Runner System Research Articles

Developing a method for evaluating color changeover in a hot-runner multi-cavity injection mold

Quality control, which nowadays almost always involves the integration of online measurement methods into the production process, is of paramount importance for injection molding. Online pressure and temperature measurement is already widespread and essential for quality and production control. On the other hand, monitoring the appearance, color, or surface defects of products is less common. It is usually carried out with a camera system installed on a conveyor belt independently of the injection molding process. However, color defects in injection molded products, which are caused by the poor distribution of the colorant, are common defects that usually occur after color changeover in injection molding. Color changeover is currently not a well-controlled procedure, and it is associated with high additional costs. It also requires a large amount of material and causes extended downtime of the injection molding equipment. Color changeover can be even more complicated due to the specific design of the injection unit, the presence of static or dynamic mixers, and the hot runner system design of the molds. In this study, we develop a measurement method to monitor color change and the amount of material and time needed to clean the injection system. This method is based on digital image processing. It can be very useful in the plastic industry and can greatly help manufacturers to develop and produce more efficient injection molding systems.

Investigation of segregation in the runner system during injection moulding

The goal of this study is to investigate segregation in the runner system during injection moulding. Segregation is a phenomenon which occurs during the injection moulding of filled or reinforced polymer systems. The effects of segregation can be so severe that the process can lead to waste products. Even though segregation is an important problem, so far it has been little researched. However, it would be very beneficial if segregation during injection moulding could be predicted through simulation software. In order to achieve that, we must first understand what causes segregation. We injection moulded several specimens using polypropylene, a transparent polymer, and used 10.8 V% ceramic beads as filler with different injection moulding parameters. We investigated the effect of melt temperature and injection rate, which were set to 180, 220, 260 °C and 5, 20, 80 cm3/s. We observed segregation with an optical microscope and used a furnace to burn the PP and measured the weight of the leftover beads in order to determine the bead content in various regions.

Visualization of Melt-Flow Behavior Inside the Runner in Ultra High Speed Injection Molding

Abstract Ultra-high-speed injection molding is a highly effective technique for realizing very thin-walled molded parts; its application to the production of new high value-added products is anticipated. The melt-flow behavior in ultra-high-speed injection molding is expected to differ from that in conventional molding. However, thus far, very few studies pertaining to the phenomena occurring within cavities and runners at such high filling speeds have been reported, thus necessitating the direct observation of melt-flow behavior inside the molds. In this study, we attempted to dynamically visualize the melt-flow behavior at the runner split portion, especially under ultra-high-speed injection molding. Visualization experiments were conducted using a glass-inserted mold, which was modified from the original visualization mold structure in order to improve the pressure endurance of the glass-inserted visible area. This paper discusses the visualization analyses of melt-flow behavior in two types of experimental split runner systems (three inclined split runners and cross-shaped runners in a cascade layout). The behavior at the runner split area was studied under low to ultra-high-filling rates. The analyses clarified the effects of inertia at the runner branching point, which has not been verified in general injection molding, and the consequent changes in the filling behavior.

Methodology to implement CAE validation in repair & redesign parts process of plastic injection molds

Repairs and redesigns for plastic injection molding parts generally is a short and straightforward process consisting of inspection, modeling, and evaluation. The present paper implements a methodology for redesigning and repairing injection molding parts based on the frontal process for developing concepts. The proposed methodology helps in the validation through Computer-Aided Engineering (CAE) in the designing stage using CAD software, ensuring the quality of the repair. Furthermore, the redesigned development has been carried out in the best way to obtain a better cooling, robustness, or plastic flow. In this research is implemented the proposed methodology in a Hot Runner System. Furthermore, a numerical simulation for three cases to evaluate the heat transfer and cooling times performed, finding the main differences in heat transfer due to drilled or milled rectangular channels, minimizing the time to reach ejection temperature and mold/part temperatures.

Deep PID Neural Network Controller for Precise Temperature Control in Plastic Injection-moulding Heating System

In this paper, deep PID neural network (PIDNN) controller is used in a nonlinear thermal regulatory control problem. We have a hot runner system and a nozzle with round tip as controlled plants. The control goal is to regulate their temperature responses for tracking a constant set point stably and precisely without exactly knowing mathematic models of plants during entire process by using deep PIDNN controller. The parameters (or weights) of controller are updated on-line based on gradient descent rule with Adam optimizer. Comparing to the results with PID control, deep PIDNN controller reduces overshoot, saves much power and enhance the control performance that temperatures almost fluctuate within ±0.2°C tolerance of set point in steady state.

