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Dr. Christian Griffiths
Department of Engineering, Swansea University, Swansea, UK

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0 Biomimetics
0 Machine Design
0 3D printing
0 Medical engineering
0 micro and nano fabrication

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micro and nano fabrication
3D printing

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Research article
Published: 14 May 2021 in Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture
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Collaborative robots are becoming increasingly important for advanced manufacturing processes. The purpose of this paper is to determine the capability of a novel Human-Robot-interface to be used for machine hole drilling. Using a developed voice activation system, environmental factors on speech recognition accuracy are considered. The research investigates the accuracy of a Mel Frequency Cepstral Coefficients-based feature extraction algorithm which uses Dynamic Time Warping to compare an utterance to a limited, user-dependent dictionary. The developed Speech Recognition method allows for Human-Robot-Interaction using a novel integration method between the voice recognition and robot. The system can be utilised in many manufacturing environments where robot motions can be coupled to voice inputs rather than using time consuming physical interfaces. However, there are limitations to uptake in industries where the volume of background machine noise is high.

ACS Style

B Birch; Ca Griffiths; A Morgan. Environmental effects on reliability and accuracy of MFCC based voice recognition for industrial human-robot-interaction. Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 2021, 1 .

AMA Style

B Birch, Ca Griffiths, A Morgan. Environmental effects on reliability and accuracy of MFCC based voice recognition for industrial human-robot-interaction. Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture. 2021; ():1.

Chicago/Turabian Style

B Birch; Ca Griffiths; A Morgan. 2021. "Environmental effects on reliability and accuracy of MFCC based voice recognition for industrial human-robot-interaction." Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture , no. : 1.

Journal article
Published: 12 March 2021 in Micromachines
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This paper studies the forces acting upon the Intraosseous Transcutaneous Amputation Prosthesis, ITAP, that has been designed for use in a quarter amputated femur. To design in a failure feature, utilising a safety notch, which would stop excessive stress, σ, permeating the bone causing damage to the user. To achieve this, the topology of the ITAP was studied using MATLAB and ANSYS models with a wide range of component volumes. The topology analysis identified critical materials and local maximum stresses when modelling the applied loads. This together with additive layer manufacture allows for bespoke prosthetics that can improve patient outcomes. Further research is needed to design a fully functional, failure feature that is operational when extreme loads are applied from any direction. Physical testing is needed for validation of this study. Further research is also recommended on the design so that the σ within the ITAP is less than the yield stress, σs, of bone when other loads are applied from running and other activities.

ACS Style

Euan Langford; Christian Griffiths; Andrew Rees; Josh Bird. The Micro Topology and Statistical Analysis of the Forces of Walking and Failure of an ITAP in a Femur. Micromachines 2021, 12, 298 .

AMA Style

Euan Langford, Christian Griffiths, Andrew Rees, Josh Bird. The Micro Topology and Statistical Analysis of the Forces of Walking and Failure of an ITAP in a Femur. Micromachines. 2021; 12 (3):298.

Chicago/Turabian Style

Euan Langford; Christian Griffiths; Andrew Rees; Josh Bird. 2021. "The Micro Topology and Statistical Analysis of the Forces of Walking and Failure of an ITAP in a Femur." Micromachines 12, no. 3: 298.

Preprint content
Published: 24 February 2021
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This paper aims to identify the capability of a highly flexible industrial robot modified with a high-speed machine spindle for drilling of Aluminum 6061-T6. With a focus on drilling feedrate, spindle speed and pecking cycle, the hole surface roughness and exit burr heights were investigated using the Taguchi design methodology. A state of the art condition monitoring system was used to identify the vibrations experienced during drilling operation and to establish which robot pose had increased stiffness, and thus the optimum workspace for drilling. When benchmarked against a CNC machine the results show that the CNC was capable of producing the best surface finish and the lowest burr heights. However, the robot system matched and outperformed the CNC in several experiments and there is much scope for further optimization of the process. Overall the proposed drilling system is far more flexible than a CNC milling machine and when considering the optimized drilling of aerospace aluminum this robotic solution has the potential to drastically improve productivity.

