WO2019112453A1

WO2019112453A1 - Method for producing three-dimensional objects

Info

Publication number: WO2019112453A1
Application number: PCT/PL2018/000116
Authority: WO
Inventors: Piotr MIKULSKI
Original assignee: Bibus Menos Sp. Z O. O.
Priority date: 2017-12-05
Filing date: 2018-11-26
Publication date: 2019-06-13
Also published as: PL423754A1

Abstract

The method for producing three-dimensional objects in 3D printing technology consists in that in the first stage a record of a three-dimensional object is created in the computer memory. Then the record of the three-dimensional object is entered into the memory of a 3D printer in the form of executive commands for kinematic and thermal elements of the 3D printer containing a printhead with an extrusion nozzle powered by thermoplastic material Above the printer work table the head with the nozzle is moved repeatedly, applying many layers of extruded material creating incrementally a three-dimensional object that is compatible with the computer record of the reference object, The material of boundary layers (1 ) is applied with at least one first head (17), and the material of at least one core layer (2,3,4,5,6,7) is applied with at least one additional self-propelled head (13,14), and portions of a three-dimensional object are produced incrementally in successive layers, where the portions produced by the first printhead (17) together with the portions produced at the same time by at least one additional printhead (13,14) constitute a three-dimensional object being produced. For the first printhead (17) printing the boundary zones of the object, different volumetric extrusion capacities of thermoplastic material are used than for at least one additional printhead (13,14) printing at least one core zone (2,3,4,5,6,7) of a three-dimensional object.

Description

Method for producing three-dimensional objects

The invention relates to a method for producing three-dimensional objects in 3D printing technology through the application of subsequent layers of thermoplastic, chemically cured and thermosetting materials.

Known rapid prototyping technologies, also known as 3D printing technologies, are based on the principle of selective application and/or selective bonding of subsequent layers of material with equal thickness.

A known solution of this type of printers for the production of three-dimensional objects is disclosed in US patent specification No. US 5121329. The apparatus presented there comprises a movable dispensing head provided with a supply of material which, after melting and settling, is solidified under the influence of a predetermined temperature, and comprises a base member with a drive along “X”,”Y” and“Z” axes according to a predetermined pattern. In this way, three- dimensional objects are created by building up material discharged from the dispensing head onto the base membrane at a controlled rate. The apparatus is computer driven in a process utilizing computer aided design (CAD) and computer-aided (CAM) software to generate drive signals for controlled movement of the dispensing head and base member as material is being dispensed. Three- dimensional objects are produced by depositing repeated layers of solidifying material until the shape of the object being produced is formed. Any material, such as self-hardening waxes, thermoplastic resins, molten metals, two-part epoxies, foaming plastics, and glass, which adheres to the previous layer with an adequate bond upon solidification, may be utilized in this technology. Each subsequent layer is defined by the previous layer, and each layer thickness is defined and closely controlled by the height at which the tip of the dispensing head is positioned above the preceding layer.

Another known solution for the production of three-dimensional objects is presented in US patent specification No. US4575330. The apparatus is used to produce three-dimensional objects by creating a cross-sectional pattern of the object to be formed on the base surface. By impinging radiation, particle

bombardment and/or chemical reaction, successive laminae, representing successive layer-like cross-sections of the object are created. They are

automatically formed and integrated together to provide a step-wise laminar buildup of portions of the object being created. With this solution, a three- dimensional object is formed incrementally from a substantially planar surface of the fluid medium during the forming process. In the solutions described above, the term fluid medium should also be understood as a medium in the form of powder. Another known solution in the field of the method for producing three- dimensional objects is described in US patent specification No. US 5155324. This solution relates to an apparatus and method for producing parts by selective laser sintering. The disclosed method selectively sinters a first layer of heat-fusible powder by directing a laser beam so that it scans the first layer of the reference object in a first direction to sinter a first cross-section of the part. A second layer of the heat-fusible powder is then disposed over the first layer, and the next cross- section of the object being produced is selectively sintered by the laser being scanned in a different direction from the first direction, for example in a direction perpendicular to the first direction. The cross-scanning resulting from scanning in different directions makes it possible to produce mechanical parts with structural strength. Each of the layers may have its outlined trace prior to the scanning, to further define the edges of the cross-section.

