WO2025133018A1

WO2025133018A1 - Material jetting

Info

Publication number: WO2025133018A1
Application number: PCT/EP2024/087752
Authority: WO
Inventors: Albertine Pauline WIJNHEIJMER; Jessica PEPE; Kim Maria Johanna ALARDS
Original assignee: Lake3d Holding BV
Current assignee: Lake3d Holding BV
Priority date: 2023-12-21
Filing date: 2024-12-19
Publication date: 2025-06-26
Anticipated expiration: 2026-06-21
Also published as: NL2036606B1

Abstract

A computer-implemented method comprising receiving an input model comprising data indicative of the physical configuration of an object to be printed using material jetting 3D printing, processing the input model data to identify portions (20) of the object vulnerable to deformation by surface tension-induced flow (Q), and modifying one or more parameters of the material jetting for the identified portions of the object.

Description

Material Jetting

FIELD

The present invention relates to material jetting, for example manufacturing an object using 3D printing.

BACKGROUND

Material jetting is a 3D printing technology based on inkjet printing. In inkjet printing, ink droplets are selectively deposited on a substrate to form a 2D image. Material jetting is very similar, but instead of creating a 2D image, droplets are deposited as a series of layers to create a 3D object.

Preventing printing artefacts such as distortion is a challenge in many 3D inkjet printing processes. Distortion may be present at one or more portions of a printed object. In particular, some portions of a material jetting printed object may exhibit excessively pointed structures, which deviate in both shape and dimension from the intended geometry of the printed structure. In existing solutions, in-line measurements, feedback systems and application of a flattening roller have been proposed to mitigate such problems. A drawback of in-line measurements is that these are time consuming and require sophisticated devices and software. A drawback of applying a roller is that in a layer comprising multiple materials, material cross contamination may occur.

It may be desirable to provide an apparatus that obviates or mitigates one or more problems associated with the prior art.

SUMMARY

According to a first aspect of the invention there is provided a computer-implemented method comprising receiving an input model comprising data indicative of the physical configuration of an object to be printed using material jetting 3D printing, processing the input model data to identify portions of the object vulnerable to deformation by surface tension-induced flow, and modifying one or more parameters of the material jetting for the identified portions of the object.

Advantageously, the invention may reduce surface deformation of an object. Identification of a portion of the object as vulnerable to deformation by surface tension- induced flow may comprise determining a ratio of edge voxels to bulk voxels.

A portion of the object may be identified as vulnerable to deformation by surface tension- induced flow when the ratio of edge voxels to bulk voxels exceeds a critical value.

The critical value may take into account data indicative of material properties of one or more inks used in the material jetting process. Material properties may be taken to include surface and interfacial properties as dictated by the composition and state of the interfaces present. For example, the surface energies and contact angles of the interfaces may be taken to be material properties.

Material properties of one or more inks may comprise data indicative of surface energies of interfaces comprising one or more inks in cured or liquid form. Data indicative of surface energies of interfaces may include interface contact angles.

Material properties of one or more inks may comprise data indicative of viscosities of the one or more inks.

The critical value may be informed by geometric parameters of the material jetting process.

A geometric parameter of the material jetting process may include thickness of printed layers and/or an acceptable deviation of layer thickness.

Identification of a portion of the object as vulnerable to deformation by surface tension- induced flow may comprise determining one or more of: the surface to volume ratio, radius of curvature, or the inclination of portions of the object.

Modification of the one or more parameters of the material jetting process may comprise reducing a volume of ink deposited at each voxel for the identified portions of the object.

Modification of the one or more parameters of the material jetting process may comprise reducing ink curing time for the identified portions of the object. The term ‘curing time’ may be taken to mean the time elapsing between ink deposition and ink curing. Modification of one or more parameters of the material jetting process may comprise varying UV intensity incident on a printed layer for the identified portions of the object.

The material jetting process may be modified such that only a portion of the voxels in a printed layer are deposited at any one time.

The material jetting process may be modified by selecting a different ink composition for deposition.

According to a second aspect of the invention there is provided a method of manufacturing comprising the method of the first aspect, the method further comprising printing the object using the parameters determined by the computer-implemented method

According to a third aspect of the invention there is provided a computer program comprising computer executable instructions that, when executed by a processor, cause the processor to perform the method of any preceding aspect.