ACS Style

Benjamin Pereira; Christian Andrew Griffiths; Benjamin Birch; Andrew Rees. Optimization of an Autonomous robotic drilling system for the Machining of Aluminum Aerospace Alloys. 2021, 1 .

AMA Style

Benjamin Pereira, Christian Andrew Griffiths, Benjamin Birch, Andrew Rees. Optimization of an Autonomous robotic drilling system for the Machining of Aluminum Aerospace Alloys. . 2021; ():1.

Chicago/Turabian Style

Benjamin Pereira; Christian Andrew Griffiths; Benjamin Birch; Andrew Rees. 2021. "Optimization of an Autonomous robotic drilling system for the Machining of Aluminum Aerospace Alloys." , no. : 1.

Journal article
Published: 20 May 2020 in Materials
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The pursuit of polymer parts produced through foam injection moulding (FIM) that have a comparable surface roughness to conventionally processed components are of major relevance to expand the application of FIM. Within this study, 22% talc-filled copolymer polypropylene (PP) parts were produced through FIM using both a physical and chemical blowing agent. A design of experiments (DoE) was performed whereby the processing parameters of mould temperatures, injection speeds, back-pressure, melt temperature and holding time were varied to determine their effect on surface roughness, Young’s modulus and tensile strength. The results showed that mechanical performance can be improved when processing with higher mould temperatures and longer holding times. Also, it was observed that when utilising chemical foaming agents (CBA) at low-pressure, surface roughness comparable to that obtained from conventionally processed components can be achieved. This research demonstrates the potential of FIM to expand to applications whereby weight saving can be achieved without introducing surface defects, which has previously been witnessed within FIM.

ACS Style

Gethin Llewelyn; Andrew Rees; Christian Griffiths; Martin Jacobi. A Design of Experiment Approach for Surface Roughness Comparisons of Foam Injection-Moulding Methods. Materials 2020, 13, 2358 .

AMA Style

Gethin Llewelyn, Andrew Rees, Christian Griffiths, Martin Jacobi. A Design of Experiment Approach for Surface Roughness Comparisons of Foam Injection-Moulding Methods. Materials. 2020; 13 (10):2358.

Chicago/Turabian Style

Gethin Llewelyn; Andrew Rees; Christian Griffiths; Martin Jacobi. 2020. "A Design of Experiment Approach for Surface Roughness Comparisons of Foam Injection-Moulding Methods." Materials 13, no. 10: 2358.

Journal article
Published: 30 March 2020 in Micromachines
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Micro-injection moulding (µ-IM) is a fabrication method that is used to produce miniature parts on a mass production scale. This work investigates how the process parameter settings result in adiabatic heating from gas trapped and rapidly compressed within the mould cavity. The heating of the resident air can result in the diesel effect within the cavity and this can degrade the polymer part in production and lead to damage of the mould. The study uses Autodesk Moldflow to simulate the process and identify accurate boundary conditions to be used in a gas law model to generate an informed prediction of temperatures within the moulding cavity. The results are then compared to physical experiments using the same processing parameters. Findings from the study show that without venting extreme temperature conditions can be present during the filling stage of the process and that venting solutions should be considered when using µ-IM.

ACS Style

Matthew Tucker; Christian A. Griffiths; Andrew Rees; Gethin Llewelyn. High Temperature Adiabatic Heating in µ-IM Mould Cavities—A Case for Venting Design Solutions. Micromachines 2020, 11, 358 .

AMA Style

Matthew Tucker, Christian A. Griffiths, Andrew Rees, Gethin Llewelyn. High Temperature Adiabatic Heating in µ-IM Mould Cavities—A Case for Venting Design Solutions. Micromachines. 2020; 11 (4):358.

