WO2018015192A1

WO2018015192A1 - Method and materials for improving adhesion to a printing bed for fdm printed objects

Info

Publication number: WO2018015192A1
Application number: PCT/EP2017/067244
Authority: WO
Inventors: Rifat Ata Mustafa Hikmet
Original assignee: Philips Lighting Holding B.V.
Priority date: 2016-07-21
Filing date: 2017-07-10
Publication date: 2018-01-25

Abstract

A method for 3D printing a 3D item (10), the method comprising providing a filament of 3D printable material and printing during a printing stage said 3D printable material on a receiver item (550), to provide said 3D item (10), wherein the printing stage comprises an initial printing stage wherein a first 3D printable material is deposited on said receiver item (550) to provide first 3D printed material (202a) with a layer height (hl) of at maximum 10 mm, and a main printing stage wherein a second 3D printable material is deposited on said first printed 3D printed material (202a) to provide a second 3D printed material (202b), wherein the first 3D printable material has a first glass transition temperature (T_gi), wherein the second 3D printable material has one or more of a second glass transition temperature (T_g2) and a second melting temperature (T_m2), of which at least one is larger than said first glass transition temperature (T_gi), wherein the method further comprises maintaining the receiver item (550) during at least part of the printing stage at a receiver item temperature (T_pp) of at least the first glass transition temperature (T_gi) and below one or more of the second glass transition temperature (T_g2) and the second melting temperature (T_m).

Description

Method and materials for improving adhesion to a printing bed for FDM printed objects

FIELD OF THE INVENTION

The invention relates to a method for manufacturing a 3D item. The invention also relates to the 3D (printed) item obtainable with said method. 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 a 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 and can be used for printing complicated object.

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), Polystyrene (PS), PE (such as expanded- high impact-Polythene (or polyethene), Low density (LDPE) High density (HDPE)), PVC (polyvinyl chloride)

Polychloroethene, etc.. Optionally, the 3D printable material comprises a 3D printable material selected from the group consisting of Urea formaldehyde, Polyester resin, Epoxy resin, Melamine formaldehyde, Polycarbonate (PC), rubber, etc.. Optionally, the 3D printable material comprises a 3D printable material selected from the group consisting of a polysulfone, a polyether sulfone, a polyphenyl sulfone, an imide (such as a poly ether imide) etc.

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 receiver item can also be heated during 3D printing. Especially, the receiver item can be the building platform or can be comprised by the building platform.

Specific examples of materials that can be used can e.g. be selected from the group consisting of acrylonitrile butadiene styrene (ABS), polylactic acid (PLA),

polycarbonate (PC), polyamide (PA), polystyrene (PS), lignin, rubber, etc.

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.

For successful printing it is necessary that the object remains adhered to the adhesion the building platform during printing of the object in order to obtain a good result. In this way dimensional changes as a result of cooling during printing can be absorbed and the printing can continue without the object getting loose from the built platform. For this purpose, various ways have been suggested (see also above).

A solution may be to make use of a polyimide film laminated onto the surface of a glass plate which is then coated with the material which is used for 3D printing.

However this method appears to be rather difficult and quite expensive.

Hence, it is an aspect of the invention to provide an alternative method of manufacturing a 3D item, which preferably further at least partly obviates one or more of above-described drawbacks, especially a method with an improved release behavior.

Here we suggest a method and materials which makes it possible to print on top of a glass (or any other metal, ceramic etc.) surface without requiring any coating step. For this purposes we suggest using a first material with a relatively low glass transition temperature to print the bottom layer of the object which is in contact with the built platform. Especially, this first material is an amorphous polymer, i.e. only essentially having a glass transition temperature and essentially not having a melting temperature. The temperature of the built platform is chosen to be around or above the glass transition temperature of this bottom layer (polymer). As a result this bottom layer is an interface layer that shows a good physical adhesion to the substrate. After printing this adhering interface layer (hereinafter also referred to as adhesion layer) a second material is printed on top of the adhesion layer to form a subsequent layer. The second material may be the main material which is to form the bulk of the object. Because this interface layer is soft it also accommodates for dimensional changes and stress forming. For good adhesion the first and second materials are chosen to be compatible (miscible). It is eventually possible to use incompatible polymers containing a compatiblizer (such as e.g. a block copolymer, or molecules with at least two segment types which are compatible with both polymers), for improving the adhesion between the layers. After printing the build plate can be cooled below the Tg of the adhesion layer and remove the object easily.