According to a fourth aspect of the invention there is provided a material jetting 3D printer comprising a substrate table and a print head system having an array of nozzles, wherein the material jetting 3D printer further comprises a controller programmed to cause the material jetting 3D printer to perform the method according to the first or second aspect.

According to a fifth aspect of the invention there is provided a computer readable medium, the computer readable medium having computer readable code embodied therein, the computer readable code being configured such that, on execution by a suitable controller, computer or processor, the controller, computer or processor is caused to perform the method according to the first or second aspect.

According to a sixth aspect of the invention there is provided a material jetting 3D printer comprising control electronics which are programmed to carry out the method according to the first or second aspect.

Features of different aspects of the invention may be combined together. BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example only, with reference to the accompanying figures, in which:

Figure 1A schematically illustrates a material jetting 3D printer at an initial stage of operation;

Figure 1 B schematically illustrates the material jetting 3D printer shown in Figure 1A at a subsequent stage of operation;

Figure 1 C schematically illustrates the material jetting 3D printer shown in Figures 1 A and 1 B at another subsequent stage of operation;

Figure 1 D schematically illustrates the material jetting 3D printer shown in Figures 1A, 1 B and 1C at another subsequent stage of operation;

Figure 2 schematically illustrates a portion of a layer printed by material jetting.

Figure 3A illustrates a hemispherical object printed by material jetting;

Figure 3B illustrates the effect of surface tension-induced flow on the printed dome shown in Figure 3B; and

Figure 4 schematically illustrates a computer implemented method according to an embodiment of the present invention.

DETAILED DESCRIPTION

In the following description an embodiment will be described with reference to a set of Cartesian axes, which are shown in the figures.

Figures 1A-D schematically illustrate a material jetting 3D printer 1 (hereafter referred to as ‘the printer T) in various stages of operation.

The printer 1 comprises a support material printhead 2, a first object material printhead 4, a second object material printhead 6, a moveable substrate table 8 and a UV source 10. The support material printhead 2, the first object material printhead 4, and the second object material printhead 6 may be collectively referred to as the printheads. The printheads 2, 4, 6 are offset from the UV source 10 such that the UV light is not incident upon nozzles of the printheads. The substrate table is disposed below the printheads 2, 4, 6 and the UV source 10 (i.e. in located in the negative z-direction). The print heads 2, 4, 6 may collectively be referred to as a printhead system. The support material printhead 2 is configured to eject droplets of a support material toward the substrate table 8. The first object material printhead 4 is configured to eject droplets of a first material toward the substrate table 8. The second object material printhead 6 is configured to eject droplets of a second material toward the substrate table 8. Each of the printheads 2, 4, 6 comprises a plurality of nozzles, each configured to eject droplets. The plurality of nozzles of may be arranged in a linear array, disposed in the y-direction. Each of the plurality of nozzles in the printhead 2,4,6 defines a y-position.

The first and second materials may have different compositions.

The substrate table 8 (which may also be referred to as a build platform) is configured to be translatable in at least the z and x-axes. In an alternative, the substrate table 8 may be rotatable or translatable in the x, y, and z-axes.

In general, the printheads and substrate table move relative to each other. In some embodiments, dynamic printheads may move relative to a static substrate table. In other embodiments, both the printhead and the substrate table may move.

The UV source 10 may have a variable intensity output.

Figure 1A shows a first layer of droplets being deposited on the substrate table 8. As the substrate table moves past the printheads 2,4,6 in the positive x-direction, the ejected droplets are received on the substrate table 8. A selected number of droplets are ejected and deposited at each x-y position in a layer. The number of droplets deposited for each x-y position may be expressed as droplets per dot (DPD). Where multiple droplets are ejected by the printhead for each x-y position, the droplets may coalesce. The ejected droplets may coalesce in flight, before being received on the substrate table 8. The coalesced droplet may be referred to as a deposited droplet 12. The deposited droplets 12 have a specified pattern or distribution in the x-y plane.

