Low surface roughness (or better surface finish) of the ... · 2 Why nanofinishing is required ? Low surface roughness (or better surface finish) of the components is necessary to

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Why nanofinishing is required ?

Low surface roughness (or better surface finish) of the components is necessary to improve

Wear resistance

Mechanical properties (fatigue life, toughness, etc.)

Optical properties

Corrosion and oxidation resistance

Aesthetic appearance

and many others

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Magnetorheological fluid based finishing (MRFF)

Magnetorheological finishing (MRF)

Source: www.qedmrf.com

MR fluid is extruded onto a rotating wheel as a thinribbon that will contact the optical surface.

Different types of configurations needs to bedeveloped for different types and sizes of workpieceto be nanofinished.

Electromagnet or permanent magnet provides thestrength (stiffness) to MR fluid.

Stiffness of the MR fluid α Magnetic Field Strength The stiffened MR fluid comes into contact with the

surface to be finished which can be optics, mirror,metallic part or anything.

Relative motion between the stiffened MR fluid andworkpiece results in material removal fromworkpiece.

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Why MRFF process ?

Nanometer surface roughness without destroying form geometry of component

Precisely controlled finishing spot for deterministic finishing (finishing only where it is required)

Applicable to almost any material (soft, brittle, hard, metal, non-metal, etc.)

No post finishing operation is required (single step finishing process)

Applicable to any size and shape of workpiece Can give finish to angstrom level surface roughness

value with sophisticated toolings.

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Magnetic particle Abrasive particle Carrier fluid StabilizersCarbonyl iron powder (CIP),

Electrolyte Iron powderCeO2, Al2O3, SiC, B4C,

Diamond powderWater, Oil, etc.

Glycerol, Grease, etc.

Magnetorheological (MR) fluid

Optimum concentration of magnetic particles and abrasive particles High yield stress under magnetic field Low off state viscosity Less agglomeration and good re-dispersibility High polishing efficiency (high removal rate without surface damage). Resistance to corrosion

No magnetic field With magnetic field With magnetic field and abrasive particles

Essential Features of MR fluid

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Application areas of MRFF process

High precision SPDT mirrorDr. Stephen Veldhuis, McMaster University

Optical glasses or lenseshttp://www.nanophase.com

Off-axis mirrorshttp://www.interspectrum.ee

Die or mold http://www.ilt.fraunhofer.de, http://www.global-plastic-injection-molding.com

Medical implantshttp://www.extrudehone.com

Nanofinishing of soft or brittle materials (glass, optic, lense, ceramics, etc.)hard materials (metals)

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Sa = 1.15 nm

Photographs AFM images Surface roughness plots

Sa = 1270 nm

Ra = 1320 nm

Ra = 8 nm

Before finishing

After finishing

Images of silicon surfaces

Ajay Sidpara, Ph.D. Thesis, IIT Kanpur

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Nanofinishing of knee joint implants

Sa = 223 nm Sa = 37.4 nm Sa = 21.7 nm

Ra = 268 nm Ra = 45.4 nm Ra = 28 nm

Initial surfaceFinished surface with

chemical added MR fluidFinished surface with water based MR fluid

Photographs

2D roughness

plots

3D roughness

plots

Ajay Sidpara, V. K. Jain (2012), “Nanofinishing of free form surfaces of prosthetic knee joint implant”, Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture. Volume 226 (11), Pages 1833-1846.

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Top view of assembly

Nanofinishing of Aircraft’s blade bearing

Bottom view of assembly

Source: http://home.iitk.ac.in/~ajays/Research.htm

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MRF machines (Q22) are commercially available for polishing highprecision spherical / aspherical lenses, mirrors, etc.

Source: www.qedmrf.com

Applications of MRF Process