Direct Metal Tooling Research Articles

Mechanical performance of additively manufactured austenitic 316L stainless steel

For tensile tests, Vickers hardness tests and microstructure tests, plate-type and box-type specimens of austenitic 316L stainless steels were produced by a conventional machining (CM) process as well as two additive manufacturing processes such as direct metal laser sintering (DMLS) and direct metal tooling (DMT). The specimens were irradiated up to a fast neutron fluence of 3.3 × 109 n/cm2 at a neutron irradiation facility. Mechanical performance of the unirradiated and irradiated specimens were investigated at room temperature and 300 °C, respectively. The tensile strengths of the DMLS, DMT and CM 316L specimens are in descending order but the elongations are in reverse order, regardless of irradiation and temperature. The ratio of Vickers hardness to ultimate tensile strength was derived to be between 3.21 and 4.01. The additive manufacturing processes exhibit suitable mechanical performance, comparing the tensile strengths and elongations of the conventional machining process.

Experimental Investigation of Deposition Pattern on the Temperature and Distortion of Direct Energy Deposition-Based Additive Manufactured Part

The effect of deposition pattern on the temperature and global distortion of Direct Metal Tooling (DMT) based Additive Manufactured (AM) is investigated through the experimental results of laser deposited SUS316. DMT is one of the Directed Energy Deposition (DED) processes. In situ temperature measurements were used to monitor the temperature of the substrates and global distortion patterns were analyzed using CMM (coordinate Measuring Machine) after the deposition. Six different patterns combining long raster and short raster patterns were considered for the case studies. The results showed that the deposition pattern affects the temperature gradient and that the peak temperature of each layer can increase or decrease according to the sequence of the deposition pattern. Also, the pattern of the first layer had a dominant influence on the longitudinal bending deflection that occurs. Based on these results, appropriate tool path schedule can be utilized to control not only the distortion but also the peak temperature of the DMT-based AM parts.

Economic efficiency of the application of additive technologies based on laser direct metal tooling in the production of aircraft parts

The paper discusses the issues of the feasibility study on the integration of additive manufacturing technologies into classical technological chains. Using the aviation part as an example, we consider a model for the formation of technological costs for the classic and proposed versions of its manufacturing technology. A comparative parametric analysis of the cost of production of aircraft parts of this type was performed according to two options.

Development of Direct Metal Tooling (DMT) Process for Injection Mold Core with Curved Conformal Cooling Channel

Development of Direct Metal Tooling (DMT) Process for Injection Mold Core with Curved Conformal Cooling Channel

A method for representation and analysis of conformal cooling channels in molds made of functionally graded tool steel/Cu materials

Advances in additive manufacturing technology (AMT) enable the direct fabrication of thermally conductive molds with heat sinks or conformal cooling channels. Although tool steels (e.g., P21, H13, SUS420J2) are popularly used as die materials because of high dimensional stability, tool steels are inefficient for cooling mold dies due to low thermal conductivity. Hence, the adoption of functionally graded tool steel/Cu materials (FGMs) has good potentials for thermally conductive molds to avoid thermal stress concentration while improving thermal conductivity. In this sense, this paper presents a new method for the representation and analysis of conformal cooling channels in molds (injection or blowing) made of functionally graded tool steel/Cu materials. A heterogeneous sweep operation combined with 2D material blending was proposed to construct heterogeneous solid models for conformal cooling channels. In addition, one-dimensional P21/Cu FGMs were fabricated using DMT (laser-aided direct metal tooling). Material properties (such as density, specific heat, thermal conductivity, coefficient of thermal expansion, and hardness) were evaluated to obtain more accurate analysis results and to verify the feasibility of such a multi-functional mold. An example is shown to illustrate the entire representation and analysis procedure.

Laser-aided direct metal tooling of manufacturing aviation details on CNC machine

This paper discusses the effectiveness of the use of hybrid technology based on Laser-aided Direct Metal Tooling with subsequent machining as an alternative to traditional methods for producing products of a complex profile for the aviation industry. The aspects of the application of Laser-aided Direct Metal Tooling in the production cycles of manufacturing products passing through the final assembly operations are considered. The paper proposes an alternative manufacturing technology through the use of Laser-aided Direct Metal Tooling at the stage of design and technological study of the manufacturing cycles of individual assembly units. The objective function of ensuring high requirements for the accuracy of the relative position of the part in the assembly, reducing the mass and dimensions of the product, which is important for modern aviation systems. A technological solution is proposed to provide technical indicators of the objective function based on combining the advantages of laser, hybrid, and additive technologies in the working area of technological equipment. Considered technical solutions for the implementation of the proposed hybrid technology in the manufacture of critical parts of the aviation industry. The aspects of the production of parts are considered from the point of view of reducing the error in the relative position of the actuating surfaces of the product, an analysis is made of the machining errors in the process of the proposed production technology, with respect to the errors arising from traditional production cycles of parts of this type.