A solution known from US patent specification No. US 5204055 discloses a method for making a component by depositing a first layer of a powder in a confined region and then depositing a binder material to selected regions of the layer of powder material to produce a layer of bonded material at the selected regions. Such steps are repeated a selected number of times to apply successive layers to previous layers in selected regions so as to form a layered component. The unbonded powder material is then removed. In some cases, the object or workpiece produced may be further processed as, for example, by heating it to further strengthen the bonding thereof.

Another known solution is disclosed in the patent specification of international application No. WO 2014/197732. In this known solution various patterns related to three dimensional printers, reinforced filaments, and their methods of use are described. In one embodiment of this solution, a void free reinforced filament is fed into an extrusion nozzle. The reinforced filament includes a core, which may be continuous or semi-continuous, and a matrix material surrounding the core. The reinforced filament is heated to a temperature greater than a melting temperature of the matrix material and less than a melting temperature of the core prior to extruding the filament from the extrusion nozzle.

Selective bonding technologies use powder applied in successive layers and bonded in specific places to form an object from successive layers of powder bonded together. After the creation of such a layered object, the powder not used for the layered construction of the object is collected and intended for the creation of further three-dimensional objects.

However, in the technologies of producing layered objects by selective application of thermoplastic material, subsequent layers of material are applied through a nozzle in computer-designated places, gradually building a three- dimensional object by applying subsequent layers of material with a nozzle.

The technologies described above are collectively known as incremental technologies, formerly also known as rapid prototyping technologies or 3D printing technologies.

The invention relates to a method for producing three-dimensional objects and a 3D printer carrying out this method, in the technology of selective application of thermoplastic materials and combination of thermoplastic materials with chemically cured or thermosetting materials. In 3D printing technologies, in the production of three-dimensional objects, as well as in other technologies for the production of such objects, an important aspect is the accuracy of the object produced. The more accurately the object is produced, the fewer finishing operations are required. In 3D printing technology, the accuracy of the object produced is mainly determined by the height/thickness of a single layer of material. The more reduced the height/thickness of a layer, the more accurate and smoother the surfaces of the incrementally built workpiece. Increasing the height/thickness of a single layer of material applied in one operation significantly accelerates the process of building the object, but at the same time reduces the smoothness of the side surfaces of the workpieces. The more reduced the thickness of a layer is, the better surface quality of the object being produced. This approach also leads to main disadvantage as reduction of single layer thickness, significantly extend build time and thus the cost of production of the whole object. For most of these types of 3D printing

technologies, mainly using selective material application, usually thermoplastic material, such as Fused Deposition Modelling (FDM) technology, or Fused Filament, Fabrication (FFF) technology, an additional problem of significant anisotropy appears resulting partially from the constant layer thickness and empty spaces resulting from the course of the material application paths.

There are known technological solutions, where the introduction of

thermoplastic materials filled with glass, carbon or aramid fibers results in workpieces with increased rigidity and strength. This type of solution is described, for example, in the patent specification of international application No. WO

2014/197732 A3, but the application of continuous fibers is a slow process and this method has a number of limitations in the geometry of creating paths of filled fibres. Continuous fibre material behaves unfavourably in the event of sudden sharp bends of paths and is therefore mainly used in multi contour paths of the contour of the layer rather than in the middle infill of the layer. This, in turn, creates high anisotropy in stiffness in relation to the vertical Z axis in which subsequent layers are added. The purpose of the invention is to accelerate rapid prototyping technologies and the incremental production of three-dimensional objects, using selective material application in layers, while maintaining high surface smoothness and improving the homogeneity of mechanical properties of objects built with these technologies, including increasing their strength and stiffness.

The invention is disclosed in claim 1 and in the subsequent claims.

