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The purpose of this paper is to present the results of an investigation into the effect of injection molding process parameters on the performance of direct metal laser sintered (DMLS) mold in producing quality Zytel nylon 66 plastic parts with consistency in part shrinkage and shot/part weight.

The injection mold for an industrial component (hub gear) was fabricated in EOS M‐250 machine using bronze‐based material. The effect of four injection molding parameters (injection pressure, melt temperature, speed, and injection time) on part shrinkage and weight were studied experimentally using L₉ orthogonal array. The weight of the part just after ejecting from the cavity, and the average shrinkage measured after cooling, were used in grey relational analysis technique to assess the effect of each molding parameter. Further, surface properties such as surface finish, wear, scratch and corrosion resistance tests were conducted on DMLS mold material samples, in order to evaluate its use in rapid manufacturing applications.

The study found that injection speed and melt temperature have significant influence on part weight and shrinkage. The optimized molding process variables were slightly more in the case of DMLS molds as compared with the parameters suggested in the plastic datasheet. Scanning electro microscope (SEM) analysis of the mold surface after producing 5,000 glass filled Nylon 66 (Zytel) moldings did not indicate any surface degradation, confirming the use of DMLS mold in rapid manufacturing of few thousands of moldings.

The grey relational analysis does not compute the effect of any two or more variables together unlike ANNOVA. Second, this study alone is not enough to estimate life of DMLS mold, although 5,000 glass filled nylon 66 moldings are successfully produced without any damage on mold surface.

This investigation demonstrates a generic approach of using grey relational analysis to quantify the effect of different molding process variables on selected quality parameters. This method can be easily extended for new processes and materials. The preliminary tests on surface finish, scratch, wear and corrosion resistance performed on DMLS mold samples have highlighted the need for improving surface properties to enhance their life. The authors are currently working on hard coating of DMLS molds as one of the solutions.

Use of grey relational analysis is new to the problem of injection molding process optimization. Moreover, effect of injection molding parameters on part weight and shrinkage in DMLS mold has not been studied previously. This study helps while considering DMLS molds for manufacturing few thousands of parts.

The purpose of this paper is to optimise the electro‐discharge machining (EDM) parameters and investigate feasibility of using direct metal laser sintering (DMLS) parts as EDM electrodes.

In this paper the effects of discharge current, pulse‐on‐time, flushing pressure are optimized for minimum tool wear rate (TWR), maximum metal removal rate (MRR) and minimum surface roughness (Ra). Taguchi‐based L₉ orthogonal array has been used for performing experiments on EDM machining of EN 24 steel using DMLS electrodes. The grey relational analysis combined with ANOVA techniques have been employed to determine the optimal level as well as their significance.

Experimental results have shown that the performance characteristics of the EDM process (TWR, MRR and surface roughness) using DMLS electrode can be quantified and controlled effectively by grey relational approach presented in the study. Current is found to be the most affective parameter in EDM machining using DMLS electrode. Excessive DMLS tool (electrode) wear was also reported, which limits the use of DMLS tool for EDM machining and it has been found out that porosity (which was about 20 per cent) was one of the primary cause.

This paper was focused on understanding the effects of important EDM parameters on three performance characteristics (TWR, MRR and surface roughness). While this study identifies that DMLS electrode wear rate is high and porosity could be one of the main cause, presently it does not cover the investigations on reducing the porosity level and its implications.

The DMLS material had shown huge potential to be used as EDM electrode. The current investigation established a structured experimental approach to understand the effects of EDM parameters on multi response characteristics. The results derived from this study helps to focus future research on two aspects including enriching the copper content and reducing the porosity level, thereby the benefits of lead time reduction in EDM electrode making could be realized.

The previous research attempts were not focussed on optimising the EDM machining process using rapid tooling electrodes. With the best of author's knowledge none of the researchers have reported these aspects especially for DMLS electrodes. Application of grey relational analysis for performance evaluation of rapid tooling‐based EDM electrodes (DMLS electrodes) appear to be completely new.

The purpose of this paper is to report on the use of a combination of indirect selective laser sintering (SLS) and machining processes to create injection mould tools, an approach designed to offer the capability to create conformal cooling channels in the core/cavity inserts together with the levels of surface finish and accuracy required to meet typical injection mould tool specifications.

The research has been pursued through three industrial case studies. In each study, existing injection mold inserts have been redesigned to give a conformally cooled tool. These have then been manufactured using indirect SLS, high‐speed machining, electro‐discharge machining and polishing. The inserts have been evaluated in industrial trials to assess their performance in terms of cycle time, energy usage, durability and quality. The insights gained from the three case studies have then been developed into a series of design rules, which may be applied in the development of tooling for new applications.

The results show that significant productivity improvements and energy use reductions in injection moulding are possible through the implementation of conformal cooling, and that the material has sufficient wear resistance to be used in production applications. However, it is recommended that modelling is always used to understand the impact of conformal cooling channels, and manufacture is carefully planned to ensure that the required internal geometry is created.

The paper presents new results on the impact of conformal cooling on the productivity and energy efficiency of injection moulding, and on the durability of the indirect SLS material in injection moulding applications. A novel “cut‐out volume” technique for powder clearing is also presented, along with a set of design rules to support further application of the work.

