Optical effects of 3D printed articles

Abstract

The invention provides a method for producing a 3D article (1) by fused deposition modeling, the method comprising a 3D printing phase comprising layer-wise depositing extrudates (321) from a 3D printable material (201) to provide the 3D article (1) comprising a 3D printed material (202), wherein the 3D article (1) comprises a plurality of layers (322) of the 3D printed material (202), wherein each layer (322) has a layer height (H) and a layer width (W), wherein the 3D printing phase comprises generating a stack (1322) of the layers (322) of the 3D printed material (202), wherein at a fixed first x,y position, a subset of the total number of layers (322) of the layer height (H) varies layer-wise, wherein (i) the layer height (H) increases for successive layers (322) and then the layer height (H) decreases for successive layers (322), or (ii) the layer height (H) decreases for successive layers and then the layer height (H) increases for successive layers (322); and wherein at least a portion of the 3D printable material (201) comprises a light transmissive polymeric thermoplastic material (401).

Description

Technical Field

[0001] This invention relates to a method for manufacturing 3D (printed) articles. Further, this invention relates to a computer program product for performing this method. The invention also relates to a 3D (printed) article obtainable using this method. Further still, this invention relates to a lighting device comprising such a 3D (printed) article. Background Technology

[0002] Variations in deposition rates are known in the art. For example, US20130095302 describes a process in which, during extrusion, the deposition rate can be varied according to, for example, a periodic square wave or similar step function with any desired duty cycle, to obtain a surface comprising periodic protrusions. These protrusions can be staggered between layers in the manufacturing process such that corresponding ridges are diagonally oriented along the surface of the complete object.

[0003] WO-2018 / 224395 discloses a method for producing 3D articles by fused deposition modeling. In this method, a stack of 3D printing material layers is generated by depositing extrusions from a 3D printable material layer by layer. The resulting layer stack has core-shell configured layers, wherein the core portion is made of a first material and the shell portion is made of a second material, and wherein the first and second materials have different transmittances. The resulting layer stack may consist only of core-shell configured layers, or it may consist of a combination of core-shell configured layers and layers containing only core portions. In both cases, the core portions of the different layers may have different dimensions. Summary of the Invention

[0004] Over the next 10 to 20 years, digital manufacturing will increasingly transform the nature of global manufacturing. One aspect of digital manufacturing is 3D printing. Currently, many different technologies have been developed to produce 3D printed objects using a variety of materials, such as ceramics, metals, and polymers. 3D printing can also be used to create molds, which can then be used to replicate objects.

[0005] For mold making purposes, polymer jetting technology has been suggested. This technology utilizes the layer-by-layer deposition of a photopolymer material, which is cured after each deposition to form a solid structure. While this technology produces a smooth surface, photopolymer materials are not very stable and also have relatively low thermal conductivity, making them unsuitable for injection molding applications.

[0006] The most widely used additive manufacturing technology is a process called Fused Deposition Modeling (FDM). Fused Deposition Modeling (FDM) is an additive manufacturing technology commonly used for modeling, prototyping, and production applications. FDM follows the "additive" principle by placing materials in layers; plastic filaments or metal wires are unwound from coils, and material is supplied to create parts. It's possible that (for example, for thermoplastics) the filaments are melted and extruded before placement. FDM is a rapid prototyping technology. Other terms for FDM are "Fused Wire Fabrication" (FFFF) or "Filament 3D Printing" (FDP), which are considered equivalent to FDM. Typically, FDM printers use thermoplastic filaments that are heated to their melting point and then extruded layer by layer (or actually filament-to-filament extrusion) to create three-dimensional objects. FDM printers are relatively fast, low-cost, and can be used to print complex 3D objects. This type of printer is used to print various shapes using a variety of polymers. The technology is also being further developed in the production of LED luminaires and lighting solutions.

[0007] There appears to be a need for 3D-printed articles that exhibit optical effects (such as under daylight and / or artificial light). 3D printing methods known from the prior art do not appear to possess this functionality, and may not (easily) allow for control over such functionality. Therefore, one aspect of the present invention is to provide alternative 3D printing methods and / or 3D (printed) articles that preferably also at least partially eliminate one or more of the aforementioned disadvantages. The object of the present invention may be to overcome or improve upon at least one disadvantage of the prior art, or to provide a useful alternative.

[0008] Among other things, this paper proposes a 3D printing method for a vase (aka spiral) pattern in the embodiments, which can create layer height variations in the z-direction and circumferential direction. This, in turn, can lead to an omnidirectional depth perception in reflection of a (virtually) perfectly planar surface illuminated by ambient light, while also potentially affecting the perception of active lighting from the inside when opened. Further, among other things, this paper suggests using fused deposition modeling in the embodiments, where the height of the deposited layers can be varied during printing. For example, the layer height during printing of each layer can be varied with respect to a sine function. When multiple layers are printed where the relative height variation increases, wavy edges can be achieved, which can be highly decorative and / or provide optical effects such as transparency, refraction, reflection, differences in transparency, translucency and translucency differences, microlens function, etc. In the embodiments, the relative height variation during printing can be reduced to a level where no height variation occurs during printing as printing continues. Among other things, structures that display lens operation can be achieved in this way. Other features, such as serrations or other functionalities, can also be used in the embodiments. In this way, lampshades with edges (such as wavy, serrated, or triangular) depending on the function being used can also be produced. The printed objects do not necessarily have straight surfaces, but their surfaces can be conical, spherical, or curved, etc. Needless to say, height variations can be used only in certain parts of the print, while the rest of the object is printed using a constant layer height.

[0009] Therefore, in a first aspect of the invention, a method for producing 3D articles is provided, particularly by fused deposition modeling. In an embodiment, the method includes a 3D printing stage, which may include depositing an extrusion layer by layer from a 3D-printable material. Thus, 3D articles comprising 3D-printable material can be provided, particularly on receiver articles. Specifically, the 3D article comprises multiple layers of 3D-printable material. Each layer may have a layer height (H) and a layer width (W). In particular, the 3D printing stage may include a stack of layers generating the 3D-printable material, wherein each stacked layer has a non-constant layer height (H), wherein at a fixed first x,y position, a subset of the total layer height (H) varies layer by layer, wherein (i) the layer height (H) increases with each successive layer, or (ii) the layer height (H) decreases with each successive layer. Specifically, in embodiments, (i) the layer height (H) increases with respect to the (first set) of consecutive layers, and then the layer height (H) decreases with respect to the (second set) of consecutive layers, or (ii) the layer height (H) decreases with respect to the (first set) of consecutive layers, and then the layer height (H) increases with respect to the (second set) of consecutive layers. Furthermore, in specific embodiments, at least a portion of the 3D printable material comprises a light-transmitting polymeric thermoplastic material.

[0010] Therefore, in particular, the present invention provides a method for producing 3D articles by using fused deposition modeling of a 3D printer, the method comprising: a 3D printing stage, during which a stack of layers of 3D printing material is generated by depositing extrusions from a 3D printable material layer by layer, at least a portion of the 3D printable material comprising a light-transmitting polymeric thermoplastic material, wherein each layer of the stacked layers has a non-constant layer height (H), and wherein at a fixed first x,y position, (i) the layer height (H) increases with respect to successive layers and then decreases with respect to successive layers, or (ii) the layer height (H) decreases with respect to successive layers and then increases with respect to successive layers.

[0011] Using this invention, 3D articles can be provided, which offer a depth impression using monocular cues. Furthermore, 3D articles can be created in this way to display light refraction and reflection effects, such as having lens functionality (or microlens functionality) and / or other optical properties. Such articles can, for example, be part of a lighting fixture. For instance, such articles can be used to provide decorative light distribution. Using this invention, a substantially flat surface can be provided, yet the surface appears curved.

[0012] As indicated above, the present invention provides a method for producing 3D articles by fused deposition modeling. Specific embodiments are further specified below. The term "3D article" may also refer to a portion of an article or a portion of a 3D printed object. In particular, the method includes a 3D printing stage comprising depositing an extrusion layer by layer from a 3D-printable material to provide a 3D article comprising the 3D-printable material. The 3D-printable material is provided (as effective 3D-printable material) on a receiver article (or on 3D-printable material on such a receiver article (and thus effectively on the receiver article)).

[0013] Specifically, the 3D article comprises multiple layers of 3D printing material. Therefore, the method can include depositing multiple layers layer by layer, particularly on top of each other. Each layer has a layer height (H) and a layer width (W). Typically, the layer height can be constant. However, in this invention, the layer height varies for certain portions of the 3D printed article. Therefore, in a specific embodiment, the layer height can vary across the layers. This can be applied to at least some layers. Thus, a single layer can have different layer heights along its length. Further, different layers can have different layer heights. Different layers can also have the same layer height. In particular, there may be a subset of layers where the layer height is not constant in the z-direction. Typically, the layer width can be constant. However, in this invention, it is optional to also vary the layer width, or to keep the layer width constant.

[0014] As indicated above, in particular, the 3D printing stage includes the stacking of layers that generate 3D printing material. As indicated above, these layers can typically have substantially the same width and height. However, in this invention, multiple layers within a stack can have non-uniform heights. More specifically, this non-uniformity can cause layer heights to increase with increasing layer count or decrease with decreasing layer count within a portion of the stack. A 3D article may comprise a single stack. However, a 3D article may also comprise multiple stacks. Furthermore, a stack may also comprise multiple (smaller) stacks or stack portions (“portions”).

[0015] Therefore, in the embodiments, the layer height (H) can increase for consecutive layers. This may mean that for multiple layers within a stack, the layer height increases in the z-direction. This increase can be continuous, meaning that the layer height increases for each consecutive layer. However, the average layer height may also increase. This increase is particularly localized. Thus, at the first x,y position, the layer height can increase in the z-direction, while at the second x,y position, the layer height can be substantially constant in the z-direction.

