Phill Dickens - Academia.edu (original) (raw)

Papers by Phill Dickens

Research paper thumbnail of Evaluation of laser ultrasonic testing for inspection of metal additive manufacturing

Laser 3D Manufacturing II, 2015

Research paper thumbnail of High Viscosity Jetting System for 3D Reactive Inkjet Printing

Research paper thumbnail of Jet array driven flow on the nozzle plate of an inkjet printhead in deposition of molten nylon materials

Journal of Materials Processing Technology, 2013

ABSTRACT During research into an inkjet-integrated manufacturing process, jetting of molten capro... more ABSTRACT During research into an inkjet-integrated manufacturing process, jetting of molten caprolactam was investigated using a piezoelectric drop-on-demand printhead. Due to the start-up purging step and the surface energy differences, a wetting melt layer on the printhead's nozzle plate was formed. With appropriate parameters, a stable jet array was made. However, contamination on the nozzle plate disturbed the jet stability resulting in jet trajectory errors and even jet failures. Particles were used to characterise the melt flow field on the nozzle plate during jetting when multiple nozzles were actuated. Particle tracking velocimetry revealed that movement of the particles followed a specific pattern when the jet array was developed. Flow pattern driven by an actuating nozzle influenced those of adjacent nozzles. The movement of particles towards and from the actuating nozzles was observed at the same time and position with velocities up to 2 mm/s. This showed that a complex flow system was generated on the nozzle plate during jetting with multiple nozzles which influenced the reliability of the inkjet printhead.

Research paper thumbnail of Jettability of reactive nylon materials for additive manufacturing applications

Journal of Manufacturing Processes, 2012

An inkjet printing process has been suggested for producing nylon 6 in an additive manufacturing ... more An inkjet printing process has been suggested for producing nylon 6 in an additive manufacturing approach and this paper reports on the jettability of molten reactive materials made by caprolactam with activator and catalyst to study the feasibility of the approach in an inkjet system. The materials physical properties which are important for jetting were characterized and then the melt supply behaviour in the system was studied and finally jetting trials were monitored to investigate the effect of parameter settings on the stability of the jet array. It was found that the surface tension and viscosity of all materials were within the suitable range. However, with the catalyst mixtures, microcrystals of the undissolved salt of the catalyst complex were found to influence the melt supply behaviour considerably. The mixtures had a narrower range of parameters where stability occurred compared with caprolactam. Monitoring the jet stability recommended a suitable range of jetting parameters for the deposition stage of researching the new approach. A higher level of instability was observed with the catalyst mixture especially when jetting with multiple nozzles due to the microcrystals.

Research paper thumbnail of Evaluation of laser ultrasonic testing for inspection of metal additive manufacturing

Laser 3D Manufacturing II, 2015

Research paper thumbnail of Jet array driven flow on the nozzle plate of an inkjet printhead in deposition of molten nylon materials

Journal of Materials Processing Technology, Mar 1, 2013

During research into an inkjet-integrated manufacturing process, jetting of molten caprolactam wa... more During research into an inkjet-integrated manufacturing process, jetting of molten caprolactam was investigated using a piezoelectric drop-on-demand printhead. Due to the start-up purging step and the surface energy differences, a wetting melt layer on the printhead's nozzle plate was formed. With appropriate parameters, a stable jet array was made. However, contamination on the nozzle plate disturbed the jet stability resulting in jet trajectory errors and even jet failures. Particles were used to characterise the melt flow field on the nozzle plate during jetting when multiple nozzles were actuated. Particle tracking velocimetry revealed that movement of the particles followed a specific pattern when the jet array was developed. Flow pattern driven by an actuating nozzle influenced those of adjacent nozzles. The movement of particles towards and from the actuating nozzles was observed at the same time and position with velocities up to 2 mm/s. This showed that a complex flow system was generated on the nozzle plate during jetting with multiple nozzles which influenced the reliability of the inkjet printhead.