This study aims to evaluate the performance of injection molding inserts produced via rapid and conventional manufacturing techniques considering the mechanical and thermal performance of the tools as well as the resulting molded part quality.

Three insert materials and manufacturing techniques were evaluated, jetted photopolymer (PolyJet) 3D printing using digital ABS, direct metal laser sintering (DMLS) using bronze and machining using stainless steel. Molding trials were performed, and the insert surface temperature, longevity and part properties were evaluated. Complementary information was acquired using computer simulation.

Similar behavior and part quality were observed in machined and DMLS inserts. The latter were used for 500 cycles without any signs of failure. PolyJet inserts had increased cycle time and slower rate of cooling which increased shrinkage and crystallinity in the molded parts. PolyJet inserts could be produced quickly at a lower cost than machined or DMLS inserts.

Cooling within the insert was not studied; inserts were cooled indirectly by the mold plates behind them. Subsequent studies will incorporate cooling lines directly into the inserts.

Little research has been done to understand the thermal behavior of inserts manufactured via rapid tooling techniques. This study provides a direct comparison between rapid tooling techniques, which is supported by simulation results and analysis of the actual molding properties.

This work aims to investigate the direct production of electrical discharge machining (EDM) electrodes by means of the selective laser sintering (SLS) technique using a new non-conventional metal-matrix composite material (TiB₂-CuNi). The influence and optimization of the main SLS parameters on the densification behavior and porosity is experimentally studied. EDM experiments are also performed to evaluate the electrodes performance.

The new EDM electrode material used was a powder system composed of TiB₂ and CuNi. Making use of a designed systematic experimental methodology, the effects of layer thickness, laser scan speed and scan line spacing were optimized, where aspects such as densification behavior, porosity and surface morphology of the samples were analyzed through microstructural and surface analysis. EDM experiments were conducted under three different regimes in order to observe the electrodes behavior and performance. The results were compared with copper powder electrodes manufactured by SLS and EDMachined under the same conditions.

The experimental results showed that the direct SLS manufacturing of composite electrodes is feasible and promising. The laser scan speed has a high effect on the densification behavior of the samples, while the effect of scan line spacing on the porosity is more visible when the overlapping degree is considered. Surface morphology was not affected by the scan line spacing, whereas balling phenomenon was reported, regardless of the scan line spacing. The EDM results showed that the TiB₂-CuNi electrodes had a much superior performance than the copper powder electrodes made by SLS, regardless of the EDM regime applied.

Generally, the machine tool itself promotes some restrictions to the SLS process optimization. It is normally attributed to the characteristics of the laser type and the amount of energy that can be delivered to the powder bed. The present investigation could not cover all the optimization potential involved with the studied material due to limitations of the SLS machine tool used.

Significant results on the direct SLS manufacturing of a new non-conventional composite material, which has a great technological potential to be used as an EDM electrode material, are presented. Valuable guidelines are given in regard to the SLS optimization of TiB₂-CuNi material and its performance as an EDM electrode. This work also provides a systematic methodology designed to be applied to the SLS process to produce EDM electrodes.

This study aims to investigate a systematic approach to the production and use of additively manufactured injection mould inserts in product development (PD) processes. For this purpose, an evaluation of the additive tooling design method (ATDM) is performed.

The evaluation of the ATDM is conducted within student workshops, where students develop products and validate them using AT-prototypes. The evaluation process includes the analysis of work results as well as the use of questionnaires and participant observation.

This study shows that the ATDM can be successfully used to assist in producing and using AT mould inserts to produce valid AT prototypes. As a reference for the implementation of AT in industrial PD, extracts from the work of the student project groups and suitable process parameters for prototype production are presented.

This paper presents the application and evaluation of a method to support AT in PD that has not yet been scientifically evaluated.

The purpose of this study is to highlight the direct fabrication of rapid tooling (RT) with desired mechanical, tribological and thermal properties using fused deposition modelling (FDM) process. Further, the review paper demonstrated development procedure of alternative feedstock filament of low-cost composite material for FDM to extend the range of RT applications.

The alternative materials for FDM and their processing requirements for fabrication in filament form as reported by various researchers have been summarized. The literature demonstrates the role of various post-processing techniques on surface finish of FDM prints. Further, low-cost materials for feedstock filament have been investigated experimentally to check their adaptability/suitability for commercial FDM setup. The approach was to realize the requirements of FDM (melt flow rate, flexibility, stiffness, glass transition temperature and mechanical strength), necessary for the successful run of an alternative filament. The effect of constituents (additives, plasticizers, surfactants and fillers) in polymeric matrix on mechanical, tribological and thermal properties has been investigated.

It is possible to develop composite material feedstock as filament for commercial FDM setup without changing its hardware and software. Surface finish of the parts can further be improved by applying various post-processing techniques. Most of the composite parts have high mechanical strength, hardness, thermal stability, wear resistant and better bond formation than standard material parts.

