process Conditions ◽

Thin Wall ◽

Optimal Process ◽

Melt Temperature ◽

Molded Parts ◽

Injection Molded

In this paper, we investigated the effect of injection molding parameters on the mechanical properties of thin-wall injection molded parts. A four-factor (melt temperature, mold temperature, injection speed and packing pressure) and three-level fractional experimental design was performed to investigate the influence of each factor on the mechanical properties and determine the optimal process conditions that maximize the mechanical properties of the part using the signal-to-noise (S/N) ratio response. The mechanical properties (e.g., elastic modulus, yield strength and strain at break) were measured by tensile tests at room temperature, at a crosshead speed of 5 mm/min, and compared with those of the injection-molded specimens. The experimental results showed that the tensile properties were highly dependent on the injection molding parameters, regardless of the type of the specimens. The values of Young modulus and yield strength of the injection-molded specimens were lower than those of the injection-molded parts, while the elongation at break was considerably lower for the injection-molded parts. The optimal process conditions were strongly dependent on the measured performance quantities (elastic modulus, yield strength and strain at break).

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Effect of Aluminum Flakes on Mechanical and Optical Properties of Foam Injection Molded Parts

Polymers ◽

10.3390/polym13172930 ◽

2021 ◽

Vol 13 (17) ◽

pp. 2930

Author(s):

Donghwi Kim ◽

Youngjae Ryu ◽

Ju-Heon Lee ◽

Sung Woon Cha

Keyword(s):

Injection Molding ◽

Flexural Modulus ◽

Molding Method ◽

Molded Parts ◽

Injection Molded ◽

Foam Injection Molding ◽

Molding Methods ◽

Plastic Products ◽

Conventional Injection Molding

Injection research using aluminum flakes has been conducted to realize metallic textures on the surface of plastic products. Several studies have focused on the effect of the orientation and quality of the flakes when using conventional injection molding methods; however, limited studies have focused on the foam injection molding method. In this study, we examined the orientation of aluminum flakes through foam injection with an inert gas and observed the changes in texture using a spectrophotometer and a gloss meter. The mechanical properties were also studied because the rigidity of the product, which is affected by the weight reduction that occurs during foaming, is an important factor. The results demonstrate that under foam injection molding, reflectance and gloss increased by 6% and 7 GU, respectively, compared to those obtained using conventional injection molding; furthermore, impact strength and flexural modulus increased by 62% and 15%, respectively. The results of this research can be applied to incorporate esthetic improvements to products and to develop functional parts.

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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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Research on dynamic characteristics of gear system considering the influence of temperature on material performance

Journal of Vibration and Control ◽

10.1177/10775463211002616 ◽

2021 ◽

pp. 107754632110026

Author(s):

Zhou Sun ◽

Siyu Chen ◽

Xuan Tao ◽

Zehua Hu

Keyword(s):

Elastic Modulus ◽

Dynamic Characteristics ◽

Poisson’S Ratio ◽

Gear System ◽

Poisson's Ratio ◽

Effect Of Temperature ◽

Time Varying ◽

Influence Of Temperature ◽

Meshing Stiffness ◽

Influence Of Temperature On

Under high-speed and heavy-load conditions, the influence of temperature on the gear system is extremely important. Basically, the current work on the effect of temperature mostly considers the flash temperature or the overall temperature field to cause expansion at the meshing point and then affects nonlinear factors such as time-varying meshing stiffness, which lead to the deterioration of the dynamic transmission. This work considers the effect of temperature on the material’s elastic modulus and Poisson’s ratio and relates the temperature to the time-varying meshing stiffness. The effects of temperature on the elastic modulus and Poisson’s ratio are expressed as functions and brought into the improved energy method stiffness calculation formula. Then, the dynamic characteristics of the gear system are analyzed. With the bifurcation diagram, phase, Poincaré, and fast Fourier transform plots of the gear system, the influence of temperature on the nonlinear dynamics of the gear system is discussed. The numerical analysis results show that as the temperature increases, the dynamic response of the system in the middle-speed region gradually changes from periodic motion to chaos.

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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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