Chicago/Turabian Style

Matthew Tucker; Christian A. Griffiths; Andrew Rees; Gethin Llewelyn. 2020. "High Temperature Adiabatic Heating in µ-IM Mould Cavities—A Case for Venting Design Solutions." Micromachines 11, no. 4: 358.

Review paper
Published: 23 January 2020 in Microsystem Technologies
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Microgrippers are commonly used for micromanipulation of micro-objects from 1 to 100 µm and attain features of reliable accuracy, low cost, wide jaw aperture and variable applied force. This paper aim is to review the design of different microgrippers which can manipulate and assemble µ-wire to PCB connectors. A review was conducted on microgrippers’ technologies, comparing fundamental components of structure and actuators’ types, which determined the most suitable design for the required micromanipulation task. Various microgrippers’ design was explored to examine the suitability and the execution of requirements needed for successful micromanipulation.

ACS Style

H. Llewellyn-Evans; C. A. Griffiths; A. Fahmy. Microgripper design and evaluation for automated µ-wire assembly: a survey. Microsystem Technologies 2020, 26, 1745 -1768.

AMA Style

H. Llewellyn-Evans, C. A. Griffiths, A. Fahmy. Microgripper design and evaluation for automated µ-wire assembly: a survey. Microsystem Technologies. 2020; 26 (6):1745-1768.

Chicago/Turabian Style

H. Llewellyn-Evans; C. A. Griffiths; A. Fahmy. 2020. "Microgripper design and evaluation for automated µ-wire assembly: a survey." Microsystem Technologies 26, no. 6: 1745-1768.

Accepted manuscript
Published: 17 January 2020 in Engineering Research Express
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A parallelogram flexible hinge microgripper design made from aluminium alloy 7075-T6 material has been designed and manufactured with purpose of being able to manipulate a 25 µm diameter platinum wire. The structure is unique in that it is actuated using a shape memory alloy. The actuator circuit is designed so that during operation one microgripper arm remains ridged during the gripping process to ensure a consistent reference point whilst the other gripper arm flexes. The focus of the study is on the shape memory alloys capability in terms of providing the correct jaw displacement and displacement time in relation to the circuit input current. The results show a repeatable relationship between displacement and the applied current. In addition, it was shown that the current across the SMA wire increases it dramatically impacts the time taken for the jaws to close. The displacement time is also due to the resistive mechanical force of the microgripper body during operation. Overall the shape memory alloy actuator and optimised gripper design are shown to be useful for a number of industrial applications.

ACS Style

Hefin Llewellyn-Evans; Christian Andrew Griffiths; Ashraf Fahmy. An experimental study into displacement of a shape memory alloy actuated robotic microgripper. Engineering Research Express 2020, 2, 015027 .

AMA Style

Hefin Llewellyn-Evans, Christian Andrew Griffiths, Ashraf Fahmy. An experimental study into displacement of a shape memory alloy actuated robotic microgripper. Engineering Research Express. 2020; 2 (1):015027.

Chicago/Turabian Style

Hefin Llewellyn-Evans; Christian Andrew Griffiths; Ashraf Fahmy. 2020. "An experimental study into displacement of a shape memory alloy actuated robotic microgripper." Engineering Research Express 2, no. 1: 015027.

Journal article
Published: 01 January 2020 in AIMS Bioengineering
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ACS Style

Joshua Bird; Euan Langford; Christian Griffiths. A study into the fracture control of 3D printed intraosseous transcutaneous amputation prostheses, known as ITAPs. AIMS Bioengineering 2020, 7, 29 -42.

AMA Style

Joshua Bird, Euan Langford, Christian Griffiths. A study into the fracture control of 3D printed intraosseous transcutaneous amputation prostheses, known as ITAPs. AIMS Bioengineering. 2020; 7 (1):29-42.

Chicago/Turabian Style

Joshua Bird; Euan Langford; Christian Griffiths. 2020. "A study into the fracture control of 3D printed intraosseous transcutaneous amputation prostheses, known as ITAPs." AIMS Bioengineering 7, no. 1: 29-42.

