Mold Wall Temperature Research Articles

Experimental determination of the shell thickness within the primary cooling zone in the continuous casting process

ABSTRACT The correct thickness of the shell solidifying within the primary cooling zone of the continuous casting machine is among the most important parameters assuring the safe operation of the casting process. The main problem is related to the fact that the actual measurement of the thickness of steel solidifying in the mould is impossible. Available continuous casting process monitoring systems allow us to calculate its approximate value on the basis of the mould wall temperature reading, and often these systems ensure failure-free steel casting. In this paper, the authors show the results of long-term research carried out when assessing anomalies occurring during the steel continuous casting process. As a result of this research, shell thickness was measured experimentally. On the basis of experimental data, a new model was proposed to describe heat transfer in the primary cooling zone.

Influence of Mould Wall Temperature and Content of Recycled Material on Shrinkage of Polymeric Part

Influence of Mould Wall Temperature and Content of Recycled Material on Shrinkage of Polymeric Part

Numerical and experimental investigation of plastic injection molding of micro‐engineered surfaces

We carried out experimental and numerical investigations into the effects of injection‐molding parameters on the transcription quality and uniformity of micro‐pillar arrays. For the experiment, we used a precise metallic mold insert, which was shaped like an inverted micro‐pillar array. This was fabricated using UV‐photolithography and a nickel electroforming process. With the mold insert, the effects of the distance from gate and uniformity on the transcription quality could be investigated experimentally by varying the main processing parameters, such as flow rate, polymer melt temperature, and mold wall temperature. The results of the injection molding experiment indicated that increasing the three processing parameters improved the transcription quality of micro‐pillar arrays. In numerical investigation, we used the interpolated domain decomposition method. This was based on 2.5D and 3D simulations, and was used to effectively solve the filling behavior of the polymer melt inside the mold which contains multi‐scale cavities. Numerical results revealed that the transcription quality was significantly affected by the mold wall temperature. Based on the experimental and numerical investigations, the local mold heating (LMH) technique for the high mold wall temperature was employed to enhance the replicability of the micro‐pillar array. The result of injection molding with LMH showed that the transcription quality and uniformity were considerably improved. These numerical and experimental results provide insights into the foundations of the field of injection molding of plastic micro‐engineered surfaces. POLYM. ENG. SCI., 58:E73–E81, 2018. © 2017 Society of Plastics Engineers

Mold Simulator Study of Heat Transfer Phenomenon During the Initial Solidification in Continuous Casting Mold

In this paper, mold simulator trials were firstly carried out to study the phenomena of the initial shell solidification of molten steel and the heat transfer across the initial shell to the infiltrated mold/shell slag film and mold. Second, a one-dimensional inverse heat transfer problem for solidification (1DITPS) was built to determine the temperature distribution and the heat transfer behavior through the solidifying shell from the measured shell thickness. Third, the mold wall temperature field was recovered by a 2DIHCP mathematical model from the measured in-mold wall temperatures. Finally, coupled with the measured slag film thickness and the calculations of 1DITPS and 2DIHCP, the thermal resistance and the thickness of liquid slag film in the vicinity of the meniscus were evaluated. The experiment results show that: the total mold/shell thermal resistance, the mold/slag interfacial thermal resistance, the liquid film thermal resistance, and the solid film thermal resistance is 8.0 to 14.9 × 10−4, 2.7 to 4.8 × 10−4, 1.5 to 4.6 × 10−4, and 3.9 to 6.8 × 10−4 m2 K/W, respectively. The percentage of mold/slag interfacial thermal resistance, liquid film thermal resistance, and solid film thermal resistance over the total mold/shell thermal resistance is 27.5 to 34.4, 17.2 to 34.0, and 38.5 to 48.8 pct, respectively. The ratio of radiation heat flux is around 14.1 to 51.9 pct in the liquid slag film.

Heat Flow and Solidification Modeling of Industrial Scale, Ingot Casting Operation

A model, based on the concept of effective thermal conductivity, was developed to study thermal fields and the resultant solidification behavior of large, round, industrial size ingots. In this, flow and turbulence phenomena during mold filling as well as subsequent solidification were not modeled explicitly but their influence was accounted for by artificially raising the thermal conductivity of solidifying steel. Thus, a conduction like equation embodying a conjugate approach was applied to simultaneously predict the evolution of temperature fields in the mold as well as in the solidifying ingot following teeming. Prior to comparing model predictions against industrial scale measurements, sensitivity of calculations to grid size, time step height, convergence criterion etc. were rigorously assessed. Similarly, modeling of interfacial resistance, chemical reactions and heat effects in the hot top as well as their influence on predicted results were evaluated computationally. Embodying mixed thermal boundary conditions (free convection + radiation) at the mold wall, temperature fields during solidification of two different industrial large ingots were predicted numerically. Parallely, mold wall temperature was monitored as a function of time and surface temperature of ingot was measured at the instant of mold stripping using hand held, radiation pyrometers. Incorporating relevant operating conditions (viz., mold dimensions and size, ingot and hot top dimensions and material, initial mold and liquid temperature etc.) into the calculation scheme, predictions were made via a computational procedure developed in-house and results thus obtained were compared against equivalent industrial scale measurements. Very reasonable agreement between the two was demonstrated.

