Comparative Analysis of Different Methods in Residual Stress Measurement for Polymeric Parts

2013 ◽  
Vol 837 ◽  
pp. 175-178
Author(s):  
Alexandra Raicu
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Stress Measurement ◽  
Polymeric Materials ◽  
Injection Molding Process ◽  
Uniform Temperature ◽  
Molding Process ◽  
Molded Parts ◽  
Injection Molded ◽  
Technological Constraints

This paper presents the measurements of the residual stresses for polymeric parts using different methods. The residual stresses are usually introduced during manufacturing and are caused by processes such as molding. In order to optimize injection molding process with polymeric material, it is important to predict the internal stress development during molding. The residual stresses are caused mainly by non-uniform temperature profile in the cavity during filling, packing and cooling stages. This research offers information and a methodology which may be applied in practical conditions for a large number of parts manufactured from the different polymeric materials and for several technological constraints. The author confirmed that all this methods which measure the residual stresses can be applied to injection molded parts.

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

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.

Calculation on the Residual Stresses of Injection-Molded Conductive-Carbon-Fiber-Filled Polymer Composites

2012 ◽  
Vol 629 ◽  
pp. 55-59
Author(s):  
Ai Yun Jiang ◽  
Jing Chao Zou ◽  
Bao Feng Zhang ◽  
Hai Hong Wu
Keyword(s):  
Carbon Fiber ◽  
Residual Stresses ◽  
Polymer Composites ◽  
Injection Molding Process ◽  
Molding Process ◽  
Filled Polymer ◽  
The Core ◽  
Packing Pressure ◽  
Core Areas ◽  
Injection Molded

For conductive-carbon-fiber-filled polymer composites, the residual stresses developed during injection molding process may affect not only the molding’s conductive property, but its dimensional stability as well. In order to improve the conductivity of the molding fabricated with this kind of composites, we investigated, using layer removal method, the distribution of the residual stresses of injection-molded conductive-carbon-fiber-filled polypropylene in this paper. The residual stresses were obtained under the actions of different processing conditions. Our results indicate that processing pressures have more significant effects on the residual stresses at the skin areas than the core areas of the sample because of fiber orientation. The tensile stresses of the molding at the core areas drop under the action of packing pressure, but the compressive stresses at the skin areas increase. The results reveal that the action of packing pressure may decrease the anisotropy of the residual stresses in the molding.

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.

scholarly journals Surface Homogeneity of Injection Molded Parts

2018 ◽  
Vol 62 (4) ◽  
pp. 284-291 ◽  
Author(s):  
László Zsíros ◽  
József Gábor Kovács
Keyword(s):  
Injection Molding ◽  
Evaluation Method ◽  
Solid Phase ◽  
Color Space ◽  
Processing Parameters ◽  
Injection Molding Process ◽  
Mold Surface ◽  
Molding Process ◽  
Molded Parts ◽  
Injection Molded

In this paper we are presenting a novel method for color inhomogeneity evaluation. We proved that this method has a higher than 95 % linear correlation coefficient if results are correlated with human visual evaluations.We applied this evaluation method to analyze the homogenization in the injection molding process, therefore we measured the homogenization properties of various solid phase masterbatches on injection molded parts. We tested the effects of the processing parameters of injection molding and analyzed various dynamic and static mixers as well. We have also measured the influence of the mold surface texture on the sensation of inhomogeneities on the part surface.We have carried out our tests on an injection grade ABS material using various masterbatches. The method was based on the digitization of the molded flat specimens. The images of these specimens were evaluated with an own developed formula using the CIELAB color space resulting high correlation with human visual inspections.

