Methods and assemblies for forming an annular object

Abstract

A method is provided for forming an annular object. This method includes: providing a frustoconical preform extending axially along an axis, wherein a sidewall of the frustoconical preform is angularly offset from the axis by a preform angle; externally drawing the frustoconical preform over an outer surface of a punch and an outer surface of a die clamp to provide an externally drawn body, wherein the outer surface of the die clamp is angularly offset from the axis by a die clamp angle that is different than the preform angle; mating a die with the die clamp to provide a die assembly, wherein the externally drawn body is clamped radially between the die and the die clamp; and translating the die assembly axially along the axis and into a bore of the punch to at least partially internally draw the externally drawn body against an inner surface of the punch.

What is claimed is: 
     
         1 . A method for forming an annular object, comprising:
 providing a frustoconical preform extending axially along an axis, wherein a sidewall of the frustoconical preform is angularly offset from the axis by a preform angle;   externally drawing the frustoconical preform over an outer surface of a punch and an outer surface of a die clamp to provide an externally drawn body, wherein the outer surface of the die clamp is angularly offset from the axis by a die clamp angle that is different than the preform angle;   mating a die with the die clamp to provide a die assembly, wherein the externally drawn body is clamped radially between the die and the die clamp; and   translating the die assembly axially along the axis and into a bore of the punch to at least partially internally draw the externally drawn body against an inner surface of the punch.   
     
     
         2 . The method of  claim 1 , wherein the die clamp angle is less than the preform angle. 
     
     
         3 . The method of  claim 1 , wherein the die clamp angle is between fifteen degrees and twenty-five degrees. 
     
     
         4 . The method of  claim 1 , wherein the preform angle is between twenty-five degrees and forty degrees. 
     
     
         5 . The method of  claim 1 , further comprising:
 clamping the frustoconical preform with an external die assembly; and   translating the external die assembly axially along the axis to at least partially externally draw the frustoconical preform over at least one of the outer surface of the punch or the outer surface of the die clamp.   
     
     
         6 . The method of  claim 5 , wherein
 the external die assembly includes an inner clamp member and an outer clamp member;   the frustoconical preform is clamped between an outer surface of the inner clamp member and an inner surface of the outer clamp member; and   the outer surface of the inner clamp member is angularly offset from the axis by an external die angle that is different that the die clamp angle. The method of  claim 6 , wherein the external die angle is equal to the preform angle.   
     
     
         8 . The method of  claim 1 , wherein the frustoconical preform comprises metal. 
     
     
         9 . The method of  claim 1 , wherein the annular object comprises an inlet lip of an aircraft propulsion system nacelle. 
     
     
         10 . The method of  claim 1 , further comprising annealing the externally drawn body following the translating of the die assembly. 
     
     
         11 . A method for forming an annular object, comprising:
 clamping a frustoconical preform with an external die assembly, wherein a surface of the external die assembly abutted against the frustoconical preform is angularly offset from an axis by an external die angle;   translating the external die assembly axially along the axis to externally draw the frustoconical preform over an outer surface of a punch and an outer surface of an internal die clamp to provide an externally drawn body, wherein the outer surface of the internal die clamp is angularly offset from the axis by a die clamp angle that is different than the external die angle;   mating an internal die with the internal die clamp to provide an internal die assembly, wherein the externally drawn body is clamped radially between the internal die and the internal die clamp; and   translating the internal die assembly axially along the axis and into a bore of the punch to at least partially internally draw the externally drawn body against an inner surface of the punch.   
     
     
         12 . The method of  claim 11 , wherein the die clamp angle is less than the external die angle. 
     
     
         13 . The method of  claim 11 , wherein the die clamp angle is greater than fifteen degrees and less than twenty-five degrees. 
     
     
         14 . The method of  claim 11 , wherein the external die angle is greater than twenty-five degrees and less than forty degrees. 
     
     
         15 . The method of  claim 11 , wherein a sidewall of the frustoconical preform is angularly offset from the axis by a preform angle, and the die clamp angle is different than the preform angle. 
     
     
         16 . The method of  claim 11 , wherein
 the external die assembly includes an inner clamp member and an outer clamp member;   the surface of the external die assembly is an outer surface of the inner clamp member; and   the frustoconical preform is clamped between the outer surface of the inner clamp member and an inner surface of the outer clamp member.   
     
     
         17 . The method of  claim 11 , wherein the frustoconical preform is formed from metal. 
     
     
         18 . The method of  claim 11 , wherein the annular object is configured as an inlet structure of a nacelle for an aircraft propulsion system. 
     
     
         19 . An assembly for forming an annular object, comprising:
 a punch, an external die assembly and an internal die assembly that comprises an internal die clamp and an internal die;   the external die assembly configured to clamp onto a frustoconical preform, and the external die assembly further configured to translate axially along an axis to externally draw the frustoconical preform over an outer surface of the punch and an outer surface of the internal die clamp to provide an externally drawn body, wherein a surface of the external die assembly configured to contact the frustoconical preform is angularly offset from the axis by an external die angle, and the outer surface of the internal die clamp is angularly offset from the axis by a die clamp angle that is different than the external die angle;   the internal die configured to mate with the internal die clamp such that the externally drawn body is clamped radially between the internal die and the internal die clamp; and   the internal die assembly configured to translate axially along the axis and into a bore of the punch to at least partially internally draw the externally drawn body against an inner surface of the punch.   
     
     
         20 . The assembly of  claim 19 , wherein
 the die clamp angle is greater than fifteen degrees and less than twenty-five degrees; and   the external die angle is greater than twenty-five degrees and less than forty degrees.