Rapid Tooling Process Research Articles

Role of Additive Manufacturing in Development of Forming Tools and Dies for Sheet Metal Forming: A Review

Price and time are two major concerns in the industry which encourages the development and manufacturing of new dies for sheet metal forming applications. Additive manufacturing (AM) and rapid tooling (RT) are now emerging techniques for producing cost-effective and fast production of sheet metal forming dies with excellent mechanical and wear resistance properties. The paper gives an insight into AM processes that were implemented in the tooling industry to enhance moulding efficiency and sheet metal forming processes. The advantages and challenges observed in using AM are highlighted and discussed as opposed to traditional tooling. The RT processes used in moulding and sheet metal formation are addressed, and their limitations are highlighted. The paper also discusses several possible application areas in which AM technologies can be used further to enhance the efficiency of the devices. Finally, discussion on current issues related to the use of AM in tooling has been presented.

Retraction: Abrasive Wear Performance of Aluminium Modified Epoxy-Glass Fiber Composites

For a long time, Aluminum filled epoxies molds have been used in rapid tooling process. These molds are very economical when applied in manufacturing of low volume of plastic parts. To improve the thermal conductivity of the material, the metallic filler material is added to it and the glass fiber improves the wear resistance of the material. These two important parameters establish the life of composites. The present work reports on abrasive wear behavior of Aluminum modified epoxy and glass fiber composite with 5 wt.% and 10 wt.% of aluminum particles. Through pin on disc wear testing machine, we studied the wear behaviors of composites, and all these samples were fabricated by using hand layup process. Epoxy resin was used as matrix material which was reinforced with Glass fiber and Aluminum as filler. The composite with 5 wt.% and 10 wt.% of Al was cast with dimensions 100 × 100 × 6 mm. The specimens were machined to a size of 6 × 6 × 4 mm for abrasive testing. Abrasive tests were carried out for different grit paper sizes, i.e., 150, 320, 600 at different sliding distance, i.e., 20, 40, 60 m at different loads of 5, 10 and 15 N and at constant speed. The weight loss due to wear was calculated along with coefficient of friction. Hardness was found using Rockwell hardness machine. The SEM morphology of the worn out surface wear was analyzed to understand the wear mechanism. Results showed that the addition of Aluminum particles was beneficial for low abrasive conditions.

Hybrid layered manufacturing of a bimetallic injection mold of P20 tool steel and mild steel with conformal cooling channels

Hybrid layered manufacturing (HLM) is one of the most efficient rapid tooling processes that uses a metal inert gas, tungsten inert gas or laser cladding processes for producing near-net shape and machining operations for finishing on the same platform. Materials saving, elimination of rough machining, reduction of programming time, ability to make conformal cooling channels (CCCs), and bimetallic objects are some of the significant advantages of HLM in tooling applications. CCCs, as against the straight cooling channels, reduce the cycle time and distortion and improve the matrix integrity. Bimetallic objects, as compared to monolithic objects, reduce the overall cost by replacing the interior with cheaper material. In this work, the HLM has been investigated for realizing bimetallic structures of P20 tool steel and mild steel. A complex bimetallic plastic injection mold with hard casing (P20 tool steel) and soft core (mild steel) along with CCCs have been built as a case study. The mechanical and microstructural characterization leads to the fine-tuning of the process parameters. The plastic injection mold with CCCs is designed through heat flow analysis using a commercial software.