Impact of the thickness of the wall of optical lenses on the production process stability

The article compares the stability of the production process of plastic optical lenses produced by the injection molding process. Moreover, it evaluates the effects caused by using very thick walls and very thin walls in plastic optical lenses. The injection process are divided into three fundamental stages. The first is the injection of plastic into the mold itself (filling). During this phase, 95–99% of the cavity volume is filled. The second phase is the so-called after-pressure, where the remaining cavity spaces are filled, and the part reaches dimensional stability. The last stage is called cooling. During the final phase, the element is solidified and becomes dimensionally stable in lower temperatures. In the current work, the authors compare the lenses that differ only in the maximum wall thickness. In the experiments, the conditions of changing pressure and injection speed were simulated. During injection, slight changes in the injection parameters may occur due to the random external influences. Those influences include the change in ambient air temperature, voltage fluctuations in the electrical system, machine vibrations, imperfect homogeneity of the material used, etc. The common process parameters that the organization uses by default were used as a basis. The after-pressure and injection pressure were changed to 102%, 105%, 98%, and 95% in the experiments. The results evaluate the proportion of non-conforming products (scrap) that appertain to each change in the parameters of production.
 The research proves the dependence between the thickness of the lens wall and the stability of the process. Although a higher total waste is expected for thick-walled lenses, the knowledge of the stability of the process in the production of lenses has not yet been recorded though it is a significant indicator for the production planning. It is known that a lower process stability is expected based on the design for these types of elements, and the researrchers were able to take measures to eliminate this risk and thus reduce the total waste and other negative impacts on production.
 Modifications to the mold can also achieve some improvement in this condition. The first step is to expand the cross-section of the inlet channel gate. The pressure is transmitted to the cavity through this cross-section. Its enlargement ensures a more even distribution of the pressure in the entire volume of the part. Another way to facilitate production is to guarantee optimal cooling of the cavity. It can be achieved by placing the cavity away from the hot runner system so that the cooling can be evenly distributed around each side of the part. The last way to solve the problem of collapse is to create a counter-deformation in the mold. That is to enlarge the cavity so that the lens sinks into the desired shape.
 These measures may include preventive debugging of the mold for multiple presses in case the press needs to be changed and preferably placing such elements on newer injection molding machines where parameters are less likely to fluctuate and avoiding moving such molds to presses for which they have not been debugged unless necessary. The work aims to prove the dependence between the thickness of the optical lens and the stability of the injection process. While waste percentage, cycle time, and other parameters are considered and quantified at the design stage of the optical lens, process stability has not yet been quantified. Proving the dependence between the above-mentioned phenomena will allow predicting the process stability of new lens designs more precisely.

Techno-economic and techno-environmental assessment and multi-objective optimization of a new CCHP system based on waste heat recovery from regenerative Brayton cycle

This investigation aims to present thermo-environmental and thermo-economic parametric studies for a new hybrid tri-generation energy system. In system, a regenerative gas turbine cycle (RGTC) is the runner system, while Kalina cycle (KC) and ejector refrigeration cycle (ERC) are considered as companion elements. The parametric study is done through validated computational program developed in EES software. Two new functions of levelized total annual emissions and costs (LTAE and LTAC), with two conventional indices of energetic and exergetic efficiencies (ηen and ηex) are defined for system evaluation. Thermodynamics modeling revealed that almost 75 % of total exergy destruction is related to the RGTC. The outputs of parametric study prove that pressure ratio of compressor and pinch-point temperature of heat exchanger 2 are the most and least effective parameters, respectively. Also, for the bottoming cycles, changes in KC design parameters resulted in creation of peak points in all the evaluation criteria; but changes in the ERC design parameters resulted in uniform (ascending or descending) behavior in the evaluation criteria. The NSGA-II optimization procedure (using MATLAB software) results in ηen,opt = 77.17 %, ηex,opt = 38.94 %, LTAEopt = 9.36 kg/kW.yr, and LTACopt = 106.04 €/kW.yr. The payback period and net present value of the tri-generation system are found as 3.74 yr and 1184525.43 €.