According to the invention, the method for producing three-dimensional objects in 3D printing technology consists of the first stage where a record of a three- dimensional object is created in the computer memory, then the record of the three-dimensional object is entered into the memory of a 3D printer in the form of executive commands for kinematic and thermal elements of the 3D printer containing a printhead with an extrusion nozzle powered by thermoplastic material and above the printer work table the head with the nozzle is moved repeatedly, applying many layers of extruded material creating incrementally a three- dimensional object that is compatible with the computer record of the reference object.

According to the invention, the method for producing three-dimensional objects is characterized in that the material of boundary layers is applied with at least one first head, and the material of at least one core layer is applied with at least one additional self-propelled head. The term core layers is understood in this patent specification as laid in the space between boundary layers. Portions of a three- dimensional object are produced incrementally in successive layers. The portions produced by the first printhead together with the portions produced by at least one additional printhead constitute a three-dimensional object being produced, wherein for the first printhead printing the boundary zones of the object, a different volumetric extrusion capacities of thermoplastic material are used than for at least one additional printhead printing at least one core zone of a three-dimensional object.

The nozzle of said at least one additional head is moved simultaneously with the nozzle of the first head above the printer work table. In a preferred embodiment of the invention, at least one core layer of

thermoplastic material with a different thickness than the thickness of the boundary layer of thermoplastic material applied by the first printhead within the same object being produced is applied through at least one additional printhead.

Boundary portions of a three-dimensional object are preferably produced using the first head with a smaller diameter of the nozzle than the diameter of the nozzle of at least one additional head designed to produce at least one core layer, wherein the core layer of a three-dimensional object is preferably produced using at least one additional printhead, where at least one layer of thermoplastic material with a thickness greater than the thickness of the boundary layers is applied using a nozzle with a larger diameter than the nozzle in the head intended for the application of the boundary layers.

In a preferred embodiment of the solution according to the invention to supply extrusion nozzles from the printheads, thermoplastic material with organic or inorganic fibers is used as core material, where after each application of the thermoplastic material path the printhead with the nozzle returns without dispensing material along the same path within the same layer, wherein the applied material path with a path length greater than or equal to the greatest fibre length contained in the thermoplastic material is used.

In a preferred embodiment of the solution according to the invention, the thickness of the subsequent core layers is calculated from the formula:

b=m-a, c=n2-a, d= , where individual symbols indicate:

ne{ R} ^A n>1 ,

R - a set of real numbers greater than 1 ,

a - thickness of the boundary layer,

b - thickness of the first core layer,

c, d - thickness of subsequent core layers which are the filling of the workpiece being built.

Each subsequent core layer may be thicker than the previous core layer by at least a part of the thickness of the boundary layer. In the solution according to the invention, it is possible to use each subsequent core layer with a different thickness than the thickness of the previous layer, and the thickness of each layer in the core zone can be many times greater than the thickness of the boundary layer within the same portion of a three-dimensional object.

Thermoplastic material may be fed through at least one printhead and liquid material based on thermosetting or chemically cured resin or a liquid mixture of organic and inorganic compounds which cures by the process of hydration or evaporation of the solvent may be fed through at least one additional printhead. In another preferred embodiment of the invention, liquid material based on thermosetting or chemically cured resin is pre-fed into a thermostated working chamber, from where it is extruded into at least one additional printhead printing the core layer of a three-dimensional object.

At least one thermoplastic boundary layer may be applied first, and then at least one resin core layer is applied in such a way that the boundary layers act as a barrier to prevent the liquid resin from flowing out of the contour of the object being produced until it is cured, and then the cycle can be repeated until the object being produced is fully formed.

According to the invention, after applying all boundary layers of the object being produced, the core layer is preferably applied in at least one operation of covering the core volume of the object with resin in such a way that the object is filled with the resin between the boundary zones.

In the solution according to the invention, it was proposed to increase the thickness of a single layer of material applied in one operation in the core zones of the object being produced. In the objects produced with 3D technology, boundary zones with higher requirements for strength and quality of the external surface were separated, and core areas, between these boundary areas, with lower requirements in this respect, were separated. The boundary areas of the object being produced were separated, and a small thickness of a single layer was left in these areas, which resulted in the low thickness layers being applied not in the whole cross-section of the object being produced, but only on portions of this cross-section. Thus, the production time of the object was shortened, without reducing the requirements as to the quality of the surface of the boundary layers.