[0016] Alternatively or additionally, in an embodiment, the layer height (H) may decrease with respect to consecutive layers. This may mean that for multiple layers within a stack, the layer height decreases in the z-direction. This decrease may be continuous, meaning that the layer height decreases for each consecutive layer. However, the average layer height may also decrease. This decrease is particularly localized. Thus, at a first x,y position, the layer height may decrease in the z-direction, while at a second x,y position, the layer height may be substantially constant in the z-direction.

[0017] Therefore, the phrase "for consecutive layer increases" and similar phrases may imply that for a specific subset of layers at a given x,y location, the layer height of the subset increases. This may imply the presence of at least two layers, particularly at least three layers, and more particularly layers selected from a total number in the range of 3 to 20, at a specific x,y location. The layer height of each layer may increase. However, in other embodiments, the increase may occur at two or more layers. Thus, in embodiments, there is a stack comprising one or more portions ("stack portions") where the layer height increases for the respective subset of layers.

[0018] Similarly, the phrase "reducing for consecutive layers" and similar phrases may imply that for a specific subset of layers at a given x,y location, the layer height of that subset is reduced. This may imply the presence of at least two layers, particularly at least three layers, and more particularly layers selected from a total number in the range of 3 to 20, at that specific x,y location. The layer height of each layer may be reduced. However, in other embodiments, the reduction may occur at two or more layers. Thus, in embodiments, there exists a stack comprising one or more portions, wherein the layer height is reduced for the respective subset of layers.

[0019] Typically, when there is a section where the floor height increases, there may also be (adjacent) sections where the floor height decreases in the same direction (or increases in the opposite direction).

[0020] In one embodiment, within the stack, there may be a variation in layer height (e.g., an increase). In other embodiments, within the same stack, there may be the same or different variations in layer height at a second location. For example, within the same stack, there may be different variations in layer height (e.g., a decrease) at a second location. Alternatively or additionally, a substantially constant layer height may exist adjacent to the first location.

[0021] In one embodiment, the increase can be substantially parallel to the z-direction. In other embodiments, the increase can be within an angle (less than 90°, such as equal to or less than 45°) with respect to the z-direction. Similarly, in one embodiment, the decrease can be substantially parallel to the z-direction. In other embodiments, the decrease can be within an angle (less than 90°, such as equal to or less than 45°) with respect to the z-direction.

[0022] Therefore, in embodiments, the 3D printing stage may include a stack of layers that generate 3D printing material, wherein at a fixed first x,y position, a subset of layers with a total layer height (H) varies layer by layer, wherein (i) the layer height (H) increases with respect to consecutive layers, or (ii) the layer height (H) decreases with respect to consecutive layers. Of course, as indicated above, the stack may also include two (or more) portions, wherein in one portion the layer height increases (for two or more consecutive layers), and in another portion the layer height decreases (for two or more consecutive layers). Thus, in embodiments using the same or different subsets of layers, portions with increasing and / or decreasing layer heights may be applied. The increase or decrease is typically defined in the z-direction (i.e., perpendicular to the x,y plane), even if the increase or decrease is at an angle to the z-direction (but may have a component parallel to the z-direction).

[0023] Specifically, the height difference between two consecutive layers is no greater than about 2.5 mm, such as a range selected from 0.1 to 2.0 mm. In locations where there is no height change, the height difference between two consecutive layers can therefore be substantially about 0.0 mm.

[0024] When the layer height is changed locally, this may mean that the height of the 3D object may change locally. This may be desirable in this embodiment. However, other embodiments are also possible (see further below).

[0025] When the layer height varies across multiple layers within a stack, different total heights may exist within the stack. Therefore, in an embodiment, the stack may have a first stack height (H11) at a fixed first x,y position, wherein the method includes generating a stack of layers with a layer height (H) at a fixed second x,y position (adjacent), thereby providing a stack with a second stack height (H12) at the fixed second x,y position, where 0.1 ≤ H12 / H11 ≤ 10, such as 0.1 ≤ H12 / H11 ≤ 5, such as 0.2 ≤ H12 / H11 ≤ 5, and in the embodiment at least 0.1 ≤ H12 / H11 ≤ 1.5. Therefore, adjacent to a relatively higher or lower portion of the stack having the first stack height, a relatively lower portion or lower portion of the stack having the second stack height may exist, respectively. The terms "first stack height" and "second stack height" may specifically refer to the height of the same stack. Such stacks may specifically share the same layer. Therefore, the lowest and highest layers of the stack will define the stack height. The stack height may vary with the stack (length), or it may be considered to be substantially constant over the stack length (see further below). Therefore, in embodiments, the stack may have multiple different stack heights.

[0026] However, in other embodiments, such a height difference may be undesirable. Therefore, in embodiments, it may be desirable to compensate for the increase or decrease in layer height at the first x,y position. This can be accomplished by adding multiple layers at the first x,y position, where the layer height decreases or increases respectively. Thus, in a specific embodiment, at a fixed first x,y position, a subset of the total number of layer heights (H) can vary layer by layer, where (i) the layer height (H) increases with respect to consecutive layers, and then decreases with respect to consecutive layers, or (ii) the layer height (H) decreases with respect to consecutive layers, and then increases with respect to consecutive layers.

[0027] Specifically, in embodiments, the height between different portions of such a stack can be relatively small. Thus, in an embodiment, the stack has a first stack height (H11) at a fixed first x,y position, wherein the method includes generating a stack with layers having substantially constant layer heights (H) at a fixed second x,y position (adjacently), thereby providing a second stack height (H12) for the stack at the fixed second x,y position, where 0.9 ≤ H12 / H11 ≤ 1.1. Therefore, adjacent to the first portion of the stack having the first stack height, there may be another portion of the stack having a second stack height, which can be substantially the same. Thus, in (other) embodiments, the stack can have multiple substantially identical heights (a substantially uniform height of the stack).

[0028] In a specific embodiment, at least a portion of the 3D printable material (and therefore at least a portion of the 3D printable material) may comprise a light-transmitting polymeric thermoplastic material. This can fundamentally facilitate differences in optical effects such as transmission, translucency, microlens function, etc. When, for example, a light-transmitting material is applied, a portion with a greater layer height may be perceived as more transparent than a portion with a lower layer height. Therefore, optical effects can be introduced by locally controlling the layer height. See also further below.

[0029] As indicated above, within the stack, there may be variations in layer height at the first location, while at another location adjacent to the first location, there may be a substantially constant layer height.

[0030] In an embodiment, the layers from the stack have the maximum total height (H) of the layers in the stack. L1 The method includes (adjacently) generating a minimum total height (H) L2 The layer has a minimum total height (H) L2 The layer in the stack is the same as the layer in the stack, where |H L1 -H L2 | / L*≤1, where L* is the distance between the two points measured along the surface of the 3D object, specifically parallel to the layer. The larger this value, the lower the quality of the 3D print may be due to the tilt angle potentially being too high. The phrase "parallel to the layer" can also generally be interpreted as parallel to the receiver object. Furthermore, the phrase "parallel to the layer" can also generally be interpreted as parallel to the x,y plane. Therefore, the term "total height" can specifically refer to the height of the layer defined relative to the xy plane. Thus, in a specific embodiment, the layers from the stack have a maximum total height (H). L1 The method includes generating a minimum total height (H). L2 The layer has a minimum total height (H) L2 The layer in the stack is the same as the layer in the stack, where |H L1 -HL2 | / L * ≤1, where L * This is the distance between the two points measured parallel to the x, y plane. Further, in a specific embodiment, stacking can be provided, where the values ​​between the minimum and (adjacent) maximum values ​​are selected from 0.1 ≤ |H|. L1 -H L2 The range | / L*≤1 is implemented, such as 0.25≤|H. L1 -H L2 | / L*≤0.8. For example, layers in a stacked section can have the maximum total height of the layers in the stack (H). L1 ) and minimum total height (H) L2 ), where 0.1≤|H L1 -H L2 | / L*≤1.

[0031] Multiple structures can be applied, for example, to the same stack. Therefore, multiple minimum and maximum values ​​may be available. They may be available in specific patterns. Thus, in an embodiment, the method may include multiple maximum total heights (H) in a 3D-printed stack. L1 ) and minimum total height (H) L2 ), where the maximum total height of each layer (H) L1 ) and minimum total height (H) L1 The spiral follows the surface of the 3D object. Therefore, in embodiments, the 3D object may include multiple objects with a maximum total height (H) in a stack. L1 ) and minimum total height (H) L2 ), where the maximum total height of each layer (H) L1 ) and minimum total height (H) L1 The spiral follows the surface of the 3D object. In embodiments, the object (such as, in particular, a stack) may include multiple stacked portions, which may be configured as a regular pattern. In particular, such a stacked portion includes at least a maximum total height (H) of the layers in the stack. L1 ) and minimum total height (H) L2 A single layer of ), where 0.1 ≤ |H L1 -H L2 | / L*≤1.

[0032] When the layer height is increased or decreased, the 3D printing volumetric flow rate and / or printing speed of the 3D printable material may be adapted, partially adapted, or not adapted to compensate for, or at least partially compensate for, the use of more or less 3D printable material, respectively. However, it may also not be adapted. Therefore, in embodiments, the layer width may remain constant, or may at least partially increase when the layer height decreases, or at least partially decrease when the layer height increases.

[0033] Therefore, in a specific embodiment, the method may include printing layers for a subset of the total number of layers having a constant layer width (W) at a fixed first x,y position. This can be useful for avoiding surface embossing and / or obtaining optical effects solely due to variations in layer thickness. In other embodiments, the volume printed per unit time and the printing speed can be kept substantially constant. This can be a relatively straightforward solution. Therefore, in an embodiment, the method includes printing layers for a subset of the total number of layers at a fixed first x,y position, where the cross-sectional area of ​​the layers is constant. A hybrid solution may also be chosen, where the width reduction is less than in the uncompensated case, but not constant. By selecting the width, possible stress can also be compensated.