Future research may be focused on improving the surface quality of parts fabricated with composite feedstock, solving issues related to the uniform distribution of filled materials during the fabrication of feedstock filament which in turns further increases mechanical strength, high dimensional stability of composite filament and transferring the technology from laboratory scale to various industrial applications.

Potential applications of direct fabrication with RT includes rapid manufacturing (RM) of metal-filled parts and ceramic-filled parts (which have complex shape and cannot be rapidly made by any other manufacturing techniques) in the field of biomedical and dentistry.

This new manufacturing methodology is based on the proper selection and processing of various materials and additives to form high-performance, low-cost composite material feedstock filament (which fulfil the necessary requirements of FDM process). Finally, newly developed feedstock filament material has both quantitative and qualitative advantage in RT and RM applications as compared to standard material filament.

Fused deposition modelling (FDM) has gained popularity owing to its capability of producing complex and customized profiles at relatively low cost and in shorter periods. The study aims to extend the use of FDM printers for 3D printing of low melting point alloy (LMPA), which has applications in the electronics industry, rapid tooling, biomedical, etc.

Solder is the LMPA with alloy’s melting temperature (around 200°C) lower than the parent metals. The most common composition of the solder, which is widely used, is tin and lead. However, lead is a hazardous material having environmental and health deteriorating effects. Therefore, lead-free Sn89Bi10Cu non-eutectic alloy in the form of filament was used. The step-by-step method has been used to identify the process window for temperature, print speed, filament length (E) and layer height. The existing FDM printer was customized for the present work.

Analysis of infrared images has been done to understand discontinuity at a certain range of process parameters. The effect of printing parameters on inter-bonding, width and thickness of the layers has also been studied. The microstructure of the parent material and deposited bead has been observed. Conclusions were drawn out based on the results, and the scope for the future has been pointed out.

The experiments resulted in the process window identification of print speed, extrusion temperature, filament length and layer height of Sn89Bi10Cu which is not done previously.

The purpose of this paper is to present the results of an investigation on the straightness, flatness and circularity achievable on two direct RT methods: direct metal laser sintering (DMLS) and stereolithography (SLA).

The steps included manufacturing of samples in eight custom designs with widely used geometric features, intelligent sampling of measurement data, and estimation of corresponding form tolerance by the least square method (LSM). The region elimination adaptive search‐based sampling method involved selecting additional sampling points around the maximum deviation in both positive and negative directions from the corresponding reference feature. The LSM solutions, which are commonly used in metrology, are used to estimate the form tolerances considering the best points along with initial measurement data points.

Application of the region elimination search‐based sampling method enables form tolerance estimation from a limited number of sample measurements. The study of the DMLS and SLA processes suggested that form accuracy of SLA samples are relatively poor, though their dimensional accuracy is much better than DMLS.

This paper was focused on estimating the form tolerances based on limited number of measurement data using region elimination search‐based sampling technique. It was assumed that build process parameters suggested by the material and RP systems vendors gives optimum results, presently it does not cover the effect of geometry and other causes of errors on form accuracy.

There are two major applications of this investigation and the corresponding knowledge base: evaluating the process capabilities of different rapid tooling processes for comparison and for selecting an appropriate process; and allocating tolerance based on manufacturability considerations, so that the designs are compatible with the process, leading to fewer iterations. A similar approach can be used for updating the capabilities of an improved process as well as include newer processes to develop a comprehensive database of RT process capabilities.

In most of the previous benchmarking studies, a given RT process is compared with conventional practice or a limited number of other RT processes, the capabilities in terms of dimensional accuracy, form tolerance, and surface properties (surface finish, wear, and scratch resistance) have not been studied very well. To the best of authors' knowledge, no efforts have been made to estimate form tolerances of the parts or tooling produced by rapid prototyping and tooling processes. Application of the region elimination search‐based sampling technique enables estimation of form tolerances that saves costly experimentations. It appears to be completely new in the rapid prototyping and tooling domain.

The following research seeks to focus on optimizing the fused deposition modeling (FDM) process of RP systems.

Early stages of this study are based on the Taguchi method in establishing rapid prototyping building factors and their various levels. The ultimate tensile strength, dimension accuracy and surface roughness (SR), are analyzed. Through analysis of variance (ANOVA) and contribution approximation, significant building factors of each quality characteristic and optimal factors level combinations of each best quality characteristic are obtained. The main steps are setting the weight for each quality characteristic of the previous Taguchi method, obtaining the estimated multiple building quality characteristics through integrating the Gray theory, and obtaining a set of optimal building factors. Finally, the result is verified by the Gray theory and the technique for order preference by similarity to ideal solution (TOPSIS) evaluation method.

It is proven that optimal multiple quality characteristic combinations of building factors can be obtained by integrating the Gray theory and the Taguchi method. The result is further verified by the TOPSIS evaluation method, showing that the model can acquire multiple building quality characteristics of rapid prototyping.

The method is only applied to FDM in this paper but a similar approach could be applied to other RP systems.

RP system use is limited by low product strength, bad SR, and the high dimension errors. This research demonstrates how optimizing the FDM process can improve this situation.

The originality of this paper lies in optimizing the rapid prototyping process by integrating the Taguchi method with the Gray relational analysis.