Core zones with lower strength requirements were automatically separated between the produced boundary zones and filled with material laid in much thicker layers, in extreme cases by filling the core zone in one operation. This resulted in a relatively small extension of the time necessary to produce the above mentioned boundary zones, however, the whole operation of producing the object in the solution according to the invention was significantly shortened.

In the solution according to the invention, the process of rapid prototyping technologies and the incremental production of three-dimensional objects was accelerated, using selective material application in layers, while maintaining high surface smoothness and improving the homogeneity of mechanical properties of objects built with these technologies, including increasing their strength and stiffness.

The subject of the invention is shown in the embodiments in the following description and in the accompanying drawings in which:

Fig. 1 - a cross-section of layers of a three-dimensional object,

Fig. 2 - a cross-section of layers of a three-dimensional object in another

embodiment,

Fig. 3 - a data processing system in an embodiment of the method according to the invention,

Fig. 4 - a schematic diagram of the main components of the device for carrying out the method according to the invention.

Fig. 1 schematically shows a cross-section of the layers of an object produced using the method according to the invention. The progressive nature of the layer thickness is shown. Differences in the thickness of the core layers of the object marked as 2, 3, 4, 5, 6 are shown schematically. These layers meet the following relation describing their height, i.e. thickness: b=nra, c=ri2-a, d=n3-a, where he{ R} ^L n>1 , where R is a set of real numbers greater than 1. Boundary layers 1 with thickness a close the inner volume of the workpiece.

A core layer 2 between the boundary layers has thickness b, where b=a m, where for example for this core layer n=3.3. However, the next core layer 3 has thickness c, where c=a n2, where for example for this core layer n=6. The next core layer 4 has thickness d, where d=a n3, where for example for this core layer n=3. In this embodiment, layers are applied in series in the following order in series: from the base layer 1 , then layers 1 ; 1 ; 1 ; 4; 2, and then 1 ; 1 ; 1 ; 5; 6; 3... and finally the boundary layer 1.

Fig. 2 shows schematically the difference in the thickness of a core layer 7 of the object and the boundary layers 1 with thickness a, on the cross-section along the axis of application of the layers, i.e. on the cross-section of these layers. In this version, a workpiece is produced in the form of walls with an empty core space into which, after the walls are made, material with viscosity low enough to fill the entire core space between the walls as accurately as possible is poured. The material is then fixed thermally or chemically or by hydration or evaporation of the solvent into a solid, or in other embodiments it remains a liquid, e.g. a non- Newtonian liquid, i.e. in other sample conditions the same liquid does not have the properties of a liquid. In this version, it is possible to obtain the highest isotropic strength properties for the workpiece being built due to the complete filling of the core with the material. Such a workpiece is made in the order of layers according to the pattern: 1 ; 1 ; 1 ; 1 ; 1 ; 1 ; 1 ; 7; 1.

Fig. 3 shows a data processing system for carrying out the method according to the invention. An external computer with CAM software containing CNC code data for the creation of layer paths on the basis of a file describing the object being produced is marked with the designation CAM. Data from the CAM computer is transferred to the internal computer of the printer marked in this figure as 3D from where the data is transferred to a dedicated CNC controller containing a motion planner performing movements along the X, Y, Z working axes of the printer, and the speed of material dispensing through the nozzles of the heads is adjusted. The CNC motion controller cooperates with head carriage drive controllers along the X, Y, Z axes, as well as with the drive controller of heads with known nozzles through which the material for building layer paths is dispensed. The CNC controller and the 3D computer of the printer cooperate with the PLC controller of the printer’s auxiliary systems and with the WM drive controller of material dispensing heads.

