RU2791611C1 - Method for manufacturing three-dimensional building elements by 3d-printing method - Google Patents

Abstract

FIELD: construction; 3D objects.

SUBSTANCE: invention relates to the field of manufacturing 3D objects using additive technology in the field of construction, in particular for the construction of enclosing structures using additive 3D printing technologies, and can be used to form products such as wood boards and bulk building parts. The technical result of the invention will expand the scope of 3D printing technologies for construction, improve the physical and mechanical properties, which will make it possible to obtain a material that is homogeneous in properties without the addition of adhesives or other substances when using additive technologies. The technical result is achieved by the fact that the method of manufacturing three-dimensional products of building elements by 3D printing includes the formation of layers from the raw mass by extrusion through a nozzle layer by layer, while hydrodynamically activated wood pulp is used as the raw material, which is squeezed out through the extruder nozzle layer by layer by the method of cold extrusion, while each underlying layer of hydrodynamically activated wood pulp is exposed to microwave radiation to redistribute moisture in it.

EFFECT: expansion of the scope of 3D printing technologies for construction, improvement of the physical and mechanical properties.

1 cl, 1 dwg

Description

The invention relates to the production of 3D objects by additive technology in the field of construction, in particular for the construction of enclosing structures using additive three-dimensional printing technologies (3D printing), and can be used to form products such as wood boards and bulk building parts.

Technological solutions and devices for the construction of enclosing structures by additive methods are in most cases developed for materials and mixtures based on mineral or air binders, composites based on them with fibrous materials or polymers. However, these solutions do not allow the use of wood or pulp as the base material. The advantage of materials based on cellulose-containing raw materials is low thermal conductivity and vapor permeability.

Most technologies are based on the extrusion formation of layers using 3D printers. Thus, a device with a print head of a construction 3D printer is known, designed for printing with a multi-component mixture, consisting of a nozzle and a mixer-extruder connected to it, including a housing, a screw containing cylindrical and conical parts, a valve for supplying individual components of the mixture and a screw drive . (Patent RU No. 179153 (13) U1, published on April 28, 2018.)

This solution, due to its versatility, has a number of significant drawbacks, such as the lack of a mechanism for controlling moisture in the process of extrusion and controlling the moisture content of layers by partially drying them. Along with this, there is no mechanism for fixing mixtures with low creep strength.

These shortcomings are partially, but not fully, solved by the method of erecting walls with a 3D printing printer by discrete printing, in which the structure is printed by continuous layer-by-layer application of the building mixture, characterized in that the erection of structures is performed by discrete printing, in which an extruder with a 3D mini-formwork, which also performs the function of an impulse heater for supplying heat, while heating the object under construction from 90 to 98 ° C, as a result of which the element gains strength faster. (Patent RU(11) No. 2703574 (13) C2, published on October 30, 2018).

However, this technical solution does not allow the water contained in the mixture to be carried out in the bulk phase, but only initiates the process of hardening of the mineral components of the mixture. This, in turn, does not allow working with other materials. Along with this, due to the high heat capacity of concrete, the process is energy-intensive and does not allow obtaining building elements with low density and, accordingly, thermal conductivity.

It is possible to reduce the thermal conductivity of products in this case by using a method and device using granules of a polystyrene concrete mixture in the form of granules, which, after heating to a temperature not exceeding 80 ° C, are fed into the extruder, where through the system and from there, through the outlet nozzle, it is squeezed onto the surface of the previously molded and the layer that has lost its mobility. To ensure the foaming of the mixture, an electric current is supplied to the movable formwork used in this case. At a temperature of more than 90 ° C, polystyrene granules soften and, under the action of the boiling isopentane contained in them, foam, multiplying in volume. In this case, the mixture with non-foamed polystyrene granules turns into a mixture with foamed polystyrene granules and changes its quality, acquiring thermal insulation properties. (Patent RU(11) No. 239244 (13) C2, published 10/16/2020).

The main disadvantage of this solution is the decrease in the mechanical strength of the material, especially the dynamic viscosity and flammability of polystyrene and the high carbon footprint from the production of this component of the mixture.

The closest analogue in terms of technological aspects is a method for creating a 3D object from materials with low adhesive strength to each other, and a device for its implementation. The essence of the claimed technical solution is that the creation of an object from materials having low adhesion strength to each other requires pre-heating of the polymer material by means of a heating element in the first print head to the required temperature, which is applied in the form of a molten base polymer material to the platform. Then, the adhesive material is heated to the required temperature by means of a heating element in the second print head, a second layer of adhesive material is applied from the second print head, after which the applied adhesive material is exposed to microwave radiation, then the cycle of applying a layer of molten base polymer material from the first print head is repeated and adhesive material, from the second print head, followed by exposure to microwave radiation, while the processes of applying layers are repeated until the required thickness of the coating layers is reached. (Patent RU(11) No. 2751442 (13), published on December 24, 2020).

