High removal rate magnetorheological finishing head

Abstract

A magnetorheological finishing head comprising magnetic pole pieces, nozzle shape, and wheel shape tailored to maximize volumetric removal rate. The carrier wheel for a ribbon of magnetorheological fluid is aspherical, preferably a toroid having a short radius perpendicular to, and the long radius parallel to, the axis of rotation, although the shape of the wheel may be any aspherical or free form parallel to the wheel's axis of rotation, e.g., toroidal or cylindrical. A magnetic field is generated by shaping the pole pieces to create a substantially uniform magnetic field over a defined gap therebetween such that the field strength in the area of the fluid ribbon is uniform. The nozzle has a non-circular opening to provide a fluid stream having a width that covers the width range of the magnetic field. It is the combination of these three features that allows for a novel MRF removal function.

1 . A magnetorheological finishing head,
 comprising,
 a) a rotatable finishing wheel having a non-spherical finishing surface; 
 b) first and second magnetic pole pieces of opposing polarity having corners disposed within said finishing wheel and having opposing faces, wherein the corners of said opposing faces closest to said finishing surface have a shape selected from the group consisting of conical, beveled, toroidal, radial, and freeform; and, 
 c) a nozzle assembly terminating in a non-circular exit. 
   
     
     
         2 . A magnetorheological finishing head,
 comprising any one of the following three elements:
 a) a rotatable finishing wheel having a non-spherical finishing surface; 
 b) first and second magnetic pole pieces of opposing polarity disposed within said finishing wheel and having opposing faces, wherein the corners of said opposing faces closest to said finishing surface have a shape selected from the group consisting of conical, beveled, toroidal, radial, and freeform; and 
 c) a nozzle assembly terminating in a non-circular exit. 
   
     
     
         3 . A magnetorheological finishing head,
 comprising any two of the following three elements:
 a) a rotatable finishing wheel having a non-spherical finishing surface; 
 b) first and second magnetic pole pieces of opposing polarity having corners disposed within said finishing wheel and having opposing faces, wherein the corners of said opposing faces closest to said finishing surface have a shape selected from the group consisting of conical, beveled, toroidal, radial, and freeform; and, 
 c) a nozzle assembly terminating in a non-circular exit. 
   
     
     
         4 . The magnetorheological finishing head in accordance with  claim 1  wherein the shape of said non-spherical finishing surface is selected from the group consisting of toroidal, cylindrical, and free-form. 
     
     
         5 . The magnetorheological finishing head in accordance with  claim 1  wherein said magnetic pole pieces are components of a magnetic system selected from the group consisting of electromagnet and permanent magnet. 
     
     
         6 . The magnetorheological finishing head in accordance with  claim 1  wherein a magnetic field above said finishing surface is substantially uniform from edge to edge of said magnetic field. 
     
     
         7 . The magnetorheological finishing head in with  claim 1  wherein said non-circular exit is a slot. 
     
     
         8 . The magnetorheological finishing head in accordance with  claim 1  wherein said rotatable finishing wheel is formed in accordance with the formula
     Z=f ( x,y )= R   y ±√[( R   y   −g ( x )) 2 - y   2 ],
 
 where g(x) is the generating curve and Z is the algebraic definition of said rotatable finishing wheel. 
 
     
     
         9 . The magnetorheological finishing head in accordance with  claim 1  wherein said first and second magnetic pole pieces are formed such that when they are energized a uniform magnetic fringing field is formed over a desired width on said rotatable finishing wheel. 
     
     
         10 . The magnetorheological finishing head in accordance with  claim 1  wherein said nozzle assembly is formed such that a ribbon of magnetorheological fluid extruded therefrom is of uniform thickness from edge to edge of said ribbon. 
     
     
         11 . The magnetorheological finishing head in accordance with  claim 1  wherein said non-circular exit of said nozzle assembly is selected from the group consisting of a slot, a slot with rounded ends, and a plurality of holes. 
     
     
         12 . The magnetorheological finishing head in accordance with  claim 2  wherein the shape of said non-spherical finishing surface is selected from the group consisting of toroidal, cylindrical, and free-form. 
     
     
         13 . The magnetorheological finishing head in accordance with  claim 2  wherein said magnetic pole pieces are components of a magnetic system selected from the group consisting of electromagnet and permanent magnet. 
     
     
         14 . The magnetorheological finishing head in accordance with  claim 2  wherein a magnetic field formed above said finishing surface is substantially uniform from edge to edge of said magnetic field. 
     
     
         15 . The magnetorheological finishing head in accordance with  claim 2  wherein said first and second magnetic pole pieces are formed such that when they are energized a uniform magnetic fringing field is formed over a desired width on said rotatable finishing wheel. 
     
     
         16 . The magnetorheological finishing head in accordance with  claim 2  wherein said nozzle assembly is formed such that a ribbon of magnetorheological fluid extruded therefrom is of uniform thickness from edge to edge of said ribbon. 
     
     
         17 . The magnetorheological finishing head in accordance with  claim 3  wherein the shape of said non-spherical finishing surface is selected from the group consisting of toroidal, cylindrical, and free-form. 
     
     
         18 . The magnetorheological finishing head in accordance with  claim 3  wherein said magnetic pole pieces are components of a magnetic system selected from the group consisting of electromagnet and permanent magnet. 
     
     
         19 . The magnetorheological finishing head in accordance with  claim 3  wherein a magnetic field formed above said finishing surface is substantially uniform from edge to edge of said magnetic field. 
     
     
         20 . The magnetorheological finishing head in accordance with  claim 3  wherein said first and second magnetic pole pieces are formed such that when they are energized a uniform magnetic fringing field is formed over a desired width on said rotatable finishing wheel. 
     
     
         21 . The magnetorheological finishing head in accordance with  claim 3  wherein said nozzle assembly is formed such that a ribbon of magnetorheological fluid extruded therefrom is of uniform thickness from edge to edge of said ribbon.