Each x-y position in a layer corresponds to a voxel in an input model. The input model may comprise data indicative of the physical configuration of the object to be printed. Data indicative of the physical configuration may include object composition and object geometry. To determine which nozzle (corresponding to a y-position) of which print head (corresponding to a composition) should eject a droplet, and to compute the specific timing of jetting this droplet (corresponding to an x-position), an output model with information on a voxel level is sent to the printer. The output model may comprise one or more bitmap files.

Turning now to Figure 1 B, the deposited droplets 12 flow to form a layer 14 having a generally uniform layer thickness 5. The layer thickness 5 is a geometric parameter of the printing process. Translation of the substrate table 8 places printed layer 14 under the UV source 10. The UV source 10 emits UV radiation which is incident on the printed layer 14, curing the printed layer.

The first and second object materials may be referred to as first and second object inks respectively. Typically, the first and second object inks are UV-curable inks. UV light triggers polymerisation of the (liquid) first and second object inks into a rigid solid form via photochemical reactions. The solidification of the first and second object inks is referred to as curing. The first and second object inks will form a finished object (once support material has been removed, as explained below) and may be collectively referred to as object inks.

The support material is used to reduce flow effects that might cause inaccuracy of printed objects and to support hollow or overhanging parts. The support material forms a support structure which supports the object inks during printing. Typically, the support material is a UV-curing material. The support material may be a soluble material that can be washed away after printing of the object has been completed. In an alternative, the support material may also be removed from an object by melting or (mechanical) breaking.

The process of printing another layer is schematically illustrated in Figures 1C. The substrate table 8 is translated in the negative z-direction by a single layer thickness 5 (ensuring a constant gap between the printheads 2, 4, 6 and a deposition surface). A second set of deposited droplets 16 is then deposited on top of the first printed layer 14 in substantially the same manner as the previously deposited droplets 12 (as described with reference to Figure 1A). The second set of deposited droplets 16 flow to form a second printed layer of uniform layer thickness 5. Figure 1 D shows the curing of the second printed layer 18 by the UV source 10. This provides a printed object having a height of 2b.

The process described with reference to Figures 1A-D may be repeated until an object of the desired height and geometry is created by cumulative addition of printed layers.

Nominally, printed layers are static and planar. In practice, printed layers are non-planar and subject to dynamic effects.

Figure 2 schematically illustrates a cross-sectional profile of an edge portion 20 of the uncured printed layer 14 of object ink on the substrate table 8. The edge portion 20 is a curved area, which extends from a substantially planar bulk portion 22 of the printed layer 14.

The term edge portion, should be taken to indicate peripheral parts of the object at an interface with a solid (e.g. the substrate table 8 or previously-cured ink) and another fluid (e.g. air or support material). The edge portion 20 has a contact angle 0, which depends upon the composition of the interface (specifically, the surface properties of substances present). In the depicted example, the edge portion 20 comprises a contact line 24, where the ink, substrate table 8 and surrounding medium meet.

The fluid (comprising object ink) of the printed layer 14 has a surface tension or equivalently, a surface energy. In general, this surface tension creates a tendency for a contact line 24 of the interface to recede.

The curved portion exerts a Young-Laplace pressure, PLP'.

where y is the surface tension of the liquid and R_x and R_y are the radii of curvature in x and y of the curved portion 20, respectively. The Young-Laplace pressure creates a negative pressure gradient from the curved portion 22 toward the bulk portion of the printed layer 22. The negative pressure gradient induces a flow of ink, Q, toward the bulk portion 22. The contact line 24 recedes and the thickness b of printed layer 14 increases commensurately - because the ink volume of the layer is conserved. Put alternatively, the printed layer 14 deforms by contracting in x-y plane extent and expanding in the z- direction.

R_x is dependent on a number of factors, including contact angle 0. A greater contact angle 0 corresponds to a smaller radius of curvature R_x. A smaller radius of curvature R_x results in a higher Young-Laplace pressure (for a given material). Material interfaces with larger contact angles experience more severe inward ink flows and thus a greater increase in layer thickness.

Curing the ink solidifies the printed layer and thus arrests any further flows of material and the resulting deformation.