Fig. 4 shows a diagram of the main components of the device for carrying out the method of applying layers of material with a progressive thickness according to the invention, together with the cross-section of the layered object. It shows the possibility of using various materials in this technology, where in this embodiment, thermoplastic materials without filler, materials with fibrous filler as well as liquid- based material in the form of organic chemically cured or thermosetting resins, or liquid materials cured by evaporation of the solvent or by hydration, to produce objects with increased isotropy of mechanical properties are used simultaneously.

A liquid material container 8 in this embodiment containing one- or multi- component resin or a suspension of liquid material is connected via a pump 9 which pumps the liquid material through a liquid material supply line 10 from the pump to a head 14. The next head 13 in this embodiment is supplied from a spool 11 of fibre-filled filament. The third head 17 is supplied from a spool 12 of non-fibre filled thermoplastic material. Thus, the head 13 nozzle dispenses material containing fibres, while the head 14 dispenses liquid material. This figure schematically shows a support block 15 of heads with a horizontal feed

mechanism of the heads when applying subsequent layers during the production of a three-dimensional object. A working chamber 16 in this embodiment contains a known thermostat assembly, not shown in this figure, for standardization of the conditions of application of subsequent layers. Through a nozzle, thermoplastic material without filler from the spool 12 of this material is dispensed from the head 17. This figure shows a work table 18 on which a three-dimensional object is produced by applying subsequent layers 1 ,3,4 as depicted, for example, in this figure in a cross-section in order to show layers with different thickness in the boundary zones and in the core zones of this object. The horizontal work table 18 with adjustable height is placed in this embodiment on a vertical extension pin 19, and the drive unit of this pin is used to adjust the thickness of the subsequent layers 1 ,3,4 applied to the previous layers. The layers 1 ,3,4 of the object being produced are shown schematically in this figure by making a cross-section of this object. The proportions of the thickness of the layers 1 ,3,4 to the dimensions of the device shown schematically in this figure, as well as in Fig. 1 and Fig.2, are altered in relation to the actual proportions in order to be able to illustrate the method according to the invention. In actual production, the boundary layers of the object produced using the method according to the invention are often less than 0.2 mm thick. Differentiation of the thickness of layers at this level of dimensions would not be possible in the figure showing at the same time the outline of the device, and thus it would not be possible to depict the subject of the invention in the drawing.

For this reason, in Fig. 1 , Fig. 2 and Fig. 4, the dimensional proportions have been changed to better illustrate the method according to the invention. Fig. 4 shows the boundary layers 1 with the smallest thickness, the core layers 4 with a greater thickness, and the core layers 3 with the greatest thickness, in a cross- section. Once produced, the object has boundary layers on all sides, which are the most durable and susceptible to finishing. In other embodiments, the strength and smoothness of boundary layers can be varied on different walls, depending on the needs. The thickest core layers 3 were formed in this embodiment as a result of the application of fibre-filled liquid material. The core layers 4 are produced in this embodiment from fibre-filled thermoplastic material. In contrast, the boundary layers 1 with the smallest thickness are produced in this embodiment from non- fibre filled material. List of designations in the figure

1. Boundary layer.

2. Core layer.

3. Core layer.

4. Core layer.

5. Core layer.

6. Core layer.

7. Core layer.

8. Container.

9. Pump.

10. Supply line.

1 1. Spool of fibre-filled material.

12. Spool of non-fibre filled material.

13. Head.

14. Head.

15. Support block of heads.

16. Working chamber.

17. Head.

18. Work table.

19. Vertical pin.

CAM. External computer with CAM software. 3D. Internal computer of the printer.

CNC. Carriage motion controller.

C,U,Z. Head carriage drive controllers.

PLC. Auxiliary system controllers.

WM. Head drive controllers.