In this case, it is impossible to exclude a thermoplastic adhesive from the composition of the mixture, which predetermines the inhomogeneity of the material and, accordingly, the low physical and mechanical characteristics of the material.

The objective of the claimed invention is to expand the scope of 3D additive technologies in the field of construction and improve the physical and mechanical properties of materials and products.

The technical result consists in expanding the functionality of devices for 3D printing, through the use of activated wood pulp, which is applied by cold extrusion with simultaneous external microwave radiation, improving the physical and mechanical properties of materials, due to the high adhesive interaction between layers, uniformity of material properties with layering.

The technical result is achieved due to the fact that the method of manufacturing three-dimensional products of building elements by 3D printing, including the formation of layers from the raw mass by extrusion through the nozzle in layers, according to the invention, hydrodynamically activated wood mass is used as the raw mass, which is squeezed out through the extruder nozzle layer-by-layer by cold extrusion, while each underlying layer of hydrodynamically activated wood pulp is exposed to microwave radiation to redistribute moisture in it.

As a raw material for printing, hydrodynamically activated wood or cellulose pulp is used, which is described in detail in [Formation of the structure of low-density slabs from hydrodynamically activated soft wood waste / V.N. Ermolin, M.A. Bayandin and others // News of higher educational institutions. Forest magazine. - 2019. - No. 5 (371). - S. 148-157. - DOI]. This makes it possible to reduce by 3-5 times the density and, accordingly, the thermal conductivity of building products and at the same time ensure the uniformity of material properties and thereby ensure high mechanical properties of products.

The principle of operation of the invention is based on the fact that the wood pulp used as a raw material is a polydisperse system. When applying the first layer with a humidity of 300 to 400%, its strength is due to the forces of capillary contraction in the porous structure of the mass and Van der Waals forces. When applying subsequent layers, to ensure an increase in the mechanical strength of the first layer and its adhesive interaction with the next layer, it is necessary to provide humidity in the contact zone of the layers at least 400-500%. This is due to the fact that initially it is necessary to provide in the contact zone of the layers the opportunity for wood particles to take the most favorable thermodynamic state and form primary bonds. To do this, it is proposed to redistribute the moisture content over the thickness of the layer. This allows you to make the impact of microwave on each previous layer. In this case, microwave allows, by heating the central part of the layer, to start the process of mass transfer (of water) from the center to the surface of the layer. Along with this, a decrease in humidity makes it possible to increase the forces of capillary contraction and the distance between particles in the center of the layer and, accordingly, increase its strength and, without significant deformations, bear the load from the layers laid above. In the process of drying, an adhesive interaction is formed between the layers, while homogeneous structures of materials from activated wood pulp are formed. The high homogeneity of the interlayer contact and the layers themselves ensure high physical and mechanical characteristics of materials and products, including building fences with a minimum density and, accordingly, thermal conductivity and vapor permeability.

An example of the implementation of the method.

A method for the manufacture of bulk wood products by 3D printing, characterized in that hydrodynamically activated wood pulp is used as the main raw material. The method operates as follows. The formation of products is carried out by layer-by-layer extrusion through the extruder nozzle 4. To ensure the formation of adhesive interaction between layers 1 and 3, the directed action of microwave radiation by magnetrons 2 on layer 1 is carried out, which leads to a redistribution of moisture over its cross section. This provides its mechanical strength with the value of the corresponding load from the layer 3 laid on top. On the surface of layer 1, the humidity increases to 400-500%, which, upon further drying, makes it possible to obtain an adhesive strength between layers 1 and 3 equal to the cohesive strength of the layers.

In FIG. 1 shows the principle of the claimed technical solution, where 1 is the first layer, 2 is magnetrons (microwave emitters), 3 is the second layer, 4 is the extruder nozzle.

The proposed invention will expand the scope of 3D printing technologies for the construction of energy-efficient buildings or products applicable to this area, as well as improve the physical and mechanical properties due to the fact that only activated wood pulp is used as a raw material. This allows you to get a material that is homogeneous in properties without the addition of adhesives or other substances, using additive technologies.

Claims (1)

A method for the manufacture of bulk products of building elements by 3D printing, including the formation of layers from the raw mass by extrusion through a nozzle in layers, characterized in that as the raw mass, hydrodynamically activated wood pulp is used, which is squeezed out through the extruder nozzle in layers by the cold extrusion method, while each underlying layer of hydrodynamically activated wood pulp is exposed to microwave radiation to redistribute moisture in it.

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