Baseplate for three-dimensional printing and associated printing method

Abstract

A baseplate (10) for Fused Filament Fabrication (FFF) three-dimensional (3D) printing and a method of FFF printing a 3D object with the use of a 3D printer and baseplate according to the present application.

Description

[0001] BASEPLATE FOR THREE-DIMENSIONAL PRINTING

[0002] FIELD OF THE INVENTION

[0003] The invention relates to a baseplate for Fused Filament Fabrication (FFF) three- dimensional (3D) printing and a method of FFF printing a 3D object with the use of a 3D printer and baseplate of the invention.

[0004] BACKGROUND

[0005] Three-dimensional or 3D printing, also known as additive manufacturing is a process for creating three-dimensional objects layer-by-layer using a 3D printer apparatus until the complete 3D object is formed. In Fused Filament Fabrication (FFF) also known as Fused Deposition Modelling (FDM) 3D printing, the material used to create the 3D object is a thermoplastic polymer. Moreover, commercial FFF 3D printers are typically provided with a glass or thin metal baseplate onto which is printed. This baseplate usually has some kind of proprietary coating on it to help the parts adhere to the surface. For printing polylactic acid (PLA) for example, hairspray is applied to plain glass which works well.

[0006] However, this method of 3D printing is currently limited by problems experienced with shrinkage which leads to warping of the 3D parts that are printed, resulting in detachment of the parts from the baseplate before completion of the 3D object. Warping is particularly problematic where semi-crystalline polymers such as high- density polyethylene (HDPE) are used as the polymer during FFF printing. Furthermore, particularly when using HDPE as the 3D printing polymer, in the case of objects having a substantial volume, the problem is further exacerbated, limiting the size of 3D objects that are able to be printed using this technique. The basic 3D printing process involves the following steps:

[0007] (i) creation of a digital model for the 3D printed object with the aid of computer design software such as SolidWorks or similar;

[0008] (ii) slicing of the design file using software such as CURA, Simplify 3D or similar to create a slice file;

[0009] (iii) printing the 3D object by sequential layering of a 3D printing polymer filament onto a baseplate or build platform using a 3D printer which extrudes the polymer layer-by-layer onto the baseplate in the shape of the digital model according to the slice file;

[0010] (iv) layer bonding of the layers into a solid 3D object, including by melting or curing; and

[0011] (v) removal of the formed 3D object from the baseplate.

[0012] When printing the 3D object onto the baseplate, an option is to initially deposit the molten printing polymer into holes in the baseplate which are then use as anchor points for the object that is printed. However, it is challenging to achieve the precise control using the 3D printing apparatus to be able to deposit the molten polymer anchors at the exact points required to support the 3D object.

[0013] HDPE (High-density polyethylene), is particularly challenging to 3D print due to the shrinkage and warping that occurs with this material. It has been described that one possible mechanism to improve the likelihood of a successful 3D print of HDPE is to lay down an initial layer or raft of HDPE on the baseplate onto which the HDPE filament layers are then printed by the 3D printer, to assist somewhat with warping and detachment of the HDPE 3D object during printing from the baseplate. However, this is not always successful, depending on the shape of the object.

[0014] HDPE is used in a wide range of products including piping and plumbing components (typically with the use of a die extrusion process rather than additive manufacturing), in the production of toys, food containers and components as well as medical devices and components thereof (although typically by moulding) due to its non-toxic nature.

[0015] A method for reproducible 3D printing of HDPE into 3D objects of varying shapes and sizes without the issues experienced in the prior art of warping, shrinkage and detachment from the build plate resulting in object failure would therefore be extremely valuable.

[0016] SUMMARY OF THE INVENTION

[0017] According to a first embodiment of the invention there is provided a baseplate for use with a 3D printing apparatus in a Fused Filament Fabrication (“FFF”) printing method, comprising three layers, wherein:

[0018] (i) the first and third (i.e. the outer) layers are comprised of a rigid material; and

[0019] (ii) the second (i.e. the middle) layer is comprised of a polymer, wherein the first or both the first and third layers define a plurality of apertures into which the second layer material extends.

