FIELD OF THE INVENTION

The invention relates to a method for manufacturing a 3D (printed) item. The invention also relates to the 3D (printed) item obtainable with such method. Further, the invention relates to a lighting device including such 3D (printed) item.

BACKGROUND OF THE INVENTION

Buckling or bulging or 3D printed walls is known in the art. A.S.J. Suiker describes in“Mechanical performance of wall structures in 3D printing processes: Theory, design tools, and experiments”, International Journal of Mechanical Sciences, 137, 145-170. DOI: 10.1016/j.ijmecsci.2018.01.010 a“a mechanistic model that can be used for analyzing and optimizing the mechanical performance of straight wall structures in 3D printing processes. The two failure mechanisms considered are elastic buckling and plastic collapse. The model incorporates the most relevant process parameters, which are the printing velocity, the curing characteristics of the printing material, the geometrical features of the printed object, the heterogeneous strength and stiffness properties, the presence of imperfections, and the non-uniform dead weight loading. The sensitivity to elastic buckling and plastic collapse is first explored for three basic configurations, namely i) a free wall, ii) a simply-supported wall and in) a fully-clamped wall, which are printed under linear or exponentially-decaying curing processes. As demonstrated for the specific case of a rectangular wall lay-out, the design graphs and failure mechanism maps constructed for these basic configurations provide a convenient practical tool for analysing arbitrary wall structures under a broad range of possible printing process parameters. Here, the simply- supported wall results in a lower bound for the wall buckling length, corresponding to global buckling of the complete wall structure, while the fully-clamped wall gives an upper bound, reflecting local buckling of an individual wall. The range of critical buckling lengths defined by these bounds may be further narrowed by the critical wall length for plastic collapse. For an arbitrary wall configuration the critical buckling length and corresponding buckling mode can be accurately predicted by deriving an expression for the non-uniform rotational stiffness provided by the support structure of a buckling wall. This has been elaborated for the specific case of a wall structure characterised by a rectangular lay-out. It is further shown that under the presence of imperfections the buckling response at growing deflection correctly asymptotes towards the bifurcation buckling length of an ideally straight wall. The buckling responses computed for a free wall and a wall structure with a rectangular lay-out turn out to be in good agreement with experimental results of 3D printed concrete wall structures. Hence, the model can be applied to systematically explore the influence of individual printing process parameters on the mechanical performance of particular wall structures, which should lead to clear directions for the optimisation on printing time and material usage. The model may be further utilised as a validation tool for finite element models of wall structures printed under specific process conditions

SUMMARY OF THE INVENTION

Within the next 10-20 years, digital fabrication will increasingly transform the nature of global manufacturing. One of the aspects of digital fabrication is 3D printing. Currently, many different techniques have been developed in order to produce various 3D printed objects using various materials such as ceramics, metals and polymers. 3D printing can also be used in producing molds which can then be used for replicating objects.

For the purpose of making molds, the use of polyjet technique has been suggested. This technique makes use of layer by layer deposition of photo-polymerisable material which is cured after each deposition to form a solid structure. While this technique produces smooth surfaces the photo curable materials are not very stable, and they also have relatively low thermal conductivity to be useful for injection molding applications.

The most widely used additive manufacturing technology is the process known as Fused Deposition Modeling (FDM). Fused deposition modeling (FDM) is an additive manufacturing technology commonly used for modeling, prototyping, and production applications. FDM works on an "additive" principle by laying down material in layers; a plastic filament or metal wire is unwound from a coil and supplies material to produce a part. Possibly, (for thermoplastics for example) the filament is melted and extruded before being laid down. FDM is a rapid prototyping technology. Other terms for FDM are “fused filament fabrication” (FFF) or“filament 3D printing” (FDP), which are considered to be equivalent to FDM. In general, FDM printers use a thermoplastic filament, which is heated to its melting point and then extruded, layer by layer, (or in fact filament after filament) to create a three-dimensional object. FDM printers are relatively fast, low cost and can be used for printing complicated 3D objects. Such printers are used in printing various shapes using various polymers. The technique is also being further developed in the production of LED luminaires and lighting solutions.

“Buckling” or“bulging” is an effect which is observed during printing and especially after cooling of objects with relatively thin and straight walls such as e.g. a rectangular box. During printing, straight sides of an object start bulging towards inwards or outwards. Upon cooling the object, this deformation becomes stronger. As a result, an object designed to have flat sides results in an FDM printed object with bulged sides.

In lighting applications, there is interest in printing thin walled objects as luminaires. For thin walled objects with a circular cross section, bulging may essentially not be observed. However, when a non-circular object with straight/curved edges and/or elongated portions are used deformation of objects in the form of bulging may be observed. This is not desirable.

Hence, it is an aspect of the invention to provide an alternative 3D printing method and/or 3D (printed) item which preferably further at least partly obviate(s) one or more of above-described drawbacks. The present invention may have as object to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

Hence, in a first aspect the invention provides a method for producing a 3D item by means of fused deposition modelling, the method comprising (i) a 3D printing stage comprising layer-wise depositing an extrudate comprising 3D printable material, to provide the 3D item comprising 3D printed material, wherein the 3D item comprises an item part comprising a 3D printed segment (“segment”) or a plurality of segments. The segment(s) may be provided with features that may reduce or prevent buckling of the segment(s). Hence, the segment(s) may be provided with features that effectively reinforce the item part. In specific embodiments, the item part may comprise two or more 3D printed segments and one or more 3D printed coupling partitions (“partition” or“coupling partition”). Especially, each 3D printed segment and each 3D printed coupling partition comprises a plurality of (parallel) configured layers of 3D printed material. In embodiments, adjacent 3D printed segments are functionally coupled via one of the one or more 3D printed coupling partitions. In

embodiments, the layers of the two or more segments may provide a first layer width (Wl). Further, the layers of the one or more 3D printed coupling partitions provide a second layer width (W2). Especially, in embodiments the method may further comprise (i) 3D printing one or more of the one or more 3D printed coupling partitions with a larger second layer width (W2) than the first layer width (Wl) of the respective adjacent 3D printed segments, and/or (ii) 3D printing one or more of the one or more 3D printed coupling partitions recessed or protruded relative to the respective adjacent 3D printed segments. Especially, hereby an anti-buckling structure may be provided which is oriented perpendicular to axes of elongation of the layers (or parallel to the z-direction or printing direction). Alternatively, or additionally, in embodiments the method may further comprise (iii) providing a segment with one or more grooves (or protrusions), defined by a plurality of layers, which one or more grooves are (thus) oriented axes of elongation of the layers.

Especially the invention (thus) provides in an aspect a method for producing a 3D item by means of fused deposition modelling, the method comprising (i) a 3D printing stage comprising layer-wise depositing an extrudate comprising 3D printable material, to provide the 3D item comprising 3D printed material, wherein the 3D item comprises an item part comprising two or more 3D printed segments and one or more 3D printed coupling partitions, each 3D printed segment and each 3D printed coupling partition comprising a plurality of parallel configured layers of 3D printed material, wherein adjacent 3D printed segments are functionally coupled via one of the one or more 3D printed coupling partitions, wherein the layers of the two or more segments provide a first layer width (W 1), wherein the layers of the one or more 3D printed coupling partitions provide a second layer width (W2), wherein the method further comprises (i) 3D printing one or more of the one or more 3D printed coupling partitions with a larger second layer width (W2) than the first layer width (Wl) of the respective adjacent 3D printed segments, and/or (ii) 3D printing one or more of the one or more 3D printed coupling partitions recessed or protruded relative to the respective adjacent 3D printed segments, and/or (iii) 3D printing the layers of at least one segment such that one or more axes of elongation (A) of the layers are configured at one side of a first plane and one or more other axes of elongation (A) are configured at another side of the first plane.