Optimization design of wide face water slots for medium-thick slab casting mold

A three-dimensional finite-element model has been established to investigate the thermal behavior of the medium-thick slab copper casting mold with different cooling water slot designs. The mold wall temperatures measured using thermocouples buried in different positions of the mold with the original designed cooling system were analyzed to determine the corresponding heat flux profile. This profile was then used for simulation to predict the temperature distribution and the thermal stress distribution of the molds. The predicted temperatures during operation matched the plant measurements. The results showed that the maximum temperature, about 635 K in the wide hot surface, was found about 60 mm below the meniscus and 226 mm from the center of the mold. For the mold with the type I modified design, there was an insignificant decrease in temperature of about 5 K, and for the mold with the type II modified design, the maximum temperature was decreased by about 15 K and the temperature of the hot surface was distributed more uniformly along the length of the mold. The corresponding maximum thermal stress at the hot surface of the mold was reduced from 408 MPa to 386 MPa with the type II modified design. The results indicated that the modified design II is beneficial to the increase of mold life and the quality of casting slabs.

Optimized Digital Proportional Integral Derivative Controller for Heating and Cooling Injection Molding System

Proportional integral derivative (PID) control is one of the conventional control strategies. Industrial PID control has many options, tools, and parameters for dealing with the wide spectrum of difficulties and opportunities in manufacturing plants. It has a simple control structure that is easy to understand and relatively easy to tune. Injection mold is warming up to the idea of cycling the tool surface temperature during the molding cycle rather than keeping it constant. This “heating and cooling” process has rapidly gained popularity abroad. However, it has discovered that raising the mold wall temperature above the resin’s glass-transition or crystalline melting temperature during the filling stage is followed by rapid cooling and improved product performance in applications from automotive to packaging to optics. In previous studies, optimization methods were mainly selected on the basis of the subjective experience. Appropriate techniques are necessary to optimize the cooling channels for the injection mold. In this study, a digital signal processor (DSP)-based PID control system is applied to injection molding machines. The main aim of this study is to optimize the control of the proposed structure, including a digital PID control method with a DSP chip in the injection molding machine.

Intelligent system for prediction of liquid metal breakouts under a mold of slab continuous casting machines

Increase in efficiency of a continuous casting machine is directly related to reduction of a shutdown period to repair and to eliminate accident consequences. One of the most widespread and severe accidents on the machine is the strand shell breakout under a mold. This article presents results of development and operation of the intelligent system for prediction of liquid metal breakouts under the mold of slab continuous casting machines. The most significant scientific results of the study are: mathematical model of copper mold wall temperatures values distributed on the mold perimeter, diagnostic criteria for strand shell sticking in the mold, and techniques and algorithms of strand shell sticking in the mold. Applying the listed results at development of continuous casting machine automation systems allow to reduce the number of accidents on continuous casting process, what is very important for the steel industry.

Precise nanoinjection molding through local film heating system

A new local film heating system (LFHS) can precisely control the local mold wall temperature in the nanoinjection molding process.

가열-냉각 사출성형 방식을 적용한 집광형 프레넬렌즈

A Fresnel lens is an optical component which can be used as a cost-effective, lightweight alternative to conventional continuous surface optics. Fresnel lens solar concentrators continue to fulfill a market requirement as a system component in high volume cost effective Concentrating Photovoltaic (CPV) electricity generation. The basic principles of the fresnel lens are reviewed and some practical examples are described. To investigate the performance space of the Fresnel lens, a fast simulation method which is a hybrid between raytracing and analytical computation is employed to generate a cache of simulation data. Injection molders are warming up to the idea of cycling their tool surface temperature during the molding cycle rather than keeping it constant. Heat and cool process are now also finding that raising the mold wall temperature above the resin’s glass-transition or crystalline melting temperature during the filling stage and product performance in applications from automotive to packaging to optics. This paper deals with the suitability of Fresnel lenses of imaging and non-imaging designs for solar energy concentration. The concentration fresnel lens confirmed machinability and optical transmittance and roughness measure through manufactured the prototype.