Therefore, in a first aspect the invention provides a method for 3D printing a 3D item (herein also indicated as "3D printed item"), the method comprising the steps of providing a filament of 3D printable material ("printable material") and printing during a printing stage said 3D printable material on a receiver item, especially with a fused deposition modeling (FDM) 3D printer, to provide said 3D item. The printing stage comprises an initial printing stage followed by a main printing stage. In the initial printing stage a first 3D printable material is deposited on said receiver item to provide an adhesion layer of the 3D item, the adhesion layer comprising first 3D printed material (202a) and having a layer height (hi) of at maximum 10 mm. In the main printing stage a second 3D printable material is deposited on the adhesion layer to provide one or more subsequent layers of the 3D item, the one or more subsequent layers comprising second 3D printed material. The first 3D printable material has a first glass transition temperature (T_gl), and the second 3D printable material has one or more of a second glass transition temperature (T_g2) and a second melting temperature (T^), of which at least one is larger than said first glass transition temperature (T_gl). The method further comprises the step of maintaining the receiver item during at least part of the printing stage at a receiver item temperature (T_pp) of at least the first glass transition temperature (T_gl) and below one or more of the second glass transition temperature (T_g2) and the second melting temperature (T^).

In some prior art solutions, a piece of polymer is sticked onto the surface of a building platform before printing. The polymer sticks to the printed item and at the end of the print stage the 3D item and the piece of polymer come all together from the surface of the building platform. This is not desirable. With the present invention, however, it is possible to print on the platform and then take the 3D printed item off after the printing and reuse the building platform without the need to stick something onto it again before starting a new 3D print. Hence, in a very easy way and in a relatively cheap way the 3D printed object under construction can be get adhered well to the printing platform while it can also be relatively easily be released from the platform after the construction has been finished. Further, due to the use of the low T_g material, the temperature ambient to the receiver item can be kept lower than the glass transition temperature and/or the melting temperature of the second polymer, which can also be indicated as "bulk polymer" or "bulk material" or "bulk 3D printable material. This allows a lower cooling down time and thus a quicker production process. Further, the present invention also allows a reduction or even prevention of the so-called elephant food problem. This elephant food problem can e.g. be caused by the weight of the rest of the model pressing down the first layers, when the lower layers have not had time to cool back into a solid, particularly when the printer has a heated bed (which is here in general the case). Herein, the term "3D printable material" may also be indicated as "printable material". Instead of the term "a receiver item" also the terms "printing platform", "print bed", "substrate" or "support" or "build plate" may be used. 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".

Therefore, the invention provides an alternative method for 3D printing a 3D item, wherein the thus printed 3D item can be relatively easily be removed from the receiver item, in fact essentially only by reducing the temperature of the receiver item to a

temperature below the glass transition temperature of the first 3D printable material. To this end, the invention provides a filament of 3D printable material and printing during a printing stage said 3D printable material on a receiver item, especially with a fused deposition modeling (FDM) 3D printer, to provide said 3D item. The term "filament" may also refer to a plurality of (different) filaments. The method may include printing sequentially different types of filaments with a single printer nozzle. Alternatively or additionally, the method may include printing sequentially different types of filaments with different printer nozzle. Hence, in embodiments the 3D printer may include multi- filament printer, i.e. a 3D printer with a plurality of printer nozzles. It is also possible to use a printer with a single nozzle but multiple feeders for different filament materials.

