Sink Mark Depth Research Articles

A Study on the Temperature Optimization of Mold and Melt Using Design of Experiments for Children's Chair

The quality of the finished product is affected by a number of factors during the plastic injection molding process. Two crucial process variables in the creation of products are melted and mold temperature. The study uses the Design of Experiments tool in Autodesk Moldflow to look at the impact of melt and mold temperatures on injection molding technology. Analytical items are specifically made of polypropylene (PP) using kids' chair mold. According to simulation analysis results, there is a remarkable effect of the melt temperature on both time at end of packing as well as deflection in the range of the analytical temperature at tmold of [40, 80]°C and tmelt of [180, 220]°C. Melt temperature also shows a notable influence not only on deflection but also on sink mark depth and volumetric shrinkage, along with the criteria to evaluate the expense of a product (time at end of packing, total part weight).

Prediction of weld-line width and sink-mark depth of plastic injection moulded parts using neural networks

Fast-moving consumer goods companies rely on thermoplastic materials like polymethyl methacrylate (PMMA) for producing large quantities of affordable packaging products. In the current study, the experimental data of plastic injection moulding was collected from existing literature. It was found that the process parameters of the plastic injection moulding process influence the defects like weld-line and sink-mark on PMMA products. Therefore, an Artificial neural network model (ANN) was developed to estimate the permissible range for these defects. The 8–11-11–2 architecture was chosen because it yielded the least values of mean square error (MSE) and average error (AE) for training, testing and validation datasets. The predicted results were compared with experimental results to determine the accuracy of the developed model. Using performance parameters and various visual illustrations, the model has been validated. The obtained correlation coefficient (R-value) of 0.99954 signifies that the ANN model has good compatibility with the experimental dataset. This can be demonstrated by the precise prediction values produced by the ANN model. Therefore, the deterioration of mechanical properties of PMMA material can be minimized as the ANN model succeeded in predicting optimal weld-line width and sink-mark depth during the plastic injection moulding process.

Multi response optimization of injection moulding process to reduce sink marks and cycle time

In the rapidly growing field of technology, there is a demand for consumer goods made of plastic. To meet needs of customer, plastic products are made in different ways. There are different plastic manufacturing process. Numerous plastic manufacturing process are thereInjection molding is involves injecting molten material into a mold and allowing it to take on the shape of the mold.There are wide ranges of products such as plastic chairs, Computer cabinet etc. are manufactured with the help of smaller and more complex profiles. Due to lack of dimensional accuracy these complex profile produces defects inside the mold. Current study provides insights into transparent thermoplastic Polypropylene products. Five plastic injection molding variable criteria are considered for reducing the depth of sink mark in injection molding for commercial grade transparent thermoplastic (Polypropylene). Melting temperature (8C), mold temperature (8C), packing time (seconds), ratio of ribs to walls (%) and rib to gate distance (mm). According to Taguchi's design L27 experiments are performed and factors are optimized using the Taguchi based utility concept for multi criteria problems. The sink mark's depth on the part's surfaceis considered as quality of product and cycle time is considered as the productivity of product. It is the one of the best techniques, which can maintain the equilibrium between two.

Parametric optimization of plastic injection moulding for FMCG polymer moulding (PMMA) using hybrid Taguchi-WASPAS-Ant Lion optimization algorithm

