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

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.

Geometry-Based Index for Predicting Sink Mark in Plastic Parts

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.

scholarly journals Study about the technique of determining residual stress of loading measuring method

2021 ◽  
Vol 13 (5) ◽  
pp. 168781402110169
Author(s):  
Liu Hong ◽  
Jiang Zheqi ◽  
Pan Danqi
Keyword(s):  
Residual Stress ◽  
Nondestructive Test ◽  
Measuring Method ◽  
Test Method ◽  
Hole Drilling ◽  
Hole Drilling Method ◽  
Molded Part ◽  
Molded Parts ◽  
Injection Molded ◽  
A New Technique

Nondestructive test method for residual stress in a structural member is always an important research subject, as a new technique for measuring residual stress loading measuring method needs to consummate for the convenience of engineering. The paper proves that nondestructive test loading measuring method is effective and accurate when compared with the result from hole-drilling method. Taking the measurement of residual stress of injection-molded part in automotive lamp as example, the residual stresses in the surface of injection-molded parts of automotive lamp measured by the two methods are very close based on the two measuring results. It shows that loading measuring method, a new method is used to measure the residual stress, has enough accuracy and credibility when it is used to measure the residual stress of complicated injection-molded part. It provides a basis for popularization and application of loading measuring method in engineering. The paper discusses the basic principles of loading measuring method and detailed procedure of the measurement of residual stress by loading measuring method; it gives out some advices to reduce the test errors.

Simulation of Internal Stress in Injection Molded Parts

2008 ◽  
Vol 575-578 ◽  
pp. 622-626
Author(s):  
Hai Hong Wu ◽  
Zhen Feng Zhao ◽  
Chang Yu Shen
Keyword(s):  
Internal Stress ◽  
Mold Wall ◽  
Maxwell Model ◽  
Finite Element Equation ◽  
Packing Pressure ◽  
Non Linear ◽  
Molded Parts ◽  
Polystyrene Plate ◽  
Injection Molded ◽  
Good Agreement

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.

Defect Minimization of an Injection Molded Plastic Component Using Conformal Cooling Channels

2021 ◽  
Vol 1019 ◽  
pp. 205-210
Author(s):  
Deepika S. Singraur ◽  
Bhushan T. Patil ◽  
Vasim A. Shaikh
Keyword(s):  
Performance Parameters ◽  
Cooling Process ◽  
Conformal Cooling ◽  
Cooling Channels ◽  
Molded Part ◽  
Cooling Method ◽  
Conformal Cooling Channels ◽  
Differential Shrinkage ◽  
Injection Molded ◽  
Injection Molded Plastic

The cooling process is an essential aspect while designing for uniform heat transfer between the mold and the molded part. Improper design and placement of cooling channels result in non-uniform cooling and thus results in differential shrinkage and warpage on the final product. The installation of the channels yet plays a crucial role in the cooling of the part. Conforming channels that are placed at an optimum distance from the part to enhance the cooling process. In this paper, the performance parameters of straight drilled channels are compared with the conformal cooling channels for an electric alarm box. The analysis indicates that the conformal cooling method improved and enhanced the cooling process and reduced the defects like warpage and differential shrinkage by 25.5% and 28.0% respectively.

Viscoelasticity Effects of Polymeric Material in Micro Injection Molding

2008 ◽  
Author(s):  
Peiman Mosaddegh ◽  
David C. Angstadt
Keyword(s):  
Oscillation Mode ◽  
Polymeric Materials ◽  
Elastic Response ◽  
Cavity Pressure ◽  
Molded Part ◽  
Molded Parts ◽  
Filling Phase ◽  
Injection Molded ◽  
Poly Ethylene ◽  
Peak Value

An experimental study has been carried out to determine the effect of viscoelasticity in comparison to viscosity on micro-injection molded parts. In this study, two different polymeric materials — Polystyrene (PS) as a viscous material and High Density Poly-Ethylene (HDPE) as a viscoelastic material — have been selected to observe the effect of melt elasticity on the filling phase of micro molding based on cavity pressure of molded part. All process parameters except temperature are the same for both polymers. Process temperatures have been selected in order to match the viscosity for both polymers used. Polymer viscosity was characterized at different shear rate and temperature. Viscoelasticity of both polymers were investigated using rotational rheometry in the oscillation mode. The mold geometry with high aspect ratio has been used and the effect of viscoelasticity on cavity pressure has been discussed. It was observed that there is retardation on the response of pressure because of elastic response of material during filling. Despite the differences in slope, peak value, area, and cycle time between two curves, they share similar trends. The only difference is their response during solidifying because of material property.

Effect of Size and Spatial Distribution of Titania Pigments in Injection Molded Parts on Surface Reflectance

2007 ◽  
Author(s):  
B. R. Dantal ◽  
A. Saigal ◽  
M. A. Zimmerman
Keyword(s):  
Spatial Distribution ◽  
Statistical Significance ◽  
Average Diameter ◽  
Area Fraction ◽  
Light Emitting ◽  
Molded Part ◽  
Molded Parts ◽  
Injection Molded ◽  
The Difference ◽  
New Applications

Titania pigments are used in molding compounds as a means to improve opacity by increasing the scattering efficiency of the medium and to develop new applications such as liquid crystal displays (LCD) and light emitting diodes (LED). The characteristics of the injection molded products are a function of molding parameters such as gate location and shear rate. In this study, quantitative measures of the particle distribution of titania pigments in polymer composites have been experimentally determined, including area fraction, average diameter, and diameter volume. A 2 × 3 × 3 ANOVA test has been conducted to assess the statistical significance of these parameters. This study deals with the size and spatial distribution of the particles. The important parameters calculated based on the Feret’s diameter are diameter-volume (dv), diameter-number (dn), and area fraction (AF). The term diameter-volume (dv) has been used to give greater significance to the large particles and thus ‘large’ indicates more and/or larger particles. The parameters have been calculated by using Image-J image processing software. MINITAB has been used to assess the statistical significance of these parameters. The results show that titania particles are not uniformly distributed within the final molded parts and they vary along the molding (longitudinal) and transverse directions of plastic flow. The difference of pigment area fraction and diameter volume at different locations within a final molded part has a significant effect on the percentage reflectance of the surface.

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