During printing, there are different stages, including at least the printing stage.

In the invention, the printing stage especially includes an initial printing stage wherein a first 3D printable material is deposited on said receiver item to provide first 3D printed material. In this stage, the "adhesion layer" is provided, which provides adhesion to the receiver item and is the basis of the remainder of the 3D printed material, which is deposited on this first 3D printed material. As indicated herein, material in a filament to be printed or being printed is indicated as "printable material"; material once deposited (i.e. printed) is indicated as "printed material". The printed material is in general arranged in filaments, as it is deposited as filament(s). The first 3D printable material is deposited until a layer height (hi) of - in embodiments - at maximum 10 mm. The layer height may depend upon to the total height or the total volume or the total mass of the 3D printed item. In specific embodiments, the initial printing stage comprises providing first 3D printed material with a layer height (hi) selected from the range of 100 μιη - 10 mm, such as selected from the range of 100-1000 μιη, like 200-1000 μιη. The initial printing stage may provide the edge part (see also below); the main printing stage may provide the body part (see also below) that is in (physical) contact with the edge part.

The first 3D printable material has a first glass transition temperature (T_gl), which can be any glass transition temperature, but especially in the range of about 50-150 °C. Further, the glass transition temperature of the first material is at least lower than the glass transition temperature of the second material; see also below. Hence, the first 3D printable material may especially comprise amorphous polymeric material (only having a glass transition temperature and not having a melting temperature).

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.

Yet further, the printing stage may include a main printing stage. In this stage essentially the remainder of the 3D may be printed. In the main printing stage a second 3D printable material is deposited on said first printed 3D printed material to provide second 3D printed material .

The second 3D printable material has a second glass transition temperature (T_g2), 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 second material. Hence, the second 3D printable material may thus also have a melting temperature, herein further especially indicated as second melting temperature (T^). Therefore, in embodiments the second 3D printable material has a second melting temperature (T^), which can be any melting temperature, but especially in the range of about 100-350 °C. Therefore, the phrase "the second 3D printable material has one or more of a second glass transition temperature (T_g2) and a second melting temperature (T^)" may especially relate to embodiments wherein the second 3D printable material only has a glass transition temperature and not a melting temperature and to embodiments wherein the second 3D printable material has both a glass transition temperature and a melting temperature.

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

In specific embodiments, the difference between the first glass transition temperature (T_gl) and the one or more of the second glass transition temperature (T_g2) and the second melting temperature (T^) 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 second melting temperature (T^) 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 first glass transition temperature (T_gi) in embodiments wherein the second 3D printable material comprise a (semi-)crystalline polymeric material.

The method further includes maintaining the receiver item during at least part of the printing stage at a receiver item temperature (T_pp) of at least the first glass transition temperature (T_gi) and below one or more of the second glass transition temperature (T_g2) and the second melting temperature (T_m). Assuming the second 3D printable material to be essentially amorphous polymeric material, the receiver item temperature is below the second glass transition temperature. Assuming the second 3D printable material to be essentially (semi-)crystalline polymeric material, the receiver item temperature is at least below the second melting temperature, and optionally below the second glass transition temperature. When the receiver item temperature is below the second glass transition temperature (and at least the first glass transition temperature), the receiver item temperature is thus in general also below the second melting temperature.

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

As indicated herein, the temperature of the receiver item is kept lower than one or more of the second glass transition temperature and the second melting temperature, such as at least 5 °C lower than the second glass transition temperature or the second melting temperature, such as at least 10 °C lower than the second glass transition temperature or the second melting 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 (T_pp) of at least about the first glass transition temperature (T_gl) 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 (T_pp) of at least the first glass transition temperature (T_gl)" and similar phrases especially indicate that the surface at which the printable material is deposited is kept at the indicated receiver item temperature (T_pp).

The first printable material and second 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 first printable material and the second printable materials may include one or more of additives or modifications which provide the different physical (and chemical) properties.