Surface tension-induced flow deformation has been described with respect to Figure 2, which shows an uncured printed layer 14 on the substrate table 8. However, deformation by the same mechanism also occurs where the uncured printed layer is deposited on a cured printed layer (e.g. printed layer 14 of Figure 1 D)

The above-described surface tension-induced flow and resultant deformation may occur for any printed layer. However, deformation is most severe in printed layers which have a high ratio of edge voxels to bulk voxels because the inward flow of the ink is an edge effect.

Equivalently, a portion of an object having a high (local) surface to volume ratio is vulnerable to deformation by surface tension-induced flow. A portion with a high surface to volume ratio is composed of printed layers with a high perimeter to cross-sectional area ratio. The ratio of the perimeter to cross sectional area is generally proportional to the ratio of edge voxels to bulk voxels. A high perimeter to cross-sectional area ratio corresponds to a high ratio of edge voxels to bulk voxels.

In addition, portions of an object having a small radius of curvature (for example, where the radius of curvature of the portion is disposed along a plane perpendicular to the substrate table) may also be vulnerable to deformation by surface tension-induced flow. A portion of an object with a small radius of curvature (for example, where the radius of curvature of the portion is disposed along a plane perpendicular to the substrate table) may be composed of printed layers with a high perimeter to cross-sectional area ratio. A high perimeter to cross-sectional area ratio closely corresponds to a high ratio of edge voxels to bulk voxels.

Portions of an object having a steep inward surface inclination may also be vulnerable to deformation by surface tension-induced flow. In particular, portions with steeply pointed forms, such as pyramids are vulnerable to deformation. A portion of an object with a steep inward surface inclination may be composed of printed layers with a high perimeter to cross-sectional area ratio. A high perimeter to cross-sectional area ratio closely corresponds to a high ratio of edge voxels to bulk voxels. In an example, where a portion of an object has a layer having a high ratio of edge voxels to bulk voxels, a steep inward surface inclination around and above the layer means that there are nearby printed layers also having a high ratio of edge voxels to bulk voxels. The steep inward surface inclination indicates the presence of a number of layers (i.e. a portion of the object) vulnerable to deformation.

Edge voxels may be defined as those voxels corresponding to the edge of the object and bulk voxels correspond to the remainder of the voxels in an object.

Object features indicative of layers having a high ratio of edge voxels to bulk voxels or (equivalently) vulnerability to deformation by surface tension-induced flow may include portions of an object having a high surface to volume ratio, or analogously a high ratio of edge voxels to bulk voxels, a small radius of curvature, or a steep inward inclination.

Figure 3A shows a printed hemispherical object. Individual layers 32 that have been used to form the hemispherical object are depicted by horizontal bands. Figure 3A depicts the hemispherical object as formed when each printed layer 32 is perfectly static and planar. The layers 32 constituting a top portion 34 have relatively high ratios of edge voxels to bulk voxels. The layers of top portion 34 are more vulnerable to deformation by surface tension-induced flow (compared with layers below the top portion).

The cumulative effect of the above described deformation by surface tension-induced flow over multiple layers is schematically illustrated in Figure 3B. The cumulative deviation of layer thickness (thickening) from a nominal value of the printed layers of the top portion 34 distorts or deforms the intended hemispherical profile. This results in a height discrepancy A and an unintended pointed profile.

Examples of portions of an object vulnerable to deformation by surface tension-induced flow may include other generally convex shapes or other protrusions such as ogives (i.e. pointed domes) or pyramids.

Figure 4 is a schematic illustration of a computer-implemented method 100 for material jetting 3D printing.

At a step S1 , an input model is received with data indicative of the physical configuration of an object to be printed. Data indicative of the physical configuration may include composition and object geometry, in the form of voxel data.

At a step S2, the input model data is processed to identify portions of the object vulnerable to deformation by surface tension-induced flow.

In cases where the input model comprises voxel data, identification of a portion of the object as vulnerable to deformation by surface tension-induced flow may comprise determining a ratio of edge voxels to bulk voxels for each continuous ink volume in a layer.

Surface tension-induced flow only acts upon continuous ink volumes of a printed layer. Therefore, discontinuous ink volumes may be considered separately from each other at step S2.

A portion of the object is identified as vulnerable to deformation by surface tension- induced flow when the ratio of edge voxels to bulk voxels exceeds a critical value. The critical value may be informed by a number of parameters.

