Manufacturing technologies toward extreme precision

Precision is one of the most important aspects of manufacturing.High precision creates high quality,high performance,exchangeability,reliability,and added value for industrial products.Over the past decades,remarkable advances have been achieved in the area of high-precision manufacturing technologies,where the form accuracy approaches the nanometer level and surface roughness the atomic level.These extremely high precision manufacturing technologies enable the development of high-performance optical elements,semiconductor substrates,biomedical parts,and so on,thereby enhancing the ability of human beings to explore the macroand microscopic mysteries and potentialities of the natural world.In this paper,state-of-the-art high-precision material removal manufacturing technologies,especially ultraprecision cutting,grinding,deterministic form correction polishing,and supersmooth polishing,are reviewed and compared with insights into their principles,methodologies,and applications.The key issues in extreme precision manufacturing that should be considered for future R&D are discussed.

Exploratory Trial to Evaluate the Hydroxyapatite Layer Formed by a New Dental Treatment System

Objective: A powder jet deposition (PJD) process can be used to create a thick hydroxyapatite (HA) layer on the human tooth surface. The purpose of this exploratory trial was to evaluate the safety and efficacy of the hydroxyapatite layer formed by a new dental treatment system for cases of caries, dentin hypersensitivity, or discolored teeth. Methods: A single facility, non-blinded study comparing before and after treatment interventions, without a comparative control, was conducted. A rubber dam was attached to the teeth followed by the application of Vaseline to the gingival margins. Extra- and intra-oral vacuums and a saliva discharge tube were used to spray HA powder over the target site with the PJD equipment. Results: The formation of an HA layer tended to reduce pain on exposure to cold water and air in the cases with caries, and increase brightness and satisfaction in the cases with tooth discoloration. The pain on exposure to air was significantly reduced in the cases with dentin hypersensitivity. PJD was not observed to cause any inflammation of the surrounding gingiva or pulpal symptoms. Conclusions: HA is anticipated to reduce the need for repeat treatment by offering superior compatibility with the tooth substance when compared with other dental materials.

Recent advances in ultrasonic-assisted machining for the fabrication of micro/nano-textured surfaces

In this paper, the state of art of ultrasonic- assisted machining technologies used for fabrication of micro/nano-textured surfaces is reviewed. Diamond machining is the most widely used method in industry for manufacturing precision parts. For fabrication of fine structures on surfaces, conventional diamond machining methods are competitive by considering the precision of structures, but have limitations at machinable structures and machining efficiency, which have been proved to be partly solved by the integration of ultrasonic vibration motion. In this paper, existing ultrasonic-assisted machin- ing methods for fabricating fine surface structures are reviewed and classified, and a rotary ultrasonic texturing （RUT） technology is mainly introduced by presenting the construction of vibration spindles, the texturing principles, and the applications of textured surfaces. Some new ideas and experimental results are presented. Finally, the challenges in using the RUT method to fabricate micro/ nano-textured surfaces are discussed with respect to texturing strategies, machinable structures, and tool wear.

Effects of Topography and Modified Layer by Plasma-Shot Treatment on High-Speed Steel

In this study,plasma shot(PS)treatment was applied to high-speed steel(HSS)surfaces using a titanium carbide electrode to confirm the effect of discharge current(Ip)on the formation of a single dimple and analyze a modified layer.The roughness of modified surfaces increased when Ip increased,and energy-dispersive X-ray spectrometry showed an increase in titanium atom density whenIp and electrode consumption volume(Ve)increased.A friction test confirmed that the modified surface's friction was reduced by discharge dimples under low-load conditions.Vickers hardness test confirmed that the hardness of the modified surface was-300-600 HV higher than that of an untreated HSS surface.Moreover,it increased with an increase inIp.However,application of PS treatment to the edge of surfaces on the workpiece caused shape deterioration.The deterioration size of the edge of the modified layer increased when Ip increased.To solve this issue,we propose a novel method named position-adjusted PS(PA-PS)treatment.PA-PS treatment is used to adjust the end of the electrode in the order of tens of micrometers from the edge of the workpiece to avoid the deterioration of the edge form.Under Ip=21 A,PA-PS formed a modified layer without deteriorating the edge shape of the workpiece,thus confirming the PS characteristics applied to HSS surfaces.Moreover,PA-PS treatment solved the shape deterioration of the edge on modified surfaces via PS treatment.