[0034] Therefore, in embodiments, the present invention also provides a method that may include changing the layer height (within the winding) while maintaining a constant wall thickness. The term "winding" may refer to a (single) layer.

[0035] As indicated above, at a first location of multiple layers in the z-direction, the layer height may increase or decrease, or it may increase or decrease first, and then decrease or increase respectively. Here, the term "first" may refer to a measurement taken from, for example, a receiver article (as an embodiment of the x,y plane). In embodiments, the increase and / or decrease may be constant. In such embodiments, the layer height increases or decreases in constant steps. However, in particular, the increase and / or decrease may be gradual. In such embodiments, the increase or decrease may be layer-by-layer. In specific embodiments, the method may include printing layers for a subset of a total number of layers having a layer height (H) at a fixed first x,y location, the layer height (H) varying in a sinusoidal or triangular manner. For example, in embodiments, the method may include printing layers for a subset of a total number of layers having a layer height (H) at a fixed first x,y location, the layer height (H) varying in a sawtooth pattern. In particular, in an embodiment, the method may include printing layers for a subset of the total number of layers at a fixed first x,y position having a stacking height that varies gradually along the surface of the object according to a mathematical function such as a sine curve or a triangle.

[0036] Therefore, in a specific embodiment, the method may include printing layers for a subset of the total number of layers at a fixed first x, y position, wherein the layer height (H) varies according to a mathematical function of a group selected from sine waves, triangles, sawtooth shapes, and squares, or combinations of two or more of these. In other specific embodiments, the method may include printing layers for a subset of the total number of layers at a fixed first x, y position, wherein the layer height (H) varies according to a mathematical function of a group selected from sine waves or triangles, sawtooth shapes, square waves, combinations of these waveforms, and wave modulation (e.g., a sine wave with a short wavelength modulated by a sine wave with a long wavelength, or a sine wave modulated by a square wave).

[0037] Therefore, in a specific embodiment, the layer height can be varied according to, for example, a periodic square wave or a similar step function with any desired duty cycle, to obtain a surface including a periodic shape (essentially in the plane of the surface). Alternatively or additionally, the layer height can be varied in a spiral or helical manner, etc.

[0038] Below, some embodiments are described regarding 3D articles. In specific embodiments, the method may include printing hollow 3D articles. In other specific embodiments, the method may include printing concave 3D articles. Furthermore, particularly portions having increased and / or decreased layer heights are single-walled. This can particularly allow the aforementioned optical effects. Thus, in embodiments, the 3D article may include one or more walls having the width of one or more layers(s). Or, in other words, the width of one or more walls of the 3D article may be defined by the width of a single layer (especially available in one or more stacks).

[0039] Furthermore, additional optical effects can be provided by including colored and / or reflective materials in the 3D printable material. Therefore, in specific embodiments, the light-transmitting polymeric thermoplastic material may include embedded particulate reflective material (see further below).

[0040] As indicated above, the method includes depositing 3D printable material during the printing stage. In this document, the term "3D printable material" refers to the material to be deposited or printed, and the term "3D printable material" refers to the material obtained after deposition. These materials can be substantially the same, as 3D printable material can specifically refer to material at high temperatures in the print head or extruder, and 3D printable material refers to the same material but at a later stage during deposition. The 3D printable material is printed as a filament and thus deposited. 3D printable material can be provided as a filament or can be formed as a filament. Therefore, regardless of the starting material applied, filaments including 3D printable material are provided through the print head and 3D printed. The term "extrudate" can be used to define 3D printable material downstream of the print head but not yet deposited. The latter is indicated as "3D printable material." In fact, extrudate includes 3D printable material because the material has not yet been deposited. After the deposition of 3D printable material or extrudate, the material is therefore indicated as 3D printable material. Essentially, these materials are the same because the thermoplastic material upstream of the printhead, downstream of the printhead, and during deposition is essentially the same material.

[0041] In this document, the term "3D printable material" may also refer to "printable material". In embodiments, the term "polymeric material" may refer to a mixture of different polymers, but in embodiments, it may also refer to a single polymer type with substantially different polymer chain lengths. Therefore, the terms "polymeric material" or "polymer" may refer to a single type of polymer, but may also refer to multiple different polymers. The term "printable material" may refer to a single type of printable material, but may also refer to multiple different printable materials. The term "printing material" may refer to a single type of printing material, but may also refer to multiple different printing materials.

[0042] Therefore, the term "3D printable material" can also refer to a combination of two or more materials. Typically, these (polymeric) materials have a glass transition temperature T0. g and / or melting temperature T m The 3D printable material is heated by the 3D printer to a temperature at least the glass transition temperature, typically at least the melting temperature, before leaving the nozzle. Therefore, in a specific embodiment, the 3D printable material includes materials having a glass transition temperature (T0). g ) and / or melting point (T m The thermoplastic polymer is used, and the printhead action includes heating the 3D printable material above its glass transition temperature, and if it is a semi-crystalline polymer, above its melting temperature. In another embodiment, the 3D printable material includes materials having a melting point (T0). mThe process involves heating the 3D printable material to be deposited onto the receiver article to a temperature at least its melting point. The glass transition temperature is typically different from the melting temperature. Melting is a transition that occurs in crystalline polymers. Melting occurs when the polymer chains break away from their crystalline structure, becoming a disordered liquid. The glass transition is a transition that occurs in amorphous polymers; that is, the polymer chains are not arranged in an ordered crystalline pattern, but are dispersed in any manner, even if they are solid. Polymers can be amorphous, essentially having a glass transition temperature rather than a melting temperature, or they can be (semi-)crystalline, typically having both a glass transition temperature and a melting temperature, usually the latter being greater than the former. The glass transition temperature can be determined, for example, by differential scanning calorimetry (DSC). The melting point or melting temperature can also be determined by DSC.

[0043] As indicated above, the present invention therefore provides a method comprising providing a filament of a 3D printable material and printing the 3D printable material on a substrate during a printing phase to provide the 3D article.

[0044] Materials that may be particularly suitable as 3D printing materials can be selected from the group consisting of metals, glass, thermoplastic polymers, silicone resins, etc. In particular, 3D printing materials include (thermoplastic) polymers selected from the group consisting of: ABS (acrylonitrile butadiene styrene), nylon (or polyamide), acetate (or cellulose), PLA (polylactic acid), terephthalates (such as PET polyethylene terephthalate), acrylic (polymethyl methacrylate, plexiglass, polymethyl methacrylate, PMMA), polypropylene (or polypropylene), polycarbonate (PC), polystyrene (PS), PE (such as expanded high-impact polyethylene (or polyethylene), low-density (LDPE) high-density (HDPE)), PVC (polyvinyl chloride), polyvinyl chloride (such as thermoplastic elastomers based on copolyester elastomers, polyurethane elastomers, polyamide elastomers, polyolefin-based elastomers, styrene-based elastomers), etc. Optionally, 3D printable materials include those selected from the group consisting of urea-formaldehyde, polyester resins, epoxy resins, melamine-formaldehyde, thermoplastic elastomers, etc. Optionally, 3D printable materials include those selected from the group consisting of polysulfones. Elastomers (especially thermoplastic elastomers) are of particular interest because they are flexible and can help obtain relatively more flexible filaments, including thermally conductive materials. Thermoplastic elastomers can include one or more styrene block copolymers (TPS(TPE-s)), thermoplastic polyolefin elastomers (TPO(TPE-o)), thermoplastic vulcanizates (TPV(TPE-v or TPV)), thermoplastic polyurethanes (TPU)(TPU)), thermoplastic copolyesters (TPC(TPE-E)), and thermoplastic polyamides (TPA(TPE-A)).

[0045] Suitable thermoplastic materials (such as those also mentioned in WO2017 / 040893) may include one or more of the following: polyacetals (e.g., polyoxyethylene and polyoxymethylene), poly(C) 1-6 Alkyl) acrylates, polyacrylamide, polyamides (e.g., aliphatic polyamides, polyphthalamides, and polyarylamides), polyamide imides, polyanhydrides, polyarylates, polyaryl ethers (e.g., polyphenylene ether), polyaryl sulfides (e.g., polyphenylene sulfide), polyarylsulfones (e.g., polyphenylene sulfone), polybenzothiazoles, polybenzoxazoles, polycarbonates (including polycarbonate copolymers, such as polycarbonate-siloxanes, polycarbonate-esters, and polycarbonate-ester-siloxanes), polyesters (e.g., polycarbonates, polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polyaryl esters) and polyester copolymers, such as polyester ethers), polyetheretherketones, polyetherimides (including copolymers, such as polyetherimide-siloxane copolymers), polyetherketoneketones, polyetherketones, polyethersulfones, polyimides (including copolymers, such as polyimide-siloxane copolymers), poly(C) 1-6 Alkyl) methacrylates, polymethacrylamide, polynorbornene (including copolymers containing norbornene units), polyolefins (e.g., polyethylene, polypropylene, polytetrafluoroethylene and their copolymers, such as ethylene-α-olefin copolymers), polyoxadiazole, polyoxymethylene, polyphthalate, polysilazane, polysiloxane, polystyrene (including copolymers such as acrylonitrile-butadiene-styrene (ABS) and methyl methacrylate-butadiene-styrene (MBS)), polysulfides, polysulfonamides, polysulfonates, polysulfones, polysulfides, polytriazines, polyureas, polyurethanes, polyvinyl alcohol, polyvinyl esters, polyvinyl ethers, polyhalogenated polyethylene, polyvinyl ketone, polyvinyl sulfide, polyvinylidene fluoride, etc., or combinations including at least one of the aforementioned thermoplastic polymers. Examples of polyamides may include, but are not limited to, the synthesis of linear polyamides, such as nylon 6,6; nylon 6,9; nylon 6,10; nylon 6,12; nylon 11; nylon 12 and nylon 4,6, preferably nylon 6 and nylon 6,6, or combinations including at least one of the foregoing. Polyurethanes that can be used include aliphatic, alicyclic, aromatic and polycyclic polyurethanes, including those mentioned above. Poly(C) 1-6 Alkyl) acrylates and poly(C) 1-6Alkyl methacrylates, including polymers such as methyl acrylate, ethyl acrylate, acrylamide, methacrylic acid, methyl methacrylate, n-butyl acrylate, and ethyl acrylate. In embodiments, polyolefins may include one or more of the following: polyethylene, polypropylene, polybutene, polymethylpentene (and copolymers thereof), polynorbornene (and copolymers thereof), poly-1-butene, poly(3-methylbutene), poly(4-methylpentene), and copolymers of ethylene and propylene, 1-butene, 1-hexene, 1-octene, 1-decene, 4-methyl-1-pentene, and 1-octadecene.