Rapid manufacturing of biodegradable pure iron scaffold using amalgamation of three-dimensional printing and pressureless microwave sintering

In the present work, a rapid tooling process using three-dimensional printing and pressureless microwave sintering has been developed for the fabrication of biodegradable pure iron. Carbonyl iron particles were used for sample preparation and phosphate-based investment material was used for mould fabrication. Cylindrical samples were fabricated successfully using the developed rapid tooling process. The fabrication experiments were planned based on response surface methodology to evaluate the effect of microwave sintering parameters, namely sintering temperature, heating rate and soaking time on sintered density, shrinkage and compressive yield strength. The results showed that sintered density and compressive yield strength increased with the rise in sintering temperature from α to γ iron transformation temperature and were found to decrease with further rise in temperature. The shrinkage was found to increase with the increase in sintering temperature. Moreover, with the increase in soaking time and decrease in heating rate, sintered density, shrinkage and compressive yield strength were found to increase. Scanning electron microscopy and the X-ray diffraction plot of the fabricated iron samples showed that even without the application of pressure proper bonding of carbonyl iron particles was achieved. Mould material contamination or oxidation was not evidenced in the experiments. A multi-objective optimization using genetic algorithm was performed to obtain optimum microwave sintering parameters for maximum sintered density as well as compressive strength and minimum shrinkage. A case study on the fabrication of scaffold for human skull was performed to test the efficacy of the developed rapid tooling process.

Abrasive Wear Performance of Aluminium Modified Epoxy-Glass Fiber Composites

For a long time, Aluminum filled epoxies molds have been used in rapid tooling process. These molds are very economical when applied in manufacturing of low volume of plastic parts. To improve the thermal conductivity of the material, the metallic filler material is added to it and the glass fiber improves the wear resistance of the material. These two important parameters establish the life of composites. The present work reports on abrasive wear behavior of Aluminum modified epoxy and glass fiber composite with 5 wt.% and 10 wt.% of aluminum particles. Through pin on disc wear testing machine, we studied the wear behaviors of composites, and all these samples were fabricated by using hand layup process. Epoxy resin was used as matrix material which was reinforced with Glass fiber and Aluminum as filler. The composite with 5 wt.% and 10 wt.% of Al was cast with dimensions 100 × 100 × 6 mm. The specimens were machined to a size of 6 × 6 × 4 mm for abrasive testing. Abrasive tests were carried out for different grit paper sizes, i.e., 150, 320, 600 at different sliding distance, i.e., 20, 40, 60 m at different loads of 5, 10 and 15 N and at constant speed. The weight loss due to wear was calculated along with coefficient of friction. Hardness was found using Rockwell hardness machine. The SEM morphology of the worn out surface wear was analyzed to understand the wear mechanism. Results showed that the addition of Aluminum particles was beneficial for low abrasive conditions.

Erratum to: Wear characteristics of Stellite6 and NOREM02 hardfaced SKD61 hot working tool steel at the elevated temperature

Recently, interest in hardfacing technology has steadily increased in effort to improve wear characteristics of hot forming dies. The objective of this paper is to investigate wear characteristics of Stellite6 and NOREM02 hardfaced SKD61 hot working tools steel at the elevated temperature. Stellite6 and NOREM02 superalloys are deposited onto the SKD61 hot working tool steel using the laser-aided direct metal rapid tooling (DMT) process. In order to examine the influence of the hardfacing materials on the hardness of hardfaced specimens, hardness experiments are performed beyond the full annealing temperature of the SKD61 material. Pin-on-disk experiments are carried out to examine wear characteristics, including the worn volume, the worn depth, the worn width, and the friction induced work hardening, of the hardfaced specimens at the elevated temperature. The morphology in the vicinity of the worn region is observed by a digital microscope and a scanning electronic microscope (SEM) to investigate the formation and the microstructure of the worn region. In addition, the efficiency of the hardfaced specimen is discussed via the comparison of wear characteristics of superalloy hardfaced specimens with those of the SKD61 specimen.