A Simulation Study on Warpage Analysis of Injection Moulded Plastic Part

A part to be injection molded is evaluated by simulation for warpage analysis. The plastic part is a supporting plate to be used in the oil filter and it’s made out of nylon material. The effect of various parameters from design to processing of plastic parts is considered and validated by simulation results. The research involved in this was designing mould, computer-aided engineering, simulation analysis, and determination of plastic part processing conditions. In this work PA66 (Grade name – Zytel 70G13HS1LNC010) material is used and the material contains 13 % of fiber. Fiber orientation is nothing but the distribution of plastic melt inside the cavity and it also plays important role in deciding the warpage of part. The effect of process parameters on part warpage is investigated from various aspects in comparison with the conventional runner system. Hot runner mould system with innovative cooling channel designs is good results-driven. Results of simulations reveal that elevated mould temperature reduces the unwanted freezing time during the injection phase and thus improves mouldability and enhances part quality. Under similar mould temperature conditions, the effect of process parameters on warpage decreases according to the following order, packing time, packing pressure, melt temperature, injection pressure, and cooling time respectively.

On the Use of Conformal Cooling in High-Pressure Die-Casting and Semisolid Casting

Today, tool life in high pressure die casting (HPDC) is of growing interest. A common agreement is that die life is primarily decided by the thermal load and temperature gradients in the die materials. Conformal cooling with the growth of additive manufacturing has raised interest as a means of extending die life. In the current paper, conformal cooling channels’ performance and effect on the thermal cycle in high-pressure die casting and rheocasting are investigated for conventional HPDC and semisolid processing. It was found that conformal cooling aids die temperature reduction, and the use of die spray may be reduced and support the die-life extension. For the die filling, the increased temperature was possibly counterproductive. Instead, it was found that the main focus for conformal cooling should be focused to manage temperature around the in-let bushing and possibly the runner system. Due to the possible higher inlet pressures for semisolid casting, particular benefits could be seen.

A comparison study of fuzzy-based multiple-criteria decision-making methods to evaluating green concept alternatives in a new product development environment

PurposeIn this paper, the four popular multiple-criteria decision-making (MCDM) methods in fuzzy environment are utilized to reflect the vagueness and uncertainty on the judgments of decision-makers (DMs), because the crisp pairwise comparison in these conventional MCDM methods seems to be insufficient and imprecise to capture the right judgments of DMs. Of these methods, as Fuzzy analytic hierarchy process (F-AHP) is used to calculate criteria weights, the other methods; Fuzzy Technique for Order of Preference by Similarity to Ideal Solution (F-TOPSIS), Fuzzy Grey relational analysis (F-GRA) and Fuzzy Preference Ranking Organization METhod for Enrichment of Evaluations (F- PROMETHEE II) are used to rank alternatives in the three different ways for a comparative study.Design/methodology/approachThe demand for green products has dramatically increased because the importance and public awareness of the preservation of natural environment was taken into consideration much more in the last two decades. As a result of this, especially manufacturing companies have been forced to design more green products, resulting in a problem of how they incorporate environmental issues into their design and evaluate concept options. The need for the practical decision-making tools to address this problem is rapidly evolving since the problem turns into an MCDM problem in the presence of a set of green concept alternatives and criteria.FindingsThe incorporation of fuzzy set theory into these methods is discussed on a real-life case study, and a comparative analysis is done by using its numerical results in which the three fuzzy-based methods reveal the same outcomes (or rankings), while F-GRA requires less computational steps. Moreover, more detailed analyses on the numerical results of the case study are completed on the normalization methods, distance metrics, aggregation functions, defuzzification methods and other issues.Research limitations/implicationsThe designing and manufacturing environmental-friendly products in a product design process has been a vital issue for many companies which take care of reflecting environmental issues into their product design and meeting standards of recent green guidelines. These companies have utilized these guidelines by following special procedures at the design phase. Along the design process consisting of various steps, the environmental issues have been considered an important factor in the end-of-life of products since it can reduce the impact on the nature. In the stage of developing a new product with the aim of environmental-friendly design, the green thinking should be incorporated as early as possible in the process.Practical implicationsThe case study was inspired from the previous work of the author, which was realized in a hot runner systems manufacturer, used in injection molding systems in a Canada. In a new product development process, the back- and front-ends of development efforts mainly determine the following criteria: cost, risk, quality and green used in this paper. The case study showed that the three fuzzy MCDM methods come to the same ranking outcomes. F-GRA has a better time complexity compared to the other two methods and uses a smaller number of computational steps. Moreover, a comparative analysis of the three F-MCDM methods; F-PROMETHEE II, F-TOPSIS and F-GRA used in ranking for green concept alternatives using the numerical results of the case study. For the case study; as seen in table 20, the three F-MCDM methods produced the numerical results on the rankings of the green concept alternatives as follows; {Concept A-Concept C–Concept B–Concept D}.Social implicationsInclusion of environmental-related criteria into concept selection problem has been gaining increasing importance in the last decade. Therefore, to facilitate necessary calculations in applying each method especially with its fuzzy extension, it can be developed a knowledge-based (KB) or an expert system (ES) to help the DMs make the required calculations of each method, and interpret its results with detailed analysis.Originality/valueThe objective of the research was to propose a F-AHP based F-MCDM approach to green concept selection problem through F-PROMETHEE II, F-TOPSIS and F-GRA methods. As the F-AHP is used to weight evaluation criteria, the other methods are respectively used for ranking the concept alternatives and determine the best concept alternative.