Applicability evaluation of direct metal tooling-based additive manufacturing for reducing ceramic liner fracture in total hip arthroplasty

Recently, the combination of a press-fit acetabular cup and ceramic articulation has been widely used for implanting cementless acetabular components and has been shown to provide good initial stability. However, this combination may lead to the failure of ceramic liners by their non-concentric seating due to acetabular cup deformation. To reduce the risk of this, we applied direct metal tooling (DMT)-based additive manufacturing (AM) with the hypothesis that DMT-based AM would minimize the deformation of the acetabular cup by increasing its strength, which would ultimately prevent the ceramic liner from fracturing. To confirm this, we performed post-fatigue tests simulating a press-fit situation for the acetabular cups subjected to DMT-based AM and compared them with the cups treated with titanium plasma spray (TPS). The post-fatigue tests were then performed under a maximum load of 14 kN for 20 × 107 cycles. The roundness and inner diameter of the cups and liners were measured in all testing phases. The results revealed no differences between the acetabular cups subjected to DMT-based AM and TPS. However, when comparing only the mean values directly, the results for the acetabular cup subjected to DMT-based AM indicated that it might have increased the strength of the acetabular cup, compared with those treated with TPS, thereby minimizing the possibility of fracture of the ceramic liner. In conclusion, DMT-based AM was shown to be at least equivalent to TPS, or could possibly supersede it. Additionally, via DMT-based AM, it is possible to control the porous structure freely, so this approach allows a greater range of applications and potential for further improvement than TPS.

A laser-aided direct metal tooling technology for artificial joint surface coating

Longevity of cementless arthroplasty is determined by the characteristics of the porous structure formed at the surface. However, currently used artificial joint surface coating technologies have several limitations. Therefore, the goal of this study was to investigate the use of an artificial surface coating technology to overcome the limitations of currently used technologies. An artificial joint surface coating that controls porosity of the porous structure formed at the surface of the artificial joint was developed based on laser-aided direct metal tooling (DMT) technology, which is a three-dimensional (3-D) additive manufacturing (AM) technology. The structural, mechanical, and physical properties of the DMT surface coating was measured in accordance with the international testing standards and compared to titanium plasma spray (TPS) surface coating, a commercially available artificial joint surface coating. DMT exhibited characteristics comparable, if not better, than the existing commercial TPS in terms of mechanical and physical properties. DMT may be useful for cementless artificial joint surface coating required the porosity control of the porous structure formed at the surface of the artificial joint and provides enhanced longevity and patient prognosis compared to the existing surface coating technologies.

Hydrogen embrittlement of 3-D printing manufactured austenitic stainless steel part for hydrogen service

Metal additive manufacturing (AM) technology as the emerging future manufacturing technology can be applied to the hydrogen service including hydrogen energy utilized industry. Direct metal tooling (DMT), one of the 3-D printing technologies, was used to manufacture an austenitic stainless steel part, and its mechanical properties and hydrogen embrittlement (HE) behavior were studied using the small specimen test technique under 10-MPa pressurized hydrogen gas. This part showed high HE resistance with minimal strain-induced transformation of austenite to martensite. This result indicates that parts produced using DMT are suitable for use in facilities for hydrogen service and hydrogen infrastructure.

3 차원 프린팅 기술을 이용한 신개념 경수로 핵연료 기술 개발에 관한 연구

To enhance the safety of nuclear reactors after the Fukushima accident, researchers are developing various types of accident tolerant fuel (ATF) to increase the coping time and reduce the generation of hydrogen by oxidation. Coated cladding, an ATF concept, can be a promising technology in view of its commercialization. We applied 3D printing technology to the fabrication of coated cladding as well as of coated pellets. Direct metal tooling (DMT) in 3D printing technologies can create a coated layer on the tubular cladding surface, which maintains stability during corrosion, creep, and wear in the reactor. A 3D laser coating apparatus was built, and parameter studies were carried out. To coat pellets with erbium using this apparatus, we undertook preliminary experiments involving metal pellets. The adhesion test showed that the coated layer can be maintained at near fracture strength.

Effect of Energy Input on the Characteristic of AISI H13 and D2 Tool Steels Deposited by a Directed Energy Deposition Process

Among the many additive manufacturing technologies, the directed energy deposition (DED) process has attracted significant attention because of the application of metal products. Metal deposited by the DED process has different properties than wrought metal because of the rapid solidification rate, the high thermal gradient between the deposited metal and substrate, etc. Additionally, many operating parameters, such as laser power, beam diameter, traverse speed, and powder mass flow rate, must be considered since the characteristics of the deposited metal are affected by the operating parameters. In the present study, the effect of energy input on the characteristics of H13 and D2 steels deposited by a direct metal tooling process based on the DED process was investigated. In particular, we report that the hardness of the deposited H13 and D2 steels decreased with increasing energy input, which we discuss by considering microstructural observations and thermodynamics.

