Interference-Fit Friction Mechanism for Stable Press Die Cushion Loads
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Solution Overview
Problem
Conventional die cushions for press machines face challenges in generating stable high-load frictional forces, leading to issues like wrinkles, cracks, and insufficient forming accuracy, especially when working with high tensile strength materials, and they often require complex load design and are not suitable for long-term durability.
Innovation Solution
A sliding frictional force generation mechanism using a carbon steel shaft and hole member with surface hardening and controlled surface roughness, employing an interference fit and lubricating oil to maintain consistent frictional force and prevent seizure and galling, allowing for a compact and rigid die cushion design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional friction dampers use synthetic resin or porous sintered metal with PTFE, then vibration energy can be absorbed in high rotational range, but high frictional force cannot be stably generated in press machine driving cycle
Solution Approach 1:
The patent changes the material parameters by using metal-on-metal contact instead of synthetic resin or PTFE composites. The shaft member and hole member are both made of metal materials, fundamentally altering the friction characteristics to enable stable high frictional force generation throughout the press machine driving cycle, not just in high rotational ranges.
Solution Approach 2:
The patent employs a composite structure where metal shaft and hole members are fitted together with specific interference tolerances. This metal composite assembly provides both the necessary frictional force and stability, replacing single-material friction damper designs with a multi-component metallic system.
2Force
If interference fit is used to fix shaft in hole, then tightening margin is obtained for fixing, but members cannot be disassembled after assembly
Solution Approach 1:
The patent applies dynamic interference fit where the shaft member can slide within the hole member along the axial direction. The interference fit provides radial tightening margin for frictional force, while axial sliding capability enables disassemblability and repositioning, combining both fixing and flexibility requirements.
Solution Approach 2:
The frictional force generation mechanism is segmented into separate shaft member and hole member components that can be independently assembled and disassembled. This segmentation allows the interference fit to provide radial constraint while maintaining axial mobility for easy operation.
3Manufacturing precision
If core piece is slidably interference-fitted to upper die, then burr generation is prevented, but tightening margin is slight and does not utilize frictional force
Solution Approach 1:
The patent significantly increases the interference fit parameters compared to conventional core piece designs. By using metal-on-metal interference fit with optimized tolerances, the system generates substantial frictional force that actively prevents burr generation, rather than relying on slight tightening margins.
Solution Approach 2:
The patent converts the potential harm of material penetration at parting surfaces into a beneficial frictional force. The interference fit between shaft and hole members generates friction that actively resists material flow and burr formation, turning the constraint into a protective mechanism.
4Manufacturing precision
If die cushion is made large area for high-load cushioning, then forming accuracy is improved, but frame rigidity decreases causing wrinkles and cracks
Solution Approach 1:
The patent concentrates the frictional force generation in a localized interference fit assembly rather than distributing it over a large area. This local quality approach allows high-load cushioning force to be generated in a compact space, maintaining frame rigidity while achieving the necessary cushioning effect for forming accuracy.
Solution Approach 2:
The use of metal-on-metal interference fit creates a high-stiffness composite structure that generates large cushioning forces in a compact design. This composite friction mechanism provides both the force magnitude and structural rigidity needed, avoiding the trade-off between area and frame strength.
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 mechanism provides a stable and durable high-load frictional force, reducing the risk of wrinkles and cracks, enabling precise forming of high tensile strength materials with improved durability and reduced heat generation, while maintaining uniform friction over time.
Implementation Method 1
a sliding frictional force generation mechanism comprising a metal hole member having a hole, a metal shaft member fitted in the hole of the hole member slidably in an axial direction
Implementation Method 2
employing an interference fit and lubricating oil to maintain consistent frictional force and prevent seizure and galling
Implementation Method 3
A sliding frictional force generation mechanism using a carbon steel shaft and hole member with surface hardening and controlled surface roughness
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A sliding frictional force generation mechanism includes a metal hole member 33 having a hole 36, a metal shaft member 31 fitted in the hole of the hole member in an axially slidable manner, and a lubrication mechanism 16 configured to supply lubricating oil serving as a cooling medium between the hole member 33 and the shaft member 31. The shaft member is fitted in the hole in an interference fit state. A die cushion device 10 for a press machine 11 including the sliding frictional force generation mechanism is also disclosed.