WO2021001392A1

WO2021001392A1 - Warpage free 3d prints

Info

Publication number: WO2021001392A1
Application number: PCT/EP2020/068445
Authority: WO
Inventors: Rifat Ata Mustafa Hikmet
Original assignee: Signify Holding B.V.
Priority date: 2019-07-02
Filing date: 2020-07-01
Publication date: 2021-01-07

Abstract

A method for producing a 3D item (1) by means of fused deposition modelling, the method comprising a 3D printing stage comprising layer-wise depositing an extrudate (321) comprising 3D printable material (201), to provide the 3D item (1) comprising 3D printed material (202), wherein the 3D item (1) comprises a plurality of layers (322) of 3D printed material (202), wherein during at least part of the printing stage the 3D printable material (201) is selected from the group comprising a first 3D printable material (1201) and a second 3D printable material (2201), and whereby the 3D printed material (202) is selected from the group comprising a first 3D printed material (1202) and a second 3D printed material (2202), respectively, wherein: • - the 3D printing stage comprises: (i) depositing first 3D printable material (1201) to provide first 3D printed material (1202) having a first height (hi); (ii) depositing on at least part of the first 3D printed material (1202) the second 3D printable material (2201) to provide second 3D printed material (2202) having a second height (h2); (iii) depositing on at least part of the second 3D printed material (2202) the first 3D printable material (1201) to provide first 3D printed material (1202); • - the second 3D printable material (2201) has a second glass transition temperature T_g2, and the first 3D printable material (1201) has one or more of a first glass transition temperature T_g1 and a first melting temperature T_m ₁, of which at least one is larger than said second glass transition temperature T _g2; and • - the first height (h1) is at maximum 2 cm.

Description

Warpage free 3D prints

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

According to WO2015/149054, 3D object printers, such as those which employ Fusion Deposition Modeling (FDM), are known. The printing process for such a device involves the deposition of printing material onto a printing platform, also referred to as a print bed. The deposited material may be melted into a pliable state, extruded through a heated nozzle and built up, layer by layer, until the final result is a 3D object. Because the layers are deposited in sequence on top of each other, print success and quality depend upon the ability to maintain registration of the object with the extruder nozzle throughout the duration of the print job to ensure that each stacked layer registers with the previous one. WO2015/149054 indicates that print success and quality may also depend upon adequate adhesion between the printed object and the print bed. Sometimes the first few layers of the printed object do not have sufficient adherence to the print bed, causing the printed object to shift, warp, or delaminate from the print bed, resulting in a failed or poor-quality printed object. The print beds for known FDM style 3D printers are typically made of metal, glass or acrylic. These print beds are not considered consumables, nor are they ideally suited to provide reliable surfaces on which the 3D printed objects can adhere solidly and consistently. Therefore, according to WO2015/149054 it is preferable to pretreat and/or cover the print bed surface of an FDM style 3D printer prior to printing an object so as to prevent damaging the print bed and to improve the likelihood that the printed object will adhere adequately to the print bed for the duration of the print. To this end, WO2015/149054 proposes a coated print bed for a 3D printer, comprising a permanent print-surface coating secured to a print bed substrate plate. The permanent print-surface coating provides an interface layer between a first layer of the applied plastic print material and the coated print bed, and that provides a high degree of adhesion of the applied plastic print material to the coated print bed. The permanent print-surface coating is selected to provide a level of adhesion sufficient for removal of the printed object at the end of the printing task. The permanent print-surface coating does not require the end user to apply anything additional to the surface of the print bed to begin printing.

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.

FDM printers use a thermoplastic filament, which is heated to its melting point and then extruded, layer by layer, to create a three-dimensional object. FDM printers are relatively fast and can be used for printing complicated objects. Warpage is an effect which is observed in FDM printed objects where the 3D printed item delaminates and becomes detached from the printing plate. For thin walled objects with a circular cross section, warpage may not be observed or may be observed to a lesser extent. However, during 3D printing massive or filled objects warpage is often observed. When thin walled non-circular object with straight/curved edges and/or elongated portions are used warpage is also often observed. The warpage problem is associated with the temperature gradient in the printer. In other words, during printing layers placed on top of one another do not all shrink to the same extent and this differential shrinking leads to bending of the layers which cause warpage (delamination). Shapes that should be straight, may thereby become curved or distorted. 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.

In order to solve the problem of warpage, it appears useful that the object needs to adhere to the to the platform (embodiment of a receiver item). For this purpose, it is herein suggested in embodiments to increase the temperature of the platform to a temperature above the glass transition temperature and/or above the melting temperature of the material used for printing. Alternatively, or additionally, measures may be taken so that instead delamination (warpage), deformations are induced within the print where the original shape is preserved. For this purpose, in embodiments at one or more places of the print, especially close to the heated platform, a polymer may be used with relatively lower glass transition temperature Tg than the Tg of the polymer used for printing the object. Alternatively, or additionally, it may be useful to the heat the sides of the object up to e.g. about 5 cm, such as 3 cm, above the platform.

Hence, in a first aspect the invention provides a method for producing a 3D item (“item” or“3D printed 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 a plurality of layers of 3D printed material, wherein during at least part of the printing stage the 3D printable material is selected from the group comprising a first 3D printable material and a second 3D printable material, and whereby (consequently) the 3D printed material is selected from the group comprising a first 3D printed material and a second 3D printed material, respectively. Especially, the 3D printing stage may comprises: (i) depositing first 3D printable material (on a receiver item) to provide first 3D printed material having a first height (hi); (ii) depositing on at least part of the first 3D printed material the second 3D printable material to provide second 3D printed material having a second height (h2); (iii) depositing on at least part of the second 3D printed material the first 3D printable material to provide first 3D printed material. In specific embodiments, the second 3D printable material has a second glass transition temperature T_g2, and the first 3D printable material has one or more of a first glass transition temperature T_gi and a first melting temperature T_mi, of which in specific embodiments at least one is larger than said second glass transition temperature T_g2. Yet further, especially the first height (hi) is in

embodiments at maximum 2 cm. Therefore, the invention especially 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 a plurality of layers of 3D printed material, wherein during at least part of the printing stage the 3D printable material is selected from the group comprising a first 3D printable material and a second 3D printable material, and whereby the 3D printed material is selected from the group comprising a first 3D printed material and a second 3D printed material, respectively, wherein (a) the 3D printing stage comprises: (i) depositing first 3D printable material to provide first 3D printed material having a first height (hi); (ii) depositing on at least part of the first 3D printed material the second 3D printable material to provide second 3D printed material having a second height (h2); (iii) depositing on at least part of the second 3D printed material the first 3D printable material to provide first 3D printed material; (b) the second 3D printable material has a second glass transition temperature T_g2, and the first 3D printable material has one or more of a first glass transition temperature T_gi and a first melting temperature T_mi, of which at least one is larger than said second glass transition temperature Tgi; and (c) the first height (hi) is at maximum 2 cm.