With such method(s), a reinforced item part may be provided as bulging of the item part may be reduced or prevented. Further, bulging or buckling may be prevented while keeping the width of the segment(s) and/or the width of the optional coupling part relatively small. With the present invention, instead of making all item parts thick, and thereby reduce or prevent buckling, the item part may be kept relatively thin and the coupling partition and/or grooves may provide an increased physical stability.

As indicated above, the invention provides a method for producing a 3D item by means of fused deposition modelling, the method comprising (i) a 3D printing stage comprising layer-wise depositing an extrudate comprising 3D printable material, to provide the 3D item comprising 3D printed material. Hence, the 3D item (or“3D printed item”) is generated via fused deposition modelling, which is herein also indicated as FDM. The method comprising a 3D printing stage comprising layer-wise depositing an extrudate. The extrudate is especially the material that is provided through the nozzle; the material escaping from the nozzle may be indicated as extrudate. The material that is used to generate the extrudate may be indicated as 3D printable material. Hence, the extrudate comprises a 3D printable material. The 3D printable material is deposited on a support, or on 3D printed material on such support. 3D printable material when deposited is herein especially indicated as 3D printed material. Hence, the 3D item that is provided with the method / obtainable with the method comprises 3D printed material. The 3D item especially comprises a plurality of layers. Layer by layer, 3D printed material is deposited, whereby the 3D item is generated. Further details, embodiments, and variants in relation to the method and 3D item is also further indicated below.

The 3D item comprises an item part. The 3D item can essentially be any part (see also below). The item part may in embodiments be a wall, such as a wall of housing, a wall of a light mixing chamber, a part of lamp shade, a part of a luminaire, etc. The item part may also be (part of) a decorative item, etc. The item part may have an overall essentially flat shape. The item part may also have an overall curvature (e.g. cylindrical) or have two curvatures in two different directions (e.g. spherical).

The item part comprises one or more segments. The segment may be part of a wall. The segment may be reinforced with a reinforcing structure or have a shape that reinforces the segment. As can be derived from the above, the segment may have an overall essentially flat shape. The segment may also have an overall curvature (e.g. cylindrical) or have two curvatures in two different directions (e.g. spherical). The segment may e.g. have a cross-sectional area having a length and width of each at least 0.5 cm, such as at least one them at least 1 cm, or both at least 1 cm. The segment may e.g. have a cross-sectional area of at least 0.25 cm ² , such as at least 1 cm ² . The printed segment comprises a plurality of parallel configured layers of 3D printed material.

In embodiments, when the coupling partitions may run perpendicular to the printing plate, the term“cross sectional area” may especially refer to the cross-sectional area which is parallel to the printing plate. In embodiments where the coupling portions may run parallel to the printing plate then the term“cross-sectional area” may refer to the cross- sectional area perpendicular to the printed plate (or receiver item). In embodiments, the item part may comprise a plurality of segments, especially segments that are functionally coupled via 3D printed coupling partitions (see also below). For instance, there may be at least about 1 segment per 100 cm ² cross-sectional area of the item part, such as at least 1 per 50 cm ² , such as at least 1 per 20 cm ² , or even at least 1 per 10 cm ² .

Hence, in embodiments the item part comprises two or more 3D printed segments and one or more 3D printed coupling partitions. Especially, the3D printed coupling partition comprises a plurality of parallel configured layers of 3D printed material.

Hence, in embodiments each 3D printed segment and each 3D printed coupling partition comprises a plurality of parallel configured layers of 3D printed material. Especially, one or more layers, especially each layer, of the coupling partition are comprises by one or more (larger) layers that are also comprised by the adjacent segments. Hence, in embodiments layer by layer the segments and bridging coupling partition are deposited. Hence, they may essentially form a monolithic item part, wherein two segments are associated to each other via a partition that may effectively reinforce the adjacent segments (relative to a single larger segment essentially having the same cross-sectional area as the two segments and coupling partition). Hence, in embodiments one or more layers, especially a plurality of layers may comprise a part in a first segment, a part in the coupling partition and a part in the second segment, whereby the first segment and second segment are adjacent to the coupling partition.

Therefore, in embodiments adjacent 3D printed segments may be functionally coupled via one of the one or more 3D printed coupling partitions. Thereby, a configuration of segment-partition-segment may be provided.

The 3D printed item may comprise a plurality of layers on top of each other, i.e. stacked layers. The width (thickness) and height of individually 3D printed layers may e.g. in embodiments be selected from the range of 100 - 5000 pm, such as 200-2500 pm, with the height in general being smaller than the width. For instance, the ratio of height and width may be equal to or smaller than 0.8, such as equal to or smaller than 0.6.

The layers of the two or more segments may provide a first layer width (Wl). This first layer width may be defined by one or more adjacent individually 3D printed layers. Hence, Wi=n*W where n is an integer.

The first layer widths of a segment may vary over its height and/or its length, though in many embodiments the layer widths will essentially be the same throughout the segment. Would the first layer width vary over the segment, an average first layer width may be applied. Would the first layer width differ between the two segments that are bridged by the coupling partition, then an average first layer width for both segments may be used. See further below for embodiments wherein the first layer width is applied.

The layers of the one or more 3D printed coupling partitions provide a second layer width (W2). This second layer width may be defined by one or more adjacent individually 3D printed layers. Hence, W2=k*W where k is an integer. In specific

embodiments, Wi=W2 and n=k.

Note that the layer width (such as layer width W2)may in embodiments be essentially constant. In other embodiments, the layer width may have different values, such that the layer width may be defined as an average layer width. For instance, the layer width may vary over the height (HI).

The second layer width of the partition may vary over its height and/or its length, though in many embodiments the layer widths will essentially be the same throughout the partition. Would the second layer width vary over the partition, an average second layer width may be applied. See further below for embodiments wherein the second layer width is applied.

As indicated above, for reinforcing several options may be chosen. Hence, amongst others the method may further comprise (i) 3D printing one or more of the one or more 3D printed coupling partitions with a larger second layer width (W2) than the first layer width (Wl) of the respective adjacent 3D printed segments. For instance, this may be done by providing more individual layers at the same height in the coupling partition than in the adjacent segments (i.e. k>n; see above). However, this may also be achieved by forcing more 3D printable material out of the nozzle while especially maintaining the same layer height. Thereby, the layer width of the individual layer(s) of the partition may become larger (while nevertheless k may be the same as n). Hence, in this embodiment the coupling partition may be created by locally (i.e. at the position of the partition) the width of the item part. In fact, in embodiments a larger segment may be divided in two smaller segments by introducing a thickening in the larger segment. In these specific embodiments, the segments and coupling portions run parallel to the printing stage.

In specific embodiments, the method comprises 3D printing the one or more of the one or more 3D printed coupling partitions with the larger second layer width (W2) larger than the first layer width (Wl) of the respective adjacent 3D printed segments, wherein W2/W1>1.2. For instance, in embodiments 1.2<W2/W1<4. As indicated above, for reinforcing several options may be chosen. Hence, amongst others alternatively or additionally the method may further comprise (ii) 3D printing one or more of the one or more 3D printed coupling partitions recessed or protruded relative to the respective adjacent 3D printed segments. For instance, by providing a kind of incaving in the direction to perpendicular to the printing direction (which is parallel to the receiver item), the adjacent segments may mechanically decouple from each other. Herein the phrase “recessed or protruded” and similar phrases are used. Relative to one side of the item part the coupling partition may be considered recessed whereas relative to another side of the item part the coupling partition may be considered protruding. The segments may have a cross- sectional plane along which axes of elongation are configured parallel. Even, in embodiments these axes may be within this plane (however, see also other embodiments further elucidated below). Especially, the protrusion, or recession, is (directed) perpendicular to this cross- sectional plane. Relative to the segments, it may be an extension or recession in a direction perpendicular to this plane.