3 차원 프린팅 기술의 열간 체적 성형 공정 적용에 관한 기초 연구 - 예비형상 설계 예 및 열간 금형강으로 적층된 표면 특성 분석

【The goal of this paper is to investigate preliminary the applicability of 3D printing technologies for the development of the hot bulk forming process and die. 3D printing technology based on the plastic material was applied to the preform design of the hot forging process. Plastic hot forging dies were fabricated by Polyjet process for the physical simulation of the workpiece deformation. The feasibility of application of Laser-aided Direct Metal Rapid Tooling (DMT) process to the fabrication of the hot bulk metal forming die was investigated. The SKD61 hot-working tool steel was deposited on the heat treated SKD61 using the DMT process. Fundamental characteristics of SKD 61 hot-working tool steel deposited specimen were examined via hardness and wear experiments as well as the observation of the morphology. Using the results of the examination of fundamental characteristics, the applicability of the DMT process to manufacture hot bulk forming die was discussed.】

A study on the effects of hardfacing thickness on wear characteristics of Stellite21 hardfaced STD61 hotworking tool steel at the elevated temperature

The aim of this paper is to investigate the effects of hardfacing thickness on wear characteristics of Stellite21 hardfaced STD 61 hotworking tool steel at the elevated temperature. Stellite21 super-alloy is deposited on the STD61 hot-working tool steel to fabricate the specimen using a laser-aided direct metal rapid tooling process. Several pin-on-disk wear experiments are carried out at temperatures beyond the full annealing temperature of the STD61. The hardness, the friction induced work hardening, the weight loss, the wear depth, and the wear width of each specimen are measured to quantitatively investigate the influence of the hardfacing thickness on the wear characteristics. The variation of friction characteristics of the worn region according to the hardfacing thickness is examined via the measurement of friction coefficients and the observation of morphologies of the worn regions for different specimens. From the results of these investigations, the proper thickness of the Stellite21 hardfaced layer on STD61 hot-working tool steel is estimated.

Investigation of Residual Stresses Induced during the Selective Laser Melting Process

The selective laser melting process (SLM), belonging to the family of additive manufacturing processes, can create complex geometry parts from a CAD file. Previously, only prototypes were created by SLM, but now this process is used to manufacture quickly and directly functional parts. For example, in the PEP (Pôle Européen de la Plasturgie), this process is used to fabricate tooling parts or injection molds with cooling channels that can’t be obtained by conventional routes. During the process, the laser beam generates violent heating and cooling cycles in the material inducing important thermal gradients in the consolidated part. The cyclic thermal expansions and contractions exceeding the maximum elastic strain of the material induce heterogeneous plastic strains and generate internal stresses the level of which can reaches the yield stress of the material and cracks may appear during the process. This paper deals with the measurement and analysis of residual stresses during the selective laser melting of a simple part in maraging steel. The objective of this study is the analysis of experimental results to validate the numerical model previously presented in [1]. Some authors have investigated the residual stresses produced in SLM parts using different experimental measurement methods such as the incremental hole drilling method in [2], the layer removal method see in [3] and [4] or the non-destructive method, by neutron diffraction in [5]. A new method is proposed to evaluate the residual stresses induced during the SLM process, a rosette is fixed on the bottom face of the support. The residual stresses in the created part are calculated from strain and temperature variations when the fused layer is consolidating during the cooling between two layers. Process parameters like the powder thickness or the time cooling between successive layers are studied in this paper. [1] L. Van Belle, G. Vansteenkiste, J.C. Boyer, Comparisons of numerical modeling of the selective laser melting, Key Engineering Materials Vols. 504-506 (2012) pp 1067-1072 [2] C. Casavola, S.L. Campanelli, C. Pappalettere, Experimental analysis of residual stresses in the selective laser melting process, Proceedings of the XIth International Congress and Exposition, June 2-5, 2008 Orlando, Florida USA [3] M. Shiomi, K. Osakada, K. Nakamura, T. Yamashita, F. Abe, Residual stress within metallic model made by selective laser melting process, CIRP Annals - Manufacturing Technology, Vol. 53, No. 1. (2004), pp. 195-198 [4] T. Furumoto, T. Ueda, M.S. Abdul Aziz, A. Hosokawa and R. Tanaka, Study on reduction of residual stress induced during rapid tooling process, influence of heating conditions on residual stress, Key Engineering Materials Vols. 447-448 (2010) pp 785-789 [5] M. Zaeh, G. Branner, Investigation on residual stresses and deformation in selective laser melting, Production Engineering, Volume 4, Number 1 (2010)