With such method, it appears that warpage may effectively be diminished or even completely prevented. Hence, in embodiments without substantial loss of desired item properties the shape of the 3D printed item may be more in conformance as designed. This may again be beneficial for the technical and/or esthetical properties of the 3D printed item.

As indicated above, the invention provides in an aspect 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 a plurality of layers of 3D printed material.

During the printing stage, at least two different types of 3D printable materials may be used. This (consequently) leads to at least two different types of 3D printed materials. In specific embodiments, on one or more layers of higher Tg or Tm printable material, are provided on a receiver item, which one or more layers may be indicated as first layer segment. On at least part of the first layer segment, one or more layers with a relatively lower Tg or Tm printable material is provided, which one or more layers may be indicated as second layer segment. This second layer segment may especially provide the anti-warpage effects and may e.g. be indicated as“warpage reducing layer” or“warpage preventing layer” or“anti-warpage layer”. Then, the remainder of the 3D printed item may be generated. This includes one or more layers of again higher Tg or Tm printable material, which one or more layers may herein be indicated as third segment.

Melting temperature may only apply to polymeric materials which are semi crystalline. Polymers which are in amorphous state after printing might have a melting temperature above Tg but in this (3D printing) application this may not be relevant.

Note that the anti-warpage layer may comprise a plurality of 3D printed layers (see also below). Further, the anti-warpage layer can be seen as a layer in the design of the 3D printed item, which is of another material than the remainder of the 3D printed item, and which is introduced for reducing or preventing warpage. For this reason, such second layer segment is especially configured relatively close to the receiver item. However, such anti- warpage layer is not provided directly on a receiver item as it may facilitate delamination from the receiver item. Hence, in general the 3D printable material for the first layer segment and second layer segment will in general be identical. However, this is not necessarily the case. At least, however, the 3D printable material for the first layer segment and second layer segment will be selected from the group of first 3D printable materials (as described herein), which have a higher Tg and/or Tm than the Tg (or Tm) of the second 3D printable material.

Herein the phrase“Tg or Tm of 3D printable material” and similar phrases especially refer to the Tg or Tm of the polymeric material of the 3D printable material (see (however) also below). Hence, the phrase“selected from the group comprising a first 3D printable material and a second 3D printable material” and similar phrases may also refer to being selected from the group comprising a first 3D printable material (selected from the group consisting of first 3D printable materials) and a second 3D printable material (selected from the group of second 3D printable materials). Hence, during at least part of the printing stage the 3D printable material is selected from the group comprising a first 3D printable material and a second 3D printable material. Hence, thereby the 3D printed material is selected from the group comprising a first 3D printed material and a second 3D printed material, respectively. Would there be other parts of the printing stage, then also other 3D printable material may be used. Such other parts of the printing stage may especially refer to parts (of the 3D printing stage) subsequent to the part of the 3D printing stage herein described. In specific embodiments, however, the 3D printing stage may essentially only include the herein described (i) depositing first 3D printable material to provide first 3D printed material having a first height (hi); (ii) depositing on at least part of the first 3D printed material the second 3D printable material to provide second 3D printed material having a second height (h2); (iii) depositing on at least part of the second 3D printed material the first 3D printable material to provide first 3D printed material.

Therefore, as indicated above the 3D printing stage comprises: (i) depositing first 3D printable material (on the receiver item) to provide first 3D printed material having a first height (hi). In this way the first layer segment is provided, which has a layer height hi. This first layer height is not necessarily everywhere the same; it may vary over the first layer segment. However, when the first layer segment is too high, the anti-warpage effect of the anti-warpage layer on (at least part of) the first layer segment may not be effective enough. Hence, in embodiments the first height (hi) is at maximum 2 cm, such as at maximum 1 cm. Especially, the first layer height is at least about 0.5 mm, such as at least about 1 mm, like in embodiments at least about 2 mm. The term“first layer segment” may also refer to a plurality of different, optionally adjacently configured, first layer segments.

In specific embodiments the first layer height may also include a bottom of the 3D printed item, which may have a height same as hi (i.e. the first layer height is defined by the bottom of the 3D item), but such bottom may also have a height which is a fraction of hi. Hence, the part of the 3D printing stage comprising depositing first 3D printable material (on the receiver item) may especially provide a base layer (with first height (hi or in

embodiments a fraction thereof)).

On at least part of this first layer segment, the second layer segment may be provided by 3D printing. In embodiments, as indicated above the 3D printing stage (further) comprises (ii) depositing on at least part of the first 3D printed material the second 3D printable material to provide second 3D printed material having a second height (h2). In this way, the second layer segment may be created. The height refers to the (absolute) layers height (and not relative to the receiver item). This second height is not necessarily

everywhere the same; it may vary over the second layer segment. However, when the second layer segment is too high, the anti-warpage may have not only anti-warpage effect but may also have undesired high impact on the mechanical properties of the 3D item. Hence, in embodiments the second height (h2) is at maximum 3 cm, such as at maximum 2 cm, such as at maximum 1 cm. Especially, the second height is at least about 0.5 mm, especially at least about 1 mm, such as at least about 2 mm, such as more especially at least about 5 mm, like at least about 10 mm. In embodiments, the second height (h2) may be selected from the range of 2-30 mm, such as 2-20 mm, such as from the range of 3-20 mm, like especially selected from the range of about 5-20 mm. The term“second layer segment” may also refer to a plurality of different, optionally adjacently configured, second layer segments.

After having printed the first layer segment and the second layer segment, only a relatively small part of the 3D item may have yet been printed. Hence, thereafter the remainder of the 3D item may be printed. As indicated above the 3D printing stage (further) comprises: (iii) depositing on at least part of the second 3D printed material the first 3D printable material to provide first 3D printed material.

As indicated above, the first 3D printable material of the third layer segment will in general be the same 3D printable material of the first layer segment. However, this is not necessarily the case. Consequently, the first 3D printed material of the third layer segment will in general be the same 3D printed material of the first layer segment. The term “third layer segment” may also refer to a plurality of different, optionally adjacently configured, third layer segments.

Hence, in embodiments a sandwich structure may be provided, wherein a first (relatively thin) layer segment (which may comprise one or more 3D printed layers of 3D printed material) and a third layer segment (which may comprise one or more 3D printed layers, but will in general comprise a plurality of 3D printed layers (especially (substantially) more than the first layer segment) of 3D printed material) sandwiches a second layer segment (which may comprise one or more 3D printed layers) of 3D printed material. The glass transition temperatures of the polymeric material in the first layer segment and third layer segment may each individually be higher than the glass transition temperature of the polymeric material of the second layer segment.