Alternatively, or additionally, it is also possible to reinforce e.g. walls against bending by introducing incavings running parallel to the printing stage or by introducing the layers with increased thickness as running parallel to the printing stage (see also below).

It appeared beneficial when the length the coupling partition bridges the adjacent segments is smaller than the width it protrudes or is recessed. The length the coupling partition bridges the adjacent segments is herein also indicated as third length and is essentially the shortest distance between the adjacent segments (thus not the length following the 3D printed layers, which may be much longer as the coupling partition protrudes).

Hence, in specific embodiments the one or more of the one or more 3D printed coupling partitions are recessed or protrude relative to the respective adjacent 3D printed segments with an extension width (W3), wherein the one or more of the one or more 3D printed coupling partitions have a third length (L3) parallel to the respective adjacent 3D printed segments and bridging a distance between the respective adjacent 3D printed segments, wherein the method comprises 3D printing the one or more of the one or more 3D printed coupling partitions with the extension width (W3) equal to or larger than the first layer width (Wl), and with the extension width (W3) larger than the third length (L3).

Further, it appears beneficial in terms of anti-buckling when the extension width is in the order of 1-25 mm and the extension length is in the order of 0.3-5 mm.

Therefore, in embodiments the method may comprise 3D printing the one or more of the one or more 3D printed coupling partitions with the extension width (W3) selected from the range of 1-30 mm, especially 1-25 mm and with the third length (L3) selected from the range of 0.3-20 mm, in embodiments selected from the range of 0.3-10 mm, such as 0.3-5 mm.

Above, two types of 3D printed coupling partitions are described: protrusions/recession and a locally increased thickness of the item part, respectively. A 3D printed item, or even an item part, may comprise one or more 3D printed coupling partitions. When there are two or more 3D printed coupling partitions, these may all be of the same type, or the two different types may be applied. Further, also a combination of these two types may be applied, i.e. a 3D printed coupling partition comprising a protrusions/recession which includes a locally increased thickness. Further, alternative or additional to these two types of 3D printed coupling partitions, also other types of anti-buckling structures may be applied, which are herein also indicated as corrugation.

As indicated above, in embodiments the plurality of parallel configured layers of 3D printed material of at least one segment of the two or more segments have axes of elongation (A) parallel to a first plane.

As also indicated above, for reinforcing several options may be chosen.

Hence, amongst others the method may alternatively or additionally comprise (iii) 3D printing the layers of the at least one segment such that one or more axes of elongation (A) are configured at one side of the first plane and one or more other axes of elongation (A) are configured at another side of the first plane. Such embodiments may lead to a recession or protrusion parallel to the axes of elongation, in contrast to the above-mentioned coupling partitions. Such embodiments also do not necessarily include a segmentation, though this is not excluded. However, in specific embodiments a repetitive structure may be provided, such as a corrugated structure.

Hence, in an embodiment (of the method) the plurality of parallel configured layers of 3D printed material of at least one segment of the two or more segments have axes of elongation (A) parallel to a first plane, wherein the method comprise 3D printing the layers of the at least one segment such that one or more axes of elongation (A) are configured at one side of the first plane and one or more other axes of elongation (A) are configured at another side of the first plane.

Especially, in embodiments the method comprises 3D printing the at least one segment with a corrugated segment structure, wherein the corrugated segment structure comprises corrugations defined by the layers with respective one or more axes of elongation (A) configured at one side of the first plane and one or more other axes of elongation (A) configured at another side of the first plane. In specific embodiments, the corrugations define a total corrugation width (W4) defined perpendicular to the first plane, wherein the method comprises 3D printing the at least one segment with a ratio of the corrugation width (W4) to the first layer width (Wl) W4/W1>3. This may also provide reinforced segments, and thus reinforced item parts.

Especially, in embodiments the method may comprise 3D printing the 3D item on a receiver item, wherein the one or more corrugations are arranged parallel to the receiver item.

Herein, terms like“parallel” or“perpendicular” may refer to essentially parallel or essentially perpendicular (see also below).

As can be derived from the above, the invention provides in one or more aspects a method for producing a 3D item by means of fused deposition modelling, the method comprising a 3D printing stage comprising layer-wise depositing an extrudate comprising 3D printable material, to provide the 3D item comprising 3D printed material, wherein the 3D item comprises an item part comprising one or more 3D printed segments, each 3D printed segment comprising a plurality of parallel configured layers of 3D printed material, wherein the layers of the segment(s) provide a first layer width (W 1), wherein the method in embodiments further comprises (i) 3D printing one or more of the one or more 3D printed segments over the length and part of the width, or over the width and part of the length, or over part of the width and part of the length with a larger second layer width (W2) or fifth layer width (W5), larger than the first layer width (Wl) of the remainder of the 3D printed segment, and/or (ii) 3D printing the layers of one or more of the one or more segments such that one or more axes of elongation (A) of the layers are configured at one side of a first plane and one or more other axes of elongation (A) are configured at another side of the first plane.

When the method comprises (i) 3D printing one or more of the one or more 3D printed segments over the length and part of the width, or over the width and part of the length, or over part of the width and part of the length with a larger second layer width (W2) or fifth layer width (W5), then, in embodiments a (kind of) coupling partition may be created.

When the method comprises (ii) 3D printing the layers of one or more of the one or more segments such that one or more axes of elongation (A) of the layers are configured at one side of a first plane and one or more other axes of elongation (A) are configured at another side of the first plane, one or more corrugations may be provided.

Hence, in some aspects the item part may comprise one or more 3D printed segments; in other aspects the item part may comprise two or more 3D printed segments. As indicated above, the method comprises depositing during a printing stage 3D printable material. Herein, the term“3D printable material” refers to the material to be deposited or printed, and the term“3D printed material” refers to the material that is obtained after deposition. These materials may be essentially the same, as the 3D printable material may especially refer to the material in a printer head or extruder at elevated temperature and the 3D printed material refers to the same material, but in a later stage when deposited. The 3D printable material is printed as a filament and deposited as such. The 3D printable material may be provided as filament or may be formed into a filament. Hence, whatever starting materials are applied, a filament comprising 3D printable material is provided by the printer head and 3D printed. The term“extrudate” may be used to define the 3D printable material downstream of the printer head, but not yet deposited. The latter is indicated as“3D printed material”. In fact, the extrudate comprises 3D printable material, as the material is not yet deposited. Upon deposition of the 3D printable material or extrudate, the material is thus indicated as 3D printed material. Essentially, the materials are the same material, as the thermoplastic material upstream of the printer head, downstream of the printer head, and when deposited, is essentially the same material.

Herein, the term“3D printable material” may also be indicated as“printable material. The term“polymeric material” may in embodiments refer to a blend of different polymers but may in embodiments also refer to essentially a single polymer type with different polymer chain lengths. Hence, the terms“polymeric material” or“polymer” may refer to a single type of polymers but may also refer to a plurality of different polymers. The term“printable material” may refer to a single type of printable material but may also refer to a plurality of different printable materials. The term“printed material” may refer to a single type of printed material but may also refer to a plurality of different printed materials.