[0020] The rigid material may comprise a metal. The metal may be selected from the group consisting of aluminium, stainless steel, mild steel or a fibre reinforced composite such as carbon or glass fibre, or combinations thereof. The material used in the first and third layers may be the same or different.

[0021] The length and breadth of the baseplate can be sized as desired to fit the particular 3D printing apparatus with which it is to be used.

[0022] In particular, the second layer polymer may be comprised of a high crystallinity polymer such as high-density polyethylene, polypropylene, nylon, acetal, polyethersulfone, and polyetheretherketone.

[0023] Further in particular, the FFF printing method is for 3D printing of a high crystallinity polymer such as described above.

[0024] The thickness of the first and third layers may be between 1 to 1.5 mm, preferably 1 ,5mm. The thickness of the second layer may be between 0.5 and 1 mm, optimally 1 mm. The plurality of apertures in the first or first and third layers are typically between about 2 to about 4 mm in diameter and spaced about 3 to 4 mm apart measured from the centres of the apertures. According to a second aspect of the invention, there is provided a method of FFF printing with the use of the baseplate of the invention as described above. In particular, the method comprises the steps of:

[0025] (a) heating the baseplate to between about 60 to about 90 °C thereby to improve adhesion of the 3D object onto the baseplate and to reduce warping while;

[0026] (b) extruding molten polymer from the 3D printing apparatus at a temperature between 220 and 240°C onto the first layer of the heated baseplate in a first layer of a 3D object to be printed, wherein the molten polymer of the first layer of the 3D object melts into the exposed polymer of the second layer of the baseplate which extends through the plurality of apertures in the first layer of the heated baseplate thereby anchoring the first layer of the 3D object to the first layer of the heated baseplate;

[0027] (c) sequentially extruding additional layers from the 3D printing apparatus of the 3D object to be printed onto the first layer of the 3D object until the complete 3D object has been formed;

[0028] (d) allowing the 3D printed object formed to cure and / or cool until solid; and

[0029] (e) separating the solid 3D printed object from the first layer of the baseplate by slicing between the base of the first layer of the 3D object and the surface of the first layer of the base plate using a sharp instrument such as a blade.

[0030] The extruding molten polymer from the 3D printing apparatus may be comprised of a filament heated in a nozzle of the 3D printing apparatus. Heating the filament in the nozzle to a temperature between 220 and 240°C melts the filament to generate the extruding molten polymer. The nozzle is capable of being displaced along a X axis and / or a Y axis to deposit the melted filament on the baseplate for the first layer. The melted filament may be further capable of being deposited on additional layers.

[0031] The temperature of the baseplate and the extruding molten polymer or filament may be maintained for the duration of the method of FFF printing.

[0032] The temperature of the extruding molten polymer allows for deposition of the material across the exposed polymer in holes provided in the baseplate. Cooling of the extruding molten polymer allows for the cooled extruding molten polymer to adhere to the polymer in the baseplate.

[0033] In one preferred embodiment of the invention, before step (b), the method includes an additional step of extruding molten polymer from the 3D printing apparatus onto the first layer of the heated baseplate to form a raft on the surface, wherein the molten polymer of the raft melts into the exposed polymer of the second layer of the baseplate which extends through the plurality of apertures in the first layer of the heated baseplate thereby anchoring the raft to the first layer of the heated baseplate.

[0034] In this embodiment, step (b) above is then performed by extruding a molten polymer for producing the 3D object from the 3D printing apparatus onto the raft, thereby anchoring the first layer of the 3D object to the raft, followed by steps (c) and (d) above. At step (e), the solid 3D printed object is removed from the raft by slicing between the first layer of the 3D object and the surface of the raft using a sharp instrument such as a blade. Any portion of the raft still attached to the base of the 3D object may be removed by cutting this from the base of the 3D object.

[0035] Any remaining raft can also be cut or, scraped off the surface of the first layer of the baseplate using a blade or chisel, thereby cleaning the first layer of the baseplate but leaving the second layer of the baseplate including its extensions into the plurality of apertures of the baseplate intact. The cleaned baseplate can then be successively used in further 3D printing processes using the process described above.

