3D Cement Extrusion Fluidizing Device for Layer Adhesion
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Solution Overview
Problem
The heterogeneity of architectural structures printed using 3D cementitious materials leads to weak interfaces between layers due to differences in rheological states, particularly when accelerating agents are used, causing structural weaknesses and limiting the speed and complexity of printing.
Innovation Solution
A system that re-fluidifies the lower layer of extruded cementitious material just before depositing the upper layer by using a fluidizing device, such as a vibrating needle or sound wave generator, to match the rheological state of freshly extruded cords with previously extruded ones, enhancing cohesion without interrupting the printing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If accelerating agents are used to speed up setting of extruded cords, then productivity is improved, but the adhesion between layers deteriorates due to rheological state differences
Solution Approach 1:
The patent applies mechanical vibration through a vibrating needle that contacts the extruded cord downstream of the extrusion head. This vibration re-fluidifies the cementitious material by disrupting the setting process, allowing the upper cord to adhere properly to the lower cord even when accelerating agents are present. The vibration frequency and amplitude are controlled to achieve optimal re-fluidification without compromising structural integrity.
Solution Approach 2:
The patent changes the rheological parameters of the extruded material by applying mechanical energy through vibration. This temporarily alters the viscosity and fluidity of the cementitious material, creating a window of opportunity for proper adhesion between layers. The parameter change is localized and temporary, affecting only the contact zone between layers.
2Reliability
If the print head moves at low speed to ensure proper layer bonding, then adhesion is improved, but productivity deteriorates due to increased printing time
Solution Approach 1:
The vibrating needle applies mechanical vibration to the lower cord, re-fluidifying it to create optimal bonding conditions. This allows the print head to maintain higher speeds while still achieving proper adhesion, as the vibration compensates for the reduced contact time between layers.
Solution Approach 2:
The vibration is applied to the lower cord before the upper cord is deposited, preparing the surface for optimal adhesion. This preliminary action ensures that when the upper cord contacts the lower cord, the material is in the ideal rheological state for bonding, regardless of print head speed.
3Reliability
If time is allowed for layers to set between extrusions, then adhesion is improved, but productivity deteriorates due to printing interruptions
Solution Approach 1:
The vibrating needle continuously or periodically vibrates the lower cord as it is being extruded, maintaining it in a re-fluidified state throughout the printing process. This eliminates the need to pause for setting, allowing continuous printing while ensuring proper adhesion between all layers.
Solution Approach 2:
The vibration application is integrated into the continuous extrusion process, maintaining useful action throughout. The system does not require interruption or waiting periods, as the vibration continuously manages the rheological state of the material to enable ongoing adhesion.
4Productivity
If accelerating agents are used to reduce printing time, then productivity is improved, but heterogeneity increases due to rheological state changes between layers
Solution Approach 1:
The vibrating needle applies consistent mechanical vibration to each lower cord, standardizing the re-fluidification process. This compensates for the variability introduced by accelerating agents, ensuring that each layer is prepared in a consistent rheological state regardless of the acceleration agent's effect on setting time.
Solution Approach 2:
The vibration systematically alters the rheological parameters of each layer in a controlled manner, creating uniformity across all layers. This parameter control counteracts the heterogeneity that would otherwise result from the use of accelerating agents.
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 improves the adhesion between layers, reduces porosity, and allows for continuous printing without waiting for layers to set, enabling the creation of complex structures with enhanced stability and reduced costs.
Implementation Method 1
means for vibrating the lower bead adapted to be able to locally vibrate said lower bead downstream of said extrusion head according to said predetermined trajectory so as to be able to modify the shear threshold of said lower bead
Implementation Method 2
a directional generator (54) of sound waves adapted to be able to generate waves (54) towards said lower bead (6) so as to be able to locally fluidize this lower bead (6)
Implementation Method 3
a directional mechanical wave generator adapted to be able to generate mechanical waves towards said lower bead of said lower layer so as to be able to locally fluidize this lower bead
Data Source
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Figure 5~6
AI summary
The invention relates to a construction material cord extrusion system for an additive manufacturing robot (9) for architectural structures (8) comprising: a construction material cord extrusion head (30) moved along a predetermined path; a construction material supply circuit (20) for said extrusion head (30); and a device for fluidizing the extruded cords adapted to be able to fluidize a previously extruded lower cord, before extruding said upper cord onto this lower cord, so as to maximize the adhesion between an upper cord being extruded and a lower cord previously extruded and fluidized by this fluidizing device.