In this fast growing world, the demand for fast-moving consumer goods (FMCG) and half of the goods are manufactured through the use of plastic. To cater to those, plastic goods are manufactured using different types of moulding process. Plastic injection moulding (PIM) is a technique of injecting molten plastic into a mould to form it. They are widely used to manufacture FMCG products like containers, remote cases, or other small, complex profiles. But sometimes these complex profile mouldings lack dimensional accuracy. The current study provides an understanding of the clear thermoplastic Polymethyl Methacrylate (PMMA) material moulding for FMCG items utilizing an injection moulding machine. The transparent top sheath used in male/female deodorants can be considered in this investigation. For the purpose of minimizing weld-line width and sink-marks depth during injection moulding of commercial grade transparent thermo-plastic (Polymethyl Methacrylate), eight plastic injection moulding criteria were considered, namely melting temperature, mould temperature, cooling time, injection pressure, back pressure, holding pressure, ambient temperature, and holding time. In accordance with Taguchi's Design, the 27 experiments were piloted, and the factors were optimized using the Taguchi-based WASPAS method (Weighted Aggregated Sum Product Assessment), the Ant Lion optimization algorithm, and analysis of variance to determine the most dominant parameter in the minimization of weld-line width and sink-mark depth of the plastic injection moulded part. It was discovered that the cooling time of the plastic injection moulded component is the most important element affecting the weld-line width as well as the depth of the sink-mark on the surface of the part.

Procedure development for predicting the sink mark of injection molded thermoplastics by finite element method

The sink mark is one common defect of the injection-molded thermoplastics, which is harmful to the part appearance. A procedure for the sink mark prediction was proposed to build the finite element method (FEM) model in Abaqus. The temperature and pressure distributions were imported as boundary conditions at a different time from the injection molding simulation software Moldflow. The user subroutines UEXPAN and UMAT were coded and implemented in Abaqus to describe the pressure-volume-temperature (PVT) behaviors under actual cooling conditions and the polymer constitutive relationship. The PVT curves of the thermoplastic were obtained by the piston-die method at a cooling rate of 5 °C/min. The crystallizing behaviors were measured by a differential scanning calorimetry and adapted to modify the PVT curves at different cooling rates. The tension-compression tests at different temperatures were performed to obtain the stress-strain curves. The simulation of injection molding was conducted in the software Moldflow. The deflection tests were conducted on the coordinate measuring machine (CMM) to validate the predicted sink mark. It was found that the subroutines of UEXPAN described the volume variations under different cooling rates successfully. Furthermore, the subroutine UMAT predicted stress-strain curves successfully at different temperatures and strain rates. The predicted sink mark in Abaqus agreed well with the measured one. The sink mark depth from Abaqus reached one third of the experimental one and had obvious improvement than that from Moldflow.

Study on reducing sink mark depth of a microcellular injection molded part with many reinforcing ribs

As a novel injection molding process, microcellular injection molding process has the characteristics of saving material, decreasing warpage and surface sink mark, improving dimensional accuracy, etc. But for the plastic part with thick reinforcing ribs, if selection of process parameters are not reasonable, foaming quality of melt will be affected and obvious sink mark defects will appear on the surface of plastic part. This paper selected a medical appliance shell with many reinforcing ribs as research object. Simulation experiments of microcellular injection molding process were performed by using orthogonal experiment method. The influence of different process parameters, such as mold cavity surface temperature, melt temperature, injection rate, cooling time, weight reduction ratio and supercritical fluid level, on the surface sink mark of microcellular injection molding part was studied by using signal-to-noise ratio analysis and analysis of variance . The results showed that mold cavity surface temperature was the most important influence factor on surface sink mark depth of microcellular injection molding part, followed by weight reduction ratio, cooling time, supercritical fluid level, injection rate and melt temperature. Meanwhile, the optimal combination of process parameters was obtained for minimizing sink mark depth of microcellular injection molding part. The average surface sink mark depth of microcellular injection molding part molded by using the optimized process parameters was only 2.62 µm, compared to 4.87 µm of average surface sink mark depth of microcellular injection molding part molded by using the process parameters before optimization, the average sink mark depth of microcellular injection molding part was reduced by 46.2%. Finally, the forming mechanism of sink mark of microcellular injection molding part at locations of reinforcing ribs was discussed, and the influence mechanism of different process parameters on surface sink mark defects of microcellular injection molding part was also analyzed.

