Machining method and machining tool for machining a curved workpiece surface, and workpiece

Abstract

In a machining method for machining a curved workpiece surface ( 210 ) of a workpiece ( 200 ), a roll-embossing operation is carried out. At least one rolling element ( 180 A, 180 B, 180 C) of a machining tool ( 100 ) is rolled here under a contact pressure against a section ( 198 ) to be machined of the curved workpiece surface. An external surface of the rolling element has a rough surface structure in at least one working section ( 190 A, 190 B, 190 C) intended for rolling contact with the workpiece surface. The contact pressure is set in such a manner that, during the rolling, a rough roll-embossed structure is produced by local deformation of workpiece material without removing material in the machined region of the workpiece surface. The machining method can be used, for example, for machining the internal surface of a bore in a workpiece, in particular for roughening the workpiece surface for a subsequent coating.

1 . A machining method for machining a curved workpiece surface of a workpiece, the method comprising the steps of:
 rolling at least one rolling element of a machining tool under a contact pressure against a section to be machined of the curved workpiece surface in a roll-embossing operation, wherein an external surface of the rolling element has a rough surface structure in at least one working section intended for rolling contact with the workpiece surface; and   setting the contact pressure in such a manner that, during the rolling, a rough roll-embossed structure is produced by local deformation of workpiece material in the region of the workpiece surface.   
     
     
         2 . The machining method as claimed in  claim 1 , wherein a roll-embossed structure having an average peak to valley height Rz of more than 10 μm is produced on the workpiece surface by the roll-embossing operation, wherein the average peak to valley height produced lies within the range of between Rz=30 μm and Rz=100 μm. 
     
     
         3 . The machining method as claimed in  claim 1 , wherein, after the roll-embossing operation, a coating is applied to the workpiece surface, wherein the coating is applied directly onto the rough roll-embossed structure produced by the roll-embossing operation, or wherein the roll-embossed structure is reworked after the roll-embossing operation with the aid of one or more reworking processes to produce a modified roll-embossed structure, and the coating is then applied onto the modified roll-embossed structure. 
     
     
         4 . The machining method as claimed in  claim 1 , wherein, during and/or after the roll-embossing operation, cleaning of the workpiece surface is carried out for eliminating material particles which are produced by the roll-embossing operation. 
     
     
         5 . The machining method as claimed in  claim 1 , wherein, during and/or after the roll-embossing operation, machining residues are extracted by suction from the roll-embossing operation. 
     
     
         6 . The machining method as claimed in  claim 1 , comprising a reworking operation which follows the roll-embossing operation and changes the shape of the roll-embossed structure in order to produce a modified roll-embossed structure. 
     
     
         7 . The machining method as claimed in  claim 1 , wherein the at least one rolling element of the machining tool is rolled under contact pressure against that section of the curved workpiece surface which is to be machined by the machining tool being guided at a predefined distance from the workpiece surface along a predefined path. 
     
     
         8 . The machining method as claimed in  claim 1 , wherein, in order to machine the internal surface of a bore, in particular a cylindrical bore, rolling of the at least one rolling element is brought about by a substantially bore-filling machining tool which is designed as a rotation tool and is driven in a rotating manner about the tool axis. 
     
     
         9 . A machining tool for machining a curved workpiece surface of a workpiece, comprising:
 a tool body which defines a tool axis, and   at least one rolling element which is carried by the tool body, is rotatable about a rolling element axis and has an external surface, wherein the external surface has a rough surface structure in at least one working section intended for rolling contact with the workpiece surface.   
     
     
         10 . The machining tool as claimed in  claim 9 , wherein the rolling element has a rolling element body which, in the working section, bears a coating having a rough surface structure, wherein the coating has a multiplicity of hard material grains bound in a binding. 
     
     
         11 . The machining tool as claimed in  claim 9 , wherein the rolling element axis of at least one rolling element runs concentrically with respect to the tool axis. 
     
     
         12 . The machining tool as claimed in  claim 9 , wherein the rolling element axis of at least one rolling element lies outside the tool axis. 
     
     
         13 . The machining tool as claimed in  claim 9 , wherein the rolling element axis of at least one rolling element runs parallel to the tool axis, and/or the rolling element axis of at least one rolling element runs radially outward and obliquely with respect to the tool axis. 
     
     
         14 . The machining tool as claimed in  claim 9 , wherein at least one rolling element has a cylinder-jacket-shaped external surface having a rough surface structure and at least one conical external surface which is adjacent to said external surface and has a rough surface structure. 
     
     
         15 . The machining tool as claimed in  claim 12 , wherein at least one carrier element which is movable relative to the tool body radially to the tool axis is arranged on the tool body, and the rolling element is mounted on the carrier element. 
     
     
         16 . The machining tool as claimed in  claim 9 , comprising a rolling element infeed system for the variably controllable infeed of the rolling element in an infeed direction running radially to the tool axis. 
     
     
         17 . The machining tool as claimed in  claim 9 , wherein a plurality of rolling elements are arranged distributed around the circumference of the tool body, and/or wherein a plurality of rolling elements distributed in a longitudinal direction of the tool are arranged on the tool body. 
     
     
         18 . The machining tool as claimed in  claim 17 , wherein, in addition to the plurality of rolling elements distributed around the circumference of the machining tool, the machining tool has a set of a plurality of further machining elements which are distributed around the circumference of the machining tool and can be infed radially independently of the rolling elements. 
     
     
         19 . The machining tool as claimed in  claim 9 , wherein the tool body has a coupling structure for coupling the machining tool onto a working spindle of a honing machine, or wherein the tool body has a coupling structure for coupling the machining tool onto the working spindle of a machining center. 
     
     
         20 . A workpiece, in particular a cylinder crankcase or cylinder sleeve, obtainable by using the machining method as claimed in  claim 1  and/or by using the machining tool as claimed in  claim 9 . 
     
     
         21 . The machining method as claimed in  claim 4 , wherein, during the cleaning, the roll-embossed structure is cleaned dry. 
     
     
         22 . The machining method as claimed in  claim 21 , wherein the roll-embossed structure is brushed by relatively soft, non-abrasive brushes and/or is pneumatically blown clear. 
     
     
         23 . The machining method as claimed in  claim 5 , wherein, in addition to the extraction by suction, the workpiece surface is blown clear. 
     
     
         24 . The machining method as claimed in  claim 6 , wherein the reworking operation comprises elimination of peaks in regions of elevations of the roll-embossed structure in order to produce a plateau structure with flattened elevations and depressions located in between on the workpiece surface. 
     
     
         25 . The machining method as claimed in  claim 24 , wherein the peaks in the region of elevations are eliminated by material-removing fine machining or by deformation. 
     
     
         26 . The machining method as claimed in  claim 7 , wherein a course of the predefined path is dependent on the curvature of the workpiece surface and on the required contact pressure. 
     
     
         27 . The machining tool according to  claim 10 , wherein the average grain size of the hard material grains is at least 15 μm. 
     
     
         28 . The machining tool according to  claim 27 , wherein the average grain size of the hard material grains lies within the range of 30 μm to 250 μm. 
     
     
         29 . The machining tool as in  claim 15 , wherein the rolling element is mounted in an elastically flexible manner on the carrier element. 
     
     
         30 . The machining tool as in  claim 18 , wherein the further machining elements are honing sticks or smoothing elements.