Note that a total height of the 3D item may thus be larger than the sum of the first height and the second height, even more especially is substantially larger (see further also below). However, especially the second 3D printable material has a second glass transition temperature T_g2, and the first 3D printable material has one or more of a first glass transition temperature T_gi and a first melting temperature T_mi, of which at least one is larger than said second glass transition temperature T_g2. Would the first 3D printable material of the third layer segment not be the same 3D printable material of the first layer segment, then the aforementioned conditions are defined in relation to the first 3D printable material of the third layer segment. In general, the third layer segment(s) provide the bulk of the mass of the 3D printed item, such as at least about 70 wt%, relative to the total weight of the 3D printed item, such as at least 80 wt%, or even at least 90 wt%.

The anti-warpage layer may be a layer that is over the entire first layer segment. In order words, all 3D printed material that is directly in contact with the receiver item (during the printing stage) comprises a first layer segment in physical contact with the receiver item and thereon the second layer segment. However, this is not necessary. In other embodiments, over (only) part of the earlier printed first 3D printed material the second 3D printable material may be provided (to provide second 3D printed material having a second height (h2)).

As indicated above, when the 3D printed item has an essentially circular cross- section (parallel to the receiver item), warpage may be low or even essentially absent.

However, when the 3D item includes (relatively thin) walls which are configured under an angle relative to each other, warpage may be an issue. Hence, especially when the 3D printed item has a polygonal cross-section (parallel to the receiver item) or a cross-section with at least two faces configured under an angle, warpage may be an issue, and the herein described invention may be of specific relevant. Hence, it may be desirable when the anti-warpage layer is at least present at edges. More especially, the second layer segment may include two or more parts configured under an angle (which is not 0° or 180°).

Therefore, in specific embodiments of the method, wherein the 3D item comprises an edge defined by at two or more adjacent 3D printed partitions, an edge part defined by adjacent parts of at least two of the two or more adjacent 3D printed partitions may comprise the second 3D printed material.

As indicated above, especially the second layer segment has a size that is enough to decrease or prevent warpage. The second layer prevents warpage by absorbing the deformation which would lead to bending and/or delamination. Likewise, when there is a plurality of second layer segments, the accumulate size is enough to decrease or prevent warpage. The above-indicated edge part may especially have an external area (Al) of at least 1 cm², such as at least 2 cm². Would for instance the edge part extends from one side of a wall to another side of the wall, the external surface at both sides is included in the external area (Al).

In general, the second layer segment may have an external area (Al) of at least 1 cm², such as at least 2 cm². Referring to the 3D printed item on the receiver item, within the first 3 (height) cm above the receiver item in the order of 1-80% of the external area of the 3D item (within these 3 cm from the receiver item) may be external area (Al) of the second layer segment, such as in the range of 5-80%, like 10-80%, such as 30-70%.

Further, it appears beneficial when not only the receiver item is heated, but when also the 3D printed material, especially the first few height centimeters above the receiver item are heated. In this way, warpage may also be prevented. Hence, in

embodiments the 3D printing stage may comprise layer-wise depositing the extrudate comprising 3D printable material on a receiver item, wherein the method may further comprise heating the receiver item at a first temperature Ti and/or at least part of the 3D printed material at a second temperature T2. In specific embodiments, Ti> T_g2-10°C, such as Ti> T_g2-5°C, such as Ti> T_g2, like especially T_g2£Ti< T_g2+20 °C. In embodiments, the method may (thus) further comprise heating at least part of the 3D printed material within the first 3 (height) cm above the receiver item, especially within the first 2 cm above the receiver item, at the second temperature T2. Further, in specific embodiments T2> T_g2-10°C, such as T2> T_g2-5°C, like T2> T_g2_, especially T_g2£T2< T_g2+20 °C. The temperature T2 may especially refer to (at least) the temperature of the surface of the 3D printed material. In specific embodiments, Ti> T_gi and/or T2> T_g2. Therefore, in embodiments the method may further comprise heating the receiver item at a first temperature Ti and at least part of the 3D printed material at a second temperature T2, wherein one or more of the following applies (especially both): (i) Ti> T_gi and (ii) T2> T_g2, wherein at least part of the 3D printed material within the first 3 cm above the receiver item is heated at the second temperature T2. For instance, in the case of PET with a glass transition temperature of about 80 °C the temperature in the region of PET may then need to be higher than about 80 °C. In the case of ABS with a glass transition temperature of about 100 °C then the temperature in the region of ABS may need to be higher than about 100 °C.

In embodiments, the first 3D printable material may have a first glass transition temperature (T_gi), which can be any glass transition temperature, but especially in the range of about 100-350 °C. In the case of a crystallizing material then it is the melting temperature T_m which is important rather than the glass transition temperature of the first material. Hence, the first 3D printable material may thus also have a melting temperature, herein further especially indicated as first melting temperature (T_mi). Therefore, in embodiments the first 3D printable material has a first melting temperature (T_mi), which can be any melting temperature, but especially in the range of about 100-350 °C. Therefore, the phrase“the first 3D printable material has one or more of a first glass transition temperature (T_gi) and a first melting temperature (T_mi)” may especially relate to embodiments wherein the first 3D printable material only has a glass transition temperature and not a melting temperature and to embodiments wherein the first 3D printable material has both a glass transition temperature and a melting temperature.

Further, in embodiments the first glass transition temperature or the first melting temperature, whichever is higher, is at least higher than the second glass transition temperature. Hence, the second 3D printable material has a second glass transition temperature (T_g2) and the first 3D printable material has one or more of a first glass transition temperature (T_gi) and a first melting temperature (T_mi) of which at least one is larger than said second glass transition temperature (Tgi). Hence, in embodiments wherein the first 3D printable material comprises polymeric material having a first glass transition temperature and a melting temperature, the melting temperature will be larger than the second glass transition temperature, though the first glass transition temperature may be smaller or larger than the second glass transition temperature. Hence, herein the phrase“wherein the first 3D printable material has one or more of a first glass transition temperature (T_gi) and a first melting temperature (T_mi), of which at least one is larger than said second glass transition temperature (T_g2),” and similar phrases are used.

In specific embodiments, at least the first glass transition temperature is at least higher than the second glass transition temperature. For instance, ABS may be used as first 3D printable material and PET may be used as second 3D printable material. Or, PC may be used as first 3D printable material, and PET or ABS may be used as second 3D printable material. Of course, other combinations may also be possible.