Effect of heat treatment on the characteristics of tool steel deposited by the directed energy deposition process

The directed energy deposition process has been mainly applied to re-work and the restoration of damaged steel. Differences in material properties between the base and the newly deposited materials are unavoidable, which may affect the mechanical properties and durability of the part. We investigated the effect of heat treatment on the characteristics of tool steel deposited by the DED process. We prepared general tool steel materials of H13 and D2 that were deposited onto heat-treated substrates of H13 and D2, respectively, using a direct metal tooling process. The hardness and microstructure of the deposited steel before and after heat treatment were investigated. The hardness of the deposited H13 steel was higher than that of wrought H13 steel substrate, while that of the deposited D2 was lower than that of wrought D2. The evolution of the microstructures by deposition and heat treatment varied depending on the materials. In particular, the microstructure of the deposited D2 steel after heat treatment consisted of fine carbides in tempered martensite and it is expected that the deposited D2 steel will have isotropic properties and high hardness after heat treatment.

DMT기술을 활용한 형상적응형 냉각채널 적용 사례 연구

The Direct Metal Tooling (DMT) process is a kind of additive manufacturing processes, which is developed using various commercial steel powders, such as P20, P21, SUS420, and other non-ferrous metal powders. The DMT process is a versatile process that can be applied to various fields, such as the molding industry, the medical industry, and the defense industry. Among them, the application of the DMT process to the molding industry is one of its most attractive and practical applications, since the conformal cooling channel cores of injection molds can be fabricated at a slightly expensive cost by using the hybrid fabrication method of DMT technology compared with parts fabricated with machining technology. The main objectives of this study are to provide various characteristics of the parts made using the DMT process compared with the same parts machined from bulk materials and evaluate the performance of the injection mold equipped with a conformal cooling channel core fabricated using the hybrid method of the DMT process.

DED방식의 적층가공을 통한 금형으로의 응용사례 및 효과

Laser aided Direct Metal Tooling(DMT) process is a kind of Additive Manufacturing processes (or 3D- Printing processes), which is developed for using various commercial steel powders such as P20, P21, SUS420, H13, D2 and other non-ferrous metal powders, aluminum alloys, titanium alloys, copper alloys and so on. The DMT process is a versatile process which can be applied to various fields like the mold industry, the medical industry, and the defense industry. Among of them, the application of DMT process to the mold industry is one of the most attractive and practical applications since the conformal cooling channel core of injection molds can be fabricated at the slightly expensive cost by using the hybrid fabrication method of DMT technology compared to the part fabricated with the machining technology. The main objectives of this study are to provide various characteristics of the parts made by DMT process compared to the same parts machined from bulk materials and prove the performance of the injection mold equipped with the conformal cooling channel core which is fabricated by the hybrid method of DMT process.

Software supports and E-manufacturing for DMT process

The working principle of the laser-aided direct metal tooling(DMT) process is the use of a laser to selectively clad metallic powder on the substrate material part. A high-powered laser beam is focused on a metal substrate to create a molten weld pool; as the laser passes by the deposit is quickly cooled, leaving behind a thin line of metal clad. The major advantage of the DMT process is its capability of depositing a multitude of materials. Since the material deposition relies only on the feeding of a powder, it is relatively simple to use multiple kinds of materials. In fact, recent research has shown that DMT is capable of manufacturing binary functionally graded materials as well. The study is to develop a software support tool, visual simulation technique, as one of the e-manufacturing capability established for a unique DMT process.

레이저 적층조형을 이용한 P21 툴 스틸과 Cu 간 기능성 경사 복합재의 제작

With the development of layered manufacturing, thermally conductive molds or molds embedding conformal cooling channels can be directly fabricated. Although P21 tool steel is widely used as a mold material because of its dimensional stability, it is not efficient for cooling molds owing to its low thermal conductivity. Hence, the use of functionally graded materials (FGMs) between P21 and Cu may circumvent a tradeoff between the strength and the heat transfer rate. As a preliminary study for the layered manufacturing of thermally conductive molds having FGM structures, one-dimensional P21-Cu FGMs were fabricated by using laser-aided direct metal tooling (DMT), and then, material properties such as the thermal conductivity and specific heat that are related to the heat transfer were measured and analyzed.