The critical value of the ratio of edge voxels to bulk voxels may be set with a view toward limiting the maximum layer thickness deviation. The maximum layer thickness deviation may be selected based on desired dimensional tolerances of the finished object to be printed. Having set an upper limit for the maximum layer thickness deviation, the critical value can be calculated based on a physical model of surface tension-induced flow in the printed layers. The model may be analytically or empirically derived, or Al-based. An example of empirically deriving the model is set out further below.

The critical value is informed by data indicative of material properties of one or more inks used in the material jetting process. Material properties of the one or more inks comprise data indicative of surface energies of interfaces comprising one or more inks in cured or liquid form. In addition, the surface properties of the substrate table should be taken into account for the first printed layer. Data indicative of surface energies of interfaces may include contact angles. As explained above with reference to Figures 2-3B, interface pressures drive the deformation process.

Data indicative of material properties of one or more inks may further comprise composition data of the materials used in the material jetting process. In particular, photo-initiator concentration can influence the surface tension and/or curing time of the printed layer. In addition, surfactant concentration influences the surface tension.

The deformation is caused by surface tension-induced flow. As such, properties, material or otherwise, of the ink relevant to fluid flow may also be used in establishing the critical value. The viscosities of the one or more inks and the (nominal) thickness of the printed layer also play a role in establishing the critical value. In addition, the duration of fluid flow also impacts the extent to which the printed layers are able to flow and deform. Thus the curing time of the ink can influence the critical value.

An empirically-derived model for identifying portions of an object vulnerable to deformation may be obtained by printing a series of trial objects. The trial objects having different shapes (e.g. domes/hemispheres, ogives or pyramids etc.) may be printed with a variety of different sizes, under varying material jetting parameters such as UV intensity output or ink composition.

The extent and/or presence of distortion can then be determined from comparison of the expected profile (e.g. from the input model) and the profile of the printed trial object itself (e.g. as determined from a 3D scan of the printed trial object) with regard to selected dimensional tolerances. Portions of the printed trial object which deviate from the expected profile more than allowed by the selected dimensional tolerances are identified as distorted portions. In an example, for some applications, the profile of the printed trial object may be allowed to deviate by up to 100 pm from the expected profile. In a further example, for some applications the profile of the printed trial object may be allowed to deviate by up to 50 pm from the expected profile.

In an example, a series of hemispherical objects may be printed with diameters from 5mm to 2mm in 1 mm increments. The resulting series of printed hemispherical objects may be examined and distorted portions of hemispheres (cf. top portion 34 in Figure 3B) identified as described above.

The lowermost and widest printed layer (cf. the lowermost layer of top portion 34 in Figure 3B) of the distorted portion may be considered to set the critical value of the ratio of edge voxels to bulk voxels because it corresponds with the onset of distortion. The smaller printed layers (above the lowermost layer) further up the distorted portion have still higher ratios of edge voxels to bulk voxels and are even more vulnerable to deformation than the base layer. Therefore, the lowermost printed layer provides an upper limit for the ratio of edge voxels to bulk voxels, above which there is an unacceptable degree of distortion present in a printed object (i.e. a critical ratio).

The radius of the lowermost printed layer of the distorted portion may also referred to as a critical radius. The critical radius has a fixed relationship with the ratio of the perimeter to cross sectional area of the lowermost printed layer. The ratio of the perimeter to cross sectional area of the lowermost printed layer is generally proportional to the critical value of the ratio of edge voxels to bulk voxels.

The above process of printing a series of trial objects can be carried out with a number of varying UV intensities, to obtain critical values of the ratio of edge voxels to bulk voxels over a range of UV intensities.

Further, for each UV intensity, trial objects may be printed with a number of varying ink compositions (e.g. varying surfactant concentration), to obtain critical values of the ratio of edge voxels to bulk voxels over a range of combinations of ink composition and UV intensity. The set of critical values obtained populates a lookup table of critical values at selected combinations of ink composition and UV intensities. By interpolation, critical values can be estimated for non-empirically tested cases, generating a calibrated two-dimensional model for the critical values.

The same process can be extended to, or adapted for, other material jetting parameters, such as those described below.

At a step S3, one or more parameters of the material jetting process are modified in relation to the identified portions of the object. This yields a processed input model further comprising data on the parameters of the material jetting process.