Turbine Blade Manufacturing Through Rapid Tooling (RT) Process and Its Quality Inspection

Rapid prototyping (RP) technologies have played vital role in product development and validation. Another aspect of RP is rapid tooling (RT). The development and manufacturing of conventional tools (die and molds) take considerable amount of time. RP technologies could be used to shorten the development time of these tools for shorten the time to production. This investigation focuses on the development of turbine blade through RT technique with quality inspection at three different stages, i.e., after manufacturing of master patterns, wax patterns, and casting in metal. Three different materials were considered for RT techniques, i.e., Room temperature vulcanization (RTV) silicon, polyurethane, and plaster of Paris. Master patterns were developed using stereolithography(SLA) and fused deposition modeling (FDM) process. Both master patterns were analyzed for surface roughness and dimensional accuracy. SLA pattern showed better results for surface finish and dimensional accuracy, and it was used for mold manufacturing. Wax patterns were produced from RTV silicon, polyurethane (PU), and plaster of Paris molds,and used for metal casting. Dimensional quality inspection was performed for both wax and metallic parts using noncontact three-dimensional (3D)digitizer. RTV silicon and SLA process were selected as the suitable mold material and process respectively for RT of turbine blade.

Micro-stereolithography tools for small-batch manufacture of polymer micro-parts

Rapid tooling solutions can be used to manufacture prototypes and small batches of parts that are critical to part and tool design verification and thus to minimize the production cost and lead time in developing new products. Layer-based manufacture of prototypes is a proven technology for an early assessment of the designs of products and, with the introduction to the market of new micro-stereography technologies, rapid tooling becomes an important option for low-volume production of polymer micro-components. Thus, to broaden the use of these technologies, it is necessary to understand the behaviour of rapid tooling inserts under cyclic thermodynamic loads. The paper investigates a rapid tooling solution for fabricating ‘soft’ inserts that are validated by injection moulding small batches of polymer parts. The mouldings produced using such soft tools are analysed and conclusions are made about the tool-making capability of the micro-stereography process. In particular, it was found that the soft inserts were fabricated with sufficient accuracy by employing this rapid tooling process. Also, it was experimentally validated that they could be applied successfully to produce small batches of functional parts, and in particular to a lens micro-device. The most important factors affecting their injection-moulding capabilities were the build orientation of the inserts and the process settings to account for the build-up of thermal energy during the replication cycles.

Applications of laser assisted metal rapid tooling process to manufacture of molding & forming tools — state of the art

Recently, researchers related to the development of eco-friendly molding and forming tools have refocused on the laser assisted metal rapid tooling process to cope the global warming and the resource depletions. The advantageous inherent features of the laser assisted metal rapid tooling process, include an additive proves, switchable supply material and material deposition along an arbitrary trajectory, provide the tool designer and manufacturer with a chance to overcome the limitations of the conventional molding and forming tools from viewpoints of the energy consumption, the environmental impact and the material usage. This paper presents recent researches related to the application of laser assisted metal rapid tooling process to manufacture molding and forming tools. In addition, key technologies of important applications are discussed. Finally, the future issues of the laser assisted metal rapid tooling process related to the development of eco-friendly molding and forming tools are described.

Prototype tooling for producing small series of polymer microparts

Layer-based manufacture of three-dimensional functional models and concept prototypes play a crucial role in the early assessment and verification of product designs. Any change of design, which is frequently needed during product development, causes the development costs to rise significantly. However, there is a limited set of materials available for layer-based manufacturing, especially for producing polymer microcomponents. Therefore, for fabricating small batches of microcomponents in the required material it is necessary to develop rapid tooling process chains, e.g. for low-pressure injection moulding. This paper investigates the moulding performance of µSL inserts as a function of tool geometry in combination with the effects of process factors. Condition monitoring techniques applied to the µ-IM process have been carried out to provide information that can be used to optimize the process. It was found that small batches of parts with fine details and relatively high aspect ratio structures can be produced and that reduced pressure loads and in particular the decrease of the µSL inserts layer thickness can extend the tool life.

