Magnetorheological finishing (MRF) is a precision surface finishing

Surface finishing

Surface finishing is a broad range of industrial processes that alter the surface of a manufactured item to achieve a certain property. Finishing processes may be employed to: improve appearance, adhesion or wettability, solderability, corrosion resistance, tarnish resistance, chemical resistance,...

 technology. Optical surfaces are polished in a computer

Computer

A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

-controlled magnetorheological

Magnetorheological fluid

A magnetorheological fluid is a type of smart fluid in a carrier fluid, usually a type of oil. When subjected to a magnetic field, the fluid greatly increases its apparent viscosity, to the point of becoming a viscoelastic solid. Importantly, the yield stress of the fluid when in its active state...

 (MR) finishing slurry. Unlike conventional rigid lap

Lapping

Lapping is a machining operation, in which two surfaces are rubbed together with an abrasive between them, by hand movement or by way of a machine.This can take two forms...

 polishing

Polishing

Polishing is the process of creating a smooth and shiny surface by rubbing it or using a chemical action, leaving a surface with a significant specular reflection In some materials polishing is also able to reduce diffuse reflection to...

, the MR fluid's shape and stiffness can be magnet

Magnet

A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, and attracts or repels other magnets.A permanent magnet is an object...

ically manipulated and controlled in real time

Real-time computing

In computer science, real-time computing , or reactive computing, is the study of hardware and software systems that are subject to a "real-time constraint"— e.g. operational deadlines from event to system response. Real-time programs must guarantee response within strict time constraints...

. The optic's final surface form and finishing results are predicted through the use of computer algorithms.

Literature

• US Patent: US5449313A
• German Patent: DE69924595T2
• Shorey et. al "Experiments and Observations Regarding the Mechanisms of Glass Removal in Magnetorheological Finishing", abstract and full text (pdf)
• Chunlin Miao, et al., "Shear stress in magnetorheological finishing for glasses," Applied Optics 48, 2585-2594 (2009) , abstract and full text (pdf)
• Chunlin Miao, et al., "Process parameter effects on material removal in magnetorheological finishing of borosilicate glass," Applied Optics 49, 1951-1963 (2010) , abstract and full text (pdf)