This study is a comment on “Numerical investigation on cooling performance of hot stamping tool with various channel designs” (Hu et al., Applied Thermal Engineering 96 (2016) 338-351, cited as Ref. ...1 in this study). Conformal cooling (CC) channels can significantly improve product quality and production efficiency, such as the reduction of differential shrinkage, warpage, and other surface defects and the shortening of the injection molding cycles. The Reynolds number is an important parameter to determine the cooling performance in CC molds. There is an optimal Reynolds number value below which the cooling is not sufficient and above which the cooling performance is not further improved but the pressure drop rises significantly. Ref. 1 proposed the optimal Reynolds number was 100,000 which is not convincing as such large a Reynolds number value will cause an unacceptable significant pressure drop in the channel. To verify and clarify this, numerical simulations were conducted using the same methods, conditions, and parameters as Ref. 1. The optimal Reynolds number was found as 20,000 rather than 100,000, which was approximately consistent with the results in other reliable references 2,3 rather than the result in Ref. 1.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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Additive manufacturing can produce parts with complex geometries in fewer steps than conventional processing, which leads to cost reduction and a higher quality of goods. One ...potential application is the production of molds and dies with conformal cooling for injection molding, die casting, and forging. AISI H13 tool steel is typically used in these applications because of its high hardness at elevated temperatures, high wear resistance, and good toughness. However, available data on the processing of H13 steel by additive manufacturing are still scarce. Thus, this study focused on the processability of H13 tool steel by powder bed fusion and its microstructural characterization. Laser power (97−216 W) and scan speed (300−700 mm/s) were varied, and the consolidation of parts, common defects, solidification structure, microstructure, and hardness were evaluated. Over the range of processing parameters, microstructural features were mostly identical, consisting of a predominantly cellular solidification structure of martensite and 19.8 %–25.9 % of retained austenite. Cellular/dendritic solidification structure displayed C, Cr, and V segregation toward cell walls. The thermal cycle resulted in alternating layers of heat-affected zones, which varied somewhat in hardness and microstructure. Retained austenite was correlated to the solidification structure and displayed a preferential orientation with {001}//build direction. Density and porosity maps were obtained by helium gas pycnometry and light optical microscopy, respectively, and, along with linear crack density, were used to determine appropriate processing parameters for H13 tool steel. Thermal diffusivity, thermal conductivity, and thermal capacity were measured to determine dimensionless processing parameters, which were then compared to others reported in the literature.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Fabricating conformal cooling channels has become easier and more cost-effective because of recent advances in additive manufacturing. Conformal cooling channels (CCCs) give better cooling ...performance than regular (straight drilled) channels during the injection molding process. The main reason for this is that CCCs may follow the paths of the molded shape, but regular channels cannot. CCCs can be used to decrease thermal stresses and warpage while also decreasing cycle time and producing a more uniform temperature distribution. Computer-aided engineering (CAE) simulations are crucial for establishing an effective and cost-effective design. This article focuses on the design optimization of an injection mold, with the goal of optimizing the location of cooling channels to reduce ejection time and increase temperature distribution uniformity. It may be inferred that the created technique is effective and appropriate for the objectives of this work.
The latest developments in additive manufacturing have enabled the creation of conformal cooling channels with improved efficiency and cost efficiency. In the context of the injection molding ...process, it has been shown that conformal cooling channels (CCCs) demonstrate improved cooling effectiveness when compared to conventional straight-drilled channels. The primary justification for this phenomenon is from the fact that conformal cooling channels (CCCs) have the capacity to adapt to the contours of a molded object, a feat that cannot be accomplished with traditional channels. Carbon–carbon composites (CCCs) possess the capacity to alleviate thermal stresses and warpage, reduce cycle durations, and attain a more uniform temperature distribution. Traditional channels employ a design method that exhibits greater intricacy compared to CCCs. The utilization of computer-aided engineering (CAE) simulations is of paramount importance in the advancement of designs that demonstrate cost effectiveness and efficiency. The aim of this research is to evaluate the efficacy of two ANSYS modules for the purpose of validating the acquired outcomes. The two modules exhibit comparable results when used on models with a more detailed mesh. Therefore, it is crucial to consider the objective of the research and the complexity of the computer-aided design (CAD) geometry while making a well-informed choice regarding the suitable ANSYS module to use.
