Variable-Stiffness Press Die for Accurate Green Body Demolding
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Solution Overview
Problem
Existing die designs for powder presses result in unwanted conicities during demolding and high production costs due to material usage and handling requirements, while also failing to produce non-rotationally symmetrical components with precision and reducing frictional forces effectively.
Innovation Solution
A die design with varying stiffness zones, where the pressing zone has significantly higher stiffness than end face zones, allowing for precise production of non-rotationally symmetrical components with reduced frictional forces and weight, enabling manual handling and reduced material usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the die has constant stiffness along the axial direction, then the structure is simple and easy to manufacture, but the green part becomes conical during demolding due to elastic expansion in the compression zone
Solution Approach 1:
The die is designed with varying stiffness along the axial direction: the compression zone has high stiffness to minimize elastic expansion during pressing, while the demolding zone has lower stiffness to reduce frictional forces during ejection. This local differentiation of mechanical properties resolves the contradiction between manufacturing simplicity and dimensional accuracy.
Solution Approach 2:
The die is segmented into distinct functional zones (compression zone and demolding zone) with different stiffness characteristics. This segmentation allows each zone to be optimized for its specific function, preventing the green part from becoming conical while maintaining overall structural integrity.
2Ease of operation
If draft angles are provided on the inner circumferential surface to reduce frictional forces, then demolding becomes easier, but the green body experiences force relaxation causing conicity
Solution Approach 1:
Instead of applying draft angles throughout the entire inner circumferential surface, the invention applies them only in the demolding zone where they are needed to reduce friction. The compression zone maintains its cylindrical shape without draft angles, preserving dimensional accuracy while achieving easy demolding in the ejection area.
3Ease of manufacture
If the die is made with uniform wall thickness, then the structure is simple and manufacturing is easier, but the die is heavy and requires expensive handling equipment
Solution Approach 1:
The die wall thickness is varied along the axial direction to match the stiffness requirements of different zones. The compression zone has greater wall thickness for high stiffness, while the demolding zone has reduced thickness for lower stiffness and weight reduction. This local optimization reduces overall die weight while maintaining structural integrity and manufacturing feasibility.
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 die design ensures dimensional accuracy, reduces frictional forces, and allows for the production of non-rotationally symmetrical components with reduced material and handling costs, enabling manual operation of presses with higher forces and minimizing conicity issues.
Implementation Method 1
the high pressing pressure also places considerable stress on the inner circumferential surface of the die. This causes the inner circumferential surface of the die to expand elastically in the radial direction
Data Source
Figure 1~3
Figure 4~6
Figure 7~9
AI summary
The invention relates to a die (1) for arrangement in a press (2) wherein the die (1) extends along an axial direction (3) between two ends (4, 5) and forms an inner circumferential surface (6) between the ends (4, 5), wherein, starting from the inner circumferential surface (6), the die (1) extends along a radial direction (7) toward an outer circumferential surface (8) and toward at least one centering surface (10) arranged on a first diameter (9) in the radial direction (7); wherein the die (1) has a pressing zone (11) at a distance from the ends (4, 5) and, in the region of the pressing zone (11), has a higher maximum first rigidity, at least as compared with zones (12, 13) arranged at the ends (4, 5), with respect to a pressing force (14) acting on the inner circumferential surface (6) in a direction of a normal vector (32); wherein the maximum first rigidity is at least 10% higher than a minimum second rigidity present in at least one zone (12, 13) arranged at one of the ends (4, 5).