[0036] The raft may be extruded onto the surface of the first layer of the baseplate in the form of a lattice or may be a solid layer on the surface of the first layer of the base plate. Preferably the raft is in the form of a lattice. Different portions of the raft lattice may have different densities as desired to provide greater or lesser support for the 3D printed object to be printed onto the raft as necessary. The lattice structure and density may be adjusted with the use of a slicing software that is compatible for use with the 3D printing apparatus. Many different slicing software are known.

[0037] The 3D printing device may have a slicing software application stored thereon which is capable of being executed to specify the width of the raft. The slicing software application may be CURA. The slicing software may allow for a user to program the spacing of the printed lattice lines in top, middle and bottom layers of the raft thereby to make portions of the lattice more or less dense. Depending on the shape of the 3D object to be printed different lattice structures and densities can be selected. For example, if strong warpage of HDPE is expected to occur during printing, a dense raft may be selected to be printed to prevent delamination of the raft due to warping of the 3D object being printed onto it.

[0038] The thickness of the raft lattice (i.e. the space between the top surface of the baseplate and the top surface of the raft lattice onto which the 3D object is printed) may also be programmed using slicing software. The spacing may be adjusted by the user depending on the shape of the 3D object being printed to allow for ease of removal of the object from the raft, but still providing for secure anchoring of the 3D object to the raft during 3D printing without detachment of the 3D object and raft from the baseplate due to warping during 3D printing.

[0039] For example, a thin-walled 3D object may be 3D printed with a lattice thickness of about 0.35 mm. However, a more solid 3D object, which would be expected to warp more, will require a smaller lattice thickness.

[0040] The width of the raft extending beyond the borders of the 3D object may additionally be specified through the slicing software. A wider border may allow for more apertures to be covered which allows for firmer attachment / adhesion to the baseplate especially for parts with a small base.

[0041] In particular, the method may be used for 3D object printing of a high crystallinity polymer such as HDPE.

[0042] The 3D printed object may be a plumbing or piping component, a food or beverage component, a toy or a medical device component. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The invention is described with reference to the following figures, which should not be seen as limiting the interpretation of the invention in any way.

[0044] Figure 1 shows a line drawing of the baseplate of the invention;

[0045] Figure 2 shows an exploded line drawing of the baseplate of the invention;

[0046] Figure 3 shows the baseplate of the invention when used with a raft to form a 3D object by FFF printing;

[0047] Figure 4 shows removal of the 3D printed object from the raft when used with the baseplate of the invention;

[0048] Figure 5 provides an illustration of a plurality of apertures and their measurements;

[0049] Figure 6 illustrates a series of photographs for 5 test samples that have been printed with a 3D printing apparatus according to the present invention;

[0050] Figure 7 shows a series of cross-section photographs of a printed object prepared according to the present invention; and

[0051] Figure 8 shows a series of photographs of a complex printed object prepared according to the present invention.

[0052] DETAILED DESCRIPTION

[0053] The invention relates to a build platform for Fused Filament Fabrication (FFF) three- dimensional (3D) printing and a method of FFF printing a 3D object with the use of a 3D printer and the build platform of the invention.

[0054] The following description of the invention is provided as an enabling teaching of the invention, is illustrative of the principles of the invention and is not intended to limit the scope of the invention. It will be understood that changes can be made to the embodiment / s depicted and described, while still attaining beneficial results of the present invention. Furthermore, it will be understood that some benefits of the present invention can be attained by selecting some of the features of the present invention without utilising other features. Accordingly, those skilled in the art will recognise that modifications and adaptations to the present invention are possible and can even be desirable in certain circumstances, and are a part of the present invention. Figure 1 shows one possible embodiment of the baseplate (10) of the invention including the first (12), second (14) and third (16) layers of the baseplate (10). The first layer (12) of the baseplate (10) defines a plurality of apertures (22) through which the second (14) layer of the baseplate (10) extend. In Figure 1 , the baseplate of the invention has been used with a raft lattice (20) onto which the 3D object (18) is 3D printed by FFF printing. The raft (20) is anchored to the first layer (12) of the baseplate by melting the polymer of the raft (20) and the polymer of the second layer (14) of the heated baseplate which extends through the plurality of apertures (22) in the first (12) and optionally the third (16) layers of the baseplate (10). The first (12) and third layers (16) are made from a metal including aluminium, stainless steel or mild steel or a composite including carbon or glass fibre. The second layer (14) is made from a polymer, in particular HDPE, as is the raft (20) and 3D object (18).