Residual Stress Measurement Of High Molecular Matter By Transmission X-Ray Diffraction

2011 ◽  
Vol 681 ◽  
pp. 381-386 ◽  
Author(s):  
Masashi Kitamura ◽  
Nishida Masayuki ◽  
Hanabusa Takao
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Stress Measurement ◽  
Quantitative Estimation ◽  
Regression Line ◽  
Polymeric Materials ◽  
Residual Stress Measurement ◽  
Stress Distributions ◽  
Transmission Method ◽  
X Ray

In this study, the residual stresses in high-density polyethylene (HDPE) were measured using an x-ray stress measurement technique. There have been few reports published of residual stress investigations in polymeric materials by x-ray stress measurements based on conventional x-ray reflection methods. There are two problems associated with this measurement. Firstly, the diffraction peaks of the polymer in the low 2q angle region and therefore the measurement accuracy for strains reduces. Secondly, the low 2q angle region makes it extremely difficult to use the sin2ψmethod. In the present study we tried to use a transmission method for measuring the residual stress in HDPE sample to resolve these problems. The HDPE sample is shaped into thin sheets which have the three kinds of crystallinity degrees. The measured data is fitted with a good linear regression line in a d-sin2ψdiagram and gradient of the regression line corresponded to the applied stress. On the other hand, the results of the residual stress measurement are deeply associated with degrees of the crystallinity in the HDPE material. The quantitative estimation of crystallinity degrees in the HDPE material was accomplished by a sink-float method. The residual stress distributions were discussed between micro-residual stresses in the crystal phase of HDPE with the amorphous phase of it. Finally, x-ray elastic constant (XEC) of HDPE was estimated and the Initial residual stresses were also measured by use of this XEC parameter.

scholarly journals Stress Whitening as an Observation Method of Residual Stress in MABS Polymer Material through the Example of Holding Pressure in an Injection Molding Process

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2871
Author(s):  
Paweł Brzęk ◽  
Tomasz Sterzyński
Keyword(s):  
Residual Stress ◽  
Injection Molding ◽  
Residual Stresses ◽  
Local Stress ◽  
Acrylonitrile Butadiene Styrene ◽  
Processing Parameters ◽  
Injection Molding Process ◽  
Molding Process ◽  
Optical Visualization ◽  
Stress Whitening

The effects such as warpage, dimensional instability and environmental stress corrosion, due to the presence of residual stresses in polymeric products, are strongly dependent on injection molding conditions. The holding time and holding pressure belongs to most important processing parameters, determining the dimensional stability and properties of injected goods. A new procedure based on a visualization technique was applied, where the levels of residual stresses of the samples were estimated. The experiments were performed for samples produced of translucent methacrylate acrylonitrile butadiene styrene (MABS), a commodity polymer with a high transparency, necessary for the optical visualization of the stress whitening. The samples produced by injecting molding were deformed to a constant elongation, to observe the dependent stress whitening effect subsequently used to evaluate the stress distribution. It was found that depending on the value of the injection holding pressure, various levels of residual stress and its distribution may be observed in MABS samples. These measurements conformed that the applied optical method is an easy-to-perform technique. The possibility to detect the residual stresses over the whole cross-section of the transparent product, without the necessity for local stress determination, is another significant advantage of this investigation procedure.

Quantitative Study of Shrinkage and Warpage Behavior for Microcellular and Conventional Injection Molding

Materials ◽  
2005 ◽  
Author(s):  
Adam Kramschuster ◽  
Ryan Cavitt ◽  
Don Ermer ◽  
Chris Shen ◽  
Zhongbao Chen ◽  
...  
Keyword(s):  
Injection Molding ◽  
Hold Time ◽  
Fractional Factorial ◽  
Injection Molding Process ◽  
Molding Process ◽  
Injection Speed ◽  
Microcellular Injection Molding ◽  
Molded Parts ◽  
Injection Molded ◽  
Factorial Design Of Experiments

This research investigated the effects of processing conditions on the shrinkage and warpage (S&W) behavior of a box-shaped, polypropylene part using conventional, microcellular, and microcellular co-injection molding. Three sets of 26-1 fractional factorial design of experiments (DOE) were employed to perform the experiments and proper statistical theory was used to analyze the data. After the injection molding process reached steady state, molded samples were collected and measured using an optical coordinate measurement machine (OCMM), which had been evaluated using a proper repeatability and reproducibility (R&R) measurement study. By analyzing the statistically significant main and two-factor interaction effects, the results show that the supercritical fluid (SCF) content (nitrogen in this case, in terms of SCF dosage time) and the injection speed affect the S&W of microcellular injection and microcellular co-injection molded parts the most, whereas pack/hold pressure and pack/hold time have the most significant effect on the S&W of conventional injection molded parts. Also, this study quantitatively showed that, within the processing range studied, a reduction in the S&W could be achieved with the microcellular injection molding and micro- cellular co-injection molding processes.