In specific embodiments, the difference between the second glass transition temperature (¾) and the one or more of the first glass transition temperature (T_gi) and the first melting temperature (T_mi) is at least 10 °C, such as at least 20 °C, especially at least 25 °C, such as at least 30 °C, even more especially a difference selected from the range of 10-150 °C, like 20-100 °C. Hence, especially the first melting temperature (T_mi) is at least 10 °C, such as at least 20 °C, especially at least 25 °C, such as at least 30 °C, larger than the second glass transition temperature (Tgi), especially in embodiments wherein the first 3D printable material comprise a (semi-)crystalline polymeric material. Alternatively or additionally, the first glass transition temperature (T_gi) is at least 10 °C, such as at least 20 °C, especially at least 25 °C, such as at least 30 °C, larger than the second glass transition temperature (T_g2).

The method further includes maintaining the receiver item during at least part of the printing stage at a receiver item temperature (Ti) of at least the second glass transition temperature (¾) and below one or more of the first glass transition temperature (T_gi) and the first melting temperature (T_m). Assuming the first 3D printable material to be essentially amorphous polymeric material, the receiver item temperature is below the first glass transition temperature. Assuming the first 3D printable material to be essentially (semi-) crystalline polymeric material, the receiver item temperature is at least below the first melting temperature, and optionally below the first glass transition temperature. When the receiver item temperature is below the first glass transition temperature (and at least the second glass transition temperature), the receiver item temperature is thus in general also below the first melting temperature.

Especially, the receiver item is maintained at a temperature of at least 5 °C larger than the second glass transition temperature, such as in the range of 5-30 °C larger than the second glass transition temperature. However, the receiver item may also be maintained at a temperature just below the second glass transition temperature, such as up to 5 °C below the second glass temperature, such as up to 2 °C below the second glass temperature.

As indicated herein, the temperature of the receiver item may in embodiments be kept lower than one or more of the first glass transition temperature and the first melting temperature, such as at least 5 °C lower than the first glass transition temperature or the first melting temperature, such as at least 10 °C lower than the first glass transition temperature or the first melting temperature. Especially, the temperature of the receiver item may in embodiments be kept lower than the first glass transition temperature, such as at least 5 °C lower than the first glass transition temperature, such as at least 10 °C lower than the first glass transition temperature.

In this way, a good basis of the 3D printed item is created, which adheres to the receiver item and which may not substantially suffer from an elephant foot. Especially, the receiver item is kept at the receiver item temperature (Ti) of at least about the second glass transition temperature (¾) during the entire initial and main printing stage. The phrase “maintaining the receiver item during at least part of the printing stage at a receiver item temperature (Ti) of at least the second glass transition temperature (T_g2)” and similar phrases especially indicate that the surface at which the printable material is deposited is kept at the indicated receiver item temperature (Ti).

The second printable material and first printable material may be essentially different, i.e. having different chemical compositions, but may also substantially be the same. In the latter embodiment, one or more of the second printable material and the first printable materials may include one or more of additives or modifications which provide the different physical (and chemical) properties. Hence, even when the Tg (or Tm) of the polymeric materials of the different 3D printable material is essentially the same, the Tg (or Tm) of the different 3D printable material may be different.

Hence, in embodiments the second printable material comprises PET and the first printable material comprises PC. In yet other embodiments, the second printable material comprises PET and the first printable material comprises polysulfone. In yet another embodiment the second printable material comprises PC and the first printable material comprises modified PC (e.g. APEC 1895 (from Covestro with a Tg of 183°C)). In yet another embodiment the second printable material comprises PET and the first printable material comprises modified PMMA.

In yet further embodiments, the second printable material comprises a second polymeric material and the first printable material comprises (essentially) the same polymeric material, and wherein one or more of (i) the second printable material comprises a glass transition temperature reducing additive, and (ii) the first printable material comprises a glass transition temperature increasing additive, applies. In such embodiments, the second printable material and first printable material may include the same type of polymers, but one or more of the second and the first printable material includes and additive, such as another polymer, that modifies the glass transition temperature. Such an additive may be a plasticizer; a solvent with high boiling point such as dimethyl phthalate.

In yet further embodiments, the second printable material comprises a second polymeric material and the first printable material comprises (essentially) the same polymeric material, and wherein one or more of (i) the second printable material comprises a glass transition temperature reducing functional group, and (ii) the first printable material comprises a glass transition temperature increasing functional group, applies. Hence, though e.g. the second printable material and first printable material may have the same backbones, due to the presence of (different) functional groups on one (or both) of the polymer(s), the second and first printable materials may have different glass transition temperatures.

Examples may e.g. include methyl methacrylate with T_g of 105°C versus ethyl methacrylate with T_g of 65 °C.

Hence, in embodiments the second printable material may comprise PET and the first printable material may comprise PC. Alternatively (or additionally) the second printable material may comprise ABS and the first printable material may comprise PC. Alternatively (or additionally), the first printable material comprises PC and the second printable material comprises a modified PC with a glass transition temperature (Tg) lower than PC. Alternatively (or additionally), the first printable material comprises PC and the second printable material comprises PMMA. Alternatively (or additionally), the second printable material may comprise ABS and the first printable material may comprise PET.

In yet further embodiments, the second printable material comprises a second polymeric material and the first printable material comprises a first polymeric material, wherein the second polymeric material and the first polymeric material comprise identical chemical groups, and wherein one or more of the following applies:

(i) the second printable material and the first printable material comprise the same polymeric material, and the second printable material comprises a glass transition temperature reducing additive;

(ii) the second printable material comprises a copolymer of the first polymeric material having a lower glass transition temperature than one or more of the first glass transition temperature (T_gi) and the first melting temperature (T_m);

(iii) the second printable material and the first printable material comprise the same polymeric material, wherein the second printable material comprises a blend of polymers, the blend having a lower glass transition temperature than one or more of the first glass transition temperature (T_gi) and the first melting temperature (T_m); and (optionally);

(iv) the second printable material and the first printable material comprise the same polymeric material, and the first printable material comprises a glass transition temperature increasing additive.

Especially, in embodiments the polymeric material of the first printable material and of the second printable material are miscible. Polymers which are miscible can be mixed on a molecular level. When mixed together they do essentially not become phase separated. Hence, at a temperature above the glass temperatures of the polymeric materials the polymeric materials may mix. This may facilitate adhesion between the layers. Therefore, at the printing temperature, i.e. the temperature of the layer (directly) under the nozzle, especially at or above the highest glass temperature (or at or above the highest melting temperature), such materials may be miscible. Hence, in embodiments the 3D printable materials may be miscible at the printing temperature.