Hence, the term“3D printable material” may also refer to a combination of two or more materials. In general, these (polymeric) materials have a glass transition temperature T _g and/or a melting temperature T _m. The 3D printable material will be heated by the 3D printer before it leaves the nozzle to a temperature of at least the glass transition temperature, and in general at least the melting temperature. Hence, in a specific embodiment the 3D printable material comprises a thermoplastic polymer having a glass transition temperature (T _g ) and /or a melting point (T _m ), and the printer head action comprises heating the 3D printable material above the glass transition and if it is a semi-crystalline polymer above the melting temperature. In yet another embodiment, the 3D printable material comprises a (thermoplastic) polymer having a melting point (T _m ), and the printer head action comprises heating the 3D printable material to be deposited on the receiver item to a temperature of at least the melting point. The glass transition temperature is in general not the same thing as the melting temperature. Melting is a transition which occurs in crystalline polymers. Melting happens when the polymer chains fall out of their crystal structures and become a disordered liquid. The glass transition is a transition which happens to amorphous polymers; that is, polymers whose chains are not arranged in ordered crystals, but are just strewn around in any fashion, even though they are in the solid state. Polymers can be amorphous, essentially having a glass transition temperature and not a melting temperature or can be (semi) crystalline, in general having both a glass transition temperature and a melting temperature, with in general the latter being larger than the former. The glass temperature may e.g. be determined with differential scanning calorimetry. The melting point or melting temperature can also be determined with differential scanning calorimetry.

As indicated above, the invention thus provides a method comprising providing a filament of 3D printable material and printing during a printing stage said 3D printable material on a substrate, to provide said 3D item.

Materials that may especially qualify as 3D printable materials may be selected from the group consisting of metals, glasses, thermoplastic polymers, silicones, etc. Especially, the 3D printable material comprises a (thermoplastic) polymer selected from the group consisting of ABS (acrylonitrile butadiene styrene), Nylon (or polyamide), Acetate (or cellulose), PLA (poly lactic acid), terephthalate (such as PET polyethylene terephthalate), Acrylic (polymethylacrylate, Perspex, polymethylmethacrylate, PMMA), Polypropylene (or polypropene), Polycarbonate (PC), Polystyrene (PS), PE (such as expanded- high impact- Polythene (or polyethene), Low density (LDPE) High density (HDPE)), PVC (polyvinyl chloride) Polychloroethene, such as thermoplastic elastomer based on copolyester elastomers, polyurethane elastomers, polyamide elastomers polyolefine based elastomers, styrene based elastomers, etc.. Optionally, the 3D printable material comprises a 3D printable material selected from the group consisting of Urea formaldehyde, Polyester resin, Epoxy resin, Melamine formaldehyde, thermoplastic elastomer, etc... Optionally, the 3D printable material comprises a 3D printable material selected from the group consisting of a polysulfone.

Elastomers, especially thermoplastic elastomers, are especially interesting as they are flexible and may help obtaining relatively more flexible filaments comprising the thermally conductive material. A thermoplastic elastomer may comprise one or more of styrenic 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)).

Suitable thermoplastic materials, such as also mentioned in W02017/040893, may include one or more of polyacetals (e.g., polyoxyethylene and polyoxymethylene), poly(Ci- ₆ alkyl)acrylates, polyacrylamides, polyamides, (e.g., aliphatic polyamides, polyphthalamides, and polyaramides), polyamideimides, polyanhydrides, polyarylates, polyarylene ethers (e.g., polyphenylene ethers), polyarylene sulfides (e.g., polyphenylene sulfides), poly aryl sulfones (e.g., polyphenylene sulfones), polybenzothiazoles,

polybenzoxazoles, polycarbonates (including polycarbonate copolymers such as

polycarbonate-siloxanes, polycarbonate-esters, and polycarbonate-ester-siloxanes), polyesters (e.g., polycarbonates, polyethylene terephthalates, polyethylene naphtholates, polybutylene terephthalates, polyarylates), 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(Ci- ₆ alkyl)methacrylates, polymethacrylamides, polynorbornenes (including copolymers containing norbornenyl units), polyolefins (e.g., polyethylenes, polypropylenes,

polytetrafluoroethylenes, and their copolymers, for example ethylene- alpha- olefin copolymers), polyoxadiazoles, polyoxymethylenes, polyphthalides, polysilazanes, polysiloxanes, polystyrenes (including copolymers such as acrylonitrile-butadiene-styrene (ABS) and methyl methacrylate-butadiene-styrene (MBS)), poly sulfides, poly sulfonamides, polysulfonates, polysulfones, polythioesters, polytriazines, polyureas, polyurethanes, polyvinyl alcohols, polyvinyl esters, polyvinyl ethers, polyvinyl halides, polyvinyl ketones, polyvinyl thioethers, polyvinylidene fluorides, or the like, or a combination comprising at least one of the foregoing thermoplastic polymers. Embodiments of polyamides may include, but are not limited to, synthetic linear polyamides, e.g., 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 a combination comprising at least one of the foregoing. Polyurethanes that can be used include aliphatic, cycloaliphatic, aromatic, and polycyclic polyurethanes, including those described above. Also useful are poly(Ci- ₆ alkyl)acrylates and poly(Ci- ₆ alkyl)methacrylates, which include, for instance, polymers of methyl acrylate, ethyl acrylate, acrylamide, methacrylic acid, methyl methacrylate, n-butyl acrylate, and ethyl acrylate, etc. In embodiments, a polyolefine may include one or more of polyethylene, polypropylene, polybutylene, polymethylpentene (and co-polymers thereof), polynorbornene (and co-polymers thereof), poly 1 -butene, poly(3-methylbutene), poly(4-methylpentene) and copolymers of ethylene with propylene, 1 -butene, 1 -hexene, 1-octene, 1-decene, 4-m ethyl-1 -pentene and 1- octadecene.

In specific embodiments, the 3D printable material (and the 3D printed material) comprise one or more of polycarbonate (PC), polyethylene (PE), high-density polyethylene (HDPE), polypropylene (PP), polyoxymethylene (POM), polyethylene naphthalate (PEN), styrene-acrylonitrile resin (SAN), polysulfone (PSU), polyphenylene sulfide (PPS), and semi-crystalline polytethylene terephthalate (PET), acrylonitrile butadiene styrene (ABS), poly(methyl methacrylate) (PMMA), polystyrene (PS), and styrene acrylic copolymers (SMMA).

The term 3D printable material is further also elucidated below, but especially refers to a thermoplastic material, optionally including additives, to a volume percentage of at maximum about 60%, especially at maximum about 30 vol.%, such as at maximum 20 vol.% (of the additives relative to the total volume of the thermoplastic material and additives).

The printable material may thus in embodiments comprise two phases. The printable material may comprise a phase of printable polymeric material, especially thermoplastic material (see also below), which phase is especially an essentially continuous phase. In this continuous phase of thermoplastic material polymer additives such as one or more of antioxidant, heat stabilizer, light stabilizer, ultraviolet light stabilizer, ultraviolet light absorbing additive, near infrared light absorbing additive, infrared light absorbing additive, plasticizer, lubricant, release agent, antistatic agent, anti-fog agent, antimicrobial agent, colorant, laser marking additive, surface effect additive, radiation stabilizer, flame retardant, anti-drip agent may be present. The additive may have useful properties selected from optical properties, mechanical properties, electrical properties, thermal properties, and mechanical properties (see also above).

The printable material in embodiments may comprise particulate material, i.e. particles embedded in the printable polymeric material, which particles form a substantially discontinuous phase. The number of particles in the total mixture is especially not larger than 60 vol.%, relative to the total volume of the printable material (including the (anisotropically conductive) particles) especially in applications for reducing thermal expansion coefficient. For optical and surface related effect number of particles in the total mixture is equal to or less than 20 vol.%, such as up to 10 vol.%, relative to the total volume of the printable material (including the particles). Hence, the 3D printable material especially refers to a continuous phase of essentially thermoplastic material, wherein other materials, such as particles, may be embedded. Likewise, the 3D printed material especially refers to a continuous phase of essentially thermoplastic material, wherein other materials, such as particles, are embedded. The particles may comprise one or more additives as defined above. Hence, in embodiments the 3D printable materials may comprises particulate additives.

The printable material is printed on a receiver item. Especially, the receiver item can be the building platform or can be comprised by the building platform. The receiver item can also be heated during 3D printing. However, the receiver item may also be cooled during 3D printing.