The modification of material jetting process parameters may be applied to only those portions identified as vulnerable to deformation by surface tension-induced flow at step S2. The material jetting process parameters are modified with respect to those used for the non-identified portions of the object.

Modification of the one or more parameters of the material jetting process comprises reducing the volume of ink deposited at each voxel. For example, when printing layers of the object identified as vulnerable to surface tension-induced flow, the DPD setting for the relevant layers may be reduced to compensate for the increased layer thickness caused by surface tension-induced flows, minimising height discrepancy.

In an example, for the layers or portions of an object identified as vulnerable to deformation by surface tension-induced flow, a smaller number of droplets may be located (compared with the number of droplets deposited at other locations). In one example 2 droplets per dot (2DPD) may deposited at locations identified as vulnerable to deformation by surface tension-induced flow, and 3 droplets per dot (3DPD) may be deposited at other locations.

In the above example, the parameter of the material jetting process that is modified is the volume of ink deposited at each voxel. In other embodiments a different parameter may be modified. For example, the modified parameter of the material jetting process may be ink curing time. By reducing the time window for (surface tension-induced) flow within the printed layers, the deformation can be arrested before it exceeds an acceptable layer thickness deviation.

The ink curing time (of UV-curing inks) can be changed by changing the UV intensity incident on a printed layer (see for example the UV source 10 of Figures 1A-D). By increasing UV intensity, the ink in a printed layer can be cured more rapidly, reducing deformation of the printed layer.

In many embodiments, the time for the ink to polymerise and solidify is short relative to the total curing time. For example, the time to translate the substrate table toward the UV source may be more significant than the time for polymerisation. As such, the dominant effect of varying UV intensity may be that the incident UV radiation can induce a change of surface energy. This may affect the behaviour of the interfaces (e.g. modified contact angles) and thus affect layer deformation. In an example, increased UV intensity decreases surface energy of the cured object ink or support material layers, increasing the contact angle at the material interface. As described above, material interfaces with larger contact angles experience more severe inward ink flows and thus a greater increase in layer thickness

Additionally, or alternatively, the material jetting process may be modified such that only a portion of the voxels in a printed layer are deposited by a given printing pass (at locations identified as vulnerable to deformation by surface tension-induced flow). In particular, a portion of voxels may be selected for printing such that the deposited droplets are more isolated from each other (i.e. with reduced contact between deposited droplets compared with unmodified material jetting processes). These more isolated deposited droplets do not undergo the same degree of surface tension-induced deformation as large continuous printed layers (see 14 and 18 of Figures 1 B and 1 D). The length scale over which these more isolated deposited droplets can contract is limited by the small length scale of these more isolated deposited droplets. After curing the first portion of voxels in a layer, other portions may be deposited during a second printing pass and then cured. Optionally, additional printing passes may be performed until the complete layer is printed.

The term more isolated may refer to a reduced degree of contact between deposited droplets. In practice, the deposited droplets may be partially fluidly connected. In an example, a complete layer may be printed over 2,3,4 or more printing passes. The number of printing passes per complete layer is a parameter of the material jetting process. Preferably, a complete layer is printed over 2 or 3 printing passes. In an example, for hemispheres in which the complete layers are printed over 3 printing passes, the critical radius may be around 25% smaller than the critical radius where the complete layers are printed over 2 printing passes. Put alternatively, using 3 printing passes per complete layer allows smaller hemispheres to be printed with an acceptable amount of distortion compared with using 2 printing passes per complete layer.

Finally, the material jetting process may be modified by selecting a different ink composition (at locations identified as vulnerable to deformation by surface tension- induced flow). For example, an ink composition having a higher surfactant concentration may have a lower surface tension (i.e. better wetting properties) and thus less susceptibility to deformation by surface tension-induced flow.

Computer-implemented method 100 may be performed by one or more processors or controllers of a material jetting 3D printer. Alternatively, computer-implemented method 100 may be performed by computing devices, processors, controllers, or other devices external to a 3D printer.

One or more further operations may optionally be carried out on the processed input model (comprising data on the parameters of the material jetting process) to yield an output model. The output model may fully specify material jetting 3D printer operations and may be used to instruct a material jetting 3D printer in printing the object. For example, the output model may comprise one or more bitmaps for each printed layer and data on the parameters of the material jetting process such as DPD or UV intensity.