[0046] In specific embodiments, the 3D printable material (and 3D printing material) includes one or more of the following: polycarbonate (PC), polyethylene (PE), polypropylene (PP), polyethylene naphthalate (PEN), styrene-acrylonitrile resin (SAN), polysulfone (PSU), polyphenylene sulfide (PPS), semi-crystalline polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), polystyrene (PS), styrene-acrylic copolymer (SMMA), and polyurethane (PU).

[0047] The term 3D printable material is further clarified below, but in particular refers to thermoplastic material, optionally including additives, which have a volume percentage of up to about 60%, especially up to about 30 vol.%, such as up to 20 vol.% (the percentage of additives relative to the total volume of thermoplastic material and additives).

[0048] Therefore, in embodiments, the printable material may include two phases. The printable material may include a phase of printable polymeric material, particularly thermoplastic material (see also below), which is particularly a substantially continuous phase. This continuous phase of the thermoplastic polymer additive may contain one or more of the following: antioxidants, heat stabilizers, light stabilizers, UV stabilizers, UV absorbers, near-infrared absorbers, infrared absorbers, plasticizers, lubricants, mold release agents, antistatic agents, antifogging agents, antimicrobial agents, colorants, laser marking additives, surface effect additives, radiation stabilizers, flame retardants, and anti-drip agents. The additives may have useful properties selected from optical, mechanical, electrical, thermal, and mechanical properties (see also above).

[0049] The printable material in the embodiments may include particulate material, i.e., particles embedded in a printable polymeric material, which form a substantially discontinuous phase. The number of particles in the total mixture relative to the total volume of the printable material (including (anisotropically conductive) particles) is particularly no more than 60 vol.%, especially in applications for reducing the coefficient of thermal expansion. For optical and surface-related effects, the number of particles in the total mixture relative to the total volume of the printable material (including particles) is equal to or less than 20 vol.%, such as up to 10 vol.%. Therefore, 3D printable material specifically refers to a continuous phase of a substantially thermoplastic material in which other materials (such as particles) can be embedded. Similarly, 3D printable material specifically refers to a continuous phase of a substantially thermoplastic material in which other materials (such as particles) are embedded. The particles may include one or more additives as defined above. Therefore, in the embodiments, the 3D printable material may include particulate additives.

[0050] As indicated above, 3D printable materials (or 3D printing materials) specifically include light-transmitting materials. More specifically, 3D printable materials (or 3D printing materials) in embodiments include light-transmitting polymeric thermoplastic materials. In specific embodiments, the light-transmitting polymeric thermoplastic material may be transparent to visible light having one or more wavelengths selected from the range of 450 to 650 nm.

[0051] Transmittance or light transmittance can be determined by providing the material with light of a specific wavelength having a first intensity and by relating the intensity of that light at that wavelength, measured after transmission through the material, to the first intensity of the light provided to the material at that specific wavelength (see also CRC Handbook of Chemistry and Physics, E-208 and E-406, 69th edition, pp. 1088-1989). In a specific embodiment, a material can be considered transmissive when, under vertical irradiation with said radiation of at least about 20%, such as at least 40%, such as at least 60%, such as especially at least 80%, such as at least about 85%, such as even at least about 90%, radiation is transmitted through a 1 mm thick layer of the material, especially even through a 5 mm thick layer of the material, at a wavelength or within a wavelength range, especially within a wavelength range or within the wavelength range of radiation generated by the radiation source described herein. The transmittance of a light-transmitting material to one or more emission wavelengths can be at least 80% / cm, such as at least 90% / cm, even more particularly at least 95% / cm, such as at least 98% / cm, such as at least 99% / cm. This means that under vertical illumination with radiation having a selected emission wavelength (such as the wavelength corresponding to the emission maximum of the luminescent material of the transparent material), for example, 1 cm 3A cubical-shaped translucent material will have at least 95% transmittance. In this document, transmittance values ​​specifically refer to transmittance without considering Fresnel losses at interfaces (e.g., with air). Therefore, the term "transmission" specifically refers to internal transmittance. Internal transmittance can be determined, for example, by measuring the transmittance of two or more bodies with different widths, across which the transmittance is measured. Based on this measurement, the contribution of Fresnel reflection loss and (therefore) internal transmittance can then be determined. Therefore, in particular, the transmittance values ​​indicated herein neglect Fresnel losses.

[0052] Transparent materials exhibit transmittance over at least one wavelength range of visible light. Specifically, they also exhibit transmittance over at least one wavelength range in the visible light spectrum, with light ultimately transmitted via forward scattering and virtually no backscattering (only interface reflection). In the most preferred materials, there is almost no substantial absorption in the wavelength range of approximately 450 to 650 nm, and light can be transmitted substantially without scattering. In particular, transparent polymeric materials are transparent to visible light across the entire wavelength range of 450 to 650 nm.

[0053] In particular, in the embodiments, the 3D printable material includes a light-transmitting polymeric thermoplastic material in which there are essentially no embedded reflective particulate materials.

[0054] Printable material is printed onto a receiver article. Specifically, the receiver article can be a build platform or can be included within a build platform. The receiver article can also be heated during 3D printing. However, the receiver article can also be cooled during 3D printing.

[0055] Among other things, the phrase “printing on a receiver article” and similar phrases include printing directly on a receiver article, or printing on a coating on a receiver article, or printing on 3D printing material previously printed on a receiver article. The term “receiver article” can refer to a printing platform, print bed, substrate, support, build plate, or build platform, etc. Instead of the term “receiver article,” the term “substrate” may also be used. Among other things, the phrase “printing on a receiver article” and similar phrases include printing also on or on a separate substrate, such as a printing platform, print bed, support, build plate, or build platform. Therefore, among other things, the phrase “printing on a substrate” and similar phrases include printing directly on a substrate, or printing on a coating on a substrate, or printing on 3D printing material previously printed on a substrate, etc. Hereinafter, the term “substrate” is used further, which can refer to a printing platform, print bed, substrate, support, build plate, or build platform, or a separate substrate, such as or on or composed of.

[0056] Printable material is deposited layer by layer, thus creating a 3D printed object (during the printing phase). The 3D printed object may exhibit a unique ribbed structure (derived from the deposited filaments). However, further stages, such as a termination stage, may be performed after the printing phase. This stage may include removing the printed object from the receiver object and / or one or more post-processing actions. One or more post-processing actions may be performed before removing the printed object from the receiver object and / or one or more post-processing actions may be performed after removing the printed object from the receiver object. Post-processing may include one or more of, for example, polishing, coating, adding functional components, etc. Post-processing may include smoothing the ribbed structure, which may result in a generally smooth surface.

[0057] Furthermore, the present invention relates to a computer program product that can be used to perform the methods described herein. Therefore, in another aspect, the present invention also provides a computer program product comprising instructions which, when executed by a computer functionally coupled to or included by a fused deposition modeling (FDM) 3D printer, cause the FDM 3D printer to perform the methods described herein.

[0058] Therefore, in one aspect, the present invention provides a computer program product that, when executed by a fused deposition modeling 3D printer functionally coupled to or by a computer included therein, causes the fused deposition modeling 3D printer to perform (one or more embodiments) the methods described herein for producing 3D articles by fused deposition modeling.

[0059] The method described herein provides 3D printed articles. Therefore, in another aspect, the present invention also provides a 3D printed article obtainable using the method described herein.

[0060] In another aspect, a 3D-printed article obtainable using the method described herein is provided. Specifically, the invention provides a 3D article comprising 3D printing material. Specifically, the 3D article comprises multiple layers of 3D printing material. Each layer has a layer height (H) and a layer width (W). Specifically, the 3D article comprises a stack of layers of 3D printing material. In a specific embodiment, at a fixed first x,y position of a subset of the total number of layers, the layer height (H) varies layer by layer. Specifically, in an embodiment, (i) the layer height (H) increases with respect to consecutive layers, or (ii) the layer height (H) decreases with respect to consecutive layers. Even more specifically, in an embodiment, (i) the layer height (H) increases with respect to consecutive layers and then decreases with respect to consecutive layers, or (ii) the layer height (H) decreases with respect to consecutive layers and then increases with respect to consecutive layers. Furthermore, also as indicated above, in a specific embodiment, at least a portion of the 3D printing material comprises a light-transmitting polymeric thermoplastic material.

[0061] Therefore, in particular, the present invention also provides a 3D article comprising a stack of layers of 3D printing material, at least a portion of which comprises a light-transmitting polymeric thermoplastic material, wherein each stacked layer has a non-constant layer height (H), and wherein at a fixed first x,y position, (i) the layer height (H) increases with respect to successive layers and then decreases with respect to successive layers, or (ii) the layer height (H) decreases with respect to successive layers and then increases with respect to successive layers.

