Method and apparatus for polishing a curved edge

Abstract

A method and an apparatus for polishing a curved edge of a molded part. A surface of the curved edge is abraded by contacting a polishing surface of a first polishing wheel to the curved edge repeatedly in a first direction concurrent with a rotational spinning direction of the first polishing wheel. The abraded surface of the curved edge is polished by contacting a polishing surface of a second polishing wheel to the curved edge in the first direction and in a second direction opposite to the first direction. The polishing surfaces of the first and second polishing wheels are shaped to conform to a portion of the surface of the curved edge of the molded part. The polishing wheel is maintained at a constant rotational speed by a controller when contacting the curved edge. The polished surface of the curved edge is visually smoothly uniform in reflective appearance.

1 . A method for polishing a curved edge of a molded part, the method comprising:
 abrading a first surface of the curved edge of the molded part by contacting a first polishing surface on a first polishing wheel to the first surface of the curved edge of the molded part repeatedly in a first direction concurrent with a rotational spinning direction of the first polishing wheel, the first polishing surface shaped to substantially conform to a portion of the first surface of the curved edge of the molded part; and   polishing the abraded first surface of the curved edge of the molded part by contacting a second polishing surface on a second polishing wheel to the abraded first surface of the curved edge of the molded part, alternating contact in the first direction and in a second direction opposite to the first direction, the second polishing surface shaped to substantially conform to the portion of the first surface of the curved edge of the molded part.   
     
     
         2 . The method of  claim 1  further comprising:
 abrading a second surface of the curved edge of the molded part by contacting a third polishing surface on the first polishing wheel to the second surface of the curved edge of the molded part repeatedly in the first direction concurrent with the rotational spinning direction of the first polishing wheel, the third polishing surface shaped to substantially conform to a portion of the second surface of the curved edge of the molded part; and 
 polishing the abraded second surface of the curved edge of the molded part by contacting a fourth polishing surface on the second polishing wheel to the abraded second surface of the curved edge of the molded part, alternating contact in the first direction and in the second direction opposite to the first direction, the fourth polishing surface shaped to substantially conform to the portion of the second surface of the curved edge of the molded part. 
 
     
     
         3 . The method of  claim 1  wherein the molded part is formed from an injection molded thermoplastic. 
     
     
         4 . The method of  claim 1  wherein the first surface of the curved edge of the molded part comprises a parting line surface defect. 
     
     
         5 . The method of  claim 4  wherein the parting line surface defect comprises a step having a displacement greater than 10 microns perpendicular to the first surface of the curved edge of the molded part. 
     
     
         6 . The method of  claim 5  wherein the first direction of abrading is into a face of the parting line surface defect. 
     
     
         7 . The method of  claim 1  further comprising:
 maintaining the first polishing wheel at a constant rotational speed when in contact with the first surface of the curved edge of the molded part. 
 
     
     
         8 . The method of  claim 7  wherein the maintaining comprises varying a position of the first polishing wheel with respect to the first surface of the curved edge of the molded part while abrading or polishing. 
     
     
         9 . The method of  claim 1  wherein the polished first surface of the curved edge of the molded part is visually smoothly uniform in reflective appearance. 
     
     
         10 . An apparatus for polishing a curved edge of a molded part, the apparatus comprising:
 a first polishing wheel comprising a first polishing surface shaped to substantially conform to a portion of a first surface of the curved edge of the molded part;   a second polishing wheel comprising a second polishing surface shaped to substantially conform to the portion of the first surface of the curved edge of the molded part;   a first positioning assembly configured to contact the first polishing surface of the first polishing wheel to the first surface of the curved edge of the molded part repeatedly in a first direction concurrent with a rotational spinning direction of the first polishing wheel to abrade the first surface of the curved edge of the molded part to a first smoothness; and   a second positioning assembly configured to contact the second polishing surface of the second polishing wheel to the first surface of the curved edge of the molded part alternately in the first direction and in a second direction opposite to the first direction to polish the abraded first surface of the curved edge of the molded part to a second smoothness.   
     
     
         11 . The apparatus of  claim 10  further comprising:
 the first polishing wheel further comprises a third polishing surface shaped to substantially conform to a portion of a second surface of the curved edge of the molded part; 
 the second polishing wheel further comprises a fourth polishing surface shaped to substantially conform to the portion of the second surface of the curved edge of the molded part; 
 the first positioning assembly further configured to contact the third polishing surface to the second surface of the curved edge of the molded part repeatedly in the first direction concurrent with the rotational spinning direction of the first polishing wheel to abrade the second surface of the curved edge of the molded part to the first smoothness; and 
 the second positioning assembly further configured to contact the fourth polishing surface to the second surface of the curved edge of the molded part alternately in the first direction and in the second direction opposite to the first direction to polish the second surface of the curved edge of the molded part to the second smoothness. 
 
     
     
         12 . The apparatus of  claim 10  wherein the molded part is formed from an injection molded thermoplastic. 
     
     
         13 . The apparatus of  claim 10  wherein the unpolished first surface of the curved edge of the molded part comprises a parting line surface defect. 
     
     
         14 . The apparatus of  claim 13  wherein the parting line surface defect comprises a step having a displacement greater than 10 microns perpendicular to the first surface of the curved edge of the molded part. 
     
     
         15 . The apparatus of  claim 14  wherein the first direction of abrading is into a face of the parting line surface defect. 
     
     
         16 . The apparatus of  claim 10  further comprising
 a controller to maintain a constant rotational speed of the first polishing wheel when in contact with the first surface of the curved edge of the molded part. 
 
     
     
         17 . The apparatus of  claim 10  wherein the second smoothness is visually smoothly uniform in reflective appearance. 
     
     
         18 . A computer readable medium for storing computer program code executed by a processor for controlling a computer aided manufacturing operation for polishing a curved edge of a molded part, the computer readable medium comprising:
 computer program code for abrading a first surface of the curved edge of the molded part by contacting a first polishing surface on a first polishing wheel to the first surface of the curved edge of the molded part repeatedly in a first direction concurrent with a rotational spinning direction of the first polishing wheel, the first polishing surface shaped to substantially conform to a portion of the first surface of the curved edge of the molded part; and   computer program code for polishing the abraded first surface of the curved edge of the molded part by contacting a second polishing surface on a second polishing wheel to the abraded first surface of the curved edge of the molded part, alternating contact in the first direction and in a second direction opposite to the first direction, the second polishing surface shaped to substantially conform to the portion of the first surface of the curved edge of the molded part.   
     
     
         19 . The computer readable medium of  claim 18  further comprising:
 computer program code for abrading a second surface of the curved edge of the molded part by contacting a third polishing surface on the first polishing wheel to the second surface of the curved edge of the molded part repeatedly in the first direction concurrent with the rotational spinning direction of the first polishing wheel, the third polishing surface shaped to substantially conform to a portion of the second surface of the curved edge of the molded part; and 
 computer program code for polishing the abraded second surface of the curved edge of the molded part by contacting a fourth polishing surface on the second polishing wheel to the abraded second surface of the curved edge of the molded part, alternating contact in the first direction and in the second direction opposite to the first direction, the fourth polishing surface shaped to substantially conform to the portion of the second surface of the curved edge of the molded part. 
 
     
     
         20 . The computer readable medium of  claim 18  further comprising:
 computer program code for maintaining the first polishing wheel at a constant rotational speed when in contact with the first surface of the curved edge of the molded part. 
 
     
     
         21 . The computer readable medium of  claim 20  wherein the maintaining comprises varying a position of the first polishing wheel with respect to the first surface of the curved edge of the molded part while abrading or polishing.