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

In yet further embodiments, the first printable material comprises a first polymeric material and the second printable material comprises (essentially) the same polymeric material, and wherein one or more of (i) the first printable material comprises a glass transition temperature reducing additive, and (ii) the second printable material comprises a glass transition temperature increasing additive, applies. In such embodiments, the first printable material and second printable material may include the same type of polymers, but one or more of the first and the second 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 first printable material comprises a first polymeric material and the second printable material comprises (essentially) the same polymeric material, and wherein one or more of (i) the first printable material comprises a glass transition temperature reducing functional group, and (ii) the second printable material comprises a glass transition temperature increasing functional group, applies. Hence, though e.g. the first printable material and second printable material may have the same backbones, due to the presence of (different) functional groups on one (or both) of the polymer(s), the first and second 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 of65 °C.

Hence, in embodiments the first printable material comprises PET and the second printable material comprises PC, or the first printable material comprises ABS and the second printable material comprises PC, or the second printable material comprises PC and the first printable material comprises a modified PC with a glass transition temperature (Tg) lower than PC. In yet further embodiments, the first printable material comprises a first polymeric material and the second printable material comprises a second polymeric material, wherein the first polymeric material and the second polymeric material comprise identical chemical groups, and wherein one or more of the following applies:

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

(ii) the first printable material comprises a copolymer of the second polymeric material having a lower glass transition temperature than one or more of the second glass transition temperature (T_g2) and the second melting temperature (T_m);

(iii) the first printable material and the second printable material comprise the same polymeric material, wherein the first printable material comprises a blend of polymers, the blend having a lower glass transition temperature than one or more of the second glass transition temperature (T_g2) and the second melting temperature (T_m); and (optionally);

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

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. During the initial printing stage, a layer with the layer height of the first printed material is provided. The term "layer" may also relate to a plurality of layers, including embodiments with a plurality of different layers. For instance, an intermediate layer between the first printed material and second printed material may also be possible. Such intermediate layer, including e.g. one or more polymers compatible with both the first polymeric material and the second polymeric material may be used when the first polymeric material and second polymeric material are not (easily) compatible.

The receiver item comprises one or more of glass, ceramic, and metal. The binding or adhesion of the first printable material to the receiver item may be essentially physical.

In yet further embodiments, the method further comprises a receiver item release stage, wherein especially the receiver item release stage comprises reducing the receiver item temperature (T_pp) to a temperature below the first glass transition temperature (Tgi) and removing the 3D item from the receiver item. In specific embodiments, the receiver item release stage may comprising reducing the receiver item temperature (T_pp) to a temperature of at least 10 °C below the first glass transition temperature (T_gl), such as at least 20 °C, especially at least 25 °C, such as at least 30 °C below the first glass transition temperature. With the method of the invention, the 3D printed item may relatively easily be released from the receiver item.

A filament that can be used in the method according to the first aspect of the invention comprises (3D printer) printable material, wherein the filament further comprises a first filament part comprising a first 3D printable material having a first glass transition temperature (T_gl) and a second filament part, configured relative to a longitudinal filament axis (A) next to the first filament part comprising a second 3D printable material having one or more of a second glass transition temperature (T_g2) and a second melting temperature (Tm2), of which at least one is larger than said first glass transition temperature (T_gl).

In this way, with a single filament both the first printable material and second printable material may be provided. As can be derived from the above the terms "first filament part" and "second filament part" may also refer to a plurality of different first filament parts or different second filament part, respectively. The term "different filament parts" and similar terms may especially refer to parts that have different chemical

compositions; further, they may have different glass transition temperatures. The filament may especially have a substantially circular cross-section (at least before leaving the printer nozzle). Hence, the filament parts may have the shape of (adjacently configured) cylinders. The filament diameter may e.g. be in the range of 100 μιη - 10 mm, such as 100-1000 μιη, like 200-1000 μιη.