Journal article
Published: 17 November 2019 in Polymers
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Unfilled and talc-filled Copolymer Polypropylene (PP) samples were produced through low-pressure foam-injection molding (FIM). The foaming stage of the process has been facilitated through a chemical blowing agent (C6H7NaO7 and CaCO3 mixture), a physical blowing agent (supercritical N2) and a novel hybrid foaming (combination of said chemical and physical foaming agents). Three weight-saving levels were produced with the varying foaming methods and compared to conventional injection molding. The unfilled PP foams produced through chemical blowing agent exhibited the strongest mechanical characteristics due to larger skin wall thicknesses, while the weakest were that of the talc-filled PP through the hybrid foaming technique. However, the hybrid foaming produced superior microcellular foams for both PPs due to calcium carbonate (CaCO3) enhancing the nucleation phase.

ACS Style

Gethin Llewelyn; Andrew Rees; Christian A. Griffiths; Martin Jacobi. A Novel Hybrid Foaming Method for Low-Pressure Microcellular Foam Production of Unfilled and Talc-Filled Copolymer Polypropylenes. Polymers 2019, 11, 1896 .

AMA Style

Gethin Llewelyn, Andrew Rees, Christian A. Griffiths, Martin Jacobi. A Novel Hybrid Foaming Method for Low-Pressure Microcellular Foam Production of Unfilled and Talc-Filled Copolymer Polypropylenes. Polymers. 2019; 11 (11):1896.

Chicago/Turabian Style

Gethin Llewelyn; Andrew Rees; Christian A. Griffiths; Martin Jacobi. 2019. "A Novel Hybrid Foaming Method for Low-Pressure Microcellular Foam Production of Unfilled and Talc-Filled Copolymer Polypropylenes." Polymers 11, no. 11: 1896.

Technical paper
Published: 03 September 2019 in Microsystem Technologies
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Microgrippers are commonly used for micromanipulation of micro-objects with dimensions from 1 to 100 µm and attain features of reliable accuracy, low cost, wide jaw aperture and variable applied force. This paper studies the design process, simulation, and testing of a microgripper which can manipulate and assemble a platinum resistance temperature probe, made from a 25 µm diameter platinum wire, a 20 mm diameter tinned copper wire, and a printed circuit board type connector. Various microgripper structures and actuator types were researched and reviewed to determine the most suitable design for the required micromanipulation task. Operation tests using SolidWorks and ANSYS software were conducted to test a parallelogram structure with flexible single-notch hinges. The best suited material was found to be Aluminium alloy 7075-T6 as it was capable of producing a large jaw tip displacement of 0.7 mm without exceeding its tensile yield strength limit. A shape memory alloy was chosen as a choice of actuator to close the microgripper jaws. To ensure a repeatably accurate datum point, the final microgripper consisted of a fixed arm and a flexible arm. An optimisation process using ANSYS studied the hinge thickness and radius dimensions of the microgripper which improved its deflection whilst reducing the experienced stress.

ACS Style

H. Llewellyn-Evans; C. A. Griffiths; A. A. Fahmy. Design process and simulation testing of a shape memory alloy actuated robotic microgripper. Microsystem Technologies 2019, 26, 885 -900.

AMA Style

H. Llewellyn-Evans, C. A. Griffiths, A. A. Fahmy. Design process and simulation testing of a shape memory alloy actuated robotic microgripper. Microsystem Technologies. 2019; 26 (3):885-900.

Chicago/Turabian Style

H. Llewellyn-Evans; C. A. Griffiths; A. A. Fahmy. 2019. "Design process and simulation testing of a shape memory alloy actuated robotic microgripper." Microsystem Technologies 26, no. 3: 885-900.

