Design of precision diamond turning lathe

Pao Yue-kong Library Electronic Theses Database

Design of precision diamond turning lathe

 

Author: Fan, Yau-sun
Title: Design of precision diamond turning lathe
Degree: M.Sc.
Year: 1995
Subject: Turning
Lathes
Machining
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Pages: ix, 151 leaves : ill. ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1182968
URI: http://theses.lib.polyu.edu.hk/handle/200/594
Abstract: During the last decades, the development in advanced technology has initialized the demand for extremely high precision components with contour accuracy in submicrometer range and surface finish of a few nanometres. Conventional means of machining these precision components include grinding, polishing and lapping. However, such machining methods are complicated in processes, expensive and time consuming in production. To cope with the increasing quality and quantity demand of precision components over a wide spectrum of industry, a number of new machining methods have been emerged. Single Point Diamond Turning is one of these alternatives to the conventional processes. Single Point Diamond turning is capable of machining a workpiece to profile accuracy of submicron range and roughness of nanometres yet in just one cutting. This kind of manufacturing technology greatly conforms to both the accuracy demand and cost-effective requirements and has exhibited a very potential prospect. In spite of its prospective future, the machine must conform to stringent requirements, these include the extremely high loop stiffness between the tool and the workpiece, the extremely smooth movement of the carriage, the capability of maintaining consistently a very small depths of cut, the control of temperature in the working space so that a thermal stability of the machine system can always be maintained, and the maintaining of a very low level of vibration. In this paper, the errors affecting the machining accuracy is first analyzed and evaluated, a small experimental oriented precision diamond turning lathe is then designed. Hydrostatic carriage system is implemented in this machine tool so that smooth/movement can always be obtained. A friction drive gear reduction mechanism is also designed such that a very fine resolution can be achieved. Laser interferometer is then applied for displacement measurement. Oil shower is utilized to reduce the thermal influence on the machining process and pneumatic isolators are used to isolate vibrations from external sources. A mathematical model using homogeneous transform matrix describing the structural loop of the machine system is also built, thus error budget can be made and the effect of individual error components can be estimated. From the calculation of error budget, it is found that Abbe offsets and thermal expansions are the dominating error sources in diamond turning.

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