In yet a further aspect, the invention also provides 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 on a receiver item, to provide the 3D item comprising 3D printed material, wherein the 3D item comprises a plurality of layers of 3D printed material, wherein the 3D printable material has a glass temperature T_g, wherein the method further comprise heating the receiver item at a first temperature Ti and/or at least part of the 3D printed material at a second temperature T2. In specific embodiments, Ti> T_g-10°C, such as Ti> T_g-5°C, like especially T_g<Ti< T_g+20 °C. In embodiments, the method may (thus) further comprise heating at least part of the 3D printed material within the first 3 (height) cm above the receiver item, especially within the first 2 cm above the receiver item, at the second temperature T2. Further, in specific embodiments T2> T_g-10°C, such as T2> T_g-5°C, like especially T_g<T2£ T_g+20 °C. In specific embodiments, Ti> T_gi and/or T2> T_g2. In specific embodiments, Ti> T_gi and/or T2> T_g2. Therefore, in embodiments the method may further comprise heating the receiver item at a first temperature Ti and at least part of the 3D printed material at a second temperature T2, wherein one or more of the following applies (especially both): (i) Ti> T_gi and (ii) T2> T_g2. Especially, in embodiments (see also above) at least part of the 3D printed material within the first 3 cm above the receiver item, such as within the first 2 cm above the receiver item, is heated at the second temperature T2.

In embodiments, the method(s) as defined above may (further) comprise controlling the first temperature Ti and the second temperature T2 individually. For instance, during at least part of the printing stage the second temperature T2 may be larger than the first temperature Ti. Hence, a control system (see also below) may be configured to control first temperature Ti and the second temperature T2 individually. The temperature of the receiver item may be controlled with methods known in the art, like resistance heating, though other methods may alternatively or additionally also be applied. The second temperature may in embodiments be controlled by applying one or more of IR radiation and (hot) gas supply, such as (hot) air, though other methods may alternatively or additionally also be applied. Hence, in embodiments the method may involve increasing the temperature of the receiver item to a temperature above the glass transition temperature and/or above the melting temperature of the 3D printable material used for printing (see also above). The invention described herein, like the methods as described above, may especially be useful for 3D items having a cross-section (parallel to the receiver item) that is essentially not circular. Hence, in embodiments wherein the 3D item may have an essentially planar item face part and would a cross-section of such 3D item parallel to the planar item face part be essentially non-circular, like e.g. having a polygonal shape, then especially the invention may be relevant.

The term“polymeric material” 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.

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 polyolefin based elastomers, styrene based elastomers, etc.. Optionally, the 3D printable material comprises a 3D printable material selected from the group consisting of Lirea 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 polyolefin 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(m ethyl 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 actions 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. Hence, in an aspect the invention (thus) provides a software product, which, when running on a computer is capable of bringing about (one or more embodiments of) the method (for producing a 3D item by means of fused deposition modelling) 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 printed material is selected from the group comprising a first 3D printed material and a second 3D printed material, wherein the 3D item comprises an item face, wherein the item face comprises an item face part, wherein the 3D item comprises an item part, wherein the item part comprises a stack of (i) a first layer segment comprising one or more layers of first 3D printed material having a first height (hi), (ii) a second layer segment comprising one or more layers of second 3D printed material having a second height (h2), and (iii) a third layer segment comprising one or more layers of first 3D printed material. Especially, in embodiments the second 3D printed material has a second glass transition temperature T_g2, and the first 3D printed material has one or more of a first glass transition temperature T_gi and a first melting temperature T_mi, of which at least one is larger than said second glass transition temperature T_g2. Further, in specific embodiments the first height (hi) is at maximum 2 cm, such as at maximum 1 cm. Yet further, of the stack of the first layer segment, the second layer segment, and the third layer segment, the third layer segment is configured most remote from the item face part. Hence, especially the invention provides (embodiments of the) 3D item comprising 3D printed material, wherein the 3D item comprises a plurality of layers of 3D printed material, wherein the 3D printed material is selected from the group comprising a first 3D printed material and a second 3D printed material, wherein the 3D item comprises an item face, wherein the item face comprises an item face part, wherein the 3D item comprises an item part, wherein the item part comprises a stack of (i) a first layer segment comprising one or more layers of first 3D printed material having a first height (hi), (ii) a second layer segment comprising one or more layers of second 3D printed material having a second height (h2), and (iii) a third layer segment comprising one or more layers of first 3D printed material; wherein: (a) the second 3D printed material has a second glass transition temperature T_g2, and the first 3D printed material has one or more of a first glass transition temperature T_gi and a first melting temperature T_mi, of which at least one is larger than said second glass transition temperature T_g2; (b) the first height (hi) is at maximum 2 cm; and (c) of the stack of the first layer segment, the second layer segment, and the third layer segment, the third layer segment is configured most remote from the item face part. The item face and item face part herein, especially refer to that part of the face of the 3D printed item (not taking into account a possible coating) that was configured closest, or even on, the receiver item during 3D printing. Hence, this part of the face of the item may in embodiments be essentially flat.

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, like at least 100 pm, such as 200-2500 pm, like at least 200 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

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. Note that the first layer segment may define the item face part. However, as at least part of the 3D printed item may also comprise a coating, a coating may be available on the first layer segment.

Further, the terms height in relation to the segments is based on the above description in relation to the method, wherein the 3D item is produced on the receiver item which is in general configured horizontal. However, the 3D item per se is herein described irrespective of its position in space. However, for the sake of understanding, the thicknesses of these layer segments are indicated with heights.

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 a difference between the second glass transition temperature (Tgi) and the one or more of the first glass transition temperature (T_gi) and the first melting temperature (T_mi) is at least 10 °C, such as at least 20 °C, and wherein the second 3D printed material comprises amorphous polymeric material.

Further, as indicated above in specific embodiments, second 3D printed material comprises PET and wherein the first 3D printed material comprises PC, or wherein the second 3D printed material comprises ABS and wherein the first 3D printed material comprises PC.

In yet further embodiments, the item face part is planar. This may be due to the fact that the 3D item is deposited layer by layer on the receiver item, which is in general essentially flat (i.e. planar). Hence, the face part may be planar. As indicated above, the face part may be defined by a coating on the first layer segment or may be defined by the first layer segment.

As indicated above, in embodiments the first height (hi) is at maximum 1 cm, and wherein the second height (h2) is selected from the range of 2-30 mm, such as especially 5-20 mm.