Research paper thumbnail of Rapid tooling analysis of Stereolithography injection mould tooling

International Journal of Machine Tools and Manufacture, Apr 1, 2007

Increasing competition in global markets is exerting intense pressure on companies to trim their ... more Increasing competition in global markets is exerting intense pressure on companies to trim their product cycles continuously. As delivery times and costs of tools are on a downward trend, the modern tool manufacturer is under pressure to produce tools quickly, accurately and at a lower cost. Reducing the time to produce prototypes is a key to speed up the development of new products. Rapid tooling (RT) with particular regard to injection mould fabrication using rapid prototyping (RP) technology of Stereolithography (SL) may lead to savings in cost and time. In this paper, SL is used to directly build rapid injection mould tools for short run production. SL tools have been evaluated to analyse the maximum number of successful injections and quality of performance. SL epoxy tools were able to resist the injection pressure and temperature and 500 injections were achieved. The tool failure mechanisms during injection are investigated and tool failure either occurs due to excessive flexural stresses, or because of excessive shear stresses. r

Research paper thumbnail of Jettability of reactive nylon materials for additive manufacturing applications

Journal of Manufacturing Processes, Aug 1, 2012

An inkjet printing process has been suggested for producing nylon 6 in an additive manufacturing ... more An inkjet printing process has been suggested for producing nylon 6 in an additive manufacturing approach and this paper reports on the jettability of molten reactive materials made by caprolactam with activator and catalyst to study the feasibility of the approach in an inkjet system. The materials physical properties which are important for jetting were characterized and then the melt supply behaviour in the system was studied and finally jetting trials were monitored to investigate the effect of parameter settings on the stability of the jet array. It was found that the surface tension and viscosity of all materials were within the suitable range. However, with the catalyst mixtures, microcrystals of the undissolved salt of the catalyst complex were found to influence the melt supply behaviour considerably. The mixtures had a narrower range of parameters where stability occurred compared with caprolactam. Monitoring the jet stability recommended a suitable range of jetting parameters for the deposition stage of researching the new approach. A higher level of instability was observed with the catalyst mixture especially when jetting with multiple nozzles due to the microcrystals.

Research paper thumbnail of Using stereolithography tools for injection moulding: research into tensile tool failure and unexpected benefits of the process

Proceedings of the Institution of Mechanical Engineers Part B Journal of Engineering Manufacture, 2000

Citation: HOPKINSON, N. and DICKENS, P.M., 2000. Using stereolithography tools for injection moul... more Citation: HOPKINSON, N. and DICKENS, P.M., 2000. Using stereolithography tools for injection moulding: research into tensile tool failure and unexpected benets of the process.

Research paper thumbnail of Selective laser melting (SLM) of pure gold for manufacturing dental crowns

Rapid Prototyping Journal, 2014

Purpose -Over the years different metals have been processed using laser-based Additive Manufactu... more Purpose -Over the years different metals have been processed using laser-based Additive Manufacturing (AM) processes but very little work has been published on the Selective Laser Melting (SLM) of gold (Au). Previously published work presented suitable processing parameters for SLM of pure gold. This paper presents the application aspect of the work to manufacturing premolar and molar dental crowns by Selective Laser Melting of pure gold.

Research paper thumbnail of Study of ejection forces in the AIMTM process

Materials & Design, 1999

The AIM TM process has been used to successfully produce short runs of injection moulded parts. O... more The AIM TM process has been used to successfully produce short runs of injection moulded parts. One of the main drawbacks w of the process is the tendency of the tools to be damaged during part ejection Jacobs PF. Recent advances in rapid tooling from stereolithography. Proceedings of the 2nd National Conference on Rapid Prototyping and Tooling Research. Buckinghamshire x TM College 1996, ISBN: 085298 982 2 . At De Montfort University a successful AIM moulding cycle has been developed in which simple shapes from polypropylene are produced and the ejection forces required are measured. Two different ejection methods are used; one uses conventional ejector pins and the other uses a conformal ejector pad. The tool surface roughness is measured before and after moulding to observe any changes caused by ejection. Results show that ejector pins require a lower ejection force than a conformal ejector pad and this may contribute to longer tool life for the AIM TM process. Possible reasons for the results are discussed along with recommendations for further work. ᮊ