금속사출성형을 이용한 STS 316L 밸브피팅 제작에 대한 연구

A net-shape forming of small and complex-shaped metal parts by metal injection molding (MIM) has economic advantages in mass production, especially for STS 316L valve fitting. STS 316L offers excellent corrosion resistance, but it has poor machinability, which is a limitation in using it for a cost-effective production where both forging and machining are employed. Simulation and experimental analysis were performed to develop a MIM STS 316L 90° elbow fitting minimizing trial and error. A Taguchi method was used to determine which input parameter was the most sensitive to possible defects (e.g. sink mark depth) during the injection molding. The final prototype was successfully built. The results indicate that the simulation tool can be used during the design process to minimize trial and error, but the final adjustment of parameters based on field experience is essential.

Minimization of sink mark depth in injection-molded thermoplastic through design of experiments and genetic algorithm

This paper deals with minimization of sink marks occurring behind the rib in plastic injection molding. In terms of rib structure and injection processing parameters, a theoretical analysis model was created. Meanwhile, finite element flow analysis with design of experiments (DOE) and genetic algorithm (GA) was integrated. Values of sink mark depth depend on design variables and technological parameters. Out of all, the four most influential variables, viz., rib thickness, mold temperature, melt temperature, and coolant temperature, were selected for optimization. The mathematic relation between sink mark depth and variables was established by conducting a set of FE analyses at various combinations of variables based on central composite design (CCD). Furthermore, the influence incidence of each factor and interaction between each variable on sink marks were investigated. The prediction model of sink marks was effectively coupled with GA for optimization of variables to minimize the sink depth. Results of the contrast analysis indicated that the proposed methodology could be used effectively in minimizing sink mark depth and parameter optimization design.

Powder injection molding process design for UAV engine components using nanoscale silicon nitride powders

Abstract The feasibility of powder injection molding to fabricate silicon nitride engine components was evaluated in the presented study. Experiments were carried out on a feedstock consisting of nanoscale silicon nitride powders mixed with magnesia, yttria and a paraffin wax–polypropylene binder system. The measured rheological and thermal properties of feedstock were used to simulate the flow of material during injection molding of a combustion engine for an unmanned aerial vehicle (UAV). Simulations based on the Box–Behnken design were used to identify the critical parameters affecting the injection molding process. The simulation results identified melt temperature as the dominant factor affecting the injection pressure, clamp force, shear stress, sink mark depth, temperature at flow front and volumetric shrinkage. Injection time was found to be the dominant factor affecting the bulk temperature and time at the end of the packing. The optimal injection molding parameters were further estimated using a non-linear programming (NLP) model. It is expected that the engineering community can use the simulation techniques discussed in the study to identify optimum processing conditions for fabricating the complex engine parts, thereby avoiding iterative expensive and time-consuming trials.

Comparative Analysis of Automotive Interior Trim Materials Based on Moldflow

The influence of different materials on the formability of plastic injection molding has been studied in current work. The automotive glove box trim cover was chosen as analytical model. This study has been focused on the influence on fill time, warpage, sink mark depth and clamp force of different materials. PP+T15, PP+T20, PP+T25, PP+T30, PP+T35, PP+T40 and ABS+PC were used for analysis in this study. The injection molding processes of automotive interior trim of different materials were analyzed by using Moldflow software, the rationality of the material choice was evaluated. Merits and drawbacks of different materials were found out through the analysis done in Moldflow. There is positive influence on reducing mold cycle and negative influence on advancing the dimension stability of part by using the kind of PP materials. Oppositely, there is negative influence on reducing mold cycle and positive influence on advancing the dimension stability of part by using ABS. It can be reduce extremely the cost for manufacturing the mold, and shorten the development cycle by using this method.

Minimizing the Warpage and Sink Mark Depth in Injection-Molded Thermoplastics

This paper deals with minimizing warpage and sink mark depth in injection-molded thermoplastics components. Automobile glove box housing trim assembled on the instrument panel was chosen as an experimental model. In these experiments, the Taguchi method and FE analysis were used to research minimizing the warpage and sink mark depth. The most influential factor was found out by using Taguchi method. Through interaction parameters experiments put into practice through Moldflow software, the interaction between each factors has been researched. The optimization packing condition for minimization of the warpage and sink mark depth was designed.

