Method and apparatus for polishing an internal surface of an aluminum extrusion hollow shape

Abstract

There is provided an electrolytic integrated polishing apparatus which enables high precision polishing of the internal surface of a long sized cylindrical workpiece such as a metallic tube. The apparatus includes a work supporting unit for disposing the cylindrical workpiece, so that the axial center of the cylindrical portion is aligned with the vertical direction, a rotation shaft supported downward along the vertical direction and free-rotatably supported in an external tube which is freely movable along the vertical direction, a tool electrode including a grindstone directed to radial directions, attached to the tip of the rotation shaft, and a plastic tube wound around the external surface of the external tube for pressurization.

1 . An electrolytic integrated polishing apparatus for polishing an internal surface of a cylindrical portion of a long sized cylindrical workpiece by integrating elution by electrolyte and abrasion by a grindstone attached to a tool electrode inserted into the cylindrical portion, said apparatus comprising a work supporting unit for disposing the long sized cylindrical workpiece so that the axial center of its cylindrical portion is aligned with the vertical direction, a rotation shaft inserted into the cylindrical portion of said long sized cylindrical workpiece, a coaxial external tube supported downward along the vertical direction to free-rotatably support said rotation shaft and inserted together with said rotation shaft into the cylindrical portion of said long sized cylindrical workpiece, a tool electrode attached to the tip of said rotation shaft, and a transportation unit for moving said rotation shaft and/or the work supporting unit along the axial direction.  
   
   
       2 . The electrolytic integrated polishing apparatus for polishing the internal surface of the cylindrical portion of a long sized cylindrical workpiece according to  claim 1 , wherein a plastic tube, inside of which can be pressurized, is spirally wound around the periphery of said external tube.  
   
   
       3 . The electrolytic integrated polishing apparatus for polishing the internal surface of the cylindrical portion of a long sized cylindrical workpiece according to  claim 2 , wherein a free ring, having approximately the same bore as the finished bore of said cylindrical portion, is free-rotatably disposed to the upper and the lower positions of the cylindrical portion of the long sized cylindrical workpiece, and a guide sleeve with a predetermined length, having approximately the same bore as the bore of said free ring, is disposed further above the free ring disposed at the upper side.  
   
   
       4 . An aluminum extrusion hollow shape finished by the electrolyte integrated polishing apparatus according to  claim 1 , wherein a length of a cylindrical portion thereof being ten times as large as a diameter thereof, or more, and a roundness of an internal surface of the cylindrical portion equal to or smaller than 10 μm and a surface roughness Rmax equal to or small than 1 μm.  
   
   
       5 . The electrolytic integrated polishing apparatus for polishing the internal surface of the cylindrical portion of a long sized cylindrical workpiece according to  claim 1 , wherein a free ring, having approximately the same bore as a finished bore of said cylindrical portion, is free-rotatably disposed to the upper and the lower positions of the cylindrical portion of the long sized cylindrical workpiece.  
   
   
       6 . The electrolytic integrated polishing apparatus for polishing the internal surface of the cylindrical portion of a long sized cylindrical workpiece according to  claim 2 , wherein a free ring, having approximately the same bore as a finished bore of said cylindrical portion, is free-rotatably disposed to the upper and the lower positions of the cylindrical portion of the long sized cylindrical workpiece.  
   
   
       7 . The electrolytic integrated polishing apparatus for polishing the internal surface of the cylindrical portion of a long sized cylindrical workpiece according to  claim 1 , wherein a hollow portion is provided inside the tool electrode, and a plastic tube, inside of which can be pressurized, is provided in said hollow portion.  
   
   
       8 . The electrolytic integrated polishing apparatus for polishing the internal surface of the cylindrical portion of a long sized cylindrical workpiece according to  claim 2 , wherein a hollow portion is provided inside the tool electrode, and a plastic tube, inside of which can be pressurized, is provided in said hollow portion.  
   
   
       9 . The internal surface of the cylindrical portion of a long sized cylindrical workpiece according to  claim 3 , wherein a hollow portion is provided inside the tool electrode, and a plastic tube, inside of which can be pressurized, is provided in said hollow portion.