Molten Metal Printhead Inverse Actuation for Stable Droplet Ejection
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Solution Overview
Problem
Conventional printheads for additive manufacturing of liquid metal experience vibrations in the piston channel, leading to issues such as unwanted droplet formation and inconsistent droplet sizes due to dynamic actuation and material flow, which affect printing quality and frequency.
Innovation Solution
A printhead design featuring a piston channel that minimizes vibrations by using an inverse actuation method with a piezoelectric actuator and a preload element, where the piston moves from an extended to a retracted position to charge the channel, and then returns to the extended position, ensuring minimal residual liquid and controlled droplet generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional actuation methods are used to eject material from the nozzle, then droplet generation can be achieved, but vibrations are induced in the piston channel leading to unwanted droplet formation and inconsistent droplet sizes
Solution Approach 1:
The patent applies inverse actuation by moving the piston away from the nozzle exit opening first to charge the piston channel, then moving it back towards the nozzle exit opening to eject the droplet. This inverted sequence reduces or eliminates vibrations in the piston channel that would otherwise cause unwanted droplet formation and size inconsistency, while maintaining high droplet generation frequency.
2Manufacturing precision
If pressure parameters are adjusted to reduce vibrations, then droplet quality can be improved, but maximum droplet delivery frequency is reduced
Solution Approach 1:
The patent employs periodic inverse actuation cycles where the piston alternates between moving away from the nozzle (charging phase) and moving towards the nozzle (ejection phase). This periodic motion pattern creates controlled vibrations that actually improve droplet quality while maintaining high delivery frequency, opposite to conventional continuous actuation methods.
3Productivity
If the piston is continuously actuated to maintain high delivery frequency, then productivity is improved, but vibrations are superimposed leading to printing quality losses
Solution Approach 1:
The patent implements preliminary charging of the piston channel by moving the piston away from the nozzle before droplet ejection. This preliminary action ensures the piston channel is fully charged with material, allowing for consistent droplet formation at high frequencies without the superimposed vibrations that degrade printing quality in conventional continuous actuation methods.
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 design achieves high droplet quality and durability by minimizing vibrations, allowing for high-speed droplet generation with frequencies up to 1500 Hz and consistent droplet formation without interference from previous processes.
Implementation Method 1
The piston is preferably moved towards a nozzle outlet opening in the ejection direction by means of a piezoelectric actuator
Data Source
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AI summary
The invention relates to a print head (1) for printing liquid molten metal in order to additively manufacture a component, said print head comprising: a nozzle component (10) having a nozzle outlet opening (12); a piston (14; 14a) by means of which the molten metal can be ejected through the nozzle outlet opening (12); an actuator assembly (16; 16a) having an actuator; and a pretensioning element, in particular a spring element, wherein the piston (14; 14a) can be moved in an actuation direction (y) by actuating the actuator from an extended position into a retracted position in which a first piston end (18) facing the nozzle outlet opening (12) is further away from the nozzle outlet opening (12) than in the extended position, and the pretensioning element (26; 26a) is provided in such a way that it pretensions the piston (14; 14a), which is in the retracted position, towards the extended position.