Study on process parameter of high performance laser cutting machine tool for copper sheet
A high performance NC laser cutting machine tool for copper sheet is designed, emphasis discussing the components of NC laser cutting machine tool and design points. Performance of high power semiconductor pulse micro-cutting of copper sheet is studied and several key parameters are given by changing assistant gas and process parameters. The experimental results show that the best cutting quality can be obtained when argon is used as assistant gas, and oxygen is on the contrary. Also, in a certain range, improving laser power and cutting speed can help in decreasing laser cutting gap, minishing heat affected area, and achieving better cutting quality.
Influence of wire addition direction in C02 laser welding of aluminum
Laser beam welding of aluminum alloys is expected to offer both the technical and economical advantages. In most cases welding wire addition is necessary from the viewpoints to suppress hot cracks, improve mechanical properties of the weld as well as to reduce demands on the edge preparation, fit-up tolerance, and beam alignment. In practice, the filler wire could be added to the weld pool either in the leading or trailing direction. In this experimental work reported, the influence of the wire addition direction on the weld efficiency and process stability was investigated by using a 5kW CO2 laser to weld aluminum alloy 6009 with a plate thickness of 3mm. Beam-on-plate welds were made either in the autogeneous mode or with filler wire AISi12. Illuminated by a double frequency Nd:YAG laser, the weld pool dynamics and the wire melting process were observed applying a high speed camera. The experimental results demonstrate that welding with filler wire in the trailing direction is more efficient and stable than in the leading direction. High speed camera photographs show that the filler wire is mainly melted through weld pool heating and plasma heating in the former case and through direct laser irradiation and plasma heating in the later case. The weld pool is of vibration when welding in the autogeneous mode or with filler wire in the leading direction. However, the weld pool is much calmer when the wire is added in the trailing direction to the weld pool.
Professional tensions in client-centered practice: using institutional ethnography to generate understanding and transformation.
For almost 20 years, occupational therapists have advocated client-centered practice. Yet client-centered practice is fraught with tensions that arise outside the practice of individual occupational therapists. This paper is guided by two questions: What produces professional tensions in client-centered practice? and What understanding and change might be generated using institutional ethnography? The sociological theory and method of institutional ethnography are described using data from an ongoing investigation of mental health services as a social institution. Illustrated are the research aim, research questions, and institutional analysis that distinguish institutional ethnography from conventional ethnography. Two professional tensions are associated with attempts to fulfill client-centered practice in mental health. One is that of working at cross-purposes with the prevailing hierarchical structure; the other tension is that of being celebrated yet subordinated in the medical and management hierarchies of health services. Although client-centered practice is difficult to do, the authors recommend institutional ethnography as a research approach to generate understanding and transformation of the context and practice of occupational therapy.