Further, as also indicated above the 3D item may comprise an edge defined by at two or more adjacent 3D printed partitions, wherein an edge part defined by adjacent parts of at least two of the two or more adjacent 3D printed partitions comprises the second 3D printed material. In specific embodiments (see also above), the edge part has an external area (Al) of at least 0.5 cm², such as especially at least 1 cm², like in specific embodiments at least 2 cm². As indicated above, in general, the second layer segment may have an external area (Al) of at least 1 cm², such as at least 2 cm². Referring to the 3D printed item on the receiver item, within the first 3 (height) cm above the receiver item in the order of 1-80% of the external area of the 3D item (within these 3 cm from the receiver item) may be external area (Al) of the second layer segment, such as in the range of 5-80%, like 10-80%, such as 30-70%. Note that the external array may (at least partly) be provided with a coating.

Warpage may also be reduced by reducing the length of walls configured perpendicular to the receiver item. For instance, a long wall may also be divided in wall parts, separated by recession or protrusion configured perpendicular to the receiver item. Hence, amongst others, isolation of segments is herein also 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).

Hence, the invention also 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).

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. 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 in embodiments sequentially with a single printer head or with two or more printer heads.

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, in embodiments sequentially with a single printer head or with two or more printer heads.

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-2d schematically depict some embodiments;

Fig. 3 schematically depict some embodiments (of the method); and

Fig. 4 schematically depicts 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.

Warpage is an effect which is observed in FDM printed objects where the print delaminates and becomes detached from the printing plate as shown in Fig. 2a. Here, it is seen that the bottom of the device 1 is curved, such that the height relative to the receiver item, indicated with reference hw is at some positions, especially at the edges, indicated with reference 450, is non-zero. References 451 indicate 3D printed partitions, here the walls, that define the edges 450. Hence, without additional measures, a well-developed 3D design may lead to a device that is deformed due to warpage.

The warpage problem may especially be associated with the temperature gradient in the printer. The lower layer(s) of 3D printed material 302 close to the receiver item have a higher temperature than the upper layers, and the temperature gradient may be largest close to the receiver item. For example, when the temperature on the receiver item is about 170°C, 1 cm above the receiver item the temperature on the 3D item 1 may there be about 120°C; 2 cm above the receiver item the temperature of the 3D item 1 may have already dropped to about 100°C. The temperature of 3D printed material was measured as function of height, and it appeared that especially within first 10 mm above the receiver item there is a large drop in temperature. This means that during printing as layers are placed on top of each other the top layer shrinks to a larger extent causing the warpage. In a simple bilayer model shown we assume top layer shrinking to a larger extent than the layer below it then it can wrap upwards. A schematic representation of a real 3D printed product is shown in Fig. 2a. As hw is non-zero, there is warpage.

Simulations were executed as function of the height of the 3D printed item (over the receiver item). It was observed that when the height of the object is few mm there is substantially no warpage. When the height of the object becomes around 1 cm warpage may be observed as the temperature may drop below the glass transition temperature of the material. When the height of the object becomes larger no further warpage takes place.

In order to solve the problem of warpage, it seems desirable that the object adheres to the to the receiver item. For this purpose, amongst others it is herein suggested to increase the temperature of the receiver item to a temperature above the glass transition temperature and/or the melting temperature of the material used for printing. Furthermore, measures are suggested to reduce delamination and to allow deformation such that the original shape is of the 3D printed item is preserved.

Fig. 2b very schematically depicts an embodiment of the method for producing a 3D item 1 by means of fused deposition modelling as described herein. The method comprises a 3D printing stage comprising layer-wise depositing an extrudate 321 comprising 3D printable material 201, to provide the 3D item 1 comprising 3D printed material 202.

The 3D item 1 comprises a plurality of layers of 3D printed material 202.

Here, very schematically the generation of essentially only three layers is schematically depicted. However, each segment may comprise a plurality of 3D printed layers (see also Fig. 2c).

During at least part of the printing stage the 3D printable material 201 is selected from the group comprising a first 3D printable material 1201 and a second 3D printable material 2201, and whereby the 3D printed material 202 is selected from the group comprising a first 3D printed material 1202 and a second 3D printed material 2202, respectively. The 3D printing stage comprises depositing first 3D printable material 1201 to provide first 3D printed material 1202 having a first height hi. The 3D printing stage further comprises depositing on at least part of the first 3D printed material 1202 the second 3D printable material 2201 to provide second 3D printed material 2202 having a second height h2. Note that by way of example, not all first 3D printed material that was provided with height hi is subsequently deposited with the second 3D printable material 2201; part of it is also deposited subsequently with the (same) first 3D printable material 1201. The 3D printing stage also comprises depositing on at least part of the second 3D printed material 2202 the first 3D printable material 1201 to provide first 3D printed material 1202.

Especially, the second 3D printable material 2201 has a second glass transition temperature T_g2, and the first 3D printable material 1201 has one or more of a first glass transition temperature T_gi and a first melting temperature T_mi, of which at least one is larger than said second glass transition temperature T_g2 of the second material.

Especially, the first printable material is compatible with the second printable material meaning that they may mix at the temperature of printing. This is desirable as a good adhesion between the (3D printed) is desirable. It is also desirable that the second 3D printable (or printed) material has a T_g2 which is lower than the temperature T2 in region I12.

The first height hi may be at maximum 2 cm, such as at maximum 1 cm. The second height h2 may be selected from the range of 2-30 mm, such as 5-20 mm.

Note that the same printer head can be used. However, also different printer heads may be used.

With the solution proposed in Fig. 2c (top drawing), warpage may be reduced, as shown with hw being zero. The inventors were able to 3D printed boxes like depicted without warpage, as the anti-warpage layer absorbed potential warpage. The boxed had bottoms.

An enlargement of part of one of the sides is shown in Fig. 2c (lower drawing). Here, it is shown that the anti-warpage layer segment with height h2 absorbs the deformation, by which the 3D item maintains its shape. Note that by way of example each of the first, second and third segments 436,437,438 comprise a plurality of layers 322. However, this is not necessarily always the case; further, the number of layers chosen is only for schematic purposes.

Fig. 2c schematically depicts an embodiment of a 3D item 1 comprising 3D printed material 202, wherein the 3D item 1 comprises a plurality of layers 322 (see also inset) of 3D printed material 202. The 3D printed material 202 is selected from the group comprising a first 3D printed material 1202 and a second 3D printed material 2202. The 3D item 1 comprises an item face 110, wherein the item face 110 comprises an item face part 111. This may be the bottom side or bottom face of the item 1.

Further, the 3D item 1 comprises an item part 431, wherein the item part 431 comprises a stack 435 of (i) a first layer segment 436 comprising one or more layers 322 of first 3D printed material 1202 having a first height hi, (ii) a second layer segment 437 comprising one or more layers 322 of second 3D printed material 2202 having a second height h2, and (iii) a third layer segment 438 comprising one or more layers 322 of first 3D printed material 1202 or another material which may have a good miscibility with first 3D printed (or printable) material.

