Wyniki wyszukiwania - BazTech

1

Micromachining electrical grade steel using pulsed Nd-YAG lasers

Jackson M. J., Robinson G. M.

Journal of Achievements in Materials and Manufacturing Engineering

|

2007

|

Vol. 20, nr 1-2

451-454

EN

Purpose: Multi-wavelength capability allows diode pumped, solid state (D.P.S.S.) lasers to perform operations such as micro machining in a variety of materials such as ceramics, metals and polymers. Results from this study reveal how traditional plasma-controlling gases have a detrimental effect on the surface morphology of machined components. The paper explains how the machining of thin plates of silicon steel can benefit the rapid production of electrical components such as transformer cores and dynamo pole pieces. Design/methodology/approach: A series of experiments was performed to investigate how shielding gas environment and gas pressure affect the ability to cut and machine silicon steel. The experiments were designed to show the differences between the use of various assist gases that shield the machining zone. Findings: The results of the work indicate that oxygen shielding gases allow silicon steel to be machined at a faster rate than using helium, argon and air. However, the surface roughness produced is highly dependent on assist gas used and the pressure at which it is delivered. Research limitations/implications: The results presented imply that assist gases perform a variety of functions and further research is required to understand how the assist gases improve machinability when machining different workpiece materials. Practical implications: The practical implications of this research indicate that a significant amount of research effort is required to optimize the type of assist gas used in laser micromachining of engineering materials. Originality/value: The paper reveals how assist gases interact with both laser and the surface of workpiece materials. It is practical value to microengineers and micromachinists working in the field of micro and nanomanufacturing.

2

Manufacture of nanocrystalline metals by machining processes

Jackson M. J., Robinson G. M., Whitfield M. D.

Journal of Achievements in Materials and Manufacturing Engineering

|

2007

|

Vol. 20, nr 1-2

27-30

EN

Purpose: The paper shows how extremely high-speed micromachining can be used as a method for manufacturing nanocrystalline feedstock from machining chips. The feedstock can be used in processes such as cold spraying that improve the surface characteristics of engineering components. Design/methodology/approach: The design and methodology relies on the construction and the correct operation of a micromachining operation that produces functional feedstock material that is produced from machining chips at spindle speeds in excess of half-a-million revolutions per minute. The approach provides an economical way of producing metal nanocrystals. Findings: The findings of the research show that intense plastic shearing of metals produces nanosized crystals in the range 30 nm to 150 nm. The crystals produced can be used to create superior funtional coatings on engineering components. Research limitations/implications: The research conducted implies that a cost effective and environmentallybenign process can produce metal nanocrystals. The limitations of the research are currently restricted to cold spraying of funtional surfaces. Practical implications: The practical implications of the research show that high-speed micromachining can be used as a method of producing nanocrystalline feedstock that can be used in a variety of secondary manufacturing processes in addition to cold spraying. Originality/value: The paper demonstrates the originality of using well-established machining processes for producing nanocrystalline metals. The paper describes how machining at extremely high speeds can be achieved to produce material that can be used to strengthen and harden engineering components.

3

Machining strain hardening metals using nanostructured thin film end mills

Jackson M. J., Robinson G. M., Morell J. S.

Journal of Achievements in Materials and Manufacturing Engineering

|

2007

|

Vol. 21, nr 1

79-82

EN

Purpose: This paper discusses improvements associated with the tool life of cutting tools used to machine alloy steels. To achieve this in an efficient manner, experiments on a variety of tool coatings are conducted on AISI M42 tool steel (58-63 HRC). Design/methodology/approach: In order to assess the impact of different tool coatings on machining process, initial experiments simulate current machining operations; this provides a benchmark standard for tool life and surface finish. Findings: The findings in the paper show that TiAlCrN and TiAlCrYN coated WC-Co cutting tools perform better than uncoated and TiN coated cutting tools. Research limitations/implications: The implications of the paper tend to indicate that dry machining of M42 tool steels can be optimized using coated cutting tools. The limitations of the paper include machining at specific cutting speeds and the employment of a short-time tool wear method. Practical implications: The practical implications of the paper show that dry machinig of hardened tool steels can be achieved under specific circumstances. Further research is needed to explain how the wear mechanism changes under various machining conditions. Originality/value: The paper presents original information on the characteristics of dry machining of tool steels under specific machining operations. The paper is of interest to manufacturing engineers.

4

Machining M42 tool steel using nanostructured coated cutting tools

Jackson M. J., Robinson G. M., Morell J. S.

Journal of Achievements in Materials and Manufacturing Engineering

|

2007

|

Vol. 23, nr 1

83-86

EN

Purpose: This paper discusses improvements associated with the life of cutting tools used to machine M42 tool steel. To achieve this in an efficient way, experiments on a variety of tool coatings are conducted on AISI M42 tool steel (58-63 HRC). Design/methodology/approach: In order to assess the impact of different tool coatings on the machining process, initial experiments simulate existing machining operations; this provides a standard for tool life and surface finish. Findings: The findings in the paper show that TiAlCrYN coated WC-Co cutting tools perform better than uncoated cutting tools. Research limitations/implications: The implications of the paper tend to indicate that machining M42 tool steels without lubricant can be optimized using coated cutting tools. The limitations of the paper include machining at one specific cutting speed and the employment of a short-time tool wear method. Practical implications: The practical implications of the paper show that dry machining of hardened tool steels can be achieved under certain circumstances. Further research is needed to explain how the wear mechanism changes with varying machining conditions. Originality/value: The paper presents original information on the characteristics of dry machining of M42 tool steel under specific machining operations. The paper is of interest to manufacturing engineers and materials scientists.

5

Development of morphology in laser dressed grinding wheels

Jackson M. J., Robinson G. M.

Journal of Achievements in Materials and Manufacturing Engineering

|

2007

|

Vol. 22, nr 1

81-84

EN

Purpose: The paper describes the development of faceted morphology in laser dressed grinding wheels. Design/methodology/approach: The approach used in the paper is based on locally melting a vitrified grinding wheel and measuring features such as grain size, cooling rate and melt depth as a function of laser fluence and relating these measures to the morphology shown in the microstructures presented in the paper. Findings: The findings of this course of research lead the authors to believe that a specific morphology is dependent upon cooling rate and laser fluence. Research limitations/implications: The findings show that further research is required to fully understand how certain morphologies form as a function of cooling rate and laser fluence. It should be noted that morphologies observed in laser processed grinding wheels include cellular and fully dendritic morphologies in addition to faceted vertices. Practical implications: The results imply that laser dressed grinding wheels can be used for machining different materials at different grinding speeds. The paper also shows that much development is needed to identify laser processing conditions that are appropriate for different workpiece materials. Originality/value: The paper shows that different morphologies can be used to machine workpiece materials under different conditions. The originality in the paper is focused on the formation on minute cutting points using increasing laser fluences.