Manufacture of an injection mould with rapid and uniform cooling characteristics for the fan parts using a DMT process

The aims of the present study is to manufacture an injection mould with a pair of conformal cooling channels in each blade of the mould for a plastic fan part via laser-aided direct metal tooling (DMT) process to achieve both rapid and uniform cooling characteristics. The features of the design and the manufacturing process for the injection mould as well as the characteristics of the manufactured mould were discussed. Three-dimensional injection moulding analyses were performed to obtain a proper design of the conformal cooling channels. Injection moulding experiments were carried out to investigate the practical applicability of the fabricated mould and the influence of the cooling time on the qualities of the moulded product. The results of the experiments showed that a plastic fan part with superior qualities can be fabricated from the designed mould when the cooling time is 13 s. The efficiency of the designed mould was examined through a comparison of the product from the newly designed mould and that from a previously designed mould with linear cooling channels in terms of product qualities as well as the cooling and cycle times. The results of the comparison showed that the newly designed mould can remarkably reduce the positional error distributions and the eccentricity of the moulded product. In addition, it was shown that the cooling and cycle times of the designed mould can be shortened to 35.0 % and 25.7 % of those of the previously designed mould, respectively.

Study on the manufacture of a thermal management mould with three different materials using a direct metal tooling rapid tooling process

The objective of this paper is to manufacture a thermal management mould with three different materials and conformal cooling channels using a laser-aided direct metal tooling process to obtain both rapid and uniform cooling characteristics. The geometry of the thermal management mould is decomposed into three parts, including a moulding part consisting of P21 injection tool steel, a mid-layer consisting of Monel 400 material, and a base part consisting of Ampcoloy 940 material, according to the functionality of each part. The base part is designed as a heat sink and the midlayer is adopted to reduce the thermal stress in the joined regions. In this paper, the features of the design and a rapid tooling process for the thermal management mould as well as the characteristics of the mould are discussed. Several injection-moulding experiments are performed to investigate the practical applicability of the fabricated mould and the effects of the cooling time on the quality of the moulded product. The results of the experiments show that the cooling time of the thermal management mould can be shortened to 3 s. Through comparison of the product from the thermal management mould with that of a previously designed mould, it is shown that the designed mould can improve both the cycle time and the quality of the product.

Application of direct laser metal tooling for AISI H13 tool steel

In the die industry, it is commonly agreed that residual tool life can be successfully extended by timely repair of damaged surfaces. Traditionally, the main repair process is tungsten inert gas (TIG) welding, but a new process called direct laser metal tooling (DLMT) emerges. DLMT is a manual process, of which results depend on the materials of the powders and tools, the laser process and parameters. This technology is a direct-metal freeform fabrication technique in which a 200 W fiber laser is used. AISI H13 tool steel is a suitable material for die casting tools because of the high resistance to thermal fatigue and dimensional stability. In this research, AISI H13 tool steel was melted with metal powder by fiber laser. Before melting AISI H13, the powders were analyzed with XRF equipment. Then, hardness distribution of laser melted zone was investigated. The microstructure in laser melted zone was discussed. In order to identify the effect of particle size of powder on the melted zone, two types of particle sizes of powders were used. Experimental results show that the mold repair process using DLMT can be applied in the mold repair industry.

Rapid hard tooling process selection using QFD‐AHP methodology

PurposeTo provide a systematic framework for mold designers, that can be used for rapid tooling (RT) process selection and prioritization of process parameters.Design/methodology/approachThis paper presents a QFD‐AHP methodology which has three phases. The first phase involves prioritizing the tooling requirements (driven by customer preferences) against a set of die/mold development attributes (such as product material, geometry, and die material and production order) through pair‐wise comparison using analytical hierarchal process (AHP). These priority ratings are used for selecting the most appropriate tooling process using quality function deployment (QFD) in the second phase. Finally, QFD is used again for identifying critical process parameters (such as layer thickness, scan pitch and laser power) for the selected RT process.FindingsThe QFD‐AHP methodology has been illustrated with industrial examples on RT for molded parts. The molds were fabricated using direct metal laser sintering and spray metal tooling processes, for example, 1 and 2, respectively, to prove that the methodology can be easily implemented in tool rooms. The issues noted in these experimental studies are also discussed for the benefit of researchers.Research limitations/implicationsThe capabilities of the RT processes presented in the paper reflect the experience of the research team in RT development. The QFD‐AHP methodology will give progressively better results with a growing body of RT process knowledge.Practical implicationsThis investigation is a key step towards the goal of developing a comprehensive system for RT process selection and manufacturability evaluation. The mold designer can use this QFD‐AHP process selection methodology, prior to detailed manufacturability analysis, to better realize the benefits of RT technologies.Originality/valueThe proposed QFD‐AHP methodology is a new approach for the tooling process selection domain, and has not been reported earlier; this can be easily used for similar applications for any manufacturing domain.