Plasma Arc Voltage Feedback for Ingot Withdrawal Control
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Solution Overview
Problem
Existing systems for forming metal ingots in withdrawal crucibles struggle to maintain a constant molten pool level due to difficulties in accurately measuring and controlling the withdrawal rate, often resulting in uneven solidification and increased waste, as traditional methods are prone to errors from heat, light, and dust interference.
Innovation Solution
The system employs plasma arc voltage feedback to control the withdrawal rate of the ingot in a withdrawal crucible, using proportional-integral-derivative (PID) control based on the measured voltage to maintain a constant distance between the plasma arc torch and the molten pool, thereby regulating the molten pool level through a closed-loop feedback system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional measurement methods are used to monitor molten pool level, then the system is simpler, but measurement precision deteriorates due to heat, light, and dust interference
Solution Approach 1:
The patent replaces traditional optical or mechanical measurement systems with a plasma arc voltage-based measurement system. The voltage of the plasma arc is measured to determine the distance between the plasma arc and the molten pool surface, eliminating the need for direct optical or mechanical measurement in the harsh environment. This substitution resolves the contradiction by using an electrical parameter (voltage) that is not affected by heat, light, or dust interference.
2Manufacturing precision
If the withdrawal rate is not precisely controlled, then the control system is simpler, but manufacturing precision deteriorates due to uneven solidification
Solution Approach 1:
The patent implements a feedback control system where the measured plasma arc voltage is used to determine the molten pool level, and this information feeds back to control the withdrawal rate of the ingot. The controller adjusts the withdrawal rate based on the voltage signal to maintain a constant molten pool level, ensuring uniform solidification. This feedback mechanism resolves the contradiction by dynamically adjusting the withdrawal rate based on real-time measurements.
Solution Approach 2:
The plasma arc itself serves a dual function: it heats the molten pool and simultaneously provides the measurement signal through its voltage. The voltage of the plasma arc inherently reflects the distance to the molten pool surface, so the system uses the plasma arc's own electrical characteristic for measurement without requiring separate sensors. This self-service approach simplifies the overall system while maintaining precision.
3Productivity
If manual operation is used, then the system is simpler, but productivity deteriorates due to human error and inefficiency
Solution Approach 1:
The system achieves full automation by using the plasma arc's own voltage signal for both measurement and control purposes. The controller automatically adjusts the withdrawal rate based on the measured voltage, eliminating the need for manual intervention. The plasma arc effectively serves itself by providing both the heating function and the measurement signal, enabling autonomous operation that improves productivity without requiring complex additional sensing systems.
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
This approach allows for precise control of the ingot withdrawal rate, reducing waste and improving surface finish quality by maintaining a constant molten pool level, even in challenging environments, and can be retrofitted into existing systems without additional hardware, enabling full automation and minimizing human error.
Implementation Method 1
the top portion of the material in a second, upper position is maintained in a liquid state with a plasma arc torch
Implementation Method 2
The voltage may be indicative of a distance between the plasma arc torch and a top surface of the second portion of the material, such as by being directly proportional to the distance
Implementation Method 3
The controller may be configured to control the withdrawal rate of the material within the mold based on the voltage of the plasma arc
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3B
AI summary
A method and a system for forming a solid casting. A material is fed into a mold having a retractable bottom. A first portion of the material at a first, lower position within the mold is allowed to solidify to thereby form a portion of the casting. The retractable bottom is withdrawn downwards at a withdrawal rate. A second portion of the material at a second, upper position within the mold is maintained in a liquid state by application of heat thereto, using a plasma arc generated by a plasma arc torch. A voltage of the plasma arc is measured, and the withdrawal rate of the retractable bottom is controlled based on the voltage of the plasma arc.