Conductance Feedback Control for Stable Metal Strip Deposition
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Solution Overview
Problem
Existing additive manufacturing processes, such as metal laser deposition, are sensitive to disturbances and exhibit non-linear behavior, leading to instability and defects due to variations in wire tip distance and other process parameters, with previous control systems relying on resistance measurements that are noisy and require complex filtering, limiting their effectiveness for real-time feedback control.
Innovation Solution
A control system that regulates the additive manufacturing process by determining electrical conductance between the metal strip and substrate, adjusting parameters like nozzle distance, movement speed, current, heat, and wire output rate to maintain a nominal conductance, allowing for stable process control without the need for complex regression models or exclusive resistance-to-distance modeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If resistance measurements are used for control, then distance information can be obtained, but the noisy resistance signal requires complex filtering and low-pass filtering which increases time lag and reduces high frequency response
Solution Approach 1:
The patent replaces the resistance-based measurement system with a conductance-based measurement system. By measuring electrical conductance instead of resistance, the system obtains a cleaner signal that requires less filtering, thereby reducing control time lag while maintaining measurement precision for distance control.
Solution Approach 2:
The patent changes the measurement parameter from resistance to conductance. This parameter change fundamentally improves the signal quality, allowing for real-time feedback control without the need for extensive filtering that would introduce time delays.
2Manufacturing precision
If resistance-based feed-forward control is used, then distance control can be achieved, but the system cannot provide feedback control during deposition due to noisy resistance signals
Solution Approach 1:
The patent substitutes the unreliable resistance-based feedback system with a conductance-based feedback system. The conductance measurements provide stable, low-noise signals that enable reliable real-time feedback control during the deposition process, improving both manufacturing precision and system reliability.
Solution Approach 2:
The patent implements a feedback control mechanism using conductance measurements. The system continuously measures conductance during deposition, compares it to reference values, and adjusts process parameters in real-time, enabling stable feedback control that was not achievable with resistance-based systems.
3Measurement precision
If complex filtering is applied to resistance signals, then measurement noise is reduced, but the high frequency response of the control loop deteriorates
Solution Approach 1:
The patent replaces the resistance measurement system with a conductance measurement system that inherently produces cleaner signals. This substitution eliminates the need for complex filtering operations, thereby preserving high frequency response while still achieving low noise levels in the measurement signal.
4Reliability
If multiple process parameters are controlled, then process stability is improved, but the control system complexity increases
Solution Approach 1:
The patent changes the fundamental measurement parameter from resistance to conductance, which provides cleaner signals and enables more effective control. This parameter change allows for multi-parameter control (distance, wire feed rate, laser power) while actually reducing overall system complexity by eliminating the need for complex filtering and signal processing infrastructure.
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 enables multi-parameter control, improving process stability and accuracy by maintaining a nominal conductance, preventing defects like droplet formation and stubbing, and allowing for real-time adjustments during deposition, enhancing the overall quality and reliability of the manufacturing process.
Implementation Method 1
determining electrical conductance between the metal strip and the substrate by measuring at least one electrical property of the supplied current
Implementation Method 2
a heat source configured to melt the metal strip into a weld pool on the substrate
Implementation Method 3
The high temperature of the weld pool and the laser radiation heats up the wire and causes it to melt
Data Source
AI summary
A control system for regulating an additive manufacturing process of an additive manufacturing apparatus, the apparatus configured to add metal to a substrate by means of metal deposition. The apparatus comprises: a nozzle for output of a metal strip, the nozzle configured to be arranged at a distance from the substrate, and configured to move relative the substrate in XYZ-axes via a position actuator. The apparatus further comprises a heat source configured to melt the metal strip into a weld pool on the substrate, and an electrical power source configured to supply current via the metal strip 20 to the substrate. The control system is configured maintain process stability, during the deposition of a layer of metal, via: determining electrical conductance between the metal strip and the substrate by measuring at least one electrical property of the supplied current; determining the difference between the determined electrical conductance, and a desired electrical conductance; and, adjusting at least one of: the substrate to nozzle distance, the speed of the nozzle movement relative the substrate, the amount of supplied current, the heat provided by the heat source, and/or the rate of output of the metal strip, based on the difference between the determined conductance and the desired conductance.