Injection Mold Unit Design of Combined Spoon-Fork (Spork) Product

This research aims to design injection molding unit construction for combined spoon and fork products that are in accordance with industrial standards. The mold unit designed consists of two kinds of layouts, namely grid layout and radial layout, the combined product spoon and fork grid layout that will be used is the LKM AI 4050 moldbase standard and the radial layout spoon and fork combined product will be used is the LKM AI 6065 moldbase standard. The optimum mold construction uses a grid layout and block runner system with dimensions of 400 x 500 mm which have a clamping force of 1,587.08 kN. Examples of machines that can be used are JSW J180AD injection machines with a maximum clamping force of 1770 kN.

Rapid Numerical Estimation of Pressure Drop in Hot Runner System.

To determine dimensions in the hot runner systems, given a material, it is necessary to predict the pressure drop according to them. Although modern injection molding simulators are able to evaluate such pressure drops, they are expensive and demanding to be employed as a design utility. This work develops a computer tool that can calculate a pressure drop from the sprue to the gate assuming a steady flow of a generalized Newtonian fluid. For a four drop hot runner system, the accuracy has been verified by comparing the obtained results with those by a commercial simulator. This paper presents how to utilize the proposed method in the hot runner design process.

Effect of Different Filling Systems on Casting Densities and Porosities of Sand Step-Casted Aluminum Al–7Si–0.3Mg (LM 25) Alloy

In spite of abundant information of conventional gating system design, casting defects such as shrinkage and gas porosities were found in castings that make the final castings extremely vulnerable to deformation. Improper fluid flow and irregular solidification of metals is due to faulty gating system design that in turn produces major casting defects. In this paper, quantitative analysis of the densities of an Al–7Si–0.3Mg (LM 25) alloy sand casting was performed using mass/volume or Archimedean porosimetry technique along with optical microscopy. Stepped geometry was casted in this study using circular, square and rectangular cross sectional runners and ingates. Single and double runners were used within each variation of runners and ingates. Electronic weighing balance and water displacement methods were used for measuring densities and porosities of the casted samples. The results showed that the average values of densities for castings using single and double circular cross sectional runners and ingates are higher i.e., 2.64 gm/cm3 and 2.64 gm/cm3 as compared to square and rectangular runner and ingate system i.e., 2.52 gm/cm3, 2.57 gm/cm3 and 2.46 gm/cm3, 2.49 gm/cm3 with lower percentage porosity defects i.e., 1.41% and 1.64% as compared to square and rectangular cross sections i.e., 5.86%, 3.82% and 8.34%, 7.18%, respectively. The densities for the casted samples for rectangular cross section are lesser of all with high porosity defects.

