Liquid Metal Level Sensing for Dross Management
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Solution Overview
Problem
Dross accumulation in drop-on-demand metal jet printers leads to inaccurate level sensing, premature print job termination, and clogged nozzles, resulting in reduced printing time and throughput due to the interference of oxides and silicates with the laser-based level sensor.
Innovation Solution
A method that adjusts the printing material level set point in the reservoir of a liquid ejector, pausing operations when a drop-out signal is received, increasing the level by a predetermined amount to cover dross, and resuming operations once a clear signal is restored, allowing continuous printing without manual intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a laser-based level sensor is used to measure melt pool height, then measurement capability is provided, but dross accumulation causes inaccurate measurements and premature print job termination
Solution Approach 1:
The patent introduces a reflective surface (mirror or retroreflector) as an intermediary between the laser sensor and the melt pool surface. This intermediary provides a stable, consistent reflection surface that is not affected by dross accumulation on the melt pool, allowing the laser sensor to maintain accurate measurements throughout the print job.
Solution Approach 2:
The patent creates an optical copy or representation of the melt pool level by reflecting the laser beam off a separate reflective surface that moves with the melt pool level. This copy provides a stable measurement interface that doesn't suffer from the same measurement problems as direct surface sensing.
2Productivity
If printing continues without interruption to maintain high throughput, then productivity increases, but dross accumulation leads to nozzle clogging and jet quality degradation
Solution Approach 1:
The patent uses the laser level sensor to provide continuous feedback on melt pool height and dross accumulation levels. When the sensor detects that dross has accumulated to a critical level (indicated by changes in reflection pattern or level measurements), the system automatically pauses printing, triggers a pump replacement, and resumes, maintaining jet quality without permanent interruption to the print job.
Solution Approach 2:
The patent implements periodic pump replacement during the print job based on laser sensor feedback. Instead of continuous operation until failure, the system periodically maintains the pump by replacing it at predetermined intervals or when sensor indicators show degradation, ensuring consistent jet quality throughout extended print jobs.
3Manufacturing precision
If nozzle replacement is performed frequently to prevent dross clogging, then jet quality is maintained, but printing time is lost and throughput decreases
Solution Approach 1:
The laser level sensor provides early warning feedback about dross accumulation trends, allowing the system to schedule pump replacements at optimal intervals. By monitoring reflection patterns and level stability, the system can predict when a pump will need replacement and schedule it during natural pauses in printing, minimizing time loss while preventing quality degradation.
Solution Approach 2:
The patent performs preliminary maintenance actions by replacing pumps proactively based on sensor indicators of accumulating dross, before actual clogging occurs. This preliminary replacement prevents jet quality degradation and avoids emergency interruptions, reducing overall time loss compared to reactive maintenance.
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 extends printing time, maintains high throughput, and prevents print defects by ensuring accurate level sensing and rejuvenating the pump, allowing for longer operation without nozzle replacement and minimizing jet quality degradation.
Implementation Method 1
a laser-based level sensor that reads from a surface of a melt pool in the reservoir
Implementation Method 2
Magnetohydrodynamic refers to the study of the magnetic properties and the behavior of electrically conducting fluids
Data Source
AI summary
A method of controlling sensing level in a liquid ejector is disclosed. The method includes filling a reservoir in communication with a liquid ejector with a printing material to a first level set point, receiving a drop out signal from a laser-based level sensor that reads from a surface of a melt pool in the reservoir, pausing an operation of the liquid ejector, adjusting the printing material level set point to a second level set point of printing material in reservoir that is higher than the first level set point, increasing a quantity of printing material in the reservoir to fill the reservoir to the second level set point, and resuming the operation of the liquid ejector.