[0062] 3D printed articles may include multiple layers on top of each other, i.e., stacked layers. The width (thickness) and height of the (individually 3D printed) layers may, for example, be selected from the range of 100 to 5000 μm (such as 200 to 2500 μm) in the embodiments, wherein the height is typically smaller than the width. For example, the ratio of height to width may be equal to or less than 0.8, such as equal to or less than 0.6.

[0063] The layers can be core-shell layers or can consist of a single material. Within the layers, the composition can also change, for example, when a core-shell printing process is applied and during the printing process, it changes from printing the first material (instead of printing the second material) to printing the second material (instead of printing the first material).

[0064] At least a portion of a 3D printed item may include a coating.

[0065] In discussing the methods, some specific embodiments regarding 3D printed articles have already been illustrated above. In the following sections, some specific embodiments regarding 3D printed articles are discussed in more detail.

[0066] As indicated above, in a specific embodiment, the stack may have a first stack height (H11) at a fixed first x, y position, wherein at a fixed second x, y position, the stacked layers have a constant layer height (H), and wherein the stack has a second stack height (H12) at a fixed second x, y position, wherein 0.1 ≤ H12 / H11 ≤ 10. However, in other embodiments, the stack may have a first stack height (H11) at a fixed first x, y position, wherein at a fixed second x, y position, the stacked layers have a constant layer height (H), and wherein the stack has a second stack height (H12) at a fixed second x, y position, wherein in particular 0.9 ≤ H12 / H11 ≤ 1.1.

[0067] Furthermore, in a specific embodiment, a subset of layers for the total number of layers may have a constant layer width (W) at a fixed first x, y position. However, as indicated above in other embodiments, the layer width may also vary with the layer as the layer height changes.

[0068] The layer height can change gradually. Specifically, for a subset of layers at a fixed first x, y position, the layer height changes gradually along the object surface, and this change can conform to a mathematical function, such as a sine curve or a triangle. Therefore, in a specific embodiment of the subset of layers at a fixed first x, y position, the layer height (H) changes sinusoidally or triangularly. In a specific embodiment, for a subset of layers at a fixed first x, y position, the layer height (H) can vary according to a mathematical function selected from a group of sine curves, triangles, zigzags, and squares, or combinations of two or more of these.

[0069] In particular, the height difference between two consecutive layers may not exceed about 2.5 mm in the embodiments, such as a range selected from 0.1 to 2.0 mm.

[0070] In specific embodiments, the 3D printing material includes one or more of the following: polycarbonate (PC), polyethylene (PE), polypropylene (PP), polyethylene naphthalate (PEN), styrene-acrylonitrile resin (SAN), polysulfone (PSU), polyphenylene sulfide (PPS), polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), polystyrene (PS), styrene-acrylic copolymer (SMMA), and polyurethane (PU). In other specific embodiments, the 3D printing material includes a light-transmitting polymeric thermoplastic material.

[0071] Further, in a specific embodiment, the translucent polymeric thermoplastic material includes embedded particulate reflective material. In other embodiments, the translucent polymeric thermoplastic material does not include embedded particulate reflective material. In other embodiments, one or more layers include a translucent polymeric thermoplastic material having embedded particulate reflective material therein, and one or more other layers include a translucent polymeric thermoplastic material with substantially no embedded particulate reflective material.

[0072] The 3D printed items obtained (using the methods described herein) can be functional. For example, 3D printed items can be lenses, collimators, reflectors, etc. Therefore, the obtained 3D items can (optionally) be used for decorative or artistic purposes.

[0073] In a specific embodiment, the 3D article is a hollow 3D article. In a specific embodiment, the 3D article is a concave 3D article. Further, particularly in an embodiment, the stack is a single-wall stack.

[0074] 3D printed items may include or be provided with functional components. Functional components can be specifically selected from the group consisting of: optical components, electrical components, and magnetic components. The term "optical component" specifically refers to components with optical functions, such as lenses, mirrors, light-transmitting elements, filters, etc. The term "optical component" can also refer to a light source (such as an LED). The term "electrical component" can refer, for example, to integrated circuits, PCBs, batteries, drivers, and also to light sources (as a light source, it can be considered both an optical component and an electrical component). The term "magnetic component" refers to, for example, magnetic connectors, coils, etc. Alternatively or additionally, functional components may include thermal components (e.g., configured to cool or heat electrical components). Thus, functional components can be configured to generate or remove heat, etc.

[0075] As indicated above, 3D printed articles can be used for various purposes. Among other things, 3D printed articles may be used for lighting. Therefore, in other aspects, the present invention also provides a lighting device that includes a 3D article as defined herein. In a specific aspect, the present invention provides a lighting system comprising (a) a light source configured to provide (visible) light and (b) a 3D article as defined herein, wherein the 3D article may be configured as (i) at least a portion of a housing, (ii) at least a portion of an illumination chamber wall, and (iii) one or more functional components, wherein the functional components may be selected from the group consisting of optical components, supports, electrically insulating components, conductive components, thermally insulating components, and thermally conductive components. Therefore, in a specific embodiment, the 3D article may be configured as (i) at least a portion of a lighting device housing, (ii) at least a portion of an illumination chamber wall, and (iii) one or more optical elements. Since a relatively smooth surface can be provided, the 3D printed article can be used as a reflector or lens, etc. In an embodiment, the 3D printed article may be configured as a light shield. The device or system may include a plurality of different 3D printed articles with different functionalities.

[0076] Returning to the 3D printing process, a specific 3D printer can be used to provide the 3D printed articles described herein. Therefore, in another aspect, the present invention also provides a fused deposition modeling (FDM) 3D printer comprising (a) a print head including a printer nozzle, and (b) a 3D printable material supply device configured to supply 3D printable material to the print head, wherein the FDM 3D printer is configured to supply said 3D printable material, wherein in a control mode, the 3D printer is configured to generate a stack of layers of 3D printable material, wherein at a fixed first x, y position for a subset of the total number of layers, the layer height (H) varies layer by layer, wherein (i) the layer height (H) increases with respect to consecutive layers, or (ii) the layer height (H) decreases with respect to consecutive layers. Specifically, in the control mode, (i) the layer height (H) increases with respect to consecutive layers, and then the layer height (H) decreases with respect to consecutive layers, or (ii) the layer height (H) decreases with respect to consecutive layers, and then the layer height (H) increases with respect to consecutive layers.

[0077] A printer nozzle may include a single opening. In other embodiments, the printer nozzle may be core-shell type, having two (or more) openings. The term "printhead" may also refer to multiple (different) printheads; therefore, the term "printer nozzle" may also refer to multiple (different) printer nozzles.

[0078] A 3D printable material supply device can supply a filament comprising 3D printable material to a print head, or can supply 3D printable material in such a way that the print head creates a filament comprising 3D printable material. Therefore, in an embodiment, the present invention provides a fused deposition modeling 3D printer comprising (a) a print head including a printer nozzle, and (b) a device configured to supply a filament comprising 3D printable material to the print head, wherein the fused deposition modeling 3D printer is configured to supply the 3D printable material to a substrate, wherein in a control mode, the 3D printer is configured to generate a stack of layers of 3D printable material, wherein at a fixed first x,y position, the layer height (H) varies layer by layer with respect to a subset of the total number of layers, wherein (i) the layer height (H) increases with respect to consecutive layers, or (ii) the layer height (H) decreases with respect to consecutive layers. Specifically, in the control mode, (i) the layer height (H) increases with respect to consecutive layers, and then the layer height (H) decreases with respect to consecutive layers, or (ii) the layer height (H) decreases with respect to consecutive layers, and then the layer height (H) increases with respect to consecutive layers.

[0079] In particular, at least a portion of the 3D printable materials selected during the 3D printing process include light-transmitting polymeric thermoplastic materials.

[0080] Specifically, the 3D printer includes a controller (or is functionally coupled to a controller) configured to perform the methods described herein in a control mode (or “operation mode”). Instead of the term “controller,” the term “control system” (see above, for example) may also be used.

[0081] The term "control" and similar terms specifically refer to determining the behavior or monitoring the operation of an element. Therefore, "control" and similar terms as used herein can, for example, refer to applying behavior to an element (determining the behavior or monitoring the operation of the element), such as, for example, measuring, displaying, actuating, turning, shifting, changing temperature, etc. Furthermore, the term "control" and similar terms can additionally include monitoring. Thus, the term "control" and similar terms may include applying behavior to an element, and also include applying behavior to an element and monitoring the element. Control of the element can be accomplished using a control system, which can also be referred to as a "controller." The control system and the element can therefore be functionally coupled, at least temporarily or permanently. The element may include a control system. In embodiments, the control system and the element may not be physically coupled. Control can be accomplished via wired and / or wireless controls. The term "control system" can also refer to multiple different control systems that are particularly functionally coupled, and for example, one control system in the control system may be a master control system, and one or more other control systems may be slave control systems. The control system may include or may be functionally coupled to a user interface.

[0082] The control system can also be configured to receive and execute commands from a remote controller. In embodiments, the control system can be controlled via an application on the device, such as a portable device like a smartphone or Apple phone, tablet, etc. Therefore, the device does not necessarily need to be coupled to the lighting system, but can be (temporarily) functionally coupled to the lighting system.

[0083] Therefore, in this embodiment, the control system can (and may also) be configured to be controlled by an application on a remote device. In such an embodiment, the control system of the lighting system can be a slave control system or a control in slave mode. For example, the lighting system can be coded, specifically a unique code for the respective lighting system. The control system of the lighting system can be configured to be controlled by an external control system that accesses the lighting system based on knowledge of the (unique) code (via user interface input with optical sensors, such as a QR code reader). The lighting system may also include components for communicating with other systems or devices, such as those based on Bluetooth, Wi-Fi, LiFi, ZigBee, BLE, or WiMAX or another wireless technology.