In analogy to what has been defined above in relation to the method, in the filament the difference between the first glass transition temperature (T_gl) and one or more of the second glass transition temperature (T_g2) and the second melting temperature is at least 10 °C, like 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 second melting temperature (T^) 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 first glass transition temperature (T_gi) when the second 3D printable material comprise a (semi-)crystalline polymeric material.

Further, the first printable material may comprise PET and the second printable material comprises PC. Alternatively, the first printable material comprises ABS and the second printable material comprises PC, etc. (see also above), or the second printable material comprises PC and the first printable material comprises a modified PC with a glass transition temperature (Tg) lower than PC (see also above).

In a further aspect, the invention also provides the 3D printed item obtainable with the herein described method and or produced with the herein described 3D printer. Hence, in an aspect the invention also provides a 3D printed 3D item comprising (i) an edge part and (ii) a body part (12) in (physical) contact with the edge part (11), wherein the edge part comprises the adhesion layer of the 3D item, and wherein the body part comprises the one or more subsequent layers of the 3D item. In other words, the edge part comprises a first 3D printed material having a first glass transition temperature (T_gi), the edge part has an edge part layer height (h2) of at maximum 10 mm, and the body part comprises a second 3D printed material having one or more of a second glass transition temperature (T_g2) and a second melting temperature (T^), of which at least one is larger than said first glass transition temperature (T_gi).

The edge part and body part are in (physical) contact. This especially implies that they are attached to each other. This may be by physical adhesion and/or chemical adhesion. The polymeric material at the interface of edge part and body part may partly mix when the second printable material is deposited on the first printed material. In this way, substantially a single body may be formed, herein also indicated as "3D item" wherein at least two parts can be distinguished. The edge part may essentially consist of the first printed material and the body part may essentially consist of the second printed material. Hence, the polymeric composition of the edge part may in embodiments differ from the body part, and (thus) the relevant temperatures (glass transition temperature and/or melting temperature) also.

In analogy to what has been defined above in relation to the method and filament, the difference between the first glass transition temperature (T_gl) and one or more of the second glass transition temperature (T_g2) and the second melting temperature is at least 10 °C, like at least 20 °C, even more especially a difference selected from the range of 10- 150 °C, like 20-100 °C. Hence, especially the second melting temperature (T^) is at least 10 °C, such as at least 20 °C, larger than the first glass transition temperature (T_gi) in

embodiments wherein the second 3D printed material comprise a (semi-)crystalline polymeric material.

In embodiments, the edge part has an edge part layer height (h2) selected from the range of 100 μιη - 10 mm, such as 100-1000 μιη, like 200-1000 μιη. The height of the filaments after printing may be smaller than before printing. In other words, the equivalent circular diameter of the filament upstream of the printer nozzle may be larger than

downstream of the printer nozzle (due to an extrusion effect). The equivalent circular diameter (or ECD) of an (irregularly shaped) two-dimensional shape is the diameter of a circle of equivalent area.

In analogy to what has been defined above in relation to the method and filament, in embodiments the first printed material comprises PET and wherein the second printed material comprises PC. In yet further embodiments, the first printed material comprises ABS and the second printed material comprises PC, though other combinations may also be possible (see also above). In yet further embodiments, or wherein the second printed material comprises PC and the first printed material comprises a modified PC with a glass transition temperature (Tg) lower than PC (see also above).

Further, as the edge part of the 3D printed item is the part that was during printing in (physical) contact with the receiver item, this edge part will in general be flat. Hence, in embodiments the edge part is planar.

The thus 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 source (like a LED), etc. 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.

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- lb schematically depict some general aspects of the 3D printer;

Figs. 2a-2d schematically depict some aspects of the invention.

The schematic drawings are not necessarily on 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 a 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, though other

embodiments are also possible. 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).