The phrase“printing on a receiver item” and similar phrases include amongst others directly printing on the receiver item, or printing on a coating on the receiver item, or printing on 3D printed material earlier printed on the receiver item. The term“receiver item” may refer to a printing platform, a print bed, a substrate, a support, a build plate, or a building platform, etc... Instead of the term“receiver item” also the term“substrate” may be used. The phrase“printing on a receiver item” and similar phrases include amongst others also printing on a separate substrate on or comprised by a printing platform, a print bed, a support, a build plate, or a building platform, etc... Therefore, the phrase“printing on a substrate” and similar phrases include amongst others directly printing on the substrate, or printing on a coating on the substrate or printing on 3D printed material earlier printed on the substrate. Here below, further the term substrate is used, which may refer to a printing platform, a print bed, a substrate, a support, a build plate, or a building platform, etc., or a separate substrate thereon or comprised thereby.

Layer by layer printable material is deposited, by which the 3D printed item is generated (during the printing stage). The 3D printed item may show a characteristic ribbed structure (originating from the deposited filaments). However, it may also be possible that after a printing stage, a further stage is executed, such as a finalization stage. This stage may include removing the printed item from the receiver item and/or one or more post processing actions. One or more post processing actions may be executed before removing the printed item from the receiver item and/or one more post processing action may be executed after removing the printed item from the receiver item. Post processing may include e.g. one or more of polishing, coating, adding a functional component, etc... Post-processing may include smoothening the ribbed structures, which may lead to an essentially smooth surface.

Further, the invention relates to a software product that can be used to execute the method described herein. Therefore, in yet a further aspect the invention also provides a computer program product, when running on a computer which is functionally coupled to or comprised by a fused deposition modeling 3D printer, is capable of bringing about the method as described herein.

The herein described method provides 3D printed items. Hence, the invention also provides in a further aspect a 3D printed item obtainable with the herein described method. In a further aspect a 3D printed item obtainable with the herein described method is provided. Especially, the invention provides a 3D item comprising 3D printed material, wherein the 3D item comprises a plurality of layers of 3D printed material, wherein the 3D item comprises an item part comprising one or more, such as two or more 3D printed segments.

The item part may comprise a shape and or additional features that may reinforce the item part. Each 3D printed segment may comprise a plurality of parallel configured layers of 3D printed material.

In specific embodiments, the item part may comprise two or more 3D printed segments and one or more 3D printed coupling partitions. Especially, each 3D printed segment and (also) each 3D printed coupling partition comprise a plurality of parallel configured layers of 3D printed material.

In specific embodiments, adjacent 3D printed segments are functionally coupled via one of the one or more 3D printed coupling partitions. Especially, the layers of the two or more segments provide a first layer width (Wl). Further, especially the layers of the one or more 3D printed coupling partitions provide a second layer width (W2).

In specific embodiments, one or more of the one or more 3D printed coupling partitions have a larger second layer width (W2) than the first layer width (Wl) of the respective adjacent 3D printed segments. Alternatively, or additionally, in embodiments one or more of the one or more 3D printed coupling partitions are recessed or protruded relative to the respective adjacent 3D printed segments. Further, alternatively or additionally, in embodiments the plurality of parallel configured layers of 3D printed material of at least one segment of the two or more segments have axes of elongation (A) parallel to a first plane, wherein one or more axes of elongation (A) are configured at one side of the first plane and one or more other axes of elongation (A) are configured at another side of the first plane.

Therefore, in an aspect the invention provides a 3D item comprising 3D printed material, wherein the 3D item comprises a plurality of layers of 3D printed material, wherein the 3D item comprises an item part comprising two or more 3D printed segments and one or more 3D printed coupling partitions, each 3D printed segment and each 3D printed coupling partition comprising a plurality of parallel configured layers of 3D printed material, wherein adjacent 3D printed segments are functionally coupled via one of the one or more 3D printed coupling partitions, wherein the layers of the two or more segments provide a first layer width (Wl), wherein the layers of the one or more 3D printed coupling partitions provide a second layer width (W2), wherein (i) one or more of the one or more 3D printed coupling partitions have a larger second layer width (W2) than the first layer width (Wl) of the respective adjacent 3D printed segments, and/or (ii) wherein one or more of the one or more 3D printed coupling partitions are recessed or protruded relative to the respective adjacent 3D printed segments.

Individual layers may be core-shell layers or may consist of a single material. Within a layer, there may also be a change in composition, for instance when a core-shell printing process was applied and during the printing process it was changed from printing a first material (and not printing a second material) to printing a second material (and not printing the first material).

At least part of the 3D printed item may include a coating.

Some specific embodiments in relation to the 3D printed item have already been elucidated below when discussing the method. Below, some specific embodiments in relation to the 3D printed item are discussed in more detail.

As indicated above, in embodiments at least one or more of the one or more 3D printed coupling partitions are recessed or protruded relative to the respective adjacent 3D printed segments. Especially, the one or more of the one or more 3D printed coupling partitions are recessed or protrude relative to the respective adjacent 3D printed segments with an extension width (W3). Further, the one or more of the one or more 3D printed coupling partitions have a third length (L3) parallel to the respective adjacent 3D printed segments and bridging a distance between the respective adjacent 3D printed segments.

As indicated above, in embodiments for the one or more of the one or more 3D printed coupling partitions the extension width (W3) may be equal to or larger than the first layer width (Wl). Alternatively, or additionally, in embodiments for the one or more of the one or more 3D printed coupling partitions the extension width (W3) may be larger than the third length (L3). In embodiments, W3/L3>1.2, especially W3/L3>1.5. In embodiments, 1.2<W3/L3<20. In specific embodiments, the extension width (W3) is selected from the range of 1-25 mm and wherein the third length (L3) selected from the range of 0.3-20 mm, in embodiments selected from the range of 0.3-10 mm, such as 0.3-5 mm.

The above-mentioned coupling partition may also be indicated as“incaving” and may especially be used to separate a larger part into two (or more) segments. In this way, buckling of the larger part may be reduced or prevented. These coupling partitions may especially be configured perpendicular to the axis of elongations of the layers (such as perpendicular to axes of elongation of layers that were originally 3D printed on top of each other). Hence, during printing these coupling partitions may be 3D printed essentially perpendicular to the receiver item. Hence, in specific embodiments the method comprises 3D printing the 3D item on a receiver item, wherein the one or more 3D printed coupling partitions are arranged essentially perpendicular to the receiver item. Note that the coupling partitions are not necessarily over the entire item part height but may also be over part of the item part height.

As indicated above, the coupling partition may also include a thickening relative to one or more the adjacent segments. In specific embodiments, the second layer width (W2) may (thus) be larger than the first layer width (Wl) of the respective adjacent 3D printed segment(s). In more specific embodiments, wherein W2/W1>1.2.

The thickening relative to the adjacent segment(s) may in embodiments configured parallel to the axes of elongation of the layers. In other embodiments, the thickening relative to the adjacent segment(s) may in embodiments be configured perpendicular to the axes of elongation of the layers.

Therefore, in embodiments the one or more of the one or more 3D printed coupling partitions protrude relative to the respective adjacent 3D printed segments with a partition width (W5), wherein the method comprises 3D printing the one or more of the one or more 3D printed coupling partitions with the partition width larger than the first layer width (Wl) of one or more of the respective adjacent 3D printed segments, wherein the method comprises 3D printing the 3D item on a receiver item, wherein the one or more 3D printed coupling partitions are arranged parallel to the receiver item.

In embodiments, one or more corrugations may be provided, which may be configured essentially parallel to the axes of elongation.

