Flexible spindle polishing

Abstract

Precise surface treatment and finishing of an enclosed, non-linear channel through a 3-dimensional printed, additively manufactured or machined part or workpiece results from insertion of a grinding wheel on a flexible shaft and controlling an orbital movement though rotational speed, grit selection and fluid viscosity of a liquid medium in the channel. Drive logic rotates the flexible shaft for controlled rotation as the orbital movement or pattern achieves controlled contact with the interior channel surface. Rotational contact by the grinding wheel removes material based on a grit size, while the orbit is controlled through the rotation, viscosity and grit size for achieving uniform coverage of the interior surface. An internal geometry, typically circular or elliptical, is preserved while attaining a smooth surface through precise material removal resulting from the controlled orbit.

What is claimed is: 
     
         1 . A polishing device for surface treatment of an interior surface of a conduit, comprising:
 a grinding wheel adapted for rotation;   a flexible shaft attached to the grinding wheel;   an abrasive surface geometry defined by an exterior of the grinding wheel; and   a drive source responsive to drive logic for rotating the flexible shaft, the flexible shaft configured for a rotation speed for attaining an orbit of the grinding wheel based on the abrasive surface geometry.   
     
     
         2 . The device of  claim 1  wherein the abrasive surface geometry further comprises a grit size, the flexible shaft configured for a rotation speed for attaining the orbit of the grinding wheel based on the grit size of the abrasive surface geometry. 
     
     
         3 . The device of  claim 2  further comprising a fluid within the conduit, wherein the drive logic is configured for controlling the rotation speed based on at least the grit size and a viscosity of the fluid. 
     
     
         4 . The device of  claim 1 , further comprising a fluid source, the fluid source configured to deliver a fluid having a viscosity and a density into the conduit, the orbit responsive to at least one of the viscosity and density for achieving a predetermined percentage of coverage of the interior surface based on consistent grinding wheel dynamics. 
     
     
         5 . The device of  claim 1  wherein the abrasive surface further comprises an abrasive height, the abrasive height indicative of a variation of the abrasive surface geometry based on the grit size. 
     
     
         6 . The device of  claim 5  wherein the abrasive surface geometry further comprises a distribution, orientation and patterning of an abrasive material adhered to the surface of the griding wheel. 
     
     
         7 . The device of  claim 1  wherein the rotation induces an elastic force in the flexible shaft, the elastic force resulting from a nonlinear path of the conduit, the orbit based on the abrasive surface geometry and the elastic force. 
     
     
         8 . The device of  claim 3  wherein the drive logic is further configured to generate, based on the rotational speed, grinding forces and hydrodynamic forces, the drive logic configured to ensure the grinding forces and hydrodynamic forces are unequal and opposed. 
     
     
         9 . The device of  claim 3  wherein the drive logic is further configured to generate, based on the rotational speed, grinding forces and hydrodynamic forces; and
 generate a net force acting in the direction of an intended orbital motion. 
 
     
     
         10 . The device of  claim 3  wherein the drive logic is further configured to generate, based on the rotational speed:
 a hydrodynamic force resulting from the viscosity and the grit size, the hydrodynamic force having components normal and outward to the interior surface, and tangential to the interior surface; and 
 a grinding force having components inward and normal to the interior surface, and tangential to the interior surface and aligned with a rotation of the grinding wheel. 
 
     
     
         11 . The device of  claim 1  wherein the orbit defines a cyclic path around the interior of the conduit, the orbit having a radius less than a radius of the conduit. 
     
     
         12 . The device of  claim 11  wherein the orbit defines an irregular path, the irregular path based on at least the rotation speed, the abrasive surface geometry, a viscosity of fluid in the conduit, and a shape of the grinding wheel. 
     
     
         13 . The device of  claim 1  wherein the shape of the grinding wheel includes at least one of an ellipsoid with a circular cross section, sphere, fluted, finned and triangular with radiused edges. 
     
     
         14 . The device of  claim 1  wherein the conduit has an internal diameter of between 0.5-300 mm. 
     
     
         15 . The device of  claim 1  wherein the grit size defines the abrasive surface geometry with a grit height between 40-120 microns. 
     
     
         16 . In a material fabrication environment for forming internal channels with curvilinear portions in a machined body, a method for smoothing a surface of the internal channels, comprising:
 attaching a grinding wheel at a distal end of a flexible shaft;   engaging a drive source with a proximal end of the flexible shaft for rotation of the grinding wheel via the flexible shaft;   inserting the grinding wheel into the channel;   creating a fluid media in communication with the channel and the grinding wheel; and   rotating the flexible shaft at a rotation speed for controlling an orbit of the grinding wheel against the surface of the channel.   
     
     
         17 . The method of  claim 16  further comprising:
 selecting an abrasive surface geometry on an outer surface of the grinding wheel; 
 selecting a viscosity of a fluid flowing through the channel; and 
 controlling the orbit of the grinding wheel based on the abrasive surface geometry and the selected viscosity. 
 
     
     
         18 . The method of  claim 17  further comprising generating a down-grinding orbit of the grinding wheel by engaging the grinding wheel against the surface of the channel in a direction the same as a rotation of the grinding wheel. 
     
     
         19 . The method of  claim 17  further comprising generating an up-grinding orbit of the grinding wheel by engaging the grinding wheel against the surface of the channel in a direction opposite to a rotation of the grinding wheel. 
     
     
         20 . The method of  claim 17 , further comprising:
 selecting a rotation speed, fluid viscosity and grit size for controlling an orbital path of a grinding wheel; and   operating the drive logic and a fluid supply for flowing the fluid based on the selected rotation speed, fluid viscosity and grit size.   
     
     
         21 . A system for surface treatment of an interior surface of a conduit, comprising:
 a grinding wheel adapted for rotation;   a flexible shaft attached to the grinding wheel and responsive to drive logic for rotation of the grinding wheel;   a fluid supply for providing fluid to an interior of the conduit; and   an abrasive surface geometry on an exterior of the grinding wheel, the drive logic for rotating the flexible shaft, the flexible shaft configured for a rotation speed for attaining an orbit of the grinding wheel based on a grit size of the abrasive surface geometry, a rotational speed of the grinding wheel and a viscosity of the fluid.