[0084] A system, apparatus, or device may perform actions in a “mode,” “operating mode,” or “mode of operation.” Similarly, in a method, actions, stages, or steps may be performed in a “mode,” “operating mode,” “mode of operation,” or “operable mode.” The term “mode” may also be indicated as “control mode.” This does not preclude the system, apparatus, or device from being suitable for providing another control mode or multiple other control modes. Likewise, this may not preclude one or more other modes from being performed before and / or after the execution of the current mode.

[0085] However, in embodiments, a control system may be available that is suited to at least provide a control mode. If other modes are available, the selection of such modes may be performed specifically via a user interface, although other options (such as performing modes based on sensor signals or (time) schemes) are also possible. Operating mode in embodiments also refers to a system, apparatus, or device that can operate only in a single operating mode (i.e., "on," without further tunability).

[0086] Therefore, in this embodiment, the control system can be controlled based on one or more of the following: input signals from the user interface, sensor signals (from sensors), and timers. The term "timer" can refer to a clock and / or a predetermined timing scheme.

[0087] Instead of the term "Fused Deposition Modeling (FDM) 3D Printer," the terms "3D Printer," "FDM Printer," or "Printer" may be used in a shorter form. Printer nozzles may also be indicated as "nozzle" or sometimes as "extruder nozzle." Attached Figure Description

[0088] Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic diagrams, wherein corresponding reference numerals indicate corresponding parts, and wherein:

[0089] Figures 1a to 1c schematically depict some general aspects of embodiments of 3D printers and 3D printing materials;

[0090] Figures 2a to 2d schematically depict some embodiments;

[0091] Figures 3a to 3c schematically depict some other embodiments and aspects;

[0092] Figure 4 The application is illustrated schematically; and

[0093] Figures 5a to 5c show some examples. The illustrations are not necessarily drawn to scale. Detailed Implementation

[0094] Figure 1a schematically depicts some aspects of a 3D printer. Reference numeral 500 indicates a 3D printer. Reference numeral 530 indicates a functional unit configured for 3D printing (especially FDM 3D printing); this reference numeral may also indicate a 3D printing stage unit. Here, only the print head for providing 3D printing material, such as an FDM 3D print head, is schematically depicted. Reference numeral 501 indicates a print head. The 3D printer of the present invention may, in particular, include multiple print heads (see below). Reference numeral 502 indicates a printer nozzle. The 3D printer of the present invention may particularly include multiple printer nozzles, although other embodiments are also possible. Reference numeral 320 indicates a filament (such as those indicated above) from which printable 3D printable material can be produced. For clarity, not all features of the 3D printer are depicted; only those particularly relevant to the present invention are depicted (see also further below).

[0095] Reference numeral 321 indicates the extrusion (of 3D printable material 201).

[0096] 3D printer 500 is configured to generate 3D article 1 by depositing multiple layers 322 layer by layer on receiver article 550, which in an embodiment may be at least temporarily cooled, wherein each layer 322 includes a 3D printable material 201, such as having a melting point T. m 3D printable material 201 can be deposited on substrate 1550 (during the printing stage). Through deposition, 3D printable material 201 has become 3D printable material 202. 3D printable material 201 escaping from nozzle 502 is also indicated as extrudate 321. Reference numeral 401 indicates thermoplastic material.

[0097] The 3D printer 500 is configured to heat the filament 320 material upstream of the printer nozzle 502. This can be accomplished, for example, using a device that includes one or more of extrusion and / or heating functions. Such a device is indicated by reference numeral 573 and is positioned upstream of the printer nozzle 502 (i.e., before the filament material leaves the printer nozzle 502). The print head 501 may (therefore) include a liquefier or heater. Reference numeral 201 indicates the printable material. During deposition, this material is indicated as the (3D) printing material, which is indicated by reference numeral 202.

[0098] Reference numeral 572 indicates a spool or roller containing material, particularly in filament form, which may be indicated as filament 320. The 3D printer 500 transforms this material into a layer 322 on a receiver article or deposited printing material in an extruder 321 downstream of the printer nozzle. Typically, the diameter of the extruder 321 downstream of the nozzle 502 is smaller than the diameter of the filament 322 upstream of the print head 501. Therefore, the printer nozzle is sometimes (also) indicated as an extruder nozzle. Arranging layers 322 one by one and / or arranging layers 322t on layers 322 can form a 3D article 1. Reference numeral 575 indicates a filament supply device, which, among other things, includes a spool or roller and a drive wheel, indicated by reference numeral 576.

[0099] The reference numeral A in the attached diagram indicates the longitudinal axis or wire shaft.

[0100] The accompanying drawing C schematically depicts a control system, such as a temperature control system configured, in particular, to control the temperature of the receiver article 550.

[0101] The control system C may include a heater capable of heating the receiver article 550 to a temperature of at least 50°C, but particularly up to a range of about 350°C, such as at least 200°C.

[0102] Alternatively or additionally, in an embodiment, the receiver plate may also be movable in one or both directions of the xy plane (horizontal plane). Further, alternatively or additionally, in an embodiment, the receiver plate may also be rotatable about the z-axis (vertical).

[0103] Therefore, the control system can move the receiver board in one or more of the x, y, and z directions.

[0104] Alternatively, the printer can have a head that can rotate during printing. This type of printer has the advantage that the printing material cannot rotate during printing.

[0105] The layers are indicated by reference numeral 322 and have a layer height H and a layer width W.

[0106] Note that the 3D printable material is not necessarily supplied to the print head as filament 320. Furthermore, filament 320 can also be generated from the 3D printable material in the 3D printer 500.

[0107] The reference numeral D in the attached figure indicates the diameter of the nozzle (through which the 3D printable material 201 is forced to pass).

[0108] Figure 1b schematically depicts the 3D article 1 being constructed in more detail during printing in 3D. Here, in this schematic, the ends of the filaments 321 are not interconnected in a single plane, although this may actually be the case in the embodiments. Reference numeral H indicates the height of the layer. Layers are indicated by reference numeral 203. Here, the layers have a substantially circular cross-section. However, they can generally be flat, such as having an external shape similar to a flat elliptical tube or flat elliptical conduit (i.e., a circular rod with a compressed diameter to have a height smaller than its width, where the sides (defining the width) are (still) rounded).

[0109] Therefore, Figures 1a and 1b schematically depict some aspects of a fused deposition modeling 3D printer 500, including (a) a first printhead 501 including a printer nozzle 502, (b) a filament supply device 575 configured to supply filament 321 comprising a 3D printable material 201 to the first printhead 501, and optionally (c) a receiver article 550. In Figures 1a and 1b, the first printable material or the second printable material, or the first printable material or the second printable material, are indicated by the common indications of printable material 201 and printable material 202, respectively. Directly downstream of the nozzle 502, when the filament 321 containing the 3D printable material is deposited, it becomes a layer 322 containing the 3D printable material 202.

[0110] Figure 1c schematically depicts a stack of 3D printed layers 322, each 3D printed layer 322 having a layer height H and a layer width W. Note that in the embodiment, the layer width and / or layer height may be different for two or more layers 322. The reference numerals in Figure 1c indicate the object surface of the 3D article (schematically depicted in Figure 1c).

[0111] Referring to Figures 1a to 1c, the deposited filaments of the 3D printable material result in a layer with a height H (and width W). After layer 322 is deposited, layer 322 is formed, and 3D article 1 is generated. Figure 1c schematically depicts a single-walled 3D article 1.

[0112] It is interesting to give light sources, luminaires, and lampshades decorative and / or optical effects (such as angle-related light scattering, light absorption, and light transmission). (Therefore) it is also interesting to have visual effects (such as enhanced light reflection) in decorative luminaires. In the case of transparent luminaires, creating (decorative) optical effects can be interesting. It may also be interesting to have (decorative) wavy features instead of straight features at the edges of, for example, lampshades (skirt-shaped housings).

[0113] For this purpose, we recommend using fused deposition modeling, among other things, where the height of the deposited layers can be varied during printing. For example, the layer height during each printing layer can be varied with respect to a sine function. When multiple layers are printed where the relative height variation increases, wavy edges are achieved, which can be very decorative. When printing continues and the relative height variation during printing is reduced to a level where no height variation occurs during printing, structures that display lens operation can be achieved. Other features, such as serrations and other features, can also be used. In this way, lampshades with edges that vary depending on the feature used can also be produced, such as wavy, serrated, or triangular. The printed object does not have a straight surface, but its surface can be conical, spherical, or curved. Needless to say, height variation can also be used only in certain parts of the printing, while the rest of the object is printed with a constant layer height. In this way, various optical effects (such as lens effects and diffraction effects with spatial variations) can be achieved.

[0114] During printing, the print head moves in the X,Y plane to deposit one layer, then the platform moves downwards and the next layer is printed. With this printing method, the layer height remains constant throughout the printing process. Among other things, we propose in this paper to vary the layer height during printing by enabling the print platform to move along the z-axis, as schematically shown in Figure 2a. Figure 2a is a schematic representation of, for example, a possible side view of a wall. Therefore, in the embodiments, we propose using fused deposition modeling, where the height of the deposited layers can be varied during printing. For example, the layer height during each layer printing can be varied with respect to a sine function. When multiple layers are printed where the relative height variation increases, wavy edges are achieved in the print, which can be very decorative, among other things. This is illustrated in Figure 2a. This shape can also have specific (optical) functionalities.

[0115] When printing continues and the relative height variation during multi-layer printing can be reduced to a level where no height variation occurs during printing, structures exhibiting light refraction-based effects, such as lens processing, can be achieved. Other features, such as serrations and other functionalities, can also be used. In this way, lampshades with edges varying depending on the features used can also be produced, such as wavy, serrated, or triangular. The printed object does not have a straight surface, but its surface can be conical, spherical, or curved. Needless to say, height variation can also be used only in certain parts of the print, while the rest of the object is printed using a constant layer height.