Hence, the invention also provides embodiments of the 3D item, wherein the plurality of parallel configured layers of 3D printed material of at least one segment of the two or more segments have axes of elongation (A) parallel to a first plane, wherein one or more axes of elongation (A) are configured at one side of the first plane and one or more other axes of elongation (A) are configured at another side of the first plane, wherein the at least one segment comprises a corrugated segment structure. Especially, the corrugated segment structure comprises corrugations defined by the layers with respective one or more axes of elongation (A) configured at one side of the first plane and one or more other axes of elongation (A) configured at another side of the first plane. Yet further, in specific embodiments the corrugations define a total corrugation width (W4) defined perpendicular to the first plane. Especially, a ratio of the corrugation width (W4) to the first layer width (Wl) is W4/W1>3.

As can be derived from the above, the invention provides in one or more aspects a 3D item comprising 3D printed material, wherein the 3D item comprises a plurality of layers of 3D printed material, wherein the 3D item comprises an item part comprising one or more 3D printed segments, each 3D printed segment comprising a plurality of parallel configured layers of 3D printed material, wherein the layers of the segment(s) provide a first layer width (Wl), wherein (i) one or more of the one or more segments have over the length and part of the width, or over the width and part of the length, or over part of the width and part of the length (one or more layers with) a second layer width (W2) or fifth layer width (W5), larger than the first layer width (Wl) of the remainder of the 3D printed segment, and/or (ii) of one or more of the one or more segments one or more axes of elongation (A) of the layers are configured at one side of a first plane and one or more other axes of elongation (A) are configured at another side of the first plane.

The (with the herein described method) obtained 3D printed item may be functional per se. For instance, the 3D printed item may be a lens, a collimator, a reflector, etc... The thus obtained 3D item may (alternatively) be used for decorative or artistic purposes. The 3D printed item may include or be provided with a functional component. The functional component may especially be selected from the group consisting of an optical component, an electrical component, and a magnetic component. The term“optical component” especially refers to a component having an optical functionality, such as a lens, a mirror, a light transmissive element, an optical filter, etc... The term optical component may also refer to a light source (like a LED). The term“electrical component” may e.g. refer to an integrated circuit, PCB, a battery, a driver, but also a light source (as a light source may be considered an optical component and an electrical component), etc. The term magnetic component may e.g. refer to a magnetic connector, a coil, etc... Alternatively, or additionally, the functional component may comprise a thermal component (e.g. configured to cool or to heat an electrical component). Hence, the functional component may be configured to generate heat or to scavenge heat, etc...

As indicated above, the 3D printed item maybe used for different purposes. Amongst others, the 3D printed item maybe used in lighting. Hence, in yet a further aspect the invention also provides a lighting device comprising the 3D item as defined herein. In a specific aspect the invention provides a lighting system comprising (a) a light source configured to provide (visible) light source light and (b) the 3D item as defined herein, wherein 3D item may be configured as one or more of (i) at least part of a housing, (ii) at least part of a wall of a lighting chamber, and (iii) a functional component, wherein the functional component may be selected from the group consisting of an optical component, a support, an electrically insulating component, an electrically conductive component, a thermally insulating component, and a thermally conductive component. Hence, in specific embodiments the 3D item may be configured as one or more of (i) at least part of a lighting device housing, (ii) at least part of a wall of a lighting chamber, and (iii) an optical element. For instance, the part of a lighting device housing may be a wall. The lighting device housing may e.g. comprise one or more item parts.

As a relative smooth surface may be provided, the 3D printed item may be used as mirror or lens, etc... In embodiments, the 3D item may be configured as shade. A device or system may comprise a plurality of different 3D printed items, having different functionalities.

Returning to the 3D printing process, a specific 3D printer may be used to provide the 3D printed item described herein. Therefore, in yet a further aspect the invention also provides a fused deposition modeling 3D printer, comprising (a) a printer head comprising a printer nozzle, and (b) a 3D printable material providing device configured to provide 3D printable material to the printer head, wherein the fused deposition modeling 3D printer is configured to provide said 3D printable material, and wherein especially the 3D printer comprises a controller (or is functionally coupled to a controller) that is configured to execute in a controlling mode (or“operation mode”) the method as described herein.

The printer nozzle may include a single opening. In other embodiments, the printer nozzle may be of the core-shell type, having two (or more) openings. The term “printer head” may also refer to a plurality of (different) printer heads; hence, the term “printer nozzle” may also refer to a plurality of (different) printer nozzles.

The 3D printable material providing device may provide a filament comprising 3D printable material to the printer head or may provide the 3D printable material as such, with the printer head creating the filament comprising 3D printable material. Hence, in embodiments the invention provides a fused deposition modeling 3D printer, comprising (a) a printer head comprising a printer nozzle, and (b) a filament providing device configured to provide a filament comprising 3D printable material to the printer head, wherein the fused deposition modeling 3D printer is configured to provide said 3D printable material to a substrate, wherein especially the 3D printer comprises a controller (or is functionally coupled to a controller) that is configured to execute in a controlling mode (or“operation mode”) the method as described herein.

The system, or apparatus, or device may execute an action in a“mode” or “operation mode” or“mode of operation”. Likewise, in a method an action or stage, or step may be executed in a“mode” or“operation mode” or“mode of operation”. The term“mode” may also be indicated as“controlling mode”. This does not exclude that the system, or apparatus, or device may also be adapted for providing another controlling mode, or a plurality of other controlling modes. Likewise, this may not exclude that before executing the mode and/or after executing the mode one or more other modes may be executed.

However, in embodiments a control system may be available, that is adapted to provide at least the controlling mode. Would other modes be available, the choice of such modes may especially be executed via a user interface, though other options, like executing a mode in dependence of a sensor signal or a (time) scheme, may also be possible. The operation mode may in embodiments also refer to a system, or apparatus, or device, that can only operate in a single operation mode (i.e.“on”, without further tunability).

Instead of the term“fused deposition modeling (FDM) 3D printer” shortly the terms“3D printer”,“FDM printer” or“printer” may be used. The printer nozzle may also be indicated as“nozzle” or sometimes as“extruder nozzle”.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

Figs la-lc schematically depict some general aspects of the 3D printer and of an embodiment of 3D printed material;

Figs. 2a-2e schematically depict some aspects of the item or item part;

Figs. 3a-3d schematically depict some further embodiments; and Fig. 4 schematically depict an application. The schematic drawings are not necessarily to scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Fig. la schematically depicts some aspects of the 3D printer. Reference 500 indicates a 3D printer. Reference 530 indicates the functional unit configured to 3D print, especially FDM 3D printing; this reference may also indicate the 3D printing stage unit.

Here, only the printer head for providing 3D printed material, such as an FDM 3D printer head is schematically depicted. Reference 501 indicates the printer head. The 3D printer of the present invention may especially include a plurality of printer heads (see below).

Reference 502 indicates a printer nozzle. The 3D printer of the present invention may especially include a plurality of printer nozzles, though other embodiments are also possible. Reference 320 indicates a filament of printable 3D printable material (such as indicated above). For the sake of clarity, not all features of the 3D printer have been depicted, only those that are of especial relevance for the present invention (see further also below).

Reference 321 indicates extrudate (of 3D printable material 201).

The 3D printer 500 is configured to generate a 3D item 1 by layer-wise depositing on a receiver item 550, which may in embodiments at least temporarily be cooled, a plurality of layers 322 wherein each layers 322 comprises 3D printable material 201, such as having a melting point T _m. The 3D printable material 201 may be deposited on a substrate 1550 (during the printing stage). By deposition, the 3D printable material 201 has become 3D printed material 202. 3D printable material 201 escaping from the nozzle 502 is also indicated as extrudate 321.