Thermomechanical environment characterisation in injection moulding and its relation to the mechanical properties of talc-filled polypropylene

This study is focused on the establishment of relationships between the injection moulding processing conditions, the applied thermomechanical environment (TME) and the tensile properties of talc-filled polypropylene, adopting a new extended concept of thermomechanical indices (TMI). In this approach, TMI are calculated from computational simulations of the moulding process that characterise the TME during processing, which are then related to the mechanical properties of the mouldings. In this study, this concept is extended to both the filling and the packing phases, with new TMI defined related to the morphology developed during these phases. A design of experiments approach based on Taguchi orthogonal arrays was adopted to vary the injection moulding parameters (injection flow rate, injection temperature, mould wall temperature and holding pressure), and thus, the TME. Results from analysis of variance for injection-moulded tensile specimens have shown that among the considered processing conditions, the flow rate is the most significant parameter for the Young’s modulus; the flow rate and melt temperature are the most significant for the strain at break; and the holding pressure and flow rate are the most significant for the stress at yield. The yield stress and Young’s modulus were found to be governed mostly by the thermostress index (TSI, related to the orientation of the skin layer), whilst the strain at break depends on both the TSI and the cooling index (CI, associated to the crystallinity degree of the core region). The proposed TMI approach provides predictive capabilities of the mechanical response of injection-moulded components, which is a valuable input during their design stage.

Numerical Simulation of the Curing and Cooling in Reaction Injection Molding Process of Nylon 6

A computer simulation model was established to analyze the curing and cooling of reaction injection molding process of nylon 6 based on theory of balance equation of energy, reaction kinetics and crystallization kinetics. The reasonable assumptions and simplifications were introduced in the model, and an explicit finite difference method with MATLAB software was applied to calculate and predict the conversion and temperature distribution within a plate type mold. The results show that the center position reaches the peak temperature about 45s. The effects of the feed temperature, wall temperature, and reaction rate constant on the temperature and conversion were discussed for searching the optimum processing conditions. The results suggests that the effect of reactive rate on crystallization, molecular weight and phase structure is decided by the value of reaction constant; the influence of the mold wall temperature on reactive rate and temperature near the boundary was great; and the control of feed temperature is important in condition of low mold temperature.

Investigation of the Moldability Parameters of PEG Based Steatite Feedstocks by Powder Injection Molding

Abstract In powder injection molding (PIM) barrel temperature, injection pressure and injection rate are important parameters for the molding of powder-binder mixtures. Improperly selected parameters lead to undesired problems such as separation of the powder-binder mixture and formation of collapses and cracks on the structure of the molded parts. In this study, steatite feedstocks based on PEG (polyethylene glycol) binders were injection molded into rectangular shape, ordered thickness with steps and zig-zag shaped mold cavities. The effects of the temperature and pressure of injection, rate of filling, temperature of the mold wall and geometry of the mold cavities were investigated. The optimum molding parameters of the feedstocks for the zig-zag shaped mold were determined to be an injection pressure of 80 to 140 MPa, a barrel temperature of 190 to 230°C, an injection rate of 5–25 · 10−6 m3 s−1 and a mold wall temperature of 32°C.

Design of U-shape milled groove conformal cooling channels for plastic injection mold

Besides the solid free-form fabrication technology, milling operation is an alternative applicable method to make complex cooling channels conform to the surface of the mold cavity. This paper presents the U-shape milled groove conformal cooling channels and proposes the design optimization process in order to obtain an optimal cooling channels’ configuration and target mold temperature. The relation between the cycle averaged thermal behavior of the mold cavity and the two-dimensional configuration of cooling channels was first investigated thoroughly by an analytical method. Design of experiment and 2D simulation were done to obtain the mold wall temperature and to check the feasibility of the analytical method. The optimization process of the free-form conformal cooling channels is based on the combination of both analytical method and 3D CAE simulation. The analytical step relies on explicit mathematic formulas, so it can approach the neighboring optimal solution quickly. Subsequently, the three-dimensional heat transfer simulation is applied to fine-tune the optimization results. A case study for a plastic car fender was investigated to verify the feasibility of the proposed method. The results show that conformal cooling channel gives a uniform cooling, reducing the cooling time and increasing the molded part’s quality with less effort of plastic designers and high computational efficiency.

