Thermo-mechanical Design Optimization of Conformal Cooling Channels using Design of Experiments Approach

Plastic injection molding is a versatile process and a major part of the present plastic manufacturing industry. Traditional die design is limited to straight (drilled) cooling channels, which don’t impart optimal thermal (or thermo-mechanical) performance. With the advent of additive manufacturing technology, design of injection molding tools with conformal cooling channels is now possible. The incorporation of conformal cooling channels can improve the thermal performance of an injection mold, though it may compromise the structural or mechanical stability of the mold. However, optimum conformal channels based on thermo-mechanical performance are not found in the literature. This paper proposes a design methodology to generate optimized design configurations of such channels in plastic injection molds. Design of experiments (DOEs) technique is used to study the effect of critical design parameters of conformal channels. In addition, a trade-off technique is utilized to obtain optimum design configurations of conformal cooling channels for “best” thermo-mechanical performance of a mold

Design, simulation and optimization of conformal cooling channels in injection molds: a review

The manufacturing of conformal cooling channels (CCC’s) is now easier and more affordable, owing to the recent developments in the field of additive manufacturing. The use of CCC’s allows better cooling performances than the conventional (straight-drilled) channels, in the injection molding process. The main reason is that CCC’s can follow the pathways of the molded geometry, while the conventional channels, manufactured by traditional machining techniques, are not able to do so. Some of the parameters that can be significantly improved by the use of CCC are cooling time, total injection time, uniform temperature distribution, thermal stress, warpage thickness. However, the design process for CCC is more complex than for conventional channels. Computer-aided engineering (CAE) simulations are important for achieving effective and affordable design. This review article focuses the main aspects related to the use of CCC’s in injection molding, as follows: Sect. 1 presents an introduction, which focuses on the most important facts about the topic of this paper. Section 2 presents a comparison between straight cooling channels and conformal cooling channels. In Sect. 3, the theoretical background of injection molding is presented. In Sects. 3 to 7, the manufacturing, design, simulation and optimization of CCC’s are presented, respectively. Section 7 is about coupled approaches, in which several systems, methods or techniques are used together for better efficiency.This research was supported by the Research Grant number POCI-01-0247-FEDER-024516, co-funded by the European Regional Development Fund,by the Operational Program "Competitiveness and Internationalization”, inthe scope of “Portugal 2020

Design of conformal cooling layers with self-supporting lattices for additively manufactured tooling

Additively manufactured (AM) conformal cooling channels are currently the state of the art for high performing tooling with reduced cycle times. This paper introduces the concept of conformal cooling layers which challenges the status quo in providing higher heat transfer rates that also provide less variation in tooling temperatures. The cooling layers are filled with self-supporting repeatable unit cells that form a lattice throughout the cooling layers. The lattices increase fluid vorticity which improves convective heat transfer. Mechanical testing of the lattices shows that the design of the unit cell significantly varies the compression characteristics. A virtual case study of the injection moulding of a plastic enclosure is used to compare the performance of conformal cooling layers with that of conventional (drilled) cooling channels and conformal (AM) cooling channels. The results show the conformal layers reduce cooling time by 26.34% over conventional cooling channels

SLM tooling for die casting with conformal cooling channels

The paper reports an experimental study of die-casting dies with conformal cooling fabricated by direct-metal additive techniques. The main objective is to compare the benefits and limitations of the application to what has been widely discussed in literature in the context of plastics injection molding. Selective laser melting was used to fabricate an impression block with conformal cooling channels designed according to part geometry with the aid of process simulation. The tool was used in the manufacture of sample batches of zinc alloy castings after being fitted on an existing die in place of a machined impression block with conventional straight-line cooling channels. Different combinations of process parameters were tested to exploit the improved performance of the cooling system. Test results show that conformal cooling improves the surface finish of castings due to a reduced need of spray cooling, which is allowed by a higher and more uniform cooling rate. Secondary benefits include reduction of cycle time and shrinkage porosity

A Thermomechanical Analysis of Conformal Cooling Channels in 3D Printed Plastic Injection Molds

Plastic injection molding is a versatile process, and a major part of the present plastic manufacturing industry. The traditional die design is limited to straight (drilled) cooling channels, which don't impart optimal thermal (or thermomechanical) performance. With the advent of additive manufacturing technology, injection molding tools with conformal cooling channels are now possible. However, optimum conformal channels based on thermomechanical performance are not found in the literature. This paper proposes a design methodology to generate optimized design configurations of such channels in plastic injection molds. The design of experiments (DOEs) technique is used to study the effect of the critical design parameters of conformal channels, as well as their cross-section geometries. In addition, designs for the "best" thermomechanical performance are identified. Finally, guidelines for selecting optimum design solutions given the plastic part thickness are provided