The 3D printer 500 is configured to generate a 3D item 10 by depositing on a receiver item 550, which may in embodiments at least temporarily be cooled, a plurality of filaments 320 wherein each filament 20 comprises 3D printable material, such as having a melting point T_m. The 3D printer 500 is configured to heat the filament 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. The 3D printer 500 transforms this in a filament or fiber 320 on the receiver item or on already deposited printed material. In general, the diameter of the filament downstream of the nozzle is reduced relative to the diameter of the filament upstream of the printer head. Hence, the printer nozzle is sometimes (also) indicated as extruder nozzle. Arranging filament by filament and filament on filament, a 3D item 10 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 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.

Fig. lb schematically depicts in 3D in more detail the printing of the 3D item 10 under construction. Here, in this schematic drawing the ends of the filaments 320 in a single plane are not interconnected, though in reality this may in embodiments be the case.

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 320 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.

Fig. 2a schematically depicts an embodiment of the method including an initial printing stage IP and a main printing stage MP. Optionally, the method may include a finalization stage F, wherein the 3D printed item is still on the receiver item, but some further processing occurs like heating, painting, including functional elements, such as electronic elements, etc. etc. The method may also include a release stage R, which may in

embodiments substantially directly follows on the main printing stage.

Fig. 2b schematically depicts a filament 320 comprising fused deposition printer printable material 201, wherein the filament 320 further comprises a first filament part 320a comprising a first 3D printable material 201a having a first glass transition temperature Tgi and a second filament part 320b, configured relative to a longitudinal filament axis A next to the first filament part 320a, comprising a second 3D printable material 201b having a second glass transition temperature T_g2 larger than said first glass transition temperature T_gl.

Fig. 2c schematically depicts the result of a method for 3D printing a 3D item

10 as described herein, wherein by 3D printing the 3D item 10 is provided on the receiver item 550, by depositing a first 3D printable material on the receiver item 550 thereby providing first 3D printed material 202a with a layer height hi , especially of at maximum 10 mm, and by depositing a second 3D printable material 201b on said first printed 3D printed material 202a to provide second 3D printed material 202b. the height of the remaining part provided during the main printing stage is indicated as h3 and may be smaller, equal to or larger than the layer height hi , in general larger than the layer height hi . Reference 1 1 indicates an edge part of the 3D printed item 10.

Fig. 2d schematically depicts the thus obtained 3D item 10, released from the receiver item. The 3D printed 3D item 10 comprises an edge part 1 1 comprising a first 3D printed material 202a having a first glass transition temperature T_gl, the edge part 1 1 having an edge part layer height h2 of at maximum 10 mm, and a body part 12 in (physical) contact with the edge part 1 1 comprising a second 3D printed material 202b having a second glass transition temperature T_g2 larger than said first glass transition temperature T_gl, and/or having a second melting temperature T^ larger than said first glass transition temperature T_gl. Relating figs. 2c to 2d, hi will be essentially the same as h2 and h3 will be essentially the same as h4.

One of the materials which is difficult to print is polycarbonate. Especially objects with relatively large contact area with the build plate show bad adhesion when directly printed on top of glass plate and printing cannot be completed.

In order to make printing possible we used a reflective PC filament and we attached to the initial part of the PC filament a segment of transparent PET filament. PC and PET are compatible and PC has a T_g of 140 °C while the Tg of PET is 80 °C. The PET segment was long enough to print 500 μιη layer of a 3D printed. The temperature of the build plate was set to be lOOC. The printing could be completed without any delamination. After the completion of printing the platform was cooled down and the object easily removed.

It is also possible to make blends or copolymers for the first layer. For example if PC is the second layer other polymer which are miscible with PC such as PMMA, PBT, ABS copolymer PC/PET can be used to produce blends. It is also possible to use lower molecular weight solvents with high boiling point such as dimethyl phthalate to reduce the T_g ofPC.

Two different polymers can be applied using filament attachment as described above, using two different heads or two different feeders.