Research paper thumbnail of The cost of additive manufacturing: machine productivity, economies of scale and technology-push

Technological Forecasting and Social Change, 2015

ABSTRACT As part of the cosmos of digital fabrication technology, Additive Manufacturing (AM) sys... more ABSTRACT As part of the cosmos of digital fabrication technology, Additive Manufacturing (AM) systems are able to manufacture three-dimensional components and products directly from raw material and 3D design data. The layer-by-layer operating process of these systems does not require the use of tools, moulds or dies.

Research paper thumbnail of Introduction to Rapid Manufacturing

An Industrial Revolution for the Digital Age, 2005

Research paper thumbnail of Emerging Rapid Manufacturing Processes

An Industrial Revolution for the Digital Age, 2005

Research paper thumbnail of Rapid prototyping for direct manufacture

Rapid Prototyping Journal, 2001

Abstract: Introduces the concept of using technologies collectively known as rapid prototyping (R... more Abstract: Introduces the concept of using technologies collectively known as rapid prototyping (RP) for the manufacture of end-use products rather than prototypes, and presents recent examples. Gives details of a cost analysis performed by De Montfort ...

Research paper thumbnail of A comparison between stereolithography and aluminium injection moulding tooling

Rapid Prototyping Journal, 2000

Abstract: Advances in rapid prototyping and machining have resulted in reduced lead times for inj... more Abstract: Advances in rapid prototyping and machining have resulted in reduced lead times for injection moulding tooling. Comparisons between aluminium and stereolithography (SL) tools are made with regard to the ejection forces required to push mouldings from the tools ...

Research paper thumbnail of Instability behaviours of a jet array in inkjet printing of molten caprolactam

Rapid Prototyping Journal, 2013

Purpose -This paper presents the findings on jet array instabilities behaviours of molten caprola... more Purpose -This paper presents the findings on jet array instabilities behaviours of molten caprolactam in research of a novel inkjet additive manufacturing process, "Jetting of Nylon". The concept requires reliable jetting of an array of mixtures of molten caprolactam and initial investigations showed that although a suitable range of parameters was found for stable jetting, there were cases that instabilities occurred due to external sources such as contamination.

Research paper thumbnail of Adaptive screen printing for rapid manufacturing

Rapid Prototyping Journal, 2007

Purpose–To develop a rapid manufacturing process for high-volume free from fabrication of parts t... more Purpose–To develop a rapid manufacturing process for high-volume free from fabrication of parts that is based on the high speed printing method which is screen printing. This technique will also be applied for printing in general. Design/methodology/approach–This ...

Research paper thumbnail of Structural design and resin drainage characteristics of QuickCast 2.0

Rapid Prototyping Journal, 2001

ABSTRACT Describes how a set of criteria for the design of build structures that allow the succes... more ABSTRACT Describes how a set of criteria for the design of build structures that allow the successful autoclaving and subsequent investment casting of stereolithography models have been developed. Details of the background research are presented along with a new design of internal build structure that allows stereolithography models to be used as sacrificial patterns in the investment casting process. Further work into the characteristics of draining uncured resin from parts built in the new structure is also presented.

Research paper thumbnail of Selective laser melting (SLM) of gold (Au)

Rapid Prototyping Journal, 2012

Purpose-Different metals have been processed using laser based Solid Freeform Fabrication (SFF) p... more Purpose-Different metals have been processed using laser based Solid Freeform Fabrication (SFF) processes but very little work has been published on the Selective Laser Melting (SLM) of gold (Au). The purpose of this research paper is to check the properties ...