Study on Reduction of Residual Stress Induced during Rapid Tooling Process: Influence of Heating Conditions on Residual Stress

This paper deals with the reduction of residual stress induced during the selective laser melting with a mixture of ferrous based metal powder. To evaluate the residual stresses induced during layered manufacturing processes, a strain gauge is attached on the bottom face of the base plate. The residual stress within the consolidated structure is calculated from the amount of strain change measured by the strain gauge when the consolidated structure is cut with an end mill. The influences of base plate thickness and consolidated structure height on the residual stresses are investigated. In addition, the effect of pre-heating and post heating by a laser beam irradiation are evaluated. The results showed that the deformation of the base plate increased with the increase of the consolidated layer and the decrease of base plate thickness, and the deformation was flattened when the consolidated structure was completely removed with the end mill. The deformation was related to the induced residual stresses. The residual stress distribution within the consolidated structure in the z direction was extremely large at the top layer of the structure and the boundary between the base plate and consolidated structure. The residual stress at the first layer of the structure decreased when the base plate was heated before consolidating the deposited powder. The residual stresses decreased when each of the consolidated layers was repeatedly heated by the laser beam irradiation.

Novel acrylic nanocomposites containing in-situ formed calcium phosphate/layered silicate hybrid nanoparticles for photochemical rapid prototyping, rapid tooling and rapid manufacturing processes

Novel acrylic nanocomposites containing calcium phosphate/layered silicate hybrid nanoparticles have been developed for use in photochemical Rapid Prototyping processes like Structural Light Modulation (SLM) and Stereolithography (SL). When tertiary alkyl amines, protonated with phosphoric acid, were added to an acrylic suspension of calcium bentonite, the cation exchange of Ca2+ rendered bentonite organophilic, caused swelling, intercalation and dispersion of silicate nanoplatelets in the monomer. The simultaneous precipitation of calcium phosphate onto the silicate nanoplatelets accounted for the in-situ formation of hybrid nanoparticles. The uniform dispersions of such hybrid nanoparticles afforded a high degree of shear thinning, reflecting the presence of anisotropic filler particles, and increased photosensitivity in SLM with respect to the unfilled resin. Young’s modulus of green and postcured parts increased by 30% at a filler content of 15 wt.% with respect to that of the unfilled benchmark material. This enhanced stiffness was paralleled by 30% increased fracture toughness. As evidenced by fracture surface analysis using Environmental Electron Microscopy (ESEM) and optical microscopy, the improved energy dissipation at the crack tip correlated with roughness of the fracture surfaces, increasing with increasing filler content. Moreover, the examination of the volumetric polymerization shrinkage and the fabrication of H-shaped diagnostic specimens revealed that the nanocomposites were processed with high accuracy, increasing with increasing filler content. Nanocomposite morphologies, examined by means of Transmission Electron Microscopy (TEM), demonstrated that the large primary bentonite particles with average diameters >10 μm fragmented into much smaller particles with average diameters in the range of 1 μm. According to TEM and Wide Angle X-Ray Scattering (WAXS), such in-situ formed nanoparticles were composed of both stacks of organoclay nanoplatelets and also isolated nanoplatelets typical for fully exfoliated organoclays.