Computer-implemented method 100 may use the ratio of edge voxels to bulk voxels as a sole criterion for identifying portions of an object vulnerable to deformation by surface tension-induced flow. Other criteria may be used in addition to, or as alternatives to, the ratio of edge voxels to bulk voxels. For example, identification of a portion of the object as vulnerable to deformation by surface tension-induced flow may comprise determining one or more of: the surface to volume ratio, radius of curvature, or the surface inclination of portions of the object. 3D inkjet additive manufacturing as used by embodiments of the invention may fabricate objects based on three-dimensional (3D) information, for example a three-dimensional computer model (or design file), of the object.

Accordingly, examples described herein not only include objects as described herein, but also methods of manufacturing such objects via additive manufacturing and computer software, firmware or hardware for controlling the manufacture of such products via additive manufacturing.

The structure of one or more objects may be represented digitally in the form of a design file. A design file, or computer aided design (CAD) file, is a configuration file that encodes one or more of the surface or volumetric configuration of the shape of the object. That is, a design file represents the geometrical arrangement or shape of the object.

Design files can take any now known or later developed file format. For example, design files may be in the Stereolithography or “Standard Tessellation Language” (.stl) format which was created for stereolithography CAD programs of 3D Systems, or the Additive Manufacturing File (.amf) format, which is an American Society of Mechanical Engineers (ASME) standard that is an extensible markup-language (XML) based format designed to allow any CAD software to describe the shape and composition of any three- dimensional object to be fabricated on any additive manufacturing printer.

Further examples of design file formats include AutoCAD (.dwg) files, Blender (.blend) files, Parasolid (,x_t) files, 3D Manufacturing Format (,3mf) files, Autodesk (3ds) files, Collada (.dae) files and Wavefront (. obj) files, although many other file formats exist.

Design files can be produced using modelling (e.g. CAD modelling) software and/or through scanning the surface of a product to measure the surface configuration of the product.

Once obtained, a design file may be converted into a set of computer executable instructions that, once executed by a processer, cause the processor to control an additive manufacturing apparatus to produce an object according to the geometrical arrangement specified in the design file. The conversion may convert the design file into slices or layers that are to be formed sequentially by the additive manufacturing apparatus. The instructions (otherwise known as geometric code or “G-code”) may be calibrated to the specific additive manufacturing apparatus and may specify the location and amount of material that is to be formed at each stage in the manufacturing process. The instructions may be according to an embodiment of the invention.

The code or instructions may be translated between different formats, converted into a set of data signals and transmitted, received as a set of data signals and converted to code, stored, etc., as necessary. The instructions may be an input to the printer 1 and may come from a part designer, an intellectual property (IP) provider, a design company, the operator or owner of the additive manufacturing system, or from other sources. The printer 1 may execute the instructions to fabricate an object according to an embodiment of the invention.

Design files or computer executable instructions may be stored in a (transitory or non- transitory) computer readable storage medium (e.g., memory, storage system, etc.) storing code, or computer readable instructions, representative of the object to be produced. As noted, the code or computer readable instructions defining the object that can be used to physically generate the object, upon execution of the code or instructions by an additive manufacturing system. For example, the instructions may include a precisely defined 3D model of the object and can be generated from any of a large variety of well-known computer aided design (CAD) software systems such as AutoCAD®, TurboCAD®, DesignCAD 3D Max, etc. Alternatively, a model or prototype of the object may be scanned to determine the three-dimensional information of the component.

Accordingly, by controlling the printer 1 according to the computer executable instructions, the printer 1 can be instructed to print the object.

In light of the above, embodiments include methods of manufacture via material jetting 3D printing. This includes the steps of obtaining a design file representing the object and instructing a printer to print the object according to the design file. The printer may include a processor that is configured to automatically convert the design file into computer executable instructions for controlling the manufacture of the object. In these embodiments, the design file itself can automatically cause the production of the object once input into the printer. Accordingly, in this embodiment, the design file itself may be considered computer executable instructions that cause the printer to manufacture the object. Alternatively, the design file may be converted into instructions by an external computing system, with the resulting computer executable instructions being provided to the printer.