Research paper thumbnail of Evaluation of laser ultrasonic testing for inspection of metal additive manufacturing

Laser 3D Manufacturing II, 2015

Research paper thumbnail of High Viscosity Jetting System for 3D Reactive Inkjet Printing

Research paper thumbnail of Jet array driven flow on the nozzle plate of an inkjet printhead in deposition of molten nylon materials

Journal of Materials Processing Technology, 2013

ABSTRACT During research into an inkjet-integrated manufacturing process, jetting of molten capro... more ABSTRACT During research into an inkjet-integrated manufacturing process, jetting of molten caprolactam was investigated using a piezoelectric drop-on-demand printhead. Due to the start-up purging step and the surface energy differences, a wetting melt layer on the printhead's nozzle plate was formed. With appropriate parameters, a stable jet array was made. However, contamination on the nozzle plate disturbed the jet stability resulting in jet trajectory errors and even jet failures. Particles were used to characterise the melt flow field on the nozzle plate during jetting when multiple nozzles were actuated. Particle tracking velocimetry revealed that movement of the particles followed a specific pattern when the jet array was developed. Flow pattern driven by an actuating nozzle influenced those of adjacent nozzles. The movement of particles towards and from the actuating nozzles was observed at the same time and position with velocities up to 2 mm/s. This showed that a complex flow system was generated on the nozzle plate during jetting with multiple nozzles which influenced the reliability of the inkjet printhead.

Research paper thumbnail of Jettability of reactive nylon materials for additive manufacturing applications

Journal of Manufacturing Processes, 2012

An inkjet printing process has been suggested for producing nylon 6 in an additive manufacturing ... more An inkjet printing process has been suggested for producing nylon 6 in an additive manufacturing approach and this paper reports on the jettability of molten reactive materials made by caprolactam with activator and catalyst to study the feasibility of the approach in an inkjet system. The materials physical properties which are important for jetting were characterized and then the melt supply behaviour in the system was studied and finally jetting trials were monitored to investigate the effect of parameter settings on the stability of the jet array. It was found that the surface tension and viscosity of all materials were within the suitable range. However, with the catalyst mixtures, microcrystals of the undissolved salt of the catalyst complex were found to influence the melt supply behaviour considerably. The mixtures had a narrower range of parameters where stability occurred compared with caprolactam. Monitoring the jet stability recommended a suitable range of jetting parameters for the deposition stage of researching the new approach. A higher level of instability was observed with the catalyst mixture especially when jetting with multiple nozzles due to the microcrystals.

Research paper thumbnail of Evaluation of laser ultrasonic testing for inspection of metal additive manufacturing

Laser 3D Manufacturing II, 2015

Research paper thumbnail of Jet array driven flow on the nozzle plate of an inkjet printhead in deposition of molten nylon materials

Journal of Materials Processing Technology, Mar 1, 2013

During research into an inkjet-integrated manufacturing process, jetting of molten caprolactam wa... more During research into an inkjet-integrated manufacturing process, jetting of molten caprolactam was investigated using a piezoelectric drop-on-demand printhead. Due to the start-up purging step and the surface energy differences, a wetting melt layer on the printhead's nozzle plate was formed. With appropriate parameters, a stable jet array was made. However, contamination on the nozzle plate disturbed the jet stability resulting in jet trajectory errors and even jet failures. Particles were used to characterise the melt flow field on the nozzle plate during jetting when multiple nozzles were actuated. Particle tracking velocimetry revealed that movement of the particles followed a specific pattern when the jet array was developed. Flow pattern driven by an actuating nozzle influenced those of adjacent nozzles. The movement of particles towards and from the actuating nozzles was observed at the same time and position with velocities up to 2 mm/s. This showed that a complex flow system was generated on the nozzle plate during jetting with multiple nozzles which influenced the reliability of the inkjet printhead.