Design and fabrication of conformal cooling channels in molds:Review and progress updates

Conformal cooling (CC) channels are a series of cooling channels that are equidistant from the mold cavity surfaces. CC systems show great promise to substitute conventional straight-drilled cooling systems as the former can provide more uniform and efficient cooling effects and thus improve the production quality and efficiency significantly. Although the design and manufacturing of CC systems are getting increasing attention, a comprehensive and systematic classification, comparison, and evaluation are still missing. The design, manufacturing, and applications of CC channels are reviewed and evaluated systematically and comprehensively in this review paper. To achieve a uniform and rapid cooling, some key design parameters of CC channels related to shape, size, and location of the channel have to be calculated and chosen carefully taking into account the cooling performance, mechanical strength, and coolant pressure drop. CC layouts are classified into eight types. The basic type, more complex types, and hybrid straight-drilled-CC molds are suitable for simply-shaped parts, complex-shaped parts, and locally complex parts, respectively. By using CC channels, the cycle time can be reduced up to 70%, and the shape deviations can be improved significantly. Epoxy casting and L-PBF show the best applicability to Al-epoxy molds and metal molds, respectively, because of the high forming flexibility and fidelity. Meanwhile, LPD has an exclusive advantage to fabricate multi-materials molds although it cannot print overhang regions directly. Hybrid L-PBF/CNC milling pointed out the future direction for the fabrication of high dimensional-accuracy CC molds, although there is still a long way to reduce the cost and raise efficiency. CC molds are expected to substitute straight-drilled cooling molds in the future, as it can significantly improve part quality, raise production rate and reduce production cost. In addition to this, the use of CC channels can be expanded to some advanced products that require high-performance self-cooling, such as gas turbine engines, photoinjectors and gears, improving working conditions and extending lifetime

Optimization of the Cooling of a Thermoplastic Injection Mold

In injection molding processes for thermoplastic parts, the polymer solidification phase in the molding cavity has a strong influence on the quality of the shaped parts and also on the process cycle time. Reducing cycle time is one of the major concerns for plastic injection industries. As cooling phase presents the most critical phase to get quality and cycle time of the part, the application of additive manufacturing (AM) technologies has been overcoming the limitations of traditional cooling system design. AM enables the construction of conformal cooling channels for higher cooling uniformity due to its almost unlimited freedom of design that can fulfil the desired functions in injection molding process equipment. The analysis of the heat transfer during the phase of cooling allows the investigation of the optimal positioning of the cold sources and their intensities. In this paper, a systematic approach is used to replace conventional channels in an injection molding tool with conformal cooling channels. A simulation is used to develop a numerical model that describes the heat transfer and predicts the cycle time of both the optimal and conventional designs. Finally, a numerical comparison is made between traditional and conformal cooling to demonstrate the beneficial effect on reducing the manufacturing cycle and enhancing part quality

Procedimiento para el análisis automatizado de la manufactura de la pieza de plástico y del molde de inyección

El proceso de manufactura mediante moldes de inyección de plástico es uno de los métodos de producción más versátiles y extendidos para la fabricación de piezas de plástico. Actualmente, existe una amplia variedad de software tipo CAD/CAE/CAM para el análisis y diseño asistido de piezas de plástico y moldes de inyección. Sin embargo, estas herramientas comerciales aún requieren de interacción humana y acceso a información geométrica interna de la pieza de plástico vinculada a su modelo CAD. La presente tesis doctoral propone una metodología universal basada en algoritmos automatizados de tipo geométrico – experto que, mediante el análisis de la geometría discreta de la pieza de plástico (malla en formato discreto definida por los elementos notables nodos y facetas), mejore y optimice el proceso actual de análisis, diseño y dimensionamiento del molde de inyección, sin recurrir a técnicas heurísticas e interacción manual por parte del usuario.Plastic injection molding is one of the most versatile and widespread manufacturing process for the plastic parts manufacture. Nowadays, there is a wide variety of CAD/CAE/CAM type software for the analysis and aided design of plastic parts and injection molds. However, these commercial tools still require human interaction and access to internal geometric information (geometric features) of the plastic part linked to their CAD model. The present PhD thesis proposes a universal methodology based on automated geometrical - expert algorithms that, by means of the analysis of the plastic part discrete geometry (mesh in discrete format defined by notable elements nodes and facets), improve and optimize the current analysis, design and dimensioning process of the injection mold, without resorting to heuristic techniques and manual interaction by the user.Tesis Univ. Jaén. Departamento Ingeniería Gráfica, Diseño y Proyectos. Leída el 3 de mayo de 2019