A literature review on injection moulding process based on runner system and process variables

Injection moulding is the fabrication process which is the most widely used for polymeric. This paper describes Injection moulding process in detail along with its process parameters and their effects on the moulding component. Runner system is playing a significant role in the quality of the moulded part. Every injection moulding method works when a plastic substance flows from the sprue of the runner system, through a gate into the mould cavity. Runner system is of two types, Hot runner and cold runner system, both having some advantages and disadvantages of each. Research has been carried out which concludes about the effectiveness of hot runner over the cold runner. It has been observed that although hot runner gives better quality of the product, many of the industries use cold runner due to the high cost and complexity of the design. The paper deals with the illustration of mould defects related to the process parameters and the need for its Optimization. This paper focuses on the effectiveness of hot runner systems and scrap reduction of the process by replacing the cold runner system with the hot runner.

Metal casting modeling software for small scale enterprises to improve efficacy and accuracy

In the modern casting and metal casting industries, casting modelling software is rapidly being used. The casting process is simulated by software in a virtual field and provides insight into mould filling, solidification and cooling, and defects in casting. The designer will model, check and confirm the procedure, managed with design optimisation through simulation casting. This essay seeks to discuss the techniques of modelling and simulation of metal casting processes with regard to several relevant case studies. The most popular cast simulation programme available and the mathematical models used are briefly presented. The simulation of the method of casting along with the findings obtained is well described. Literature case studies showed that by providing a detailed knowledge of mould filling and solidification, gating, runner and feeding system setup, and other process parameters, simulation instruments play a crucial role in manufacturing high quality defect free cast products. Recent attempts are being explored to incorporate casting simulations into mechanical simulations of results, which is very exciting in predicting service life for cast goods. The result is that simulations in the casting processes have been well developed and more developments in simulation techniques are required to estimate durability of castings.

Numerical simulation aided design of heat sink using Z-cast

In this paper study the flow of the molten metal into the cavities during filling and to find out the defects of the air entrapment in the complex geometry of the component, which challenges the optimized gating design. To establish an easy and free-flowing gating design for the component and to drive out the air present in the cavities effectively to obtain a defect free component. To completely design the runner and gating system to the component to get the best cycle time to produce large volumes easily. The model was meshed to the given quality factor (FDM Mesh). The defects can be predicted prior to the die designing to optimize the casting process to minimize the rejection and improve productivity and quality of the component. Intricate components can be easily designed by using the simulation tool to detect the defects of the proposed gating and the runner design. Percentage of components clearing the quality test during iteration-1 was 56% and after iteration −2 it got improved to 95%. The complete phenomenon of the liquid metal flow in the die can be observed and analyzed to predict the behaviour of the liquid metal accommodating the cavity. The ‘Heat Sink” was successfully designed to eliminate the defects and proposed design was altered. Several defects of the proposed gates, where the gates were not filling the cavities due to the obstructions in the configuration of the component. The ribs on the component were obstructing the free flow of the metal in the component in the initial design where the air got entrapped between the ribs and were creating voids. This could be easily observed during the simulation. Hence all the necessary parameters were collected after the modification and the gating system redesigned in a way where there could be no defects, during the filling or in the solidification of the component.

A current state of art applied to injection moulding manufacturing process – A review

Abstract Injection moulding (IM) appears to be one of the most important techniques for manufacturing plastics products worldwide. As IM is a complicated process, so it is technically very difficult to take into account all the changes taking place during the process. To enhance efficiency of the process and to have consistent product quality, proper input parameter’s setting is critically important. The numbers of input process parameters are: melt temperature, mold temperature, injection pressure, injection speed, injection time, holding pressure, holding time and cooling time. The responses/output may be mechanical properties, defects e.g., warpage, shrinkage, sink mark, residual thermal stress etc., and aesthetic requirement for example surface finish/roughness. Literature review shows that most of the researchers have optimized the process parameters and established a correlation between the parameters and the behavior of the material under investigation. Others performed optimization research regarding some specific areas of IM viz. cooling channel design, location of the gate, runner system design etc. Some of the studies were focused on monitoring control system to monitor the process during production to ensure quality and minimize the defects. Researchers have used many different techniques to model and optimize the IM manufacturing process. These techniques include mathematical modelling, simulation, design of experiments (DOE) and artificial intelligence (AI). Some of the examples of these techniques are Taguchi method, evolutionary algorithm (EA), artificial neural networks (ANN), genetic algorithms (GA), fuzzy logic, response surface methodology (RSM), particle swarm optimization (PSO), analysis of variance (ANOVA) etc. This paper aims to review and present the various studies concerning the process parameters and their influence over the quality of product. Throughout this review, the process parameters, response, material used and the technique applied to optimization research in the field of IM are highlighted.