Conformal cooling channels are widely adopted in the mold industry because of rapid and uniform cooling during injection molding. These complicated cooling channel geometries become feasible via ...selective laser melting (SLM) technology. However, the SLM fabricated internal channel surface shows high surface roughness of about 10 μm Ra. This rough surface can cause stress concentration, reducing the fatigue life of the mold. Therefore, the objective of this study is to investigate the surface finish of the SLM fabricated conformal channels by abrasive flow machining (AFM), which is widely used in the surface finishing of internal channels. To fulfill this objective, a combination of single/multiple and straight/helical channels for conformal cooling channel geometries are employed. Seven different types of conformal cooling channels (ø3mm) inside the bar are fabricated using SLM. The bar is put in the AFM fixture, and the internal channels are polished by flowing AFM media (ULV50%-54) through the channel at the same extrusion pressure of 80 bars for ten cycles. Fourteen bars (seven before AFM and seven after AFM) are machined to have the internal channel surfaces exposed for surface roughness measurement. Surface topographies of the exposed surfaces of seven types of internal channels are obtained using focus variation microscopy. The areal roughness parameters, such as arithmetical mean height (Sa) on the internal channel surfaces before and after AFM. By comparing SLM as-built conformal channel surfaces with AFM finished ones, AFM is shown to be effective in improving all SLM conformal cooling channels’ arithmetical mean height, Sa. Areal roughness parameters, such as developed interfacial area ratio (Sdr), root mean square gradient (Sdq), reduced peak height (Spk), reduced valley height (Svk), and skewness (Ssk), on those internal surfaces, were found to be sensitive to surface finishing by AFM.
•Seven different types of conformal cooling channels (3ø) including straight/helical channels were fabricated by SLM.•Their internal channel surfaces were finished by abrasive flow machining (AFM).•Their internal channel surfaces (seven before AFM and seven after AFM) were exposed by grooving.•Their channel surface topographies were obtained by focus variation microscopy.•Their channel surface topography evolution was analyzed in terms of areal parameters, such as Sa, Spk, Svk, and Ssk.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Injection moulding is a manufacturing process widely used in industry. A major step in this technique is the design of efficient cooling channels for the molten material. In this paper we develop a ...mathematical model for the automatic generation of conformal cooling channels which follow the shape of the mould. We focus on the core of the mould and then we extend the technique to the correspondent cavity. We start by decomposing the core mould into approximate convex regions and then we classify them. While for narrow regions we use a strategy hereby called zigzagging, in the remaining cases we automatically generate cooling channels with spiral shapes. The design of those smooth spiral curves is guided by the iso-contours of a boundary-distance map. Our approach encompasses decomposition, classification and design in an automatic integrated system. The development of an algorithm for the automatic generation of cooling channels represents a big contribution to the typical methodology used by mould designers, since it dramatically decreases the time spent by a specialist on this task.
•Mathematical model for the automatic design of cooling channels•Covers a wide range of possible moulds geometries•Efficiency in the time for the design process and the uniform cooling of the material
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Additive manufacturing (AM) is widely used for tooling applications: Complex conformal cooling channels are designed to increase and homogenize the cooling rate of a mold insert. The list of ...available steel grades in laser powder bed fusion is currently very limited and does not satisfy highly mechanically demanding applications; hard stainless steel metals printable without cracking are lacking. Herein, the influence of the particle size distribution and atomization process on the printability of a new tooling steel tailored for AM (L40) is observed on an EOS M290 printer based on microstructural observations and mechanical testing. Several batches with different powder size distributions of either gas‐ or water‐atomized powder are processed and studied. The aim of using water‐atomized powder is to reduce both the environmental footprint and the cost of the feed material. Dense built parts (other 99% density) are achieved using water‐ and gas‐atomized powders. The hardness is in all cases superior to 50 HRC, which is above the standard requirement for injection molding applications. The ductility of gas‐atomized parts is four times higher than that measured on heat‐treated maraging steel. Water‐atomized samples reach a ductility similar to that of maraging steel.