As indicated above, the second 3D printed material 2202 may have a second glass transition temperature T_g2, and the first 3D printed material 1202 has one or more of a first glass transition temperature T_gi and a first melting temperature T_mi, of which at least one is larger than said second glass transition temperature T_g2. Further, especially the first height hi is at maximum 2 cm. As indicated above, in embodiments the first height hi may be at maximum 1 cm. In embodiments, the second height h2 may be selected from the range of 2- 30 mm, such as especially 5-20 mm. The total height is indicated with h4.

As schematically depicted, of the stack 435 of the first layer segment 436, the second layer segment 437, and the third layer 438, it is the third layer segment 438 that is configured most remote from the item face part 111. Hence, the first layer segment 436 may define the item face part 111. However, as the 3D item may also be coated, a coating on the first layer segment 436 may defined item face part 111. Here, in the schematic drawing no coating is depicted.

The embodiments according to the invention may provide an item face part 111 that is planar, in contrast to the version schematically depicted in Fig. 2a.

Fig. 2d schematically depicts an embodiment on the left side similar to the embodiment schematically depicted in Fig. 2c. On the right side, another embodiment is schematically depicted wherein only on part of the first 3D printed material 1202 the second 3D printable material was deposited to provide second 3D printed material 2202.

The 3D item 1 comprises an edge 450 defined by at two or more adjacent 3D printed partitions 451, here the walls of the 3D item which are configured under an angle of 90°. An edge part 461, defined by adjacent parts 462 of at least two of the two or more adjacent 3D printed partitions 451, comprises the second 3D printed material 2202. In embodiments, the edge part 461 may have an external area A1 which may especially be about 0.5*2* length of the side (in cm) cm², or of at least 1 cm². Referring to the edge part 461 indicated with reference 46 , the external area A1 may be the sum of the external area at the outside (as presently viewed), but also at the inside of the 3D item, which has a box shape. Hence, for a side with length 5 cm, the desired external A1 may be about 5 cm².

Fig. 3 schematically depicts embodiments of the method wherein the 3D printing stage comprises layer-wise depositing the extrudate 321 comprising 3D printable material 201 on a receiver item 550, wherein the method may further comprise heating the receiver item 550 at a first temperature Ti and/or at least part of the 3D printed material 202 at a second temperature T2. In this embodiment it is not necessary to use two different materials and warpage can be accommodated in the same material, see lower drawing.

Heating of the 3D printed material 202 may be executed with a heating device 570, which may provide hot air and/or IR radiation especially at a point above the printing plate. In embodiments where single material is used, see lower drawing, in embodiments Ti> T_gi and/or in embodiments T2>T_gi. In embodiments with two materials, see upper embodiment (like Fig. 2b, bottom drawing) especially in embodiments Ti> T_gi and/or in embodiments T₂> T_g2.

Especially, at least part of the 3D printed material 202 within the first 3 cm above the receiver item 550 is heated at the second temperature T2. The height over the receiver item 550 is indicated with h5.

Hence, in the areas where warpage would be observed a material may be used with a lower glass transition temperature than the material used for printing the rest of the object. For example, when a box with flat sides and a bottom is printed using a polycarbonate (Tg=145°C) warpage was observed at the comers of the object (see Fig. 2a). Hence, as indicated above it is herein suggested to use polymer with a lower Tg in the regions of the object close to the build plate. The positions of these areas are chosen such that the temperature is around the glass transition temperature of the second material. Due to lower transition temperature in these areas they become deformed but stay flat instead getting detached. In these areas deposited layers which would normally ran parallel to each other fan out. Figs. 2c and 3 shows schematically where low glass transition material can be included, such as edge parts 461.

Also, an example was created wherein PC with a Tg of 145 °C is used to print a box, where PET with a Tg of 80 °C is used as second 3D printable material / 3D printed material. PET is very suitable because in the h2 regions the surface temperature T2 was 100°C thus material with a T_g2 lower than 100°C. In Fig. 2d (but also Fig. 2c) it can be seen that instead of inducing warpage the fanning out deformation takes place in the areas where PET is used avoiding delamination. Furthermore, PC and PET are polymers which can be mixed thus they have good layer adhesion with each other.

As indicated above, another possibility is to print the bottom of the object using two different materials with two different glass transition temperatures. Higher glass transition temperature is used to print the upper and lower layers and the layers in between are printed using material with a lower glass transition temperature which may also be lower than the temperature at least part of region h2 as shown in Fig. 2c. Warpage can then be compensated by the deformation in the layer with a lower transition temperature, in the bottom layer. In this way footprint of the object remains not altered.

In an example, PC was used to print a box and polystyrene was used as the low Tg material in the bottom of the box. Fig. 2c shows the bottom which remains rectangular together with the cross-section of the bottom layer where the deformation took place. It is also possible to compensate for any irregular deformation effects during the design of the object.

As indicated above, another possibility for inducing deformation in the side walls for avoiding warpage induced delamination is to heat up the side walls close to the building stage to around the glass transition of the polymer. Heating can be induced either remotely by IR or by placing extra heating elements around the area where the printing of the object would take place.

Very schematically, Fig. 3 shows configurations which can be used for extra heating of the side walls above the building plate.

In an experiment, in order to induce deformation in the walls and avoid warpage induce deformation we heated the side walls of a box and printed the walls of the just above building plate (1 cm high (h5)) to be thinner than the rest of the object. The result is was also that warpage was prevented.

Hence, warping is a type of deformation that may cause the corners of a printed object to lift and detach from the building platform. Typically, no warping is observed up until a height of around a centimeter is reached, and when the layer stack becomes even higher no further warping takes place. Warping may be prevented by ensuring that the printed object adheres to the building platform. In a first solution the following is proposed: use a first printing material with a first glass transition temperature and a second printing material with a second glass transition temperature, the second glass transition temperature being lower than the first glass transition temperature. During printing the building platform has a temperature that may be above the first glass transition temperature. The object may be printed using the first printing material, except for regions of the object where warping would occur. These regions are printed with the second printing material. For example, when the printed object is a box with flat sides made of polycarbonate, warping would typically occur at the corners of the box when the sides of the box have reached a certain minimum height. To prevent such warping, PET may e.g. be used to print these comer regions.

Alternatively, in a second solution the following is proposed: use only one printing material and heat the side walls close to the building platform to around the glass transition temperature of the printing material. Heating can be done either remotely by infrared radiation or by placing extra heating elements around the area where printing of the object takes place. Additionally, one can print the walls just above the building platform such that they are thinner than the rest of the object.

Of course, the second solution can also be combined with the first solution where at least two different 3D printable materials are used.

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.

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).