Journal article
Published: 01 January 2019 in AIMS Electronics and Electrical Engineering
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ACS Style

M. P. Cooper; C. A. Griffiths; K. T. Andrzejewski; C. Giannetti. Motion optimisation for improved cycle time and reduced vibration in robotic assembly of electronic components. AIMS Electronics and Electrical Engineering 2019, 3, 274 -289.

AMA Style

M. P. Cooper, C. A. Griffiths, K. T. Andrzejewski, C. Giannetti. Motion optimisation for improved cycle time and reduced vibration in robotic assembly of electronic components. AIMS Electronics and Electrical Engineering. 2019; 3 (3):274-289.

Chicago/Turabian Style

M. P. Cooper; C. A. Griffiths; K. T. Andrzejewski; C. Giannetti. 2019. "Motion optimisation for improved cycle time and reduced vibration in robotic assembly of electronic components." AIMS Electronics and Electrical Engineering 3, no. 3: 274-289.

Original article
Published: 05 September 2018 in The International Journal of Advanced Manufacturing Technology
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Adoption of robots in the manufacturing environment is a way to improve productivity, and the assembly of electronic components has benefited from the adoption of highly dedicated automation equipment. Traditionally, articulated 6-axis robots have not been used in electronic surface mount assembly. However, the need for more flexible production systems that can be used for low to medium production builds means that these robots can be used due to their high degrees of flexibility, excellent repeatability and increasingly lower investment costs. This research investigated the application of an articulated robot with six degrees of freedom to assemble a multi-component printed circuit board (PCB) for an electronic product. A heuristic methodology using a genetic algorithm was used to plan the optimal sequence and identify the best location of the parts to the assembly positions on the PCB. Using the optimised paths, a condition monitoring method for cycle time evaluation was conducted using a KUKA KR16 assembly cell together with four different robot path motions. The genetic algorithm approach together with different assembly position iterations identified an optimisation method for improved production throughput using a non-traditional but highly flexible assembly method. The application of optimised articulated robots for PCB assembly can bridge the gap between manual assembly and the high-throughput automation equipment.

ACS Style

K. T. Andrzejewski; M. P. Cooper; C. A. Griffiths; C. Giannetti. Optimisation process for robotic assembly of electronic components. The International Journal of Advanced Manufacturing Technology 2018, 99, 2523 -2535.

AMA Style

K. T. Andrzejewski, M. P. Cooper, C. A. Griffiths, C. Giannetti. Optimisation process for robotic assembly of electronic components. The International Journal of Advanced Manufacturing Technology. 2018; 99 (9-12):2523-2535.

Chicago/Turabian Style

K. T. Andrzejewski; M. P. Cooper; C. A. Griffiths; C. Giannetti. 2018. "Optimisation process for robotic assembly of electronic components." The International Journal of Advanced Manufacturing Technology 99, no. 9-12: 2523-2535.

Journal article
Published: 01 January 2018 in AIMS Bioengineering
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ACS Style

E. Langford; C.A. Griffiths. The mechanical strength of additive manufactured intraosseous transcutaneous amputation prosthesis, known as the ITAP. AIMS Bioengineering 2018, 5, 133 -150.

AMA Style

E. Langford, C.A. Griffiths. The mechanical strength of additive manufactured intraosseous transcutaneous amputation prosthesis, known as the ITAP. AIMS Bioengineering. 2018; 5 (3):133-150.

Chicago/Turabian Style

E. Langford; C.A. Griffiths. 2018. "The mechanical strength of additive manufactured intraosseous transcutaneous amputation prosthesis, known as the ITAP." AIMS Bioengineering 5, no. 3: 133-150.

