Hot Pressed Pilot Hole Geometry for Accurate Burring Alignment
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Solution Overview
Problem
Hot pressing methods face challenges in maintaining positional accuracy of positioning holes due to thermal expansion and contraction of sheet materials, leading to potential misalignment and quality degradation of hot pressed products.
Innovation Solution
A method involving the formation of pilot holes with specific opening shapes, including alternately arranged convex and concave portions, to facilitate accurate burring processes during hot pressing, ensuring proper alignment and reducing the risk of cracks in burred portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a circular pilot hole is used for burring during hot pressing, then the positioning accuracy is affected due to thermal expansion and contraction, but using a specially shaped pilot hole with convex and concave portions increases the complexity of hole formation
Solution Approach 1:
The patent applies asymmetry by designing the pilot hole with an asymmetric shape featuring alternating convex and concave portions rather than a simple circular shape. This asymmetric geometry creates specific engagement points that guide the burring punch, ensuring accurate positioning even when thermal expansion and contraction occur during hot pressing. The asymmetric design transforms the hole formation from a simple circular cut to a more complex patterned opening that serves as a precise positioning reference.
Solution Approach 2:
The patent implements preliminary action by forming the pilot hole with the specific convex and concave portion shape before the hot pressing process begins. This pre-formed pilot hole serves as a positioning reference that guides the subsequent burring punch during hot pressing. By preparing the pilot hole in advance with the correct geometry, the system ensures that the burring operation can proceed accurately despite the thermal effects that will occur during pressing, eliminating the need for real-time adjustment during the hot pressing process.
2Strength
If the burring punch diameter is made larger to ensure proper burring, then cracks may form in the flange portion, but making it smaller reduces positioning accuracy
Solution Approach 1:
The patent applies local quality by creating variations in the pilot hole geometry with specific convex and concave portions at different locations. The convex portions provide localized engagement points for the burring punch that concentrate the positioning function, while the concave portions allow material flow and reduce stress concentration during burring. This localized geometric variation enables the use of an optimally sized burring punch that maintains positioning accuracy without causing cracks in the flange portion.
Solution Approach 2:
The patent uses the specially shaped pilot hole as an intermediary element between the positioning requirement and the burring operation. The convex and concave portions of the pilot hole act as intermediate features that guide the burring punch into correct alignment while distributing the mechanical stresses during burring. This intermediary pilot hole structure mediates between the need for precise positioning and the need to prevent cracks, allowing the burring punch of appropriate diameter to perform both functions effectively.
3Manufacturing precision
If plates with positioning holes are welded to the base material after hot pressing, then positioning accuracy can be maintained, but production efficiency decreases due to additional welding steps
Solution Approach 1:
The patent merges the positioning hole formation and the positioning reference creation into a single integrated step. Instead of forming holes in separate plates and then welding those plates to the base material, the invention forms the pilot holes directly in the base material itself with the specific convex and concave portion shape. This consolidation eliminates the need for separate positioning plates and welding operations, maintaining positioning accuracy while significantly improving production efficiency by reducing the number of manufacturing steps.
Solution Approach 2:
The patent extracts the positioning function from separate auxiliary plates and integrates it directly into the base material through the specially shaped pilot holes. By removing the need for separate positioning plates and their associated welding operations, the invention maintains the essential positioning reference function while eliminating the harmful additional manufacturing steps. The convex and concave portions of the pilot holes provide the positioning reference function that previously required separate components.
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
This approach enhances the positional accuracy and quality of hot pressed products by maintaining alignment during the burring process, even with thermal expansion, and prevents cracks in flange portions, allowing for high-quality manufacturing with improved production efficiency.
Implementation Method 1
the sheet material expands when heated and thermally contracts when press-molded during hot pressing
Implementation Method 2
the sheet material expands when heated and thermally contracts when press-molded during hot pressing
Implementation Method 3
forming a burred portion at the pilot hole by using a burring punch included in a die set while molding the sheet material heated in the heating step
Data Source
AI summary
A method for manufacturing a hot pressed product by heating a sheet material and quenching the sheet material while molding the sheet material includes a hole forming step of forming a pilot hole in the sheet material; a heating step of heating the sheet material in which the pilot hole is formed; and a molding step of forming a burred portion at the pilot hole by using a burring punch included in a die set while molding the sheet material in the die set. The pilot hole has an opening shape in which convex portions and concave portions are alternately arranged. A diameter of a circumscribed circle that is in contact with the convex portions is greater than a punch diameter of the burring punch. A diameter of an inscribed circle that is in contact with the concave portions is less than the punch diameter of the burring punch.