Sheared End Face Reshaping for Metal Blank Surface Finish
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Solution Overview
Problem
Progressive forming machines often produce metal blanks with unsatisfactory surface roughness on sheared end faces due to residual surface irregularities, which can be a problem for applications requiring high quality or smooth finishes, even under high forming pressures.
Innovation Solution
A method involving a sequence of steps to reshape the sheared end face from a planar to a concave and then a convex configuration, with optional flattening, using tapered punch and die tools with central vents to prevent fluid obstruction and ensure proper material conformance to tooling, effectively improving surface finish.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high compressive forces are applied in reshaping blows, then some surface roughness is eliminated, but residual surface roughness remains unsatisfactory
Solution Approach 1:
The surface finishing process is divided into multiple sequential stages: initial shearing, first reshaping blow, second reshaping blow, and optional flattening. Each stage progressively improves the surface finish, with the final stage achieving Rz=16 or less. This segmented approach allows incremental improvement without requiring excessive force in a single step.
Solution Approach 2:
The blank is pre-tapered adjacent to the end face before the forming operations begin. This preliminary action ensures that material can flow freely during the subsequent reshaping blows, preventing flash and allowing the surface finish to improve progressively through each stage rather than requiring extremely high compressive forces all at once.
2Stability of the object's composition
If the blank end material is radially restricted during reshaping, then material confinement is achieved, but flash occurs around the punch
Solution Approach 1:
The blank is pre-tapered adjacent to the end face before forming operations begin. This preliminary tapering creates a gradual transition zone that allows material to flow smoothly during reshaping, preventing sudden radial restriction that would cause flash around the punch while still maintaining adequate material confinement for proper forming.
3Temperature
If oil/coolant and/or air are present during forming, then cooling and lubrication are provided, but these fluids obstruct material conformance to the tool face
Solution Approach 1:
A central vent is incorporated into the punch or tool, which extracts or removes the accumulated oil/coolant and/or air from the forming zone during the reshaping operation. This allows the beneficial cooling and lubrication effects to occur while preventing fluid accumulation that would otherwise obstruct the blank end material from conforming closely to the tool face, thereby achieving both temperature control and surface precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method significantly enhances the surface smoothness of metal blanks, achieving a surface finish of Rz=16 or less, thereby improving both functionality and aesthetics of the finished parts.
Implementation Method 1
The blank adjacent its end is tapered so that it is smallest at the end face prior to being formed into a convex shape. The taper advantageously ensures that the blank end material is not radially restricted and caused to flash around the punch when it is being reshaped.
Implementation Method 2
The tool or punch that converts the end face from concave to convex has a unique central vent for exhausting oil/coolant and/or air, thereby preventing these fluids from obstructing the blank end material from closely conforming to the face of the tool.
Implementation Method 3
The process involves a sequence of steps in which an end surface is forced into a non-planar configuration, is then driven into a reverse configuration and then, is optionally flattened. In the preferred embodiment, the first blow forces the end face into a concave configuration and at a successive station the end face is forced into a convex configuration.
Data Source
AI summary
A method of improving the surface finish of a sheared end face of a cylindrical blank in a progressive forming machine comprising deforming the end face out of its original as sheared transverse plane into a first shape concentric with the axis of the blank that slightly departs from the original plane a distance that increases with proximity to the axis of the blank, thereafter deforming the end face from the first shape into a second shape in a direction opposite a direction the first shape was displaced from the original shear plane, the second shape slightly departing from a transverse plane a distance that increases with proximity to the axis of the blank.