Given the above, the design and manufacture of implementations of the subject matter and the operations described in this specification can be realized using digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. For instance, hardware may include processors, microprocessors, electronic circuitry, electronic components, integrated circuits, etc. Implementations of the subject matter described in this specification can be realized using one or more computer programs, i.e., one or more modules of computer program instructions, encoded on computer storage medium for execution by, or to control the operation of, data processing apparatus. Alternatively or in addition, the program instructions can be encoded on an artificially-generated propagated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal that is generated to encode information for transmission to suitable receiver apparatus for execution by a data processing apparatus. A computer storage medium can be, or be included in, a computer-readable storage device, a computer-readable storage substrate, a random or serial access memory array or device, or a combination of one or more of them. Moreover, while a computer storage medium is not a propagated signal, a computer storage medium can be a source or destination of computer program instructions encoded in an artificially-generated propagated signal. The computer storage medium can also be, or be included in, one or more separate physical components or media (e.g., multiple CDs, disks, or other storage devices).

While specific embodiments of the invention have been described above, the invention may be practiced otherwise than as described. The descriptions above are intended to be illustrative, not limiting. Thus it will be apparent to a person skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.

Claims

CLAIMS:

1. A computer-implemented method comprising: receiving an input model comprising data indicative of the physical configuration of an object to be printed using material jetting 3D printing; processing the input model data to identify portions of the object vulnerable to deformation by surface tension-induced flow; and modifying one or more parameters of the material jetting for the identified portions of the object.

2. The method of claim 1 , wherein identification of a portion of the object as vulnerable to deformation by surface tension-induced flow comprises determining a ratio of edge voxels to bulk voxels.

3. The method of claims 1 or 2 wherein a portion of the object is identified as vulnerable to deformation by surface tension-induced flow when the ratio of edge voxels to bulk voxels exceeds a critical value.

4. The method of claim 3 wherein the critical value takes into account data indicative of material properties of one or more inks used in the material jetting process.

5. The method of claim 4 wherein material properties of one or more inks comprise data indicative of surface energies of interfaces comprising one or more inks in cured or liquid form.

6. The method of any of claims 4 to 5, wherein material properties of one or more inks comprise data indicative of viscosities of the one or more inks.

7. The method of any of claims 4 to 6 wherein the critical value is informed by geometric parameters of the material jetting process.

8. The method of claim 7 wherein geometric parameter of the material jetting process includes thickness of printed layers and/or an acceptable deviation of layer thickness.

9. The method of any preceding claim, wherein identification of a portion of the object as vulnerable to deformation by surface tension-induced flow comprises determining one or more of: the surface to volume ratio, radius of curvature, or the inclination of portions of the object.

10. The method of any preceding claim wherein modification of the one or more parameters of the material jetting process comprises reducing a volume of ink deposited at each voxel for the identified portions of the object.

11. The method of any preceding claim wherein modification of the one or more parameters of the material jetting process comprises reducing ink curing time for the identified portions of the object.

12. The method of any preceding claim wherein modification of one or more parameters of the material jetting process comprises varying UV intensity incident on a printed layer for the identified portions of the object.

13. The method of any preceding claim wherein the material jetting process is modified such that only a portion of the voxels in a printed layer are deposited at any one time.

14. The method of any preceding claim wherein the material jetting process is modified by selecting a different ink composition for deposition.

15. A method of manufacturing comprising the method of any preceding claim, the method further comprising printing the object using the parameters determined by the computer-implemented method

16. A computer program comprising computer executable instructions that, when executed by a processor, cause the processor to perform the method of any of claims 1 to 14.

17. A material jetting 3D printer comprising a substrate table and a print head system having an array of nozzles, wherein the material jetting 3D printer further comprises a controller programmed to cause the material jetting 3D printer to perform the method according to any of claims 1 to 15.

18. A computer readable medium, the computer readable medium having computer readable code embodied therein, the computer readable code being configured such that, on execution by a suitable controller, computer or processor, the controller, computer or processor is caused to perform the method according to any of the claims 1 to 15.

19. A material jetting 3D printer comprising control electronics which are programmed to carry out the method according to any of claims 1 to 15.