Chapter
Published: 17 October 2017 in Magnetoelastic Waves
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This chapter looks at the condition monitoring of the micro-injection moulding process (µ-IM). This manufacturing process has been applied successfully to a wide range of products in the micro-scale and is also an appropriate technology for manufacturing meso-parts with both micro- and nano-features. Improvement in the quality and the accuracy of parts made from polymers can be successfully achieved by determining the optimum conditions for replication. Process control in manufacturing is critical, and condition monitoring of µ-IM is a control method for improved understanding of the effects of selected parameter settings. This chapter reports on the condition monitoring methods used to improve the factors that affect part’s quality. For each of the examples, the Taguchi design of experiments (DOE) method is used together with demonstrations of various experimental set-ups and the acquisition of data. The chapter advises on the obtainment of information regarding the behaviour of the µ-IM and the significant factors affecting the process. The selected case studies demonstrate the condition monitoring of the cavity pressure, forces, temperature distribution and air evacuation. For each, the research findings are discussed and conclusions are made.

ACS Style

C. A. Griffiths. Condition Monitoring in Micro-Injection Moulding. Magnetoelastic Waves 2017, 121 -143.

AMA Style

C. A. Griffiths. Condition Monitoring in Micro-Injection Moulding. Magnetoelastic Waves. 2017; ():121-143.

Chicago/Turabian Style

C. A. Griffiths. 2017. "Condition Monitoring in Micro-Injection Moulding." Magnetoelastic Waves , no. : 121-143.

Journal article
Published: 16 August 2016 in Surface and Coatings Technology
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Microinjection moulding is a key enabling technology for replicating miniaturized components and parts with functional features at the micrometer and even sub-micrometer length scale. The micro moulding tools used in the process chain are critical for delivering high quality parts for the duration of the product life cycle, and recently tool coatings such as Diamond-like carbon (DLC) have been used to extend their use and enhance the performance. The micro injection moulding process has high injection speeds with cyclic heat transfer characteristics, and little is understood on how the localised heat transfer at the surface will influence the DLC surface coating delamination and cracking. In this research a microinjection moulding process using three different polymers, Polypropylene (PP), Acrylonitrile butadiene styrene (ABS) and Polyether ether ketone (PEEK) is studied. Finite element analysis (FEA) simulation is utilised to identify the process temperature factors that lead to tool thermal expansion and dimensional changes that directly impact the life cycle of the coating. The theoretical and FEA results show that the mould material and the two coatings experience a significantly different thermal expansion from each other. It has also been shown that at the micro scale heat loss at the tool surface is dominant, and the variation in heat has a significant influence on the different thermal expansion rates. In particular the DLC coated micro rib features are particularly susceptible to high variations in heat transfer. The research identifies areas of the tool surface that experience sudden heat variation across the part surface, and concludes that through process optimisation it is possible to reduce the potential for DLC coating delamination and cracking during service.

ACS Style

C.A. Griffiths; A. Rees; R.M. Kerton; O.V. Fonseca. Temperature effects on DLC coated micro moulds. Surface and Coatings Technology 2016, 307, 28 -37.

AMA Style

C.A. Griffiths, A. Rees, R.M. Kerton, O.V. Fonseca. Temperature effects on DLC coated micro moulds. Surface and Coatings Technology. 2016; 307 ():28-37.

Chicago/Turabian Style

C.A. Griffiths; A. Rees; R.M. Kerton; O.V. Fonseca. 2016. "Temperature effects on DLC coated micro moulds." Surface and Coatings Technology 307, no. : 28-37.

Research article
Published: 06 August 2016 in Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture
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As additive manufacturing expands from rapid prototyping into rapid production, it is becoming more important to consider the mechanical performance of candidate products in addition to their functional attributes as a prototype. This study demonstrates how a design of experiments approach can be used to optimise the tensile and notched bending properties of the materials used in the process, while also considering the time of production and material efficiency. Such an approach can allow manufacturers to optimise the build in terms of the time, cost and material properties according to the requirements of the product. The main conclusion of this study was that when considering the significant contributors, similar build parameters result in optimised properties for both specimen types. It was also found that the layer height, being insignificant to the mechanical properties of both specimens, was critical to the cost control in terms of build time and material usage. Thus, the maximum layer height could be used to incorporate cost control into the design without affecting final performance.