Research paper thumbnail of Rapid tooling analysis of Stereolithography injection mould tooling

International Journal of Machine Tools and Manufacture, Apr 1, 2007

Increasing competition in global markets is exerting intense pressure on companies to trim their ... more Increasing competition in global markets is exerting intense pressure on companies to trim their product cycles continuously. As delivery times and costs of tools are on a downward trend, the modern tool manufacturer is under pressure to produce tools quickly, accurately and at a lower cost. Reducing the time to produce prototypes is a key to speed up the development of new products. Rapid tooling (RT) with particular regard to injection mould fabrication using rapid prototyping (RP) technology of Stereolithography (SL) may lead to savings in cost and time. In this paper, SL is used to directly build rapid injection mould tools for short run production. SL tools have been evaluated to analyse the maximum number of successful injections and quality of performance. SL epoxy tools were able to resist the injection pressure and temperature and 500 injections were achieved. The tool failure mechanisms during injection are investigated and tool failure either occurs due to excessive flexural stresses, or because of excessive shear stresses. r

Research paper thumbnail of Jettability of reactive nylon materials for additive manufacturing applications

Journal of Manufacturing Processes, Aug 1, 2012

An inkjet printing process has been suggested for producing nylon 6 in an additive manufacturing ... more An inkjet printing process has been suggested for producing nylon 6 in an additive manufacturing approach and this paper reports on the jettability of molten reactive materials made by caprolactam with activator and catalyst to study the feasibility of the approach in an inkjet system. The materials physical properties which are important for jetting were characterized and then the melt supply behaviour in the system was studied and finally jetting trials were monitored to investigate the effect of parameter settings on the stability of the jet array. It was found that the surface tension and viscosity of all materials were within the suitable range. However, with the catalyst mixtures, microcrystals of the undissolved salt of the catalyst complex were found to influence the melt supply behaviour considerably. The mixtures had a narrower range of parameters where stability occurred compared with caprolactam. Monitoring the jet stability recommended a suitable range of jetting parameters for the deposition stage of researching the new approach. A higher level of instability was observed with the catalyst mixture especially when jetting with multiple nozzles due to the microcrystals.

Research paper thumbnail of Using stereolithography tools for injection moulding: research into tensile tool failure and unexpected benefits of the process

Proceedings of the Institution of Mechanical Engineers Part B Journal of Engineering Manufacture, 2000

Citation: HOPKINSON, N. and DICKENS, P.M., 2000. Using stereolithography tools for injection moul... more Citation: HOPKINSON, N. and DICKENS, P.M., 2000. Using stereolithography tools for injection moulding: research into tensile tool failure and unexpected benets of the process.

Research paper thumbnail of Selective laser melting (SLM) of pure gold for manufacturing dental crowns

Rapid Prototyping Journal, 2014

Purpose -Over the years different metals have been processed using laser-based Additive Manufactu... more Purpose -Over the years different metals have been processed using laser-based Additive Manufacturing (AM) processes but very little work has been published on the Selective Laser Melting (SLM) of gold (Au). Previously published work presented suitable processing parameters for SLM of pure gold. This paper presents the application aspect of the work to manufacturing premolar and molar dental crowns by Selective Laser Melting of pure gold.

Research paper thumbnail of Study of ejection forces in the AIMTM process

Materials & Design, 1999

The AIM TM process has been used to successfully produce short runs of injection moulded parts. O... more The AIM TM process has been used to successfully produce short runs of injection moulded parts. One of the main drawbacks w of the process is the tendency of the tools to be damaged during part ejection Jacobs PF. Recent advances in rapid tooling from stereolithography. Proceedings of the 2nd National Conference on Rapid Prototyping and Tooling Research. Buckinghamshire x TM College 1996, ISBN: 085298 982 2 . At De Montfort University a successful AIM moulding cycle has been developed in which simple shapes from polypropylene are produced and the ejection forces required are measured. Two different ejection methods are used; one uses conventional ejector pins and the other uses a conformal ejector pad. The tool surface roughness is measured before and after moulding to observe any changes caused by ejection. Results show that ejector pins require a lower ejection force than a conformal ejector pad and this may contribute to longer tool life for the AIM TM process. Possible reasons for the results are discussed along with recommendations for further work. ᮊ