The 3D printer 500 may be configured to heat the filament 320 material upstream of the printer nozzle 502. This may e.g. be done with a device comprising one or more of an extrusion and/or heating function. Such device is indicated with reference 573, and is arranged upstream from the printer nozzle 502 (i.e. in time before the filament material leaves the printer nozzle 502). The printer head 501 may (thus) include a liquefier or heater. Reference 201 indicates printable material. When deposited, this material is indicated as (3D) printed material, which is indicated with reference 202.

Reference 572 indicates a spool or roller with material, especially in the form of a wire, which may be indicated as filament 320. The 3D printer 500 transforms this in an extrudate 321 downstream of the printer nozzle which becomes a layer 322 on the receiver item or on already deposited printed material. In general, the diameter of the extrudate 321 downstream of the nozzle 502 is reduced relative to the diameter of the filament 322 upstream of the printer head 501. Hence, the printer nozzle is sometimes (also) indicated as extruder nozzle. Arranging layer 322 by layer 322 and/or layer 322t on layer 322, a 3D item 1 may be formed. Reference 575 indicates the filament providing device, which here amongst others include the spool or roller and the driver wheels, indicated with reference 576.

Reference A indicates a longitudinal axis or filament axis. Reference C schematically depicts a control system, such as especially a temperature control system configured to control the temperature of the receiver item 550.

The control system C may include a heater which is able to heat the receiver item 550 to at least a temperature of 50 °C, but especially up to a range of about 350 °C, such as at least 200 °C.

Alternatively, or additionally, in embodiments the receiver plate may also be moveable in one or two directions in the x-y plane (horizontal plane). Further, alternatively or additionally, in embodiments the receiver plate may also be rotatable about z axis (vertical). Hence, the control system may move the receiver plate in one or more of the x-direction, y- direction, and z-direction.

Alternatively, the printer can have a head can also rotate during printing. Such a printer has an advantage that the printed material cannot rotate during printing.

Layers are indicated with reference 322, and have a layer height H and a layer width W.

Note that the 3D printable material is not necessarily provided as filament 320 to the printer head. Further, the filament 320 may also be produced in the 3D printer 500 from pieces of 3D printable material.

Reference D indicates the diameter of the nozzle (through which the 3D printable material 201 is forced).

Fig. lb schematically depicts in 3D in more detail the printing of the 3D item 1 under construction. Here, in this schematic drawing the ends of the filaments 321 in a single plane are not interconnected, though in reality this may in embodiments be the case. Reference H indicates the height of a layer. Layers are indicated with reference 203. Here, the layers have an essentially circular cross-section. Often, however, they may be flattened, such as having an outer shape resembling a flat oval tube or flat oval duct (i.e. a circular shaped bar having a diameter that is compressed to have a smaller height than width, wherein the sides (defining the width) are (still) rounded).

Hence, Figs la-lb schematically depict some aspects of a fused deposition modeling 3D printer 500, comprising (a) a first printer head 501 comprising a printer nozzle 502, (b) a filament providing device 575 configured to provide a filament 321 comprising 3D printable material 201 to the first printer head 501, and optionally (c) a receiver item 550. In Figs la-lb, the first or second printable material or the first or second printed material are indicated with the general indications printable material 201 and printed material 202, respectively. Directly downstream of the nozzle 502, the filament 321 with 3D printable material becomes, when deposited, layer 322 with 3D printed material 202.

Fig. lc schematically depicts a stack of 3D printed layers 322, each having a layer height H and a layer width W. Note that in embodiments the layer width and/or layer height may differ for two or more layers 322. Reference 252 in Fig. lc indicates the item surface of the 3D item (schematically depicted in Fig. lc).

Referring to Figs la-lc, the filament of 3D printable material that is deposited leads to a layer having a height H (and width W). Depositing layer 322 after layer 322, the 3D item 1 is generated.

During printing the 3D printed material cools. This cooling may be non- uniform over the 3D printed material of the item, especially when the item dimensions increase during printing. This ununiform cooling may result is ununiform shrinkage; this may lead to buckling/bulging. This can be prevented by increasing the wall width. This may however be undesirable. This means that when width gets larger the prints get too heavy and use a large amount of material. For this reason, amongst others a type of splitting the surface into smaller segments is suggested, in order to be able to use smaller thicknesses. However, the segments need to be mechanically“isolated” from each other so that shrinkage in segments can be considered to have no influence on each other. For the purpose of isolation of segments, amongst others the use of incaving’s parallel to the edges as shown in Figs. 2a, 2b and e.g. 3a.

Also, other options are proposed. For instance, another possibility is to increase the moment of inertia of area of side surfaces. This can be done by increasing the wall thickness considerably at especially at places where buckling would take place (see e.g. Fig. 2c). It is also possible to include structures which would make buckling difficult. Fig. 2d shows the effect of including V groves running parallel to the surface. It was found that e.g. including groves with a depth of 1=12 mm prevents the buckling of the walls with a thickness of 1.6 mm. In order to prevent buckling or to reduce it significantly herein various methods are proposed which can be used alternatively or in combination. These methods may amongst others involve bringing in incaving’s in the walls of the print, increasing the wall thickness locally and using structures in the wall which makes bending of the wall difficult.

Figs. 2a-2b schematically depict an embodiment of a 3D item 1 comprising 3D printed material 202. Fig. 2a is a (perspective) side view; fig. 2b is a top view or cross- sectional view. Hence, the cross-sectional area of one of the segments 410 may be height HI (see Fig. 2a) times the length of the axis of elongation A between an edge and the coupling partition (see Fig. 2b). The length of the axis of elongation A between an edge and the coupling partition in Fig. 2b is in fact the shortest distance between the left and the right edge, minus L3. Reference 1200 indicates an anti-buckling structure, i.e. a structure configured to reduce or prevent buckling (or bulging).

The 3D item 1 comprises a plurality of layers 322 of 3D printed material 202. Here, the 3D item 1 may comprise a wall or a shade, of which part is schematically depicted. The 3D item 1 comprises an item part 400, which is here schematically depicted.

In this embodiment, the item part 400 comprises two or more 3D printed segments 410 and one or more 3D printed coupling partitions 420. Each 3D printed segment 410 and each 3D printed coupling partition 420 comprising a plurality of parallel configured layers 322 of 3D printed material 202.

As schematically depicted, adjacent 3D printed segments 410 are functionally coupled via the 3D printed coupling partitions 420. Here, the anti-buckling structure 1200 is coupling partition 420. Hence, e.g. a decoupling groove may be applied as anti-buckling structure 1200.

The layers 322 of the two or more segments 410 provide a first layer width Wl, wherein the layers 322 of the one or more 3D printed coupling partitions 420 provide a second layer width W2.

In Fig. 2a the segments 410 have a length L2, which may be the same or which may be different. The segments have a height, which is here by way of example the same height as the height HI of the item.

As shown in Figs. 2a and 2b, the 3D printed coupling partition 420 is recessed (when seen from below in Fig. 2b) or protruded (when seen from above in Fig. 2b) relative to the respective adjacent 3D printed segments 410. The coupling partition 420 is an embodiment of an anti-buckling structure. The anti-buckling structure is indicated with reference 1200.

Reference w2’ indicates the depth of the recession or of the cavity at the other side of the protrusion.

The 3D printed coupling partitions 420 may be recessed or protrude relative to the respective adjacent 3D printed segments 410 with an extension width W3 (see Fig. 2b). Further, the 3D printed coupling partition 420 may have a third length L3 parallel to the respective adjacent 3D printed segments 410 and bridging a distance between the respective adjacent 3D printed segments 410. Especially, the extension width W3 is equal to or larger than the first layer width W 1. Further, the extension width W3 may also be larger than the third length L3.

In embodiments, the extension width W3 is selected from the range of 1-25 mm and wherein the third length L3 selected from the range of 0.3-10 mm, such as 0.3-5 mm.