Sink-mark minimization in injection molding through response surface regression modeling and genetic algorithm

This paper deals with minimization of sink depths in injection-molded thermoplastic components by integrating finite element (FE) flow analysis with central composite design (CCD) of experiments and genetic algorithm (GA). Sink-mark depth depends on various process and design variables. Out of all, four most influential variables viz. melt temperature, mold temperature, pack pressure, and rib-to-wall ratio were used for optimization. A set of FE analyses were conducted at various combinations of variables based on the CCD array. A second-order-response surface regression model (RSRM) was developed based on the CCD. The second-order model was effectively coupled with GA for optimization of variables to minimize the sink depth. Results are encouraging and the proposed methodology could be used effectively in minimizing sink-mark depths.

Effects of Process Parameters and Two-Way Interactions on Sink Mark Depth of Injection Molded Parts by Using the Design of Experiment Method

Sink mark is one of the flaws occurring on the surface of injection-molded parts caused by inappropriate mold design and process parameters. Sink marks are often quite visible and significantly impair the surface quality of the parts. In this reports, an L27(313) experimental matrix designed based on the Taguchi method was conducted to investigate the effect of process parameters and two-way interactions on sink mark depth of injection molded parts, and to minimize the sink mark depth. The relative significance of each processing parameter on the sink marks was analyzed using analysis of variance (ANOVA) and F-test. A plate cavity with bosses of various thicknesses was used in the investigation. Experiments were carried out on a CJ80E II injection-molding machine, and sink mark depths were measured by a movable bridge 3D COMERO. For the factors and interactions selected in the main experiments, the boss thickness and melt temperature were found to be the principal factors affecting sink mark formation in injection-molded parts. Experimental investigation can help to understand the formation mechanism of sink marks, and to optimize the surface quality of injection-olded parts.

Mechanism Dominating the Generation of Sink-Mark and Residual Stress in a Press-Formed Glassware from a Thermal Engineering Viewpoint.

This paper deals with an experimental study on the generation of sink-mark and residual stress in a press formed glassware. Since both phenomena appear in the cooling process after pressing, it is considered that they were related with the growth of solidification layer on the press-formed surface. In this paper, the growth of solidification layer in a glassware and the generation of residual stress due to non-uniform shrinkage of glass, i.e. the generation of thermal tempering stress were numerically predicted, and the mechanism dominating the generation of sink-mark and residual stress frozen in a press-formed glassware was discussed by comparing the numerical results with those measured in actual glassware, which were press-formed in this study. The obtained results can be summarized as follows: (1) With elongating the pressing duration, both the sink-mark depth and the compressive residual stress at the pressed surface decrease while temperature at the pressed surface are little affected by the pressing duration. (2) The pressing-duration dependency of the sink mark and residual stress at the pressed surface is qualitatively explained well by a hypothesis that the thermal tempering stress starts to appear in the glass just after the deformation of the pressed surface, i.e. the generation of sink-mark stops due to the rigidity of solidification layer, and that the switchover timing becomes later as the pressing duration is elongated. (3) The compressive residual stress at the pressed surface is considered to consist of the thermal tempering stress due to non-uniform shrinkage of glass and the bending stress in the solidification layer due to sink mark generation.

Experimental Study on Sink-Mark Generation on the Press-Formed Glass under the Asymmetrical Cooling Condition.

