杯形砂轮——Grinding

SPECIAL ISSUE -ORIGINAL ARTICLE

New systematic and time-saving procedure to design cup grinding wheels for the application of ultrasonic-assisted grinding

Christian Brecher &Ralf Schug &Andreas Weber &Christian Wenzel &Sophia Hannig

Received:13June 2008/Accepted:8July 2009/Published online:22July 2009#Springer-Verlag London Limited 2009

Abstract Since glass and ceramic materials have beneficial properties,they have gained more importance in numerous technical applications during the last 30years.For example,nowadays,ceramics are used as artificial hip joints or as mechanical seals for highest relative speeds.Glass compo-nents are used for multitude of optical applications like cameras and reflectors.But besides a lot of advantages,the processing of these materials is very difficult.In particular,this contains the manufacturing of small components like microreactor plates or glass wafers with hundreds of small holes,ing ultrasonic-assisted grinding,the treatment can significantly be optimized and higher removal rates can be realized.For the generation of ultrasonic waves,often piezoactors are used that excite the grinding tools with vibrations of 20kHz and amplitudes of a few microns (Markov 1966;Kuttruff 1988).Using an ultrasonic wave,the tool geometry is strongly restricted to guarantee the hybrid functionality (Siegert 2002;Dawe Instruments Ltd.1967;Derks 1984).The paper describes a new way to calculate the design of tools suitable for their use in ultrasonic-assisted grinding.As a machining process,the manufacturing of spherical optics with cup-grinding wheels is selected.

Keywords Ultrasonic-assisted grinding .Method to design vibrating components .Coupling of simulation tools

1Introduction

The ultrasonic-assisted grinding is a hybrid process cou-pling two different energy forms into one process zone at the same time.The kinematic is defined by the sum of the conventional spindle rotation and a high-frequency axial ultrasonic oscillation of the tool [1].Compared to conven-tional grinding processes,the advantage of the ultrasonic-assisted grinding is an increase of the material removal rate and a higher economic efficiency especially for the manufacturing of hard and brittle materials such as glass and ceramics.In particular,ultrasonic-assisted grinding holds high potentials to increase the competitive position of producers of machine tools in the area of application of producing glass for optical use [2].

The advantages of the process of ultrasonic-assisted grinding are well known for about 50years.The combina-tion of the rotation and the oscillation leads to a noncontinuous contact of the tool with the workpiece with ultrasonic frequency.Furthermore,the oscillation of the tool causes microcrushes and microcracks on the workpiece surface [1,7].As a result of these effects,the feed forces are significantly reduced.In contrast,the force reduction can be used to increase the feed motion speed and the removal rates of the grinding process.Figure 1shows the reduction of the feed forces during glass grinding with cup-grinding wheels depending on the ultrasonic amplitude x a .The right side of the same figure shows the possible increase of removal rates up to 230%using ultrasonic waves [2].

To realize these advantages,the grinding tool is stimulated with ultrasonic waves.Therefore,a piezoelectric ultrasonic converter and a booster element are integrated in a grinding spindle (Fig.2).The ultrasonic converter consists of piezoelements and additional masses.While

C.Brecher

Werkzeugmaschinenlabor (WZL),RWTH Aachen University,Aachen,Germany

C.Brecher :R.Schug :A.Weber :C.Wenzel :S.Hannig (*)Fraunhofer Institute for Production Technology,Aachen,Germany

e-mail:sophia.hannig@ipt.fraunhofer.de

Int J Adv Manuf Technol (2010)47:153–159DOI 10.1007/s00170-009-2204-7