Note that the first layer width W 1 may be provided by a single layer but may also be provided by two or more (individually printed) layers (see e.g. Fig. 3c).

In other embodiments, which may be combined with one or more of the previous described embodiments, the 3D printed coupling partition 420 has a larger second layer width W2 than the first layer width W1 of the respective adjacent 3D printed segments 410, see Fig. 2c where the illustrated cross-section is perpendicular to A axes this may be at one side of the segments 410 (see Fig. 2c, left partition 420) or may be at one side of the segments 410 (see Fig. 2c, right partition 420).

In embodiments, the second layer width W2 is larger than the first layer width W1 of the respective adjacent 3D printed segments 410. For instance, W2/W1>1.2. note that when there are more than one partitions 420, these do not necessarily all have the same dimensions. In other embodiments, two or more partitions may essentially have the same dimensions.

Fig. 2d schematically depict an embodiment (a cross sectional view of a segment 410) with corrugations.

Hence, the invention also provides embodiments of the 3D item 1 wherein the plurality of parallel configured layers 322 of 3D printed material 202 of one (or more) segment(s) 410 have axes of elongation A parallel to a first plane 430. As schematically depicted, one or more axes of elongation A are configured at one side of the first plane 430 and one or more other axes of elongation A are configured at another side of the first plane 430. Hence, in embodiments the segment 410 may comprise a corrugated segment structure, wherein the corrugated segment structure comprises corrugations 440 defined by the layers 322 with respective one or more axes of elongation A configured at one side of the first plane 430 and one or more other axes of elongation A configured at another side of the first plane 430.

The corrugations 440 are examples of anti-buckling structure(s) 1200.

Fig 2e schematically depicts in a single drawing a plurality of variants. In the upper part of the drawings, embodiments are schematically depicted wherein (the) one or more of the one or more 3D printed coupling partitions 420 protrude relative to the respective adjacent 3D printed segments 410 with a partition width W5. Hence, for generating such structure(s), the (herein described) method may comprise 3D printing the one or more of the one or more 3D printed coupling partitions 420 with the partition width W5, especially larger than the first layer width W1 of one or more of the respective adjacent 3D printed segments 410, Further, such method may comprises 3D printing the 3D item 1 on a receiver item (not shown, but e.g. perpendicular to the plane of drawing and parallel to W4)), wherein the one or more 3D printed coupling partitions 420 are arranged parallel to the receiver item. Here again, anti-buckling structures 1200 are shown wherein, by way of example, one is arranged at one side of the segment(s) 410, see the upper coupling partition, and wherein, by way of example, another one is arranged to protrude at both sides of the segment(s) 410. Effectively, anti -buckling structures 1200 are thickenings which separate adjacent 3D printed segments 410.

In the lower part of Fig. 2e, an embodiment is schematically depicted which may be the result of a method (further) comprising 3D printing the at least one segment 410 with a corrugated segment structure, wherein the corrugated segment structure comprises corrugations 440 defined by the layers 322 with respective one or more axes of elongation A (or axes A of elongation) (see also Fig. 2d) configured at one side of the first plane 430 and one or more other axes of elongation A configured at another side of the first plane 430. Such method may e.g. comprise 3D printing the 3D item 1 on a receiver item (see above), wherein the one or more corrugations 440 are arranged parallel to the receiver item.

In specific embodiments, the corrugations 440 define a total corrugation width W4 defined perpendicular to the first plane 430. Especially, a ratio of the corrugation width W4 to the first layer width W 1 may be W4/W 1>3.

Fig. 2e is an example of an embodiment where one or more of the one or more segments have one or more axes of elongation (A) of the layers configured at one side of a first plane and one or more other axes of elongation (A) are configured at another side of the first plane.

Fig. 3a schematically depict an embodiment of the 3D item 1 with one or more item parts 400, and with a plurality of segments 410 and partition 420. The cross-sectional area of e.g. the front right segment 410 may be the area of the perspective plane, which has height HI, and width length is delimited by the two adjacent partitions 420.

The item 1, and similar items, may e.g. be obtainable by a method comprising 3D printing the one or more of the one or more 3D printed coupling partitions 420 with the partition width W5 larger than the first layer width W1 of one or more of the respective adjacent 3D printed segments 410, wherein the method comprises 3D printing the 3D item 1 on a receiver item, wherein the one or more 3D printed coupling partitions are arranged parallel to a receiver item (not shown, but the item 3 may have been erected from such item with the lower part of item 1 resting on the receiver item).

Item 1 is an embodiment where one or more of the one or more segments have over the length and part of the width, or over the width and part of the length, or over part of the width and part of the length (one or more layers with) a second layer width (W2) or fifth layer width (W5), larger than the first layer width (Wl) of the remainder of the 3D printed segment.

Fig. 3b schematically depicts some embodiments of partitions and corrugations 420, bridging two segments 410.

Fig. 3c schematically depicts an embodiment of a segment-partition-segment arrangement. As shown, the partition 420 may also be considered a kind of a corrugation.

Fig. 3c also schematically depicts an embodiment wherein the first layer width Wl is defined by two individually printed layer 322, each having a width W.

Fig. 3d schematically depicted part of a possible 3D item 1, which clearly shows the layers structure of layers 322, which are used to define by 3D printing segments, 410, partitions 420, and corrugations 440.

Fig. 4 schematically depicts an embodiment of a lamp or luminaire, indicated with reference 2, which comprises a light source 10 for generating light 11. The lamp may comprise a housing or shade or another element, which may comprise or be the 3D printed item 1. Here, the half sphere (in cross-sectional view) schematically indicates a housing or shade. The lamp or luminaire may be or may comprise a lighting device 1000 (which comprises the light source 10). Hence, in specific embodiments the lighting device 1000 comprises the 3D item 1. The 3D item 1 may be configured as one or more of (i) at least part of a lighting device housing, (ii) at least part of a wall of a lighting chamber, and (iii) an optical element. Hence, the 3D item may in embodiments be reflective for light source light 11 and/or transmissive for light source light 11. Here, the 3D item may e.g. be a housing or shade. The housing or shade comprises the item part 400. For possible embodiments of the item part 400, see also above.

Amongst others, isolation of segments is herein proposed, such as by using incavings parallel to the edges. Such incavings also appear to improve or even solve the problem of warpage (where the corners of the printed object get curved away from the printing plate). The term“substantially” herein, such as“substantially consists”, will be understood by the person skilled in the art. The term“substantially” may also include embodiments with“entirely”,“completely”,“all”, etc. Hence, in embodiments the adjective substantially may also be removed. Where applicable, the term“substantially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. The term“comprise” includes also

embodiments wherein the term“comprises” means“consists of’. The term“and/or” especially relates to one or more of the items mentioned before and after“and/or”. For instance, a phrase“item 1 and/or item 2” and similar phrases may relate to one or more of item 1 and item 2. The term "comprising" may in an embodiment refer to "consisting of but may in another embodiment also refer to "containing at least the defined species and optionally one or more other species".

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

The devices herein are amongst others described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation or devices in operation.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "to comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. The invention also provides a control system that may control the apparatus or device or system, or that may execute the herein described method or process. Yet further, the invention also provides a computer program product, when running on a computer which is functionally coupled to or comprised by the apparatus or device or system, controls one or more controllable elements of such apparatus or device or system.

The invention further applies to a device comprising one or more of the characterizing features described in the description and/or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterizing features described in the description and/or shown in the attached drawings.

The various aspects discussed in this patent can be combined in order to provide additional advantages. Further, the person skilled in the art will understand that embodiments can be combined, and that also more than two embodiments can be combined. Furthermore, some of the features can form the basis for one or more divisional applications.

It goes without saying that one or more of the first (printable or printed) material and second (printable or printed) material may contain fillers such as glass and fibers which do not have (to have) influence on the on T _g or T _m of the material(s).