In this paper, we present an experimental study on the sink-mark generation of the press-formed glassware affected by the asymmetry of the thermal condition during the press-forming process, bottom surface of the press-formed glassware is in contact with the bottom mold during entire forming process, while the upper surface is cooled by the plunger mold only in the short pressing duration. The depth of sink-marks appear on the upper and bottom surfaces were measured for various forming conditions, and the obtained results were summarized as follows : (1) The depth of sink-mark on the upper (plunger-mold side) surface decreases with lowering the initial temperature of plunger mold and with elongation of pressing duration, while the sink-mark depth on the bottom surface is hardly influenced with them. (2) Lowering the initial temperature of bottom mold enhances the cooling of whole glass in the mold cavity, and thus results in reducing the depth of sink-mark on both surfaces of the glassware. However, when the initial temperature of bottom mold is set under 460°C, miniature wrinkles appear on the bottom surface of the glass, and the sink-mark depth on the upper surface increases with lowering the initial temperature of the bottom mold. (3) The sink-mark depth on the bottom surface decreases with elongating the take-out time, but sink-mark on the upper surface becomes deeper at the same time.

Estimation of Sink Mark Depth in Compression Molded SMC Parts with Substructures

Sink mark, a surface defect along the centerline over a substructure is observed when compression molding of SMC (Sheet Molding Compounds) applies in fabrication of a thin plate with substructures. The magnitude of sink mark formed depends on process parameters used in manufacturing process. The surface quality of the external panels in automotive industry is so critical that this kind of defect should be eliminated during manufacturing stages. Thus, the effect of process parameters on sink mark depth formed in the compression molded thin plate with substructures was experimentally investigated in the present study. In order to estimate the effect of the process parameters such as molding temperature, mold closing speed, depth of the rib, corner radius of the rib, and final molded part thickness of flat portion on the magnitude of sink mark depth under the given experimental conditions, the non-dimensionalized molding parameters were determined based on physical relevances among various parameters. Then, the non-dimensionalized depth of sink mark was determined through dimensional analysis based on the experimental data. It was further tested by comparing the estimated values of sink mark depth with the experimental data. According to this comparison, reasonably accurate prediction was obtained. Compared to the previous study in the literature, the sink mark depths were quantitatively determined according to the various processing parameters and the non-dimensional equation to predict the sink mark level was derived in the present investigation. In addition, the orientation and distribution of fiberglass which directly affect the formation and magnitude of the depth of sink mark were investigated by taking the photographs of the cross-sectional area of the compression molded specimen by SEM (Scanning Electron Microscope). The non-dimensionalized equation for prediction of sink mark depth proposed in the present investigation will be useful in estimating the magnitude of sink mark depth in compression molded SMC plates with substructures and the experimental observations were useful in understanding the formation of sink mark during compression molding.

A Parametric Study of Sink Marks in Injection-Molded Plastic Parts using the Finite Element Method

Abstract A numerical procedure to simulate the formation of a sink mark near the base of a rib in an injection-molded plastic part has been developed. This method uses two commercially available software packages, C-Mold and Abaqus, to model the injection molding process. The C-Mold software uses a generalized Hele-Shaw formulation to simulate the mold filling, packing and cooling stages of injection molding. From this analysis, pressure and temperature histories in the rib area are derived. These are used to determine the initial conditions and boundary conditions for a sequentially-coupled thermal / structural finite element analysis of a cross-section of the rib, using the Abaqus software. An elastic-plastic material model with temperature-dependent material properties is employed. The thermal/structural finite element analysis provides an accurate model of the two-dimensional cooling and shrinkage behavior of the part during molding. To verify the accuracy of the method, the dependence of sink mark depth on various geometric and molding parameters has been analyzed. The predicted sink mark depth is found to be in good agreement with experimental results from the literature.

A study of injection molding (3rd report. Partial thermal shrinkage in the boss strucutres).

In the injection molding process, when the melted resin solidified by the cooling effect from the die, non-equivalence of the cooling history caused the Sink-mark growth in the resin, near boss structures. In this study, relations between Sink-Mark depth in the boss structure and some molding parameters are experimentally evaluated, and especially the effect of the forming pin is considered. Also, cooling simulation by thermal analysis is done. In considering the P-V-T characteristics and cooling history of the resin, the experimental results are quantitatively explained.