ACS Style

Chrisian A Griffiths; Jack Howarth; Gabriela De Almeida-Rowbotham; Andrew Rees. A design of experiments approach to optimise tensile and notched bending properties of fused deposition modelling parts. Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 2016, 230, 1502 -1512.

AMA Style

Chrisian A Griffiths, Jack Howarth, Gabriela De Almeida-Rowbotham, Andrew Rees. A design of experiments approach to optimise tensile and notched bending properties of fused deposition modelling parts. Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture. 2016; 230 (8):1502-1512.

Chicago/Turabian Style

Chrisian A Griffiths; Jack Howarth; Gabriela De Almeida-Rowbotham; Andrew Rees. 2016. "A design of experiments approach to optimise tensile and notched bending properties of fused deposition modelling parts." Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 230, no. 8: 1502-1512.

Journal article
Published: 30 July 2016 in Journal of Cleaner Production
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Direct digital manufacture and additive manufacture has expanded from rapid prototyping into rapid production and has the possibility to produce personalised high quality products with the batch size of one. Affordable additive manufacturing machines and open source software enables a wide spectrum of users. With a populace empowered with the possibility of producing their own products, this disruptive technology will inevitably lead to a change in energy and material consumption. With such an unpredictable impact on society it is timely to consider the economic and environmental issues of growth in this sector. This work demonstrates a Design of Experiments approach for part optimisation with a consideration of scrap weight, part weight, energy consumption and production time. The main conclusion of this study was that through optimisation of machine build parameters a desired response is possible and compromises between output responses such as scrap and production time can be identified. The research also showed that identical build parameters for different designs can yield different output responses, highlighting the importance of developing design specific models. The scientific value of the work lies in the contribution of new data sets for models in additive manufacturing. Together with the optimisation method adopted, the results allow for a more detailed and accurate assessment of the economic and environmental impact of 3D printed products at the design stage.

ACS Style

C.A. Griffiths; J. Howarth; G. De Almeida-Rowbotham; A. Rees; R. Kerton. A design of experiments approach for the optimisation of energy and waste during the production of parts manufactured by 3D printing. Journal of Cleaner Production 2016, 139, 74 -85.

AMA Style

C.A. Griffiths, J. Howarth, G. De Almeida-Rowbotham, A. Rees, R. Kerton. A design of experiments approach for the optimisation of energy and waste during the production of parts manufactured by 3D printing. Journal of Cleaner Production. 2016; 139 ():74-85.

Chicago/Turabian Style

C.A. Griffiths; J. Howarth; G. De Almeida-Rowbotham; A. Rees; R. Kerton. 2016. "A design of experiments approach for the optimisation of energy and waste during the production of parts manufactured by 3D printing." Journal of Cleaner Production 139, no. : 74-85.

Journal article
Published: 01 January 2015 in Procedia CIRP
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This paper focuses on tuning the micro injection moulding process parameters. In this study four process parameters namely, barrel temperature, mould temperature, holding pressure and injection speed were considered. In order to capture their behaviour a L16 Orthogonal Array with two levels for each parameter was employed to produce the design of a 15mm x 20mm x 1mm microfluidic platform using Cyclic Olefin Copolymer (COC), a common polymer. The demoulding force was measured during the micro injection moulding process. The sixteen trials were repeated ten times to incorporate process variation, systematic and random noise in the experimental procedure. The results were analysed using Taguchi method to identify the influence of the process parameters upon the demoulding force and their sensitivity to noise. In addition, the results also indicated either the presence or absence of the two level interactions between these process parameters. This study has contributed to understanding the characteristics of these process parameters in terms of their main effects, interactions and sensitivity to noise and to tune them for their optimal performance

ACS Style

Michael Packianather; Christian Griffiths; Wan Kadir. Micro Injection Moulding Process Parameter Tuning. Procedia CIRP 2015, 33, 400 -405.

