Direct ink writing of dense pastes containing macroparticles
Karlström, Anton (2024)
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe2024052032751
https://urn.fi/URN:NBN:fi-fe2024052032751
Tiivistelmä
Inorganic materials can include many different elements, can be manufactured in many ways and are mainly dependent on the feedstock and the intended application. The intended industrial application for this thesis has an established manufacturing method but that method is limited to moulds to create the sought-after shapes and is combined with a post-processing step to achieve the final properties. The utilization of moulds limits the design freedom; geometries that can be used and tailor-made applications are, therefore, time consuming and expensive. By using additive manufacturing (AM) these challenges could be overcome.
The goal of this work was to develop a method for creating strong and tailor-made inorganic materials containing macroparticles for industrial application by AM. To make the inorganic material malleable for the build-up and creation of the sought-after shape, binders or additives must be added. In the conventional manufacturing of inorganic materials, more binder results in higher porosity and lower strength of the post-processed products. The hypothesis was that similar phenomena would occur for the AM, therefore, the content of inorganic material was increased and optimized in this work.
Direct ink writing (DIW) is the AM technique that was used in this work. DIW works by extruding an ink paste from a syringe; the paste is then deposited automatically according to predetermined settings established by computer software. The paste is deposited in a layer-by-layer fashion without any necessary solidification mechanism. The shape of the object is only controlled by precise rheological properties and since the paste is deposited by extrusion through a nozzle, shear-thinning properties of a viscoelastic solid are required both to be extrudable and preserve the shape after extrusion. DIW was used due to the customizable nature of the paste, which enables inorganic addition and can be compensated by changing the rheological properties.
The post-processed objects were tested by 4-point bending and analyzed by microscopy images, scanning electron microscopy images and porosity measurement. Since the paste’s rheological properties are of high importance for the outcome, rheology measurements were also conducted on relevant samples and complemented with relevant parameters for describing the depositing behaviour. Furthermore, the true size of deposited, dried, and post-processed objects was documented along with other relevant observations during the process.
The results show that the printing substrate utilized has impact on the strength and drying behaviour of the objects. As anticipated, the strength increases with higher solid loading but only up to a point. The solid loading heavily influences the rheological properties of the paste along with the used particle type and size. Furthermore, the particle size distribution affects the whole process, including rheology, drying behaviour and strength of the objects.
With the findings from this work, a theoretical strength increase of approximately 80% is possible compared to the initial tested methods. By further optimising the method, AM for industrial applications might be possible.
The goal of this work was to develop a method for creating strong and tailor-made inorganic materials containing macroparticles for industrial application by AM. To make the inorganic material malleable for the build-up and creation of the sought-after shape, binders or additives must be added. In the conventional manufacturing of inorganic materials, more binder results in higher porosity and lower strength of the post-processed products. The hypothesis was that similar phenomena would occur for the AM, therefore, the content of inorganic material was increased and optimized in this work.
Direct ink writing (DIW) is the AM technique that was used in this work. DIW works by extruding an ink paste from a syringe; the paste is then deposited automatically according to predetermined settings established by computer software. The paste is deposited in a layer-by-layer fashion without any necessary solidification mechanism. The shape of the object is only controlled by precise rheological properties and since the paste is deposited by extrusion through a nozzle, shear-thinning properties of a viscoelastic solid are required both to be extrudable and preserve the shape after extrusion. DIW was used due to the customizable nature of the paste, which enables inorganic addition and can be compensated by changing the rheological properties.
The post-processed objects were tested by 4-point bending and analyzed by microscopy images, scanning electron microscopy images and porosity measurement. Since the paste’s rheological properties are of high importance for the outcome, rheology measurements were also conducted on relevant samples and complemented with relevant parameters for describing the depositing behaviour. Furthermore, the true size of deposited, dried, and post-processed objects was documented along with other relevant observations during the process.
The results show that the printing substrate utilized has impact on the strength and drying behaviour of the objects. As anticipated, the strength increases with higher solid loading but only up to a point. The solid loading heavily influences the rheological properties of the paste along with the used particle type and size. Furthermore, the particle size distribution affects the whole process, including rheology, drying behaviour and strength of the objects.
With the findings from this work, a theoretical strength increase of approximately 80% is possible compared to the initial tested methods. By further optimising the method, AM for industrial applications might be possible.