Die Cushion Load Control Using a Compression Spring Model
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Solution Overview
Problem
Existing die cushion control methods struggle to prevent abnormal pushing-up of the cushion pin due to mismatches in switching time between position control and pressure control, caused by setting errors, thickness variations, and inertial forces.
Innovation Solution
A die cushion control apparatus that includes a hydraulic cylinder, a drive motor, position and pressure sensors, and a processor that generates control commands based on the cushion target position and load commands, using a compression spring model to prevent abnormal pushing-up of the cushion pin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If switching from position control to pressure control is performed based on press slide height, then the die cushion apparatus can generate reaction force for drawing, but the cushion pin may unintentionally rise and cause damage due to mismatched switching time
Solution Approach 1:
The patent implements feedback control by continuously monitoring the actual cushion position via position sensor and comparing it with the target cushion position. The controller adjusts the cushion load 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 prevents the cushion pin from unintentionally rising and causing damage.
Solution Approach 2:
The patent establishes a target cushion position before the actual cushion operation begins. The target position is calculated based on the press slide position and cushion pin geometry. By having the target position predetermined, the system can proactively adjust the cushion load to prevent position deviations before they lead to harmful pushing-up actions.
2Manufacturing precision
If position control is used to hold cushion pin position, then the workpiece is supported properly, but switching to pressure control too early causes the cushion pin to rise beyond the predetermined position
Solution Approach 1:
The patent uses feedback control to continuously monitor the cushion position and adjust the cushion load accordingly. The controller compares the actual cushion position with the target position and modifies the pressure control output to maintain position precision during the transition from position control to pressure control, preventing the cushion pin from rising beyond the predetermined position.
Solution Approach 2:
The patent dynamically adjusts the cushion load based on the current operating conditions and position deviations. Rather than using a fixed switching point, the system adaptively transitions between control modes by continuously monitoring position feedback and adjusting the cushion load in real-time, ensuring both position precision and switching safety.
3Power
If pressure control is applied before upper die contact with workpiece, then drawing reaction force is generated early, but the cushion pin rises until mechanically restrained causing potential damage
Solution Approach 1:
The patent implements feedback control that monitors the cushion position and prevents it from rising beyond the target position. Even when pressure control is applied early, the feedback mechanism detects position deviations and adjusts the cushion load to keep the cushion pin at the correct position, preventing mechanical restraint and potential damage to the workpiece or die.
Solution Approach 2:
The patent applies preliminary anti-action by establishing a target cushion position and using feedback control to counteract any tendency of the cushion pin to rise. The system proactively adjusts the cushion load in opposition to potential position deviations, preventing the harmful pushing-up action before it occurs.
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 solution effectively prevents abnormal pushing-up of the cushion pin, even with setting errors, by continuously controlling both cushion position and load, ensuring the cushion pin does not rise beyond a predetermined position, thus preventing damage to the workpiece or die.
Implementation Method 1
a hydraulic cylinder that supports a cushion load generating member (14) that generates a cushion load
Data Source
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.