[0055] It is, however, to be appreciated, that depending on the thickness of the base of the 3D object (18) to be printed, it is possible to print the 3D object (18) directly onto the surface of the first (12) layer of the baseplate (10) such that the molten polymer of the first layer of the 3D object (18) melts into the second layer (14) that extends through the plurality of apertures (22) in the first layer (12) of the heated baseplate (10), thereby anchoring the base of the 3D object (18) to the baseplate (10) for the 3D printing process.

[0056] Figure 2 shows an alternative embodiment in which both the first (12) and third (16) layers of the baseplate (10) define a plurality of apertures (22) through which the second layer (14) of the baseplate (10) extend. Additionally, Figure 2 shows a particular embodiment where the aperture (22) walls in the first (12) and / or third (16) layers of the baseplate (10) are chamfered on the side adjacent the second layer (14), thereby to make it more difficult to pull the second layer polymer (14) out of the apertures (22) when removing the raft (22) and / or the 3D object (18) from the baseplate (10).

[0057] Figure 3 shows a photograph of a 3D object formed on a raft anchored to the baseplate of the invention and Figure 4 shows removal of the 3D object from the raft by means of a sharp blade. The raft can be removed from the first or third layer of the baseplate in the same way to provide a clean baseplate for reuse in subsequent 3D printing processes. Figure 5 illustrates the plurality of apertures, together with their respective measured angles and distances.

[0058] Figure 6 provides a series of photographs for 5 test samples printing according to the invention described herein, where each set of samples have been exposed to a particular test. Figure 6(a) illustrates the sample exposed to a tensile test. The results of the test are provided below.

[0059] Graph 1 illustrating a plotted graph of stress (MPa) versus Strain (%)

[0060] Table 1 showing the tensile testing results for the specimens.

[0061] The Young’s modulus has been calculated as follows E = o / e (where E is Young’s modulus, o is the stress, and e is the strain). The Young’s modulus (modulus of elasticity) from the test ranges between 1155,019 MPa and 1286,592 MPa while the tensile strength ranges between 19 MPa and 21 MPa. Both the young’s modulus and tensile strength fall within the values from literature for HDPE. Figure 6(b) illustrates the sample exposed to a compression test. Figure 6(c) illustrates the sample exposed to a bending test. Figure 6(d) illustrates the sample exposed to an impact test. These tests were performed to confirm that the HDPE is suitable for a non-loadbearing cosmetic implant and meets ASTM (American Society for Testing and Materials) and ISO (International Organization for Standardization) standards.

[0062] Figure 7(a) provides a cross-section of a cube printed in three directions (X, Y, Z axes) illustrated in Figure 7(b). Figure 7(c) provides a cross-section of the same cuber that has been subjected to a surface roughness test. In these images, there is illustrated how the cube has been printed with high precision and accuracy in three directions / dimensions. The surface roughness also illustrates the aesthetics of the printed parts I 3D objects, where it is usually measured on the vertical and horizontal surfaces.

[0063] Figures 8(a) to 8(d) provide different views of a complex object that has been printed according to the present invention. Importantly, complex printed objects required solid infill, which induces significant internal stresses and typically causes warping during FFF printing of HDPE. The applicant believes that these parts I 3D objects could not have been successfully printed without anchoring them to the baseplate using conventional printing methods, which demonstrates the effectiveness of the invention in enabling warp-resistant, high-integrity HDPE printing. The complex geometry was printed with one or two outer walls and then with as little infill as possible to help reduce warping. The Applicant does not believe that this complex object and its geometry would have been possible to print without the baseplate described according to the present invention.

