Die Cushion Load Control to Prevent Cushion Pin Pushing-Up
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Solution Overview
Problem
Existing die cushion control systems face issues with mismatched timing in switching from position control to pressure control, leading to unintended cushion pin rising and potential damage to workpieces or dies due to setting errors and thickness variations.
Innovation Solution
A die cushion control apparatus and method that utilizes a processor to control the hydraulic cylinder based on a compression spring model, calculating deflection length and generating load or pressure commands to prevent abnormal cushion pin movement by continuously referencing the load characteristic curve, ensuring the cushion pin does not rise beyond its standby position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If switching from position control to pressure control is performed based on press slide height, then control automation is improved, but cushion pin position stability deteriorates due to timing mismatch
Solution Approach 1:
The patent implements feedback control by detecting the actual cushion pin position using a position sensor and comparing it with the target position. The controller adjusts the hydraulic pressure based on the position deviation, ensuring the cushion pin remains at the correct position even when switching between position control and pressure control modes. This feedback mechanism resolves the timing mismatch problem by continuously monitoring and correcting cushion pin position rather than relying solely on predetermined press slide height thresholds.
2Productivity
If pressure control is activated before upper die contact with workpiece, then productivity is improved through earlier pressure application, but harmful effects occur due to cushion pin pushing-up
Solution Approach 1:
The position sensor continuously monitors the cushion pin position and provides feedback to the controller. When the cushion pin approaches the standby position (indicating potential pushing-up), the controller detects this through position deviation and adjusts or stops pressure application accordingly. This prevents the harmful effect of cushion pin pushing-up and potential damage to workpieces or dies, while still allowing productivity benefits from timely pressure control activation.
Solution Approach 2:
The system applies preliminary anti-action by using the position sensor to detect cushion pin position trends before actual pushing-up occurs. The controller proactively adjusts pressure control parameters or stops pressure application when the cushion pin approaches the standby position, preventing the harmful effect rather than reacting after damage occurs. This anticipatory control enables earlier pressure application for productivity while preventing damage.
3Manufacturing precision
If position control switching threshold is adjusted to account for setting errors, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The feedback mechanism using position sensors eliminates the need for complex preliminary adjustments or multiple threshold settings for different error conditions. The system automatically adapts to setting errors and thickness variations by continuously measuring actual cushion pin position and adjusting control parameters accordingly. This simplifies the overall system while maintaining high manufacturing precision, as the feedback loop handles compensation automatically rather than requiring complex pre-programmed adjustments.
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
Prevents cushion pin pushing-up during press working, thereby avoiding damage to workpieces and dies by maintaining the cushion pin at its standby position even with setting errors, ensuring precise control and safety.
Implementation Method 1
a hydraulic cylinder (12) that supports a cushion load generating member (14, 15) that generates a cushion load
Implementation Method 2
the processor, assuming that the hydraulic cylinder includes a compression spring model, acquires a deflection length of a compression spring as a target deflection length when an upward load of the cushion load generating member is equal to a set load
Data Source
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AI summary
A compression spring model included in a processor in the die cushion control apparatus refers to a load characteristic curve of a compression spring when assuming that a hydraulic cylinder is a compression spring, generates a cushion load command in accordance with a spring constant and a deflection amount of a compression spring and generates a control command based on a deviation between the generated cushion load command and an actual cushion load. In accordance with the control command, the drive motor and the hydraulic pump are driven, and an upward load is generated on the cushion pin by the hydraulic cylinder. Thus, even when the cushion pin rises due to a setting error or the like for the press die height, the cushion load command decreases in accordance with the deflection amount of the compression spring and inhibits an abnormal pushing-up action of the cushion pin.