Two-Stage Molded Part Forming to Minimize Giga Steel Springback
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Solution Overview
Problem
The challenge is to manufacture molded members with excellent shape holdability by minimizing springback, which is a significant issue in cold stamping of giga steels due to their high strength and poor ductility.
Innovation Solution
A method involving two molding operations is employed. The first molding operation creates a base material with specific flange and web configurations, and the second operation compresses the initial product to form a final product with improved shape retention. This method includes forming vertical bead portions on the second web member to enhance rigidity and reduce springback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cold stamping is used to manufacture giga steels with high strength, then manufacturing cost is reduced and productivity is improved, but shape holdability deteriorates due to springback
Solution Approach 1:
The patent applies preliminary action by performing a first molding operation before the final molding operation. In this first operation, a preliminary molded product is formed with specific geometric features (first upper flange with greater length than second upper flange, and first web members with greater length than second web members). This preliminary shaping creates favorable stress distribution conditions that prevent springback in the subsequent final molding operation, thereby achieving both high productivity and excellent shape holdability.
Solution Approach 2:
The patent utilizes parameter changes by transforming the material state through the first molding operation. The base material is initially formed into a preliminary molded product with specific dimensional parameters (flange lengths and web member lengths) that are deliberately designed to be larger than the final product dimensions. This parameter transformation creates compressive residual stress distribution that counteracts springback during the second molding operation.
2Shape
If complex shapes with deep depth and changing cross-section are formed, then collision characteristics are improved, but manufacturing difficulty increases due to necking and cracks
Solution Approach 1:
The patent applies segmentation by dividing the manufacturing process into two distinct molding operations. The first operation creates a preliminary molded product with simplified geometry (flanges and web members), and the second operation forms the final complex shape. This segmentation allows each operation to focus on specific geometric requirements, reducing the risk of necking and cracks that would occur if the entire complex shape were formed in a single operation.
Solution Approach 2:
The first molding operation serves as a preliminary action that prepares the material in an optimal state for the final forming operation. By pre-forming the base material into a structure with appropriate flange and web member dimensions, the material is better prepared to withstand the complex deformation required for the final shape, thereby reducing manufacturing difficulty.
Data Source
AI summary
The present invention provides a method for manufacturing molded parts, the method being characterized by comprising: a first molding step for molding a base material to form a first molded part including a first upper flange and a pair of first web members extending in intersecting directions from the left and right ends of the first upper flange; and a second molding step for compressing the first molded part to form a second molded part including a second upper flange and a pair of second web members extending in intersecting directions from the left and right ends of the second upper flange, wherein, in a width direction cross section, the first upper flange is longer than the second upper flange and the first web members are longer than the second web members.