[0064] Therefore, the applicant believes that the performance of the invention illustrated in the printing of these complex parts / objects provides significant real-world performance evidence of a product that could not have been prepared according to conventional printing methods (such as FFF) with the use of HDPE, as other methods are not able to hold down the party while the printing process is performed, which usually results in the corners of the parts / objects staring to lift when printed on other bases. Typically, the printing of high crystallinity polymers usually result in the comers of the parts staring to lift when printed on other bases. With more layers laid down, the worst this curling becomes and can consequently completely deform the part / object.

[0065] In 3D printing, it is important that the printed part / object matches the geometry of the CAD design or else it defeats the purpose of the process. Therefore, the advantage of the baseplate according to the present invention is to hold down the part / object during printing or else it deforms when it becomes partially detached. The curling can even result in the part / object completely detaching from the base which results in a failed print. In practice, one would usually never print a part / object solid using the FFF printing process since it induces a lot of internal stress while printing and also wastes material.

[0066] Importantly, the Applicant believes that the baseplate and method described according to the present can be used, but is not limited to, the printing of any high crystallinity polymer used in any industrial application, hobby, sport or medical application.

Claims

CLAIMS1 . A baseplate for use with a 3D printing apparatus in a Fused Filament Fabrication (“FFF”) printing method, the baseplate comprising:- a first layer and a third layer that are comprised of a rigid material; and- a second layer that is comprised of a polymer, wherein the first layer and the third layer define an outer layer, the second layer defines a middle layer, and wherein the first layer or both the first layer and the third layer define a plurality of apertures into which the second layer material extends.

2. The baseplate according to claim 1 wherein the rigid material comprises a metal selected from the group consisting of aluminium, stainless steel, mild steel, carbon, glass fibre, or combinations thereof.

3. The baseplate according to claim 1 wherein the material used in the first and third layers is the same or different.

4. The baseplate according to claim 1 wherein the length and width of the baseplate is sized as desired to fit a 3D printing apparatus with which it is to be used.

5. The baseplate according to claim 1 wherein the second layer polymer is comprised of a high crystallinity polymer selected from the group consisting of high-density polyethylene, polypropylene, nylon, acetal, polyethersulfone, polyetheretherketone, or combinations thereof.

6. The baseplate according to claim 1 wherein the thickness of the first layer and the third layer is between 1 mm and 1 .5 mm.

7. The baseplate according to claim 1 wherein the thickness of the second layer is between 0.5 mm and 1 mm.

8. The baseplate according to claim 1 wherein the plurality of apertures in the first layer, or both the first layer and the third layer have diameters between 2 mm and 4 mm and spaced apart by distances between 3 mm and 4 mm.

9. A method of Fused Filament Fabrication (“FFF”) printing with the use of the baseplate according to claims 1 - 8, wherein the method comprises the steps of: a) heating the baseplate to between about 60 to about 90°C, thereby to improve adhesion of a 3D object onto the baseplate and to reduce warping; b) extruding molten polymer from the 3D printing apparatus at a temperature between 220 and 240°C onto the first layer of the heated baseplate in a first layer of a 3D object to be printed, wherein the molten polymer of the first layer of the 3D object melts into the exposed polymer of the second layer of the baseplate which extends through the plurality of apertures in the first layer of the heated baseplate, thereby anchoring the first layer of the 3D object to the first layer of the heated baseplate; c) sequentially extruding additional layers from the 3D printing apparatus of the 3D object to be printed onto the first layer of the 3D object until the complete 3D object has been formed; d) allowing the 3D printed object formed to cure and / or cool until solid; and e) separating the solid 3D printed object from the first layer of the baseplate by slicing between the base of the first layer of the 3D object and the surface of the first layer of the base plate using a sharp instrument such as a blade.

10. The method according to claim 9, wherein the step of extruding molten polymer from the 3D printing apparatus comprises extruding a filament heated in a nozzle of the 3D printing apparatus.