Claims

CLAIMS:

1. A method for producing a 3D item (1) by means of fused deposition modelling, wherein the 3D item (1) comprises a plurality of layers (322) of a 3D printed material (202), and an edge (450) defined by two adjacent 3D printed partitions (451), wherein the method comprising a 3D printing stage comprising layer-wise depositing an extrudate (321) comprising a 3D printable material (201), wherein during at least part of the printing stage the 3D printable material (201) is selected from the group comprising a first 3D printable material (1201) and a second 3D printable material (2201), and whereby the 3D printed material (202) is selected from the group comprising a first 3D printed material (1202) and a second 3D printed material (2202), respectively, wherein:

the 3D printing stage comprises: (i) depositing first 3D printable material (1201) to provide first 3D printed material (1202) having a first height (hi); (ii) depositing on at least part of the first 3D printed material (1202) the second 3D printable material (2201) to provide second 3D printed material (2202) having a second height (h2); (iii) depositing on at least part of the second 3D printed material (2202) the first 3D printable material (1201) to provide first 3D printed material (1202);

the second 3D printable material (2201) has a second glass transition temperature T_g2, and the first 3D printable material (1201) has one or more of a first glass transition temperature T_gi and a first melting temperature T_mi, of which at least one is larger than said second glass transition temperature ¾;

the first height (hi) is at maximum 2 cm, and

an edge part (461) defined by adjacent parts (462) of the two adjacent 3D printed partitions (451) comprises the second 3D printed material (2202).

2. The method according to claim 1, wherein the first height (hi) is at maximum 1 cm, wherein the second height (h2) is selected from the range of 2-30 mm.

3. The method according to claim 1, wherein the edge part (461) has an external area (Al) of at least 1 cm².

4. The method according to any one of the preceding claims, wherein the 3D printing stage comprises layer-wise depositing the extrudate (321) comprising 3D printable material (201) on a receiver item (550), wherein the method further comprise heating the receiver item (550) at a first temperature Ti and at least part of the 3D printed material (202) at a second temperature T2, wherein Ti> T_gi and wherein T2> T_g2, wherein at least part of the 3D printed material (202) within the first 3 cm above the receiver item (550) is heated at the second temperature T2.

5. The method according to any one of the preceding claims, wherein a difference between the second glass transition temperature T_g2 and the one or more of the first glass transition temperature T_gi and the first melting temperature T_mi is at least 20 °C, and wherein the second 3D printable material (2201) comprises an amorphous polymeric material.

6. The method according to any one of the preceding claims, wherein the second 3D printable material (2201) comprises PET and wherein the first 3D printable material (1201) comprises PC, or wherein the second 3D printable material (2201) comprises ABS and wherein the first 3D printable material (1201) comprises PC, or wherein the first 3D printable material (1201) comprises PC and the second 3D printable material (2201) comprises PMMA, or wherein the first 3D printable material (1201) comprises ABS and the second 3D printable material (2201) comprises PET.

7. The method according to any one of the preceding claims, wherein the second 3D printable material (2201) comprises a second polymeric material and wherein the first 3D printable material (1201) comprises a first polymeric material, wherein the second polymeric material and the first polymeric material comprise identical chemical groups, and wherein one or more of the following applies:

(i) the second 3D printable material (2201) and the first 3D printable material (1201) comprise the same polymeric material, and the second 3D printable material (2201) comprises a glass transition temperature reducing additive;

(ii) the second 3D printable material (2201) comprises a copolymer of the first polymeric material having a lower glass transition temperature than one or more of the first glass transition temperature T_gi and the first melting temperature T_m;

(iii) the second 3D printable material (2201) and the first 3D printable material (1201) comprise the same polymeric material, wherein the second 3D printable material (2201) comprises a blend of polymers, the blend having a lower glass transition temperature than one or more of the first glass transition temperature T_gi and the first melting temperature T_m; and

(iv) the second 3D printable material (2201) and the first 3D printable material (1201) comprise the same polymeric material, and the first printable material (1201) comprises a glass transition temperature increasing additive.

8. A 3D item (1) comprising 3D printed material (202), wherein the 3D item (1) comprises a plurality of layers (322) of a 3D printed material (202), and an edge (450) defined by two adjacent 3D printed partitions (451), wherein the 3D printed material (202) is selected from the group comprising a first 3D printed material (1202) and a second 3D printed material (2202), wherein the 3D item (1) comprises an item face (110), wherein the item face (110) comprises an item face part (111), wherein the 3D item (1) comprises an item part (431), wherein the item part (431) comprises a stack (435) of (i) a first layer segment

(436) comprising one or more layers of first 3D printed material (1202) having a first height (hi), (ii) a second layer segment (437) comprising one or more layers of second 3D printed material (2202) having a second height (h2), and (iii) a third layer segment (438) comprising one or more layers of first 3D printed material (1202); wherein:

the second 3D printed material (2202) has a second glass transition temperature T_g2, and the first 3D printed material (1202) has one or more of a first glass transition temperature T_gi and a first melting temperature T_mi, of which at least one is larger than said second glass transition temperature ¾;

the first height (hi) is at maximum 2 cm; and

of the stack (435) of the first layer segment (436), the second layer segment

(437), and the third layer segment (438), the third layer segment (438) is configured most remote from the item face part (111).

9. The 3D printed 3D item (10) according to claim 8, wherein a difference between the second glass transition temperature (¾) and the one or more of the first glass transition temperature (T_gi) and the first melting temperature (T_mi) is at least 10 °C, and wherein the second 3D printed material (2202) comprises amorphous polymeric material.

10. The 3D printed 3D item (10) according to any one of the preceding claims 8-9, wherein the second 3D printed material (2202) comprises PET and wherein the first 3D printed material (1202) comprises PC, or wherein the second 3D printed material (2202) comprises ABS and wherein the first 3D printed material (1202) comprises PC, or wherein the second 3D printed material (2202) comprises PMMA and wherein the first 3D printed material (1202) comprises PC, or wherein the second 3D printed material (2202) comprises PET and wherein the first 3D printed material (1202) comprises ABS. 11. The 3D printed 3D item (10) according to any one of the preceding claims 8-

10, wherein the item face part (111) is planar.

12. The 3D printed 3D item (10) according to any one of the preceding claims 8-

11, wherein the first height (hi) is at maximum 1 cm, and wherein the second height (h2) is selected from the range of 2-30 mm.

13. The 3D printed 3D item (10) according to any one of the preceding claims 8-

12, wherein the edge part (461) has an external area (Al) of at least 2 cm². 14. A lighting device (1000) comprising the 3D item (1) according to any one of the preceding claims 8-13, wherein the 3D item (1) is 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.