[0116] Figure 2a schematically depicts an embodiment where height variations are not (fully) compensated, resulting in a change in the total height (see the lower height at reference numeral H12 and the higher height at reference numeral H11). However, Figure 2b schematically illustrates an embodiment where height variations are compensated. Therefore, the total height is substantially constant. In the embodiment, the lower height at reference numeral H12 and the higher height at reference numeral H11 may refer to the height of the stack, or a portion of the stack 1322.

[0117] Referring to Figures 2a-2b and 1a-1c, among other things, the present invention provides a method for producing a 3D article 1 by fused deposition modeling. This method may include a 3D printing stage comprising depositing an extrusion layer-by-layer from a 3D-printable material to provide (on a receiver article 550) a 3D article 1 comprising 3D printing material 202. The 3D article 1 comprises a plurality of layers 322 of 3D printing material 202. Each layer 322 has a layer height H and a layer width W, one or more of which may vary along the layer. Thus, in an embodiment, the 3D printing stage may include a stack 1322 of layers 322 of 3D printing material 202, wherein at a fixed first x,y position, the layer height H varies layer-by-layer with respect to a subset of the total number of layers 322. In an embodiment, the stack 1322 may be a single-walled stack. This first x,y position is indicated by x1,y1 in Figure 2b. The layer height H of the continuous layer 322 can be increased and / or the layer height H of the continuous layer 322 can be decreased. Therefore, in a specific embodiment, (i) the layer height H increases with respect to the continuous layer 322 and then decreases with respect to the continuous layer 322 (see x1y1), or (ii) the layer height H decreases with respect to the continuous layer and then increases with respect to the continuous layer 322 (actually to the left and right of the first x,y position).

[0118] Referring to FIG2a, stack 1322 has a first stack height H11 at a fixed first x, y position. The method may include generating a stack 1322 having a layer 322 having a layer height H at a fixed second x, y position, thereby providing a stack 1322 having a second stack height H12 at the fixed second x, y position, wherein 0.1 ≤ H12 / H11 ≤ 10, such as 0.1 ≤ H12 / H11 ≤ 5, such as 0.2 ≤ H12 / H11 ≤ 5, and in embodiments at least 0.1 ≤ H12 / H11 ≤ 1.5. However, referring to FIG2b, the stack 1322 has a first stack height H11 at a fixed first x,y position, wherein the method includes generating a stack 1322 with a layer 322 at a fixed second x,y position, the layer 322 having a substantially constant layer height H, thereby providing a second stack height H12 for the stack 1322 at the fixed second x,y position, wherein, for example, 0.9 ≤ H12 / H11 ≤ 1.1.

[0119] Referring to Figures 2a and 2b, stack 1322 can in particular share the same layer 322. Therefore, the lowest and highest layers of the stack will define the stack height. This stack height may vary with the stack (length) (see Figure 2a), or it may be considered to be substantially constant over the stack length (see Figure 2b).

[0120] Furthermore, referring to Figures 2a to 2b, the layers from stack 1322 have the maximum total height (H) of the layers in the stack. L1 The method includes (adjacently) generating a minimum total height (H) of layers in a stack. L2 The same layer as ) where |H L1 -H L2 | / L*≤1, where L* is the distance between the two points measured along the surface of the 3D object, specifically parallel to layer 322, such as particularly parallel to the x,y plane. Furthermore, in a specific embodiment, stacking can be provided, where the value between the minimum and (adjacent) maximum values ​​is selected from 0.1≤|H L1 -H L2 The range | / L*≤1 is implemented, such as 0.25≤|H. L1 -H L2 | / L*≤0.8. Here, the minimum total height and maximum total height are defined relative to the lowest layer or plane layer, which may or may not be available on the receiver item. By example, the minimum and maximum heights are indicated here for a specific layer. The height difference between the minimum and maximum heights is greatest for that layer.

[0121] Referring to Figure 2a, the stack 1322 comprises two substantially identical stacked portions 1322'.

[0122] The layer height can vary in different ways along the section height (see also below). In an embodiment, the (waveform) amplitudes are aligned along the printing direction or along a line extending at an angle to the printing direction. This is schematically depicted in Figure 2c. The amplitudes are either aligned along the printing direction (i.e., they are directly above each other, see I) or they are shifted along the printing direction (see II).

[0123] Depth perception can be divided into monocular and binocular cues. The former has the advantage that the observer's position and orientation are less dependent on the perceived depth and therefore do not require extensive processing. The monocular cues described in this proposal are based on texture gradients and contrast.

[0124] Conventional 3D printing uses regularly spaced layer heights to create surfaces. If the layer heights vary during the printing process, this can be applied to different printing sections. Among other things, a vase (aka spiral) pattern printing method has been proposed, which creates variations in layer height in both the z-direction and the circumferential direction. This, in turn, results in an omnidirectional perception of depth in reflections of a perfectly planar surface illuminated by ambient light, and may also affect the perception of how actively illuminated from the inside is when the surface is opened.

[0125] In Figure 2d, depth perception is interpreted using texture gradients, which are caused by brightness variations associated with the elliptical shape of the printed trajectory. Here, layer height varies only in the z-direction. Variations in layer height result in variations in brightness: small layer heights, indicated by A, produce rapid alternations between high-brightness and low-brightness surface areas, effectively resulting in nearly uniform surface brightness: one cannot distinguish individual dark and bright contributions. Large layer heights, indicated by B, produce low-frequency alternations between high-brightness and low-brightness, making the individual components of surface brightness clearly distinguishable when close to the texture. The light illuminating item 1 is indicated by reference numeral 11. This could be, for example, light from a light source (see Figure 2d). Figure 4 But this could also be sunlight.

[0126] To achieve texture variations in the circumferential direction, it may be necessary to vary the layer height within each layer. To create a uniform lamp wall thickness without cavities—that is, a constant trajectory width—it may be necessary to compensate for both the extrusion and the z-coordinate during printing. Since the z-coordinate in this configuration also depends on the layer height below a predefined location, it may be necessary to consider those previous layer heights directly below that location. This contrasts sharply with conventional 3D printing, where the z-coordinate may be confined to a constant position during single-rotation printing, or within a single layer height in the case of a spiral mode.

[0127] Different items were created. The high-frequency texture appears much brighter than the low-frequency texture: the layers in the high-frequency texture are thinner, so the low-brightness surface areas within these layers contribute less to the average brightness of that area. In the low-frequency texture, the low-brightness areas contribute more to the average brightness, so they appear darker. Examples were also created where one can immediately identify that the low-frequency texture is actually more transparent than the high-frequency texture with more Lambertian scattering. Clearly, the modulation of transmittance depends heavily on the optical properties of the chosen filament material. Examples were created where the variations in layer height (and therefore texture) are not directly visible from the distance from which the images were taken; it is the difference in reflectivity of ambient light that gives the impression of depth.

[0128] As can be seen from Figure 2e, the maximum value (indicated by ma) and the minimum value (indicated by mi) and the position in the layer can follow a curve in the form of a spiral on the surface, such as a spiral that produces a decorative effect.

[0129] Referring to Figures 2c and 2e, the increase in layer height can be substantially parallel to the z-direction. In other embodiments, this increase can be within an angle (less than 90°, such as equal to or less than 45°) with respect to the z-direction. Similarly, in embodiments, the decrease can be substantially parallel to the z-direction. In other embodiments, this decrease can be within an angle (less than 90°, such as equal to or less than 45°) with respect to the z-direction.

[0130] Figure 3a schematically depicts two possible cross-sectional views. In both embodiments, the layer height H varies with height. In the left embodiment indicated by I, the layer width W remains substantially constant. In the right embodiment indicated by II, the layer width also varies. Therefore, in one embodiment, a subset of the total number of layers 322 at a fixed first x, y position can have a substantially constant layer width W. However, in other embodiments, a subset of the total number of layers 322 at a fixed first x, y position can have a constant cross-sectional area of ​​the layer 322.

[0131] As indicated above, in an embodiment, the method includes printing a subset of layers 322 of the total number of layers 322 at a fixed first x,y position having a layer height H that varies in a sinusoidal or triangular manner. Alternatively, in an embodiment, the method may include printing a subset of layers 322 of the total number of layers 322 at a fixed first x,y position having a layer height H that varies like a sawtooth. For example, in an embodiment, the method may include printing a subset of layers 322 of the total number of layers 322 at a fixed first x,y position, wherein the stacking height varies gradually along the surface of the object according to a mathematical function, such as varying sinusoidally or triangularly. Figure 3b schematically depicts some possibilities for layer heights, such as sinusoidal (I), sawtooth (II), and step-by-step (III), in the upper figure. Note that in the later embodiments, it is also considered that not every next layer should have a different layer height H. Layers are indicated on the x-axis. In the lower figure of Figure 3b, possible layer widths are schematically depicted. In this embodiment, the sinusoidal layer height can be compensated for by the arcsine layer width (I). However, in this embodiment, the layer width can also be chosen to be constant (IV) (see also Figure 3a, Embodiment I). Curve II in the top and bottom figures of Figure 3b is also used as an embodiment to show that the layer height and layer width can be controlled such that the cross-sectional area remains substantially constant. However, as indicated by curve IV, the width can also remain constant, or be partially used to compensate for increases or decreases in layer height. These figures are highly illustrative.

[0132] Therefore, at least a portion of the 3D printable material 201 specifically includes a light-transmitting polymeric thermoplastic material 401. In embodiments, the 3D printable material 201 and the 3D printable material 202 include one or more of polycarbonate PC, polyethylene PE, polypropylene PP, polyethylene naphthalate PEN, styrene-acrylonitrile resin SAN, polysulfone PSU, polyphenylene sulfide PPS, polyethylene terephthalate PET, polymethyl methacrylate PMMA, polystyrene PS and styrene-acrylic copolymer SMMA, and polyurethane (PU).