11. The method according to claim 10, wherein heating the filament in the nozzle to a temperature between 220°C and 240°C melts the filament to generate the molten polymer for extrusion.

12. The method according to claim 10, wherein the nozzle is capable of being displaced along the X axis and / or the Y axis to deposit the melted filament onto the baseplate to form a first layer.

13. The method according to claim 12 wherein the molten polymer is capable of being deposited onto additional layers.

14. The method according to claim 9 wherein the temperature of the baseplate and the molten polymer is maintained for the duration of the FFF printing method.

15. The method according to claim 9 wherein the temperature of the extruding molten polymer allows for deposition of the material across the exposed polymer in holes provided in the baseplate.

16. The method according to claim 9 wherein cooling of the extruding molten polymer allows for the cooled polymer to adhere to the polymer in the baseplate.

17. The method according to claim 9 wherein, before step (b), the method comprises an additional step of extruding molten polymer from the 3D printing apparatus onto the first layer of the heated baseplate to form a raft on the surface, wherein the molten polymer of the raft melts into the exposed polymer of the second layer of the baseplate which extends through the plurality of apertures in the first layer of the heated baseplate thereby anchoring the raft to the first layer of the heated baseplate.

18. The method according to claim 17, wherein step (b) is performed by extruding a molten polymer for producing the 3D object from the 3D printing apparatus onto the raft, thereby anchoring the first layer of the 3D object to the raft, followed by steps (c) and (d).

19. The method according to claim 17 wherein in step (e), the solid 3D printed object is removed from the raft by slicing between the first layer of the 3D object and the surface of the raft using a sharp instrument.

20. The method according to claim 19 wherein any portion of the raft still attached to the base of the 3D object is removed by cutting it from the base of the 3D object.

21. The method according to claim 19, wherein any remaining raft is cut or scraped off the surface of the first layer of the baseplate using a blade or a chisel, thereby cleaning the first layer of the baseplate but leaving the second layer of the baseplate, including its extensions into the plurality of apertures of the baseplate, intact.

22. The method according to claim 21 wherein the cleaned baseplate is used in further 3D printing processes.

23. The method according to claim 17 wherein the raft is extruded onto the surface of the first layer of the baseplate in the form of either a lattice or a solid layer on the surface of the first layer of the baseplate.

24. The method according to claim 23 wherein different portions of the raft lattice have different densities as desired to provide greater or lesser support for the 3D printed object to be printed onto the raft as necessary.

25. The method according to claim 24 wherein the lattice structure and density are capable of being adjusted with the use of a slicing software that is compatible for use with the 3D printing apparatus.

26. The method according to claim 17 wherein the 3D printing apparatus has a slicing software application stored thereon which is capable of being executed to specify the width of the raft.

27. The method according to claim 26 wherein the slicing software application is CURA.

28. The method according to claim 26 wherein the slicing software allows a user to program the spacing of the printed lattice lines in top, middle and bottom layers of the raft thereby to make portions of the lattice more or less dense.

29. The method according to claim 26 wherein the slicing software application allows a user to select different lattice structures and densities to print a desired 3D object according to its shape.

30. The method according to claim 26 wherein the slicing software application allows a user to program and select the desired thickness of the raft lattice.

31. The method according to claim 26, wherein the slicing software application allows a user to program and adjust the spacing depending on the shape of the 3D object being printed, to allow for ease of removal of the object from the raft,while still providing secure anchoring of the 3D object to the raft during 3D printing, without detachment of the 3D object and raft from the baseplate due to warping during 3D printing.

32. The method according to claim 26 wherein the slicing software application allows a user to program and adjust the width of the raft extending beyond the borders of the 3D object.

33. The method according to claim 32 wherein a wider border allows more apertures to be covered to allow for firmer adhesion to the baseplate.

34. The method according to claim 9 for 3D object printing of a high crystallinity polymer.

35. The method according to claim 34 wherein the high crystallinity polymer is HDPE.

36. The method according to claims 10 - 35 wherein the 3D printed object is an object selected from the group consisting of a plumbing component, piping component, food component, beverage component, toy component, medical device component, or combinations thereof.

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