Micro cold forming tools from hypereutectoid 8%Cr-steels by spray forming and selective laser melting

Abstract In cold forming several options exist to meet the requirements of producing specific products, e. g. tool shape and lubrication. In the field of micro cold working such measures are not available. When geometrical tool dimensions become smaller the microstructure of the tool materials can interfere with tool making and the forming process, respectively. Aim of this work was to produce hypereutectoid Cr-steels by spray forming and selective laser melting to provide adapted tool materials. Spray forming is regarded as a fast primary forming process with subsequent hot working steps. Selective laser melting is a rapid tooling process for producing near net shape products from powder. Both techniques are known to deliver fine and homogeneous microstructure due to rapid solidification. Powder from spray forming overspray was used as feedstock for selective laser melting. Results are shown from alloy variations in vanadium, niobium and carbon of the steel X110CrMoV8-2 and their effect on microstructure, mechanical properties and friction coefficient of the materials using the strip-pulling test after hardening and tempering. The generated materials with hardness up to 63 HRC are micro-machinable to micro swaging tools with working diameter of less than 1 mm.

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.

Rapid tooling route selection and evaluation for sand and investment casting

Today, a number of direct routes using rapid prototyping (RP) processes (fused deposition modelling (FDM), laminated object manufacturing (LOM), stereolithography apparatus (SLA), selective laser sintering (SLS), etc.), as well as indirect routes (RP coupled with secondary or soft-tooling processes like RTV vacuum casting) are available for rapid fabrication of tooling for sand and investment casting processes. Each route is unique in terms of geometric, material, quality and cost characteristics; no comprehensive database of their capabilities has been reported, especially for metal casting applications. The problem of selecting the optimal rapid tooling (RT) route is a complex multi-criteria decision-making problem. This paper describes a systematic approach for RT route selection and planning. A database of RT process capabilities was generated through benchmarking experiments, covering 20 different widely used RT routes (both direct and indirect: two- and three-step processes) involving an impeller pattern. In this approach, RT process route selection involves translating the tooling requirements specified by the casting engineer into weighted tooling attributes using quality function deployment and analytic network process (QFD-ANP), which along with part specifications is used for RT route selection by calculating the overall process compatibility indices. The routes are ranked as per the value of the overall compatibility index. Once the optimal route is selected, process planning is carried out by retrieving a similar process plan using case-based reasoning (CBR). The methodology has been implemented in a software program using Visual C + + programming language in a Windows environment. The methodology is demonstrated and validated with an industrial example of a separator body casting. It has proved to be a robust evaluation and decision-making tool for selecting appropriate tooling route for a given casting based on customer requirements.

Development of precision spray forming for rapid tooling

The aim of the work is to improve the capability of the precision spray forming (PSF) rapid tooling process so that it can be extended to various applications. This work comprises the upgrading of the current spray-forming machine from single atomizer to twin atomizers, so that the capability is much improved in terms of insert size and complexity. As a result, the insert size is increased from about 200 mm to 400 mm in diameter, and the process is more reliable to make complex structures. Know-how is accumulated for making large and/or complex inserts with controllable surface and internal soundness. A process of spray forming conformal cooling channels in die inserts or other components used at elevated temperatures is also developed and various mould inserts are spray formed. In this paper the plant modification is described. It is shown that the twin atomizers are more reliable in spray forming small inserts of about 200 mm in diameter and of high complexity than the single atomizer system. Spray forming of disc type inserts up to 400 mm diameter is demonstrated. Influence of deposition temperature and substrate moving speed, as well as the treatment of the ceramic mould surface is determined and the technical measures to prevent surface defects related to large insert spray forming are specified.

Development, evaluation, and selection of rapid tooling process chains for sand casting of functional prototypes

This paper discusses the results obtained from studies on different rapid tooling process chains for improved design and manufacture of foundry equipment for sand casting of prototypes in final material for functional and pre-production tests of vehicles, using the three-dimensional printing process as core technology. Subsequently, while considering aspects such as time, cost, quality (accuracy and surface roughness), and tool life, a framework for evaluation and selection of the most suitable process chain in accordance to specific requirements is presented. Apart from only using these process chains for prototype manufacturing, initial results from a study to apply one of these process chains in automated sand casting full production is also presented. This research builds on an in-depth characterization of the accuracy and repeatability of a three-dimensional printing process.