[0133] As schematically depicted in Figure 3c, in an embodiment, the light-transmitting polymeric thermoplastic material 401 includes particulate reflective material 410 embedded therein.

[0134] Figure 4An embodiment of a lamp or illuminator, indicated by reference numeral 2, is schematically depicted, comprising a light source 10 for generating light 11. The lamp may include a housing or light shield or another element, which may include or be a 3D-printed article 1. Here, a hemisphere (in the cross-sectional view) schematically indicates a housing or light shield. The lamp or illuminator may be or may include an lighting device 1000 (which includes the light source 10). Thus, in a specific embodiment, the lighting device 1000 includes a 3D article 1. The 3D article 1 may be configured as one or more of the following: (i) at least a portion of the lighting device housing, (ii) at least a portion of the lighting chamber wall, and (iii) one or more optical elements. Thus, in an embodiment, the 3D article may be reflective and / or transmissive to the light source 11. Here, the 3D article may be, for example, a housing or light shield. The housing or light shield includes an article portion 400. Possible embodiments of the article portion 400 are also described above.

[0135] Figures 5a and 5b depict images of possible lamp housings. The depth impression is achieved using layer height variations in the z-direction and circumferential direction. Note that the overall profile is simply a smooth variation and is essentially constant. In a specific embodiment, the method may include printing a recessed 3D article 1. Figure 5c shows an image of a 3D article obtainable, for example, by varying the layer height during a sinusoidal change in each layer during printing. When multiple layers are printed where the relative height variation increases, wavy edges can be achieved in the print. Figures 5a and 5c also schematically depict that stack 1322 may also include multiple (smaller) stacks. Referring to Figure 5c, stack 1322 includes multiple substantially identical stack portions 1322'. Therefore, stacks may include multiple smaller stacks, which in embodiments may be configured as a regular pattern.

[0136] The term "multiple" refers to two or more.

[0137] The terms "basically" or "substantially" and similar terms used herein will be understood by those skilled in the art. The term "basically" or "substantially" may also include embodiments with "entirely," "completely," "all," etc. Therefore, in embodiments, the adjective "basically" or "substantially" may also be removed. Where applicable, the term "basically" or "substantially" may also refer to 90% or higher, such as 95% or higher, particularly 99% or higher, even more particularly 99.5% or higher, including 100%.

[0138] The term "comprising" also includes embodiments of which "comprise" means "to make up".

[0139] The term “and / or” specifically refers to one or more items mentioned before and after “and / or”. For example, the phrase “item 1 and / or item 2” and similar phrases may refer to one or more of item 1 and item 2. The term “comprising” may mean “consisting of” in one embodiment, but may also mean “containing at least the defined species and optional one or more other species” in another embodiment.

[0140] Furthermore, the terms first, second, third, etc., used in this description and claims are used to distinguish similar elements and are not necessarily used to describe a sequential or chronological order. It should be understood that such terms are interchangeable where appropriate, and the embodiments of the invention described herein can operate in sequences other than those described or illustrated herein.

[0141] The equipment, apparatus, or system may be described herein during operation. As will be apparent to those skilled in the art, the invention is not limited to the method of operation or the equipment, apparatus, or system in operation.

[0142] It should be noted that the above embodiments are illustrative and not limiting of the invention, and those skilled in the art will be able to devise many alternative embodiments without departing from the scope of the appended claims.

[0143] In the claims, any reference numerals placed between parentheses should not be construed as limiting the claims.

[0144] The use of the verb "comprise" and its variations does not exclude the presence of elements or steps other than those stated in the claims. Unless the context clearly requires otherwise, throughout the description and claims, the words "comprise," "comprising," etc., should be interpreted as inclusive, not exclusive or exhaustive; that is, in the sense of "including but not limited to."

[0145] The article "a" or "one" preceding an element does not preclude the existence of multiple such elements.

[0146] This invention can be implemented by hardware comprising several different elements and by a suitably programmed computer. In the device, apparatus, or system claims listing several components, several of these components can be implemented by a single identical hardware article. The fact that certain measures are described in mutually different dependent claims does not indicate that a combination of these measures cannot be used advantageously.

[0147] The present invention also provides a control system that can control a device, apparatus, or system, or perform the methods or processes described herein. Furthermore, the present invention also provides a computer program product that, when functionally coupled to or executed by a computer included therein, controls one or more controllable elements of such device, apparatus, or system.

[0148] The present invention is also applicable to devices, apparatuses, or systems that include one or more characterizing features described in this description and / or shown in the accompanying drawings. The invention also relates to methods or processes that include one or more characterizing features described in the description and / or shown in the accompanying drawings.

[0149] The various aspects discussed in this patent can be combined to provide additional advantages. Furthermore, those skilled in the art will understand that embodiments can be combined, and more than two embodiments can be combined. Additionally, some features can form the basis for one or more divisional applications.

[0150] Needless to say, one or more of the first (printable) material and the second (printable) material may contain fillers such as glass and fibers, which affect the T of the (multiple) materials. g or T m No impact.

Claims

1. A method for producing a 3D article (1) by fused deposition modeling using a 3D printer, the method comprising a 3D printing stage during which a stack (1322) of layers (322) of a 3D printing material (202) is generated by layer-by-layer deposition of an extrusion (321) from a 3D printable material (201), at least a portion of the 3D printable material (201) comprising a light-transmitting polymeric thermoplastic material (401). Each layer (322) of the stack (1322) has a non-constant layer height H. At the fixed first x, y position: (i) The layer height H increases for consecutive layers (322), and then the layer height H decreases for consecutive layers (322), or (ii) The layer height H decreases for consecutive layers, and then the layer height H increases for consecutive layers (322). The stack (1322) has a first stack height H11 at the fixed first x,y position, and The method includes: The stack (1322) having the following layer (322) is generated at a fixed second x, y position, thereby providing the stack (1322) having a second stack height H12 at the fixed second x, y position, wherein 0.9≤H12 / H11≤1.1, and the layer (322) has a layer height H.

2. The method according to claim 1, wherein the layers (322) from the stack (1322) have a maximum total height H. L1 The method includes: Generate a generator with a minimum total height H L2 The layer (322) has the minimum total height H L2 The layer (322) is the same layer as the layer in the stack, where |H L1 -H L2 | / L ≤1, where L It is the distance between these two points measured parallel to the x, y plane.

3. The method according to claim 2, comprising: 3D printed multiple maximum total heights H in the stack (1322) L1 and minimum total height H L2 The maximum total height H of each layer L1 and minimum total height H L2 All follow a spiral on the surface of the 3D article (1), and the method described therein includes printing a concave 3D article (1).

4. The method according to any one of the preceding claims, wherein the method comprises: Print the layer (322) for a subset of the total number of target layers (322) having a constant layer width W at the fixed first x,y position.

5. The method according to any one of the preceding claims, wherein the method comprises: Print the layer (322) for a subset of the total number of layers (322) at the fixed first x,y position having the following layer height H, the layer height varying according to a mathematical function selected from a group of the following: sine curve, triangle, zigzag and square or a combination of two or more of these.

6. The method according to any one of the preceding claims, wherein the light-transmitting polymeric thermoplastic material (401) is transparent to visible light having one or more wavelengths selected from the range of 450 nm to 650 nm.

7. The method according to any one of the preceding claims, wherein the 3D printable material (201) and the 3D printing material (202) comprise one or more of the following: polycarbonate (PC), polyethylene (PE), polypropylene (PP), polyethylene naphthalate (PEN), styrene-acrylonitrile resin (SAN), polysulfone (PSU), polyphenylene sulfide (PPS), polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), polystyrene (PS), styrene-acrylic copolymer (SMMA), and polyurethane (PU).

8. A 3D article (1) comprising a stack (1322) of layers (322) of 3D printing material (202), at least a portion of said 3D printing material (202) comprising a light-transmitting polymeric thermoplastic material (401). Each layer (322) of the stack (1322) has a non-constant layer height H. At the fixed first x, y position: (i) The layer height H increases for consecutive layers (322), and then the layer height H decreases for consecutive layers (322), or (ii) The layer height H decreases for consecutive layers, and then the layer height H increases for consecutive layers (322). The stack (1322) has a first stack height H11 at the fixed first x,y position, and At a fixed second x, y position, the layer (322) of the stack (1322) has a constant layer height H, wherein the stack (1322) has a second stack height H12 at the fixed second x, y position, where 0.1≤H12 / H11≤10.

9. The 3D article (1) according to claim 8, wherein 0.9 ≤ H12 / H11 ≤ 1.1; and wherein the layer (322) of the subset of the total number of layers (322) at the fixed first x,y position has a constant layer width W.

10. The 3D article (1) according to any one of claims 8 to 9, wherein a subset of the total number of layers (322) at the fixed first x,y position, the layer height H varies sinusoidally or triangularly; wherein the 3D article (1) is a concave 3D article (1); wherein the stack (1322) is a single-wall stack.

11. The 3D article (1) according to any one of claims 8 to 10, wherein the 3D printing material (202) comprises one or more of the following: polycarbonate (PC), polyethylene (PE), polypropylene (PP), polyethylene naphthalate (PEN), styrene-acrylonitrile resin (SAN), polysulfone (PSU), polyphenylene sulfide (PPS), polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), polystyrene (PS), styrene-acrylic copolymer (SMMA), and polyurethane (PU), wherein the 3D printing material (202) comprises a light-transmitting polymeric thermoplastic material (401).

12. A lighting device (1000) comprising a 3D article (1) according to any one of claims 8 to 11, wherein the 3D article (1) is configured as (i) at least a portion of a lighting device housing, (ii) at least a portion of a lighting chamber wall, and (iii) one or more optical elements.

13. A computer program product comprising instructions which, when executed by a computer functionally coupled to or included in a fused deposition modeling 3D printer, cause the fused deposition modeling 3D printer to perform the method described in any one of claims 1 to 7.

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