Herein, the devlopment of a new tooling steel (L40) for laser powder bed fusion is reported. The ductility of gas‐atomized parts is four times higher than that measured on a heat‐treated maraging steel. The hardness is above 50 HRC, making the material perfectilly suitable for injection molding tools in additive manufacturing.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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•The ECO mold with a surface-type conformal cooling channel was designed using CFD analysis.•The ECO mold was additively manufactured via LPBF in practice.•The additively manufactured ...ECO mold was utilized in the casting production line.•The casting time and carbon emission were reduced by 21% and 0.6 kg of CO2, respectively.•The microstructural characteristic and mechanical evaluation of the as-cast product were improved.
This study proposes an eco-friendly (ECO) mold that is fabricated using the laser powder bed fusion (LPBF) method, which utilizes a three-dimensional (3D) cooling channel. Unlike previous studies, we designed surface-type conformal cooling channels (CCC) based on the design concept for additive manufacturing, at a constant depth corresponding to the casting part. Pin fins were installed inside the surface-type cooling channels and aligned through numerical analysis to induce the turbulence of the coolant uniformly through the cooling channel while generating less thermal stress during solidification of the as-cast Al-Si alloy-based product, which increased the cooling efficiency of the proposed ECO mold. Moreover, the ECO mold was utilized to cast an automobile piston to demonstrate its feasibility at an industrial level. The results showed that, the casting process decreased significantly from 133 to 105 s per piston (21% reduction) compared to the conventional mold with a single columnar cooling channel. Additionally, the average grain size of the ECO mold decreased from 502 to 398 µm. The ultimate tensile strength and Rockwell hardness increased by 12.5% and 5.5%, respectively.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Additive manufacturing (AM) techniques such as selective laser melting (SLM) can enable the construction of injection moulding (IM) tools with conformal cooling channels that significantly improve ...performance through higher cooling uniformity and reduced cycle times. Design of IM cooling systems is typically achieved using commercial IM numerical modelling software originally developed for conventionally cooled mould designs. However, the accuracy of IM modelling software in predicting the performance of SLM manufactured tools with conformal cooling, across a range of moulding materials and processing conditions, has not been thoroughly evaluated in the literature. Furthermore, the SLM manufacturability and mechanical properties of tool steels typically applied in IM, such as AISI H13, are not well documented. This work addresses these deficiencies through the following: quantification of SLM H13 material properties, in particular fatigue strength which has not been previously reported; design and manufacture of a mould tool with easily exchangeable conventionally and conformally cooled inserts; and subsequent experimental validation of IM simulation software predictions under a range conditions. Result of mechanical testing showed SLM H13 parts to offer lower mechanical properties in the as-built condition compared to conventional materials; however, these increased substantially following residual stress reduction with heat treatment. Evaluation of the temperature prediction accuracy of IM numerical models showed generally high accuracy for conformally cooled SLM tools, although marginally lower when compared to conventionally cooled moulds. The outcomes of this work offer designers typical material property data for SLM manufactured H13 tooling, as well as an indication of the expected prediction accuracy of current commercial IM simulation software when applied to conformally cooled SLM tooling.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Purpose
Additive manufacture (AM) such as selective laser melting (SLM) provides significant geometric design freedom in comparison with traditional manufacturing methods. Such freedom enables the ...construction of injection moulding tools with conformal cooling channels that optimize heat transfer while incorporating efficient internal lattice structures that can ground loads and provide thermal insulation. Despite the opportunities enabled by AM, there remain a number of design and processing uncertainties associated with the application of SLM to injection mould tool manufacture, in particular from H13/DIN 1.2344 steel as commonly used in injection moulds. This paper aims to address several associated uncertainties.
Design/methodology/approach
A number of physical and numerical experimental studies are conducted to quantify SLM-manufactured H13 material properties, part manufacturability and part characteristics.
Findings
Findings are presented which quantify the effect of SLM processing parameters on the density of H13 steel components; the manufacturability of standard and self-supporting conformal cooling channels, as well as structural lattices in H13; the surface roughness of SLM-manufactured cooling channels; the effect of cooling channel layout on the associated stress concentration factor and cooling uniformity; and the structural and thermal insulating properties of a number of structural lattices.
Originality/value
The contributions of this work with regards to SLM manufacture of H13 of injection mould tooling can be applied in the design of conformal cooling channels and lattice structures for increased thermal performance.