Claims

1. The method for producing three-dimensional objects in 3D printing

technology consisting in that in the first stage a record of a three-dimensional object is created in the computer memory, then the record of the three- dimensional object is entered into the memory of a 3D printer in the form of executive commands for kinematic and thermal elements of the 3D printer containing at least one printhead with an extrusion nozzle powered by thermoplastic material, and above the printer work table the head with the nozzle is moved repeatedly, applying many layers of extruded material creating incrementally a three-dimensional object that is compatible with the computer record of the reference object, characterised in that the material of boundary layers (1 ) is applied with at least one first head (17), and the material of at least one core layer (2, 3, 4, 5, 6, 7) is applied with at least one additional self-propelled head (13,14) and portions of a three-dimensional object are produced incrementally in successive layers, where the boundary portions produced by the first printhead (17) together with the core portions produced subsequently by at least one additional printhead (13,14) constitute a three-dimensional object being produced, wherein for the first printhead

(17) printing the boundary zones of the object, different volumetric extrusion capacities of thermoplastic material are used than for at least one additional printhead (13,14) printing at least one core zone (2, 3, 4, 5, 6, 7) of a three- dimensional object.

2. The method for producing objects according to claim 1 , characterised in that the nozzle of said at least one additional head (13,14) is moved simultaneously with the nozzle of the first head (17) above the printer work table (18).

3. The method for producing objects according to claim 1 , characterised in that by means of at least one core layer (2, 3, 4,5, 6) of thermoplastic material with a different thickness than the thickness of the boundary layers (1 ) of thermoplastic material applied by the first printhead (17) within the same object being produced is applied through at least one additional printhead

(13,14).

4. The method for producing objects according to claim 1 , 2 or 3, characterised in that at least one core layer (2, 3, 4, 5, 6, 7) of thermoplastic material with a thickness greater than the thickness of the boundary layers (1 ) is applied using a nozzle with a larger diameter than the nozzle in the head (17) intended for the application of the boundary layers.

5. The method for producing objects according to claim 4, characterised in that to supply extrusion nozzles from the printheads (17,13,14),

thermoplastic material with organic or inorganic fibres is used as core material, where after each application of the thermoplastic material path the printhead (17,13,14) with the nozzle returns without dispensing material along the same path within the same layer (1 ,2, 3, 4, 5, 6, 7), wherein the applied material path with a path length greater than or equal to the greatest fiber length contained in the thermoplastic material is used.

6. The method for producing objects according to claim 4, characterised in that the thickness (a,b,c) of the subsequent core layers (2, 3, 4, 5, 6, 7) is calculated from the formula:

b=m-a, c=n2-a, d=n3, where individual symbols indicate:

ne{ R} ^L n>1 ,

R - a set of real numbers,

a - thickness of the boundary layer,

b - thickness of the first core layer, c, d - thickness of subsequent core layers which are the filling of the workpiece being built.

7. The method for producing objects according to claim 6, characterised in that each subsequent core layer (3, 4, 5, 6, 7) is thicker than the previous core layer by at least a part of the thickness of the boundary layer (1 ).

The method for producing objects according to one of claims 4 or 6,

characterised in that each subsequent core layer (3, 4, 5, 6, 7) with a different thickness than the thickness of the previous layer is used, and the thickness of each layer in the core zone is many times greater than the thickness of the layer (1 ) in the boundary layer within the same portion of a three-dimensional object.

The method for producing objects according to claim 1 , characterised in that thermoplastic material is fed through at least one printhead (17), and liquid material based on thermosetting or chemically cured resin or a liquid mixture of organic and inorganic compounds which cures by the process of hydration or evaporation of the solvent is fed through at least one additional printhead (13,14).

10. The method for producing objects according to claim 9, characterised in that liquid material based on thermosetting or chemically cured resin is prefed into a thermostated working chamber (16), from where it is extruded into at least one additional printhead (13,14) printing the core layer of a three- dimensional object.

11. The method for producing objects according to claim 9 and 10 characterised in that at least one thermoplastic boundary layer (1 ) is applied first, and then at least one resin core layer (2, 3, 4, 5, 6, 7) is applied in such a way that the boundary layers (1 ) act as a barrier to prevent the liquid resin from flowing out of the contour of the object being produced until it is cured, and then the cycle can be repeated until the object being produced is fully formed.

12. The method for producing objects according to claim 1 characterised in that after applying all boundary layers (1 ) of the object being produced, the core layer (2, 3, 4, 5, 6, 7) is applied in at least one operation of covering the core volume of the object with resin in such a way that the object is filled with the resin between the boundary zones.