Experimental and simulation analysis on multi-gate variants in sand casting process

The present work proposes an improved multi-gate designs (MGDs) in sand casting process, using both experimental and simulation (FLOW 3D) approaches, aiming to produce defect-free component. In this regard, the variant MGDs were developed and compared with the existing designs reported in the previous studies. Accordingly, the following new MGDs: side sprue serial connection (SSSC), centre sprue serial connection (CSSC), side sprue parallel connection (SSPC), centre sprue parallel connection (CSPC) and centre sprue runner extension parallel connection (CS-RE-PC) were modelled for both techniques. The experimental set-ups were developed for the aforementioned designs to study the flow behaviour of aluminium alloy and water. The validity of aluminium alloy flow characteristics in closed mould condition was checked with the water mould experimentation. The quality of the casting was examined by visual inspection, optical microscopy, ultrasonic and X-ray tests. From the results obtained, it was evident that CS-RE-PC mould set-up or design was most suitable with a runner system for four-cavity application. This design exhibited best flow rate, as a nearly defect-free casting component was produced. Comparison of the FLOW 3D simulation results with similar experimental findings provided potential opportunity to reduce both cast product rejection rate and rework, and consequently it aids enhancement of the productivity and profitability in a manufacturing/casting industry.

Optimization designation of static mixer geometry considering mixing effect

The polymer materials used in the injection molding process have a non-Newtonian characteristic. Consequently, a flow imbalance problem often occurs, even if an H-type runner system is employed. This problem can be addressed by placing a static mixer in the runner. However, the performance of the mixer is highly dependent on its design. Accordingly, the present study employs the Taguchi design methodology to optimize four geometry parameters of the passive mixer, namely the baffle lattice angle (Factor A), the baffle lattice thickness (Factor B), the mixer length (Factor C) and the baffle inset pattern angles (Factor D). For each run in the orthogonal array, the temperature distribution at the mixer outlet is evaluated by Moldex3D simulations. The parameter settings which result in the maximum temperature uniformity [i.e., the maximum signal-to-noise (S/N) ratio] are then taken as the optimal design. The validity of the optimization results is confirmed by means of ANSYS Fluent and Image J simulations. The Taguchi results show that the optimal parameter settings for the passive mixer are as follows: lattice angle = 45° (A2); lattice thickness = 0.5 mm (B1); mixer length = 30 mm (C3); and inset pattern angles = 45°–45°–90° (D2). The Moldex3D simulation results show that the optimal mixer design improves the Taguchi S/N ratio by 1.17 dB compared to the original mixer design. Furthermore, the ANSYS Fluent simulations show that the mixing index is improved from 0.5121 (original design) to 0.4213 (optimal design).

Development of Advanced Hybrid Polymer Melt Delivery Systems for Efficient High Precision Injection Molding

Abstract A novel melt manipulation “RheoDrop” concept for hot runner injection molding is presented. In this concept, a controlled rotational shear is applied to a polymer melt in the hot drop to reduce its viscosity without raising the temperature. This is achieved by providing a transient rotational motion to the valve pin in the hot drop. This strategy is developed to mitigate issues associated with cold slug formation during injection molding in hot runner systems. The cold slug formation is particularly relevant for injection molding of engineering plastics such as liquid crystal polymers (LCPs) for medical and electronic applications. Analytical and experimental investigations were performed to validate the concept. The efficacy of the concept is assessed analytically utilizing a combination of two software modules, autodesk, moldflow and ansys fluent. The results confirmed that the concept was able to produce enough shear to reduce the dynamic viscosity between injection molding cycles. A prototype RheoDrop system was designed and developed and retrofitted in a four drop hot runner system mold to experimentally validate the concept. Preliminary experiments were performed utilizing acrylonitrile butadiene styrene, and parts were successfully fabricated at temperatures that are too low for traditional molding in a hot runner system.