scholarly journals Shrinkage and Warpage Minimization of Glass-Fiber-Reinforced Polyamide 6 Parts by Microcellular Foam Injection Molding

Polymers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 889 ◽  
Author(s):  
Youngjae Ryu ◽  
Joo Seong Sohn ◽  
Chang-Seok Yun ◽  
Sung Woon Cha
Keyword(s):  
Injection Molding ◽  
Polyamide 6 ◽  
Injection Molding Process ◽  
Microcellular Foam ◽  
Molding Process ◽  
Glass Fiber Reinforced ◽  
Molded Parts ◽  
Injection Molded ◽  
Process Factors ◽  
Foam Injection Molding

Shrinkage and warpage of injection-molded parts can be minimized by applying microcellular foaming technology to the injection molding process. However, unlike the conventional injection molding process, the optimal conditions of the microcellular foam injection molding process are elusive because of core differences such as gas injection. Therefore, this study aims to derive process conditions to minimize the shrinkage and warpage of microcellular foam injection-molded parts made of glass fiber reinforced polyamide 6 (PA6/GF). Process factors and levels were first determined, with experiments planned accordingly. We simulated designed experiments using injection molding analysis software, and the results were analyzed using the Taguchi method, analysis of variance (ANOVA), and response surface methodology (RSM), with the ANOVA analysis being ultimately demonstrating the influence of the factors. We derived and verified the optimal combination of process factors and levels for minimizing both shrinkage and warpage using the Taguchi method and RSM. In addition, the mechanical properties and cell morphology of PA6/GF, which change with microcellular foam injection molding, were confirmed.

Tailored Inserts Based on Continuous Fibre for Local Bearing Reinforcement of Short Fibre Thermoplastic Components

2017 ◽  
Vol 742 ◽  
pp. 82-89
Author(s):  
Katharina Arnaut ◽  
Axel S. Herrmann
Keyword(s):  
Load Transfer ◽  
Injection Molding Process ◽  
Complex Geometries ◽  
Molding Process ◽  
Cycle Times ◽  
Bearing Strength ◽  
Continuous Fibre ◽  
Molded Parts ◽  
Injection Molded ◽  
Economical Process

The injection molding process is an economical process for manufacturing of thermoplastic components. Complex geometries can be realized with high automation and short cycle times. However the mechanical properties of injection-molded parts are not suitable for mechanical demanding components even by adding short or long fibre. As bold connections are used frequently for load transfer, the load introduction area particularly is limited by low bearing strength. The present paper shows the influence of tailored inserts based on continuous fibre on the bolt-loaded hole of injected test specimen.

Effect of Weld Line Defects on Electrical Conductivity of Injection Molded Parts with Carbon Nano Fibers/PP Composites

2011 ◽  
Vol 233-235 ◽  
pp. 1136-1140
Author(s):  
Lei Xie ◽  
Xiao Yong Tian ◽  
Wang Qing Wu ◽  
Di Chen Li ◽  
Bing Yan Jiang ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Injection Molding ◽  
Conductive Polymer ◽  
Weld Line ◽  
Injection Molding Process ◽  
Molding Process ◽  
Molded Part ◽  
Molded Parts ◽  
Line Defects ◽  
Injection Molded

As well known, the weld line defect in injection molding process results detrimental to mechanical properties and surface quality. However, the electrical conductivity of the injection molded part is influenced as well. In this study, in order to reveal the mechanism of the weld line affecting the electrical conductivity of injection molding parts, the conductive polymer composites with various carbon nanofibers filling contents were compounded. Those composites were formed as the tensile samples with and without weld line defects by injection molding process. According to the electrical resistance measurements for the samples, it can be found that at relative low filling content of 10wt%, the weld line contributes to increase the electrical conductivity of the injection molding parts due to its effect on nanofibers’ orientation. However, when the filling content is higher than 20wt%, this effect is not significant any more.

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