The reflectivity, wettability and scratch durability of microsurface features molded in the injection molding process using a dynamic tool tempering system

In this paper the replication qualities of periodically and randomly arranged micro-features molded in the injection molding process and their effects on surface properties are studied. The features are molded in PC, PMMA and PP at different mold wall temperatures in order to point out the necessity and profitability of a variotherm mold wall temperature control system. A one-dimensional heat conduction model is proposed to predict the cycle times of the variotherm injection molding processes. With regard to these processes, the molding results are compared to the molded surface feature heights using an atomic force microscope. In addition, the effects of the molded surface features on macroscopic surfaces are characterized in terms of light reflection using a spectrometer and in terms of water wettability by measuring the static contact angle. Furthermore, due to the sensitivity of the surface features on the molded parts, their durability is compared in a scratch test with a diamond tip. This leads to successful implementation in applications in which the optical appearance, in terms of gloss and reflection, and the water repellence, in terms of drag flow and adhesion, are of importance.

Study on the replication quality of micro-structures in the injection molding process with dynamical tool tempering systems

The injection molding of micro-structures is a promising mass-production method for a broad range of materials. However, the replication quality of these structures depends significantly on the heat flow during the filling stage. In this paper, the filling and heat transfer of v-groove and random structures below 5 μm is investigated with the help of an AFM (atomic force microscope) and thermo couples. A numerical model is developed to predict the filling of surface structures during the filling and packing stage. The model implies the use of simple fully developed flow models taking the power-law material model into account. This permits investigation into which ways several processing parameters affect the polymer flow in the surface structures. The mold wall temperature, which has significant effects on the polymer flow, is varied by using a variothermal mold temperature control system to validate the model proposed.

Warpage of Film Insert Molded Parts and Optimum Processing Conditions

Abstract Three dimensional flow and structural analyses were carried out for film insert injection molding in order to evaluate the warpage and long term viscoelastic deformation of the film insert molded (FIM) tensile specimen. The predicted warpage after ejection and annealing was utilized as the input to the orthogonal array in order to obtain priority of significant factors and optimum molding conditions. Various injection molding factors influenced the degree of shrinkage of the injected substrate, i.e., packing pressure and mold wall temperature difference determined warpage of the FIM part after ejection. Warpage of the annealed FIM part was affected mainly by heat treatment conditions of the inserted film and annealing time of the part because annealing conditions had larger effects than the other processing factors. Optimum processing conditions and the relative significance of processing factors were obtained for warpage of FIM parts by using the Taguchi's method.

Optimisation of process conditions in powder injection moulding of microsystem components using robust design method Part 2 – Secondary design parameters

Powder injection moulding (PIM) is a proper fabrication method for microsystem technology components. This paper studies the process control of PIM to create thin walled, high aspect ratio geometries, which can be easily found in microtechnology based electro chemical, mechanical and biological systems (MECS). The powder used in this study is gas atomised 316L stainless steel with a median particle size of 10 μm. The effects of reducing the thickness of high aspect ratio geometries on the secondary design parameters including the maximum wall shear stress, cooling time and standard deviations of the melt front velocity and areas are studied. The study shows process parameters including fill time, feedstock injection temperature, mould wall temperature and switchover position can be optimised using the Taguchi robust design method.

Study on Weld Characteristics of Thin-wall Injection Molded Polypropylene Plates

This paper deals with a fundamental study on the weld structure of thin-wall injection molded polypropylene plates. Effects of the mold temperature and plate thickness on the weld characteristics were investigated. In the experiment, several measurements were performed; distribution of the optical retardation, specific latent heat for fusion, V notch depth and width, and tensile strength of the specimen. The results indicated that the fountain flow of the melt occurred in the filling stage even with a plate thickness of 0.3 mm. It was also shown that molecular orientation in the weld region was relatively low. Thermal property measurement showed that crystallinity of the molded specimen was affected not only by the mold wall temperature but also by the plate thickness. Mechanical strength reduction by the existence of the weld was experimentally confirmed through the tensile test, and it was shown that the thin-wall polypropylene plate molded at high mold temperature broke from the weld region under small strain.

Numerical Simulation of Molding Hele-Shaw Flow of Polymeric Liquid Crystals

To develop a general-purpose program for predicting the molding flow of polymeric liquid crystals, we present a basic model and its computational procedure. The flow is modeled by the Transversely Isotropic Fluid theory, which is equivalent to the Leslie-Ericksen equations in the high viscosity limit. In the modeling, the Hele-Shaw approximation is applied to reduce computational power. A finite difference technique is used to solve the governing equations, except for the angular momentum equation, which is solved by a streamline integration method. Two molds with thin and simple shape cavities are selected to evaluate the model. The computational results for the locations of the flow front, and for the distributions of the temperature and the molecular orientation show that the model successfully predicts a smooth molding process and that the molecular orientation direction depends strongly on the position in the gap direction. Since alignment of molecules is disordered by the occurrence of tumbling behavior, which depends on the fluid temperature and shear strain, the mold wall temperature and the gate position are important for effective molding.