Research paper thumbnail of The cost of additive manufacturing: machine productivity, economies of scale and technology-push

Technological Forecasting and Social Change, 2015

ABSTRACT As part of the cosmos of digital fabrication technology, Additive Manufacturing (AM) sys... more ABSTRACT As part of the cosmos of digital fabrication technology, Additive Manufacturing (AM) systems are able to manufacture three-dimensional components and products directly from raw material and 3D design data. The layer-by-layer operating process of these systems does not require the use of tools, moulds or dies.

Research paper thumbnail of Introduction to Rapid Manufacturing

An Industrial Revolution for the Digital Age, 2005

Research paper thumbnail of Emerging Rapid Manufacturing Processes

An Industrial Revolution for the Digital Age, 2005

Research paper thumbnail of Rapid prototyping for direct manufacture

Rapid Prototyping Journal, 2001

Abstract: Introduces the concept of using technologies collectively known as rapid prototyping (R... more Abstract: Introduces the concept of using technologies collectively known as rapid prototyping (RP) for the manufacture of end-use products rather than prototypes, and presents recent examples. Gives details of a cost analysis performed by De Montfort ...

Research paper thumbnail of A comparison between stereolithography and aluminium injection moulding tooling

Rapid Prototyping Journal, 2000

Abstract: Advances in rapid prototyping and machining have resulted in reduced lead times for inj... more Abstract: Advances in rapid prototyping and machining have resulted in reduced lead times for injection moulding tooling. Comparisons between aluminium and stereolithography (SL) tools are made with regard to the ejection forces required to push mouldings from the tools ...

Research paper thumbnail of Instability behaviours of a jet array in inkjet printing of molten caprolactam

Rapid Prototyping Journal, 2013

Purpose -This paper presents the findings on jet array instabilities behaviours of molten caprola... more Purpose -This paper presents the findings on jet array instabilities behaviours of molten caprolactam in research of a novel inkjet additive manufacturing process, "Jetting of Nylon". The concept requires reliable jetting of an array of mixtures of molten caprolactam and initial investigations showed that although a suitable range of parameters was found for stable jetting, there were cases that instabilities occurred due to external sources such as contamination.

Research paper thumbnail of Adaptive screen printing for rapid manufacturing

Rapid Prototyping Journal, 2007

Purpose–To develop a rapid manufacturing process for high-volume free from fabrication of parts t... more Purpose–To develop a rapid manufacturing process for high-volume free from fabrication of parts that is based on the high speed printing method which is screen printing. This technique will also be applied for printing in general. Design/methodology/approach–This ...

Research paper thumbnail of Structural design and resin drainage characteristics of QuickCast 2.0

Rapid Prototyping Journal, 2001

ABSTRACT Describes how a set of criteria for the design of build structures that allow the succes... more ABSTRACT Describes how a set of criteria for the design of build structures that allow the successful autoclaving and subsequent investment casting of stereolithography models have been developed. Details of the background research are presented along with a new design of internal build structure that allows stereolithography models to be used as sacrificial patterns in the investment casting process. Further work into the characteristics of draining uncured resin from parts built in the new structure is also presented.

Research paper thumbnail of Selective laser melting (SLM) of gold (Au)

Rapid Prototyping Journal, 2012

Purpose-Different metals have been processed using laser based Solid Freeform Fabrication (SFF) p... more Purpose-Different metals have been processed using laser based Solid Freeform Fabrication (SFF) processes but very little work has been published on the Selective Laser Melting (SLM) of gold (Au). The purpose of this research paper is to check the properties ...