Molten Pool Feedback Control for Accurate Additive Manufacturing
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Solution Overview
Problem
In additive manufacturing, errors occur between the target and actual shapes of objects due to asymmetrical energy distribution and surface tension, which are not accurately addressed by existing position correction methods, especially when machining directions change.
Innovation Solution
An additive manufacturing system that includes an information processing apparatus to analyze molten pool images, calculate center positions and widths, and adjust machining parameters to correct the machining point position and molten pool width, ensuring accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If the position of the welding torch is corrected based on image detection of molten pool ends without considering progress direction, then the position correction can be implemented, but the accurate position of the molten pool ends cannot be detected when the progress direction changes, resulting in poor shape accuracy
Solution Approach 1:
The patent applies dynamics by making the molten pool end detection method adaptive to changing progress directions. The system dynamically adjusts the detection approach based on whether the progress direction is constant or changing, transitioning from simple horizontal endpoint detection to progress-direction-aware detection methods that calculate endpoints relative to the current machining direction, thereby maintaining accuracy throughout the additive manufacturing process
Solution Approach 2:
The patent changes the detection parameters based on progress direction information. When the progress direction changes, the system modifies how molten pool endpoints are identified by incorporating directional vectors and angle calculations, rather than using fixed horizontal reference lines, thus adapting the detection parameters to match the dynamic machining conditions
2Ease of manufacture
If the center of the molten pool is displaced due to beam blockage by fed material, then the position at which melt is deposited is displaced, but the beam energy distribution cannot be uniformly controlled
Solution Approach 1:
The patent implements feedback by using image processing to detect the actual position of the molten pool center and comparing it with the target position. When displacement is detected caused by beam blockage, the system feeds back correction information to adjust the machining head position, compensating for the asymmetric energy distribution and restoring bead placement accuracy despite the presence of fed material in the beam path
Solution Approach 2:
The patent applies preliminary anti-action by proactively compensating for the expected beam blockage effect. The system detects the molten pool position in real-time and pre-adjusts the machining parameters or head position to counteract the anticipated displacement caused by material fed into the beam path, preventing the error from occurring in the first place
3Productivity
If beads are deformed and attracted to each other by surface tension before complete solidification, then the beads are stacked with shape errors, but the surface tension effect cannot be eliminated
Solution Approach 1:
The patent uses feedback control to monitor the molten pool state and detect bead formation characteristics. By analyzing image data of the molten pool and newly formed beads, the system detects shape deviations caused by surface tension effects and adjusts machining parameters such as beam power, scanning speed, or material feed rate in real-time to compensate for the deformation, maintaining shape accuracy while preserving rapid bead stacking
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 system achieves high-accuracy shape manufacturing by correcting machining point positions and adjusting molten pool parameters, reducing errors and improving object shape consistency.
Implementation Method 1
an additive manufacturing apparatus that melts a material with a beam emitted from a machining head
Implementation Method 2
Energy of the heat source is absorbed by the workpiece, whereby a molten pool is formed on the workpiece
Implementation Method 3
stacking beads which are solidified products of molten material
Implementation Method 4
the beads may be deformed and attracted to each other by the action of surface tension at the interface between the beads before the beads are completely solidified
Data Source
AI summary
An information processing apparatus includes: an image analysis unit that acquires an image of a molten pool formed on a workpiece and information on a progress direction of a machining point on the workpiece, and obtains an end point of the molten pool; and a molten pool information calculation unit that calculates a center position and a width of the molten pool using position information on the end point. An additive manufacturing apparatus includes: a control unit that adjusts a machining parameter of the additive manufacturing apparatus using a calculation result of the width of the molten pool; and a machining point correction unit that corrects a position of the machining point using a calculation result of the center position of the molten pool such that the molten pool having a center position matching a program command position that is based on a machining program is formed.