AMA Style

Michael Packianather, Christian Griffiths, Wan Kadir. Micro Injection Moulding Process Parameter Tuning. Procedia CIRP. 2015; 33 ():400-405.

Chicago/Turabian Style

Michael Packianather; Christian Griffiths; Wan Kadir. 2015. "Micro Injection Moulding Process Parameter Tuning." Procedia CIRP 33, no. : 400-405.

Conference paper
Published: 09 February 2012 in SPIE LASE
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Bio-inspired surfaces targeting functional characteristics such as anti-reflectivity, self-cleaning effects or a drag reduction are of significant interest to industry. In this feasibility study, process chains for the mass production of so-called shark skin structured surfaces are investigated. Due to their drag reduction properties, such bio-inspired surfaces are of relevance to a number of applications in which particular aqua- and aerodynamic characteristics are required. The design of the shark skin structure relies on a bio-mimetic analytical model to generate the 3D surface model necessary to achieve the targeted surface functionality. The process chains presented combine laser ablation as a method for micro structuring masters for high throughput replication employing injection molding. In particular, three different process chains that rely on micro second (μs), nano second (ns) and pico second (ps) laser ablation systems to pattern mold inserts were investigated. Then, these inserts were integrated into a tool for micro injection molding and replication trials were carried out. The results show that all three laser sources can be utilized to create this kind of micro cavities. This research indicates that these micro structures can be replicated successfully, but further work is required to optimize the replication and laser structuring process.

ACS Style

Steffen Scholz; Alexander Kolew; Christian Griffiths. Laser structuring of metallic mold inserts by using μs, ns, and ps-laser ablation. SPIE LASE 2012, 82440J -82440J-11.

AMA Style

Steffen Scholz, Alexander Kolew, Christian Griffiths. Laser structuring of metallic mold inserts by using μs, ns, and ps-laser ablation. SPIE LASE. 2012; ():82440J-82440J-11.

Chicago/Turabian Style

Steffen Scholz; Alexander Kolew; Christian Griffiths. 2012. "Laser structuring of metallic mold inserts by using μs, ns, and ps-laser ablation." SPIE LASE , no. : 82440J-82440J-11.

Journal article
Published: 09 May 2006 in The International Journal of Advanced Manufacturing Technology
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Micro-injection moulding is one of the key technologies for micro-manufacture because of its mass-production capability and relatively low component cost. The aspect ratios achievable in replicating micro features are one of the most important process characteristics and constitute a major manufacturing constraint in applying injection moulding in a range of micro-engineering applications. This research studies the effects of five process and one size factors on the achievable aspect ratios, and the role they play in producing micro components in different polymer materials. In particular, the following factors are considered: barrel temperature, mould temperature, injection speed, holding pressure, the existence of air evacuation and the sizes of micro features. The study revealed that the barrel temperature and the injection speed are the key factors affecting the aspect ratios of micro features replicated in PP and ABS. In case of POM, in addition to these two factors, the mould temperature is also an important factor for improving the replication capabilities of the micro-injection moulding process. For all three materials, an increase of feature sizes improves the melt flow. However, the melt fill of micro features does not increase linearly with the increase of their sizes.

ACS Style

Baichuan Sha; Stefan Dimov; Christian Griffiths; Michael S. Packianather. Micro-injection moulding: Factors affecting the achievable aspect ratios. The International Journal of Advanced Manufacturing Technology 2006, 33, 147 -156.

AMA Style

Baichuan Sha, Stefan Dimov, Christian Griffiths, Michael S. Packianather. Micro-injection moulding: Factors affecting the achievable aspect ratios. The International Journal of Advanced Manufacturing Technology. 2006; 33 (1-2):147-156.

Chicago/Turabian Style

Baichuan Sha; Stefan Dimov; Christian Griffiths; Michael S. Packianather. 2006. "Micro-injection moulding: Factors affecting the achievable aspect ratios." The International Journal of Advanced Manufacturing Technology 33, no. 1-2: 147-156.