Cementitious Bead Extrusion with Admixture Injection
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Solution Overview
Problem
Existing 3D printing systems for cementitious materials face challenges in producing complex architectural structures with overhangs without slowing down printing speed, as the cementitious material must be in a rheologically compatible state for pumping while also being viscous enough to form self-supporting layers, limiting flow rate and complexity of the produced parts.
Innovation Solution
A system that includes a print head with a mixing chamber and an admixture device with needles injecting adjuvants to modify the cementitious material's properties before extrusion, allowing for optimized pumping and rheological adjustments to achieve properties similar to traditional construction techniques, enabling continuous and uniform deposition with the ability to print overhangs without slowing down.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the cementitious material is kept in a rheological state close to its pumping limit to prevent sagging, then the material stability is improved, but the printing speed and flow rate are significantly reduced
Solution Approach 1:
The patent applies preliminary action by pre-mixing the cementitious material with specific additives (viscosifying agents, superplasticizers, retarders) before extrusion to achieve the desired rheological properties in advance. This allows the material to maintain stability during extrusion without requiring excessive slowing down of the printing process, as the material properties are optimized beforehand rather than adjusted in real-time during printing.
Solution Approach 2:
The patent implements parameter changes by systematically adjusting the rheological parameters of the cementitious material through controlled addition of chemical additives. The viscosity, yield stress, and flow characteristics are modified within specific ranges to achieve optimal balance between pumpability and structural stability, enabling faster printing speeds without sacrificing material stability.
2Strength
If the cementitious material viscosity is increased to form self-supporting layers, then the structural strength is improved, but the flow rate and complexity of produced parts are limited
Solution Approach 1:
The patent applies parameter changes by precisely controlling the viscosity and yield stress of the cementitious material through chemical additives. The material is formulated to have optimal viscosity ranges that provide sufficient structural strength for self-supporting layers while maintaining adequate flow rate for complex geometries. This allows production of highly complex parts with overhangs and intricate details without sacrificing structural integrity.
Solution Approach 2:
The patent employs composite materials by combining cementitious binder with multiple functional additives including viscosifying agents, superplasticizers, and retarders. This composite formulation creates a material system where each component contributes specific properties: structural strength from the binder, controlled viscosity from viscosifying agents, improved flow from superplasticizers, and extended working time from retarders. The synergistic interaction enables simultaneous achievement of high structural strength and high flow rate for complex part production.
3Stability of the object's composition
If temporary reinforcements or discontinuities are added to support large overhangs, then the structural stability is improved, but the printing process becomes slower and more complex
Solution Approach 1:
The patent applies parameter changes by optimizing the rheological parameters of the cementitious material to achieve sufficient structural stability for large overhangs without requiring temporary reinforcements. The material formulation allows the extruded layers to maintain their shape and support subsequent layers inherently, eliminating the need for additional support structures or discontinuities, thus simplifying the printing process while maintaining structural stability.
4Productivity
If the flow rate is increased to improve printing speed, then the productivity is improved, but the material rheological state becomes incompatible with pumping
Solution Approach 1:
The patent implements parameter changes by optimizing the rheological parameters of the cementitious material to enable high flow rates during extrusion while maintaining pumping compatibility. The material is formulated with specific viscosity and yield stress ranges that allow it to flow easily under extrusion pressure but remain pumpable through the delivery system. This enables high printing speeds without compromising the reliability of the pumping and material delivery system.
Solution Approach 2:
The patent applies preliminary action by pre-formulating the cementitious material with optimal rheological properties before the printing process begins. The material is prepared in advance with controlled viscosity, yield stress, and flow characteristics that are compatible with both high-speed extrusion and reliable pumping. This preliminary optimization of material parameters eliminates the need for real-time adjustments during printing, enabling sustained high printing speeds with reliable material delivery.
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
Enables the production of complex architectural parts with improved printing speed and precision, maintaining material properties suitable for traditional construction resistance without the need for molds or formwork, while ensuring continuous and uniform material deposition.
Implementation Method 1
an admixture device connected to said printing head upstream of said outlet nozzle and opening into said mixing chamber so as to be able to inject admixtures modifying the characteristics of the cementitious material before ejection of said cementitious material beads by said outlet nozzle
Implementation Method 2
a pump for feeding the line with cementitious material from the storage tank
Implementation Method 3
an outlet nozzle configured to form cementitious material beads
Data Source
Figure 1~3
Figure 4a~5
AI summary
The invention relates to a system for extruding cementitious material beads for a robot used for the additive manufacturing of architectural structures, comprising: a head for depositing beads of cementitious material, referred to as printhead (30), comprising an inlet mouth (31) and an outlet nozzle (34) configured to form beads of cementitious material; a feed circuit (20) for said printhead (30), comprising a reservoir (10) for storing cementitious material, a feed conduit (21) connecting said storage reservoir (10) to said printhead (30), and a booster pump (22) for said feed conduit (21), characterised in that it further comprises an additive-injection device (40) connected to said printhead (30), upstream of said outlet nozzle (34), for injecting additives that modify the properties of the cementitious material prior to the discharge of said cementitious material beads by said outlet nozzle (34)