A survey of models, analysis tools and compensation methods for the control of machines with friction

Ductile-Regime Grinding: A New Technology for Machining Brittle Materials

https://escholarship.org/content/qt8rf718jm/qt8rf718jm.pdf?t=krnesf

Recent Advances in Mechanical Micromachining

The miniaturization of machine components is perceived by many as a requirement for the future technological development of a broad spectrum of products. Miniature components can provide smaller footprints, lower power consumption and higher heat transfer, since their surface-to-volume ratio is very high. To create these components, micro-meso-scale fabrication using miniaturized mechanical material removal processes has a unique advantage in creating 3D components using a variety of engineering materials. The motivation for micro-mechanical cutting stems from the translation of the knowledge obtained from the macro-machining domain to the micro-domain. However, there are challenges and limitations to micro-machining, and simple scaling cannot be used to model the phenomena of micro-machining operations. This paper surveys the current efforts in mechanical micro-machining research and applications, especially for micro-milling operations, and suggests areas from macro-machining that should be examined and researched for application to the improvement of micro-machining processes.

Investigation of micro-cutting operations

Manufacturing and measurement of freeform optics

Centering a part on a spindle for precision machining is a tedious, time-consuming task. Currently, a skilled operator must measure the run-out of a part using a displacement gauge, then tap the part into place using a plastic or rubber hammer. This paper describes a method to automatically center a part on a vacuum chuck with initial run-out as large as 2.5 mm. The method involves measuring the magnitude and direction of the radial run-out and then actuating the part until the part and spindle centerlines are within 5 μm of each other. The run-out can be measured with either a touch probe mounted to a machine axis or an electronic gauge. The part is tapped into place with a linear actuator driven by a voice coil motor This paper includes an analysis of run-out measurement uncertainty as well as the design, performance modeling, and testing of the alignment actuator. This actuator was employed for part realignment and successfully positioned a hemispherical part with an initial run-out of 1-2.5 mm to within 5 μm of the spindle centerline. This capability shows that the run-out of a part manually placed on flat vacuum chuck can be automatically corrected.

Automated Part Centering With Impulse Actuation

In grinding operations, wheel speed significantly affects surface finish and chip thickness. The grinding wheel speed represents an equilibrium condition based upon the energy input by the grinding motor and the energy removed by the grinding process. An analysis of these energy relationships allows prediction of wheel speed and shows how it changes during grinding because of changes in chip geometry. The analysis also reveals that some wheel speeds are energetically preferred. Wheel speed measurements and images of ground surfaces corroborate the analytical predictions. The presence of narrow ranges of preferred wheel speed has implications for selection of grinding conditions and adoption of wheel speed control.

Thomas A. Dow

Papers

Automated Part Centering With Impulse Actuation

Wheel speed equilibria in precision contour grinding

Closure to “Discussion of ‘Analysis of Traction Forces in a Precision Traction Drive’” (1986, ASME J. Tribol., 108, p. 409)

Thermoelastic effects in an elastohydrodynamically lubricated contact