Temperatures indicated herein may have tolerances of about 5 °C, such about

2 °C, especially in the range of up to about 100 °C. From about 100 °C, the tolerances may be about 10 °C, such as about 5 °C, especially such about 2 °C.

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 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 3D printing a 3D item (10), the method comprising the steps of:

providing a filament (320) of 3D printable material (201) and printing during a printing stage said 3D printable material (201) on a receiver item (550), to provide said 3D item (10),

wherein the printing stage comprises an initial printing stage followed by a main printing stage,

wherein in the initial printing stage a first 3D printable material (201a) is deposited on said receiver item (550) to provide an adhesion layer of the 3D item (10), the adhesion layer comprising first 3D printed material (202a) and having a layer height (hi) of at maximum 10 mm,

wherein in the main printing stage a second 3D printable material (201b) is deposited on the adhesion layer to provide one or more subsequent layers of the 3D item (10), the one or more subsequent layers comprising a second 3D printed material (202b), wherein the first 3D printable material (201a) has a first glass transition temperature (T_gl), and the second 3D printable material (201b) has one or more of a second glass transition temperature (T_g2) and a second melting temperature (T^), of which at least one is larger than said first glass transition temperature (T_gl),

wherein the method further comprises the step of:

maintaining the receiver item (550) during at least part of the printing stage at a receiver item temperature (T_pp) of at least the first glass transition temperature (T_gl) and below one or more of the second glass transition temperature (T_g2) and the second melting temperature (T^).

2. The method according to claim 1, wherein a difference between the first glass transition temperature (T_gl) and the one or more of the second glass transition temperature (T_g2) and the second melting temperature (T^) is at least 10 °C, and wherein the first 3D printable material (201a) comprises amorphous polymeric material.

3. The method according to any one of the preceding claims, wherein with the adhesion layer has a layer height (hi) selected from the range of 100-1000 μιη.

4. The method according to any one of the preceding claims, wherein the first 3D printable material (201a) comprises PET and wherein the second 3D printable material

(201b) comprises PC, or wherein the first 3D printable material (201a) comprises ABS and wherein the second 3D printable material (201b) comprises PC, or wherein the second 3D printable material (201b) comprises PC and the first 3D printable material (201a) comprises a modified PC with a glass transition temperature (Tg) lower than PC.

5. The method according to any one of the preceding claims, wherein the first 3D printable material (201a) comprises a first polymeric material and wherein the second 3D printable material (201b) comprises a second polymeric material, wherein the first polymeric material and the second polymeric material comprise identical chemical groups, and wherein one or more of the following applies:

(i) the first 3D printable material (201a) and the second 3D printable material (201b) comprise the same polymeric material, and the first 3D printable material (201a) comprises a glass transition temperature reducing additive;

(ii) the first 3D printable material (201a) comprises a copolymer of the second polymeric material having a lower glass transition temperature than one or more of the second glass transition temperature (T_g2) and the second melting temperature (T_m);

(iii) the first 3D printable material (201a) and the second 3D printable material (201b) comprise the same polymeric material, wherein the first 3D printable material (201a) comprises a blend of polymers, the blend having a lower glass transition temperature than one or more of the second glass transition temperature (T_g2) and the second melting temperature (T_m); and

(iv) the first 3D printable material (201a) and the second 3D printable material (201b) comprise the same polymeric material, and the second printable material (201b) comprises a glass transition temperature increasing additive.

6. The method according to any one of the preceding claims, wherein the receiver item (550) comprises one or more of glass, ceramic, and metal, and wherein the method further comprises a receiver item release stage, wherein the receiver item release stage comprises reducing the receiver item temperature (T_pp) to a temperature below the first glass transition temperature (T_gl) and removing the 3D item (10) from the receiver item (550).

7. The method according to claim 6, comprising reducing the receiver item temperature (T_pp) to a temperature of at least 10 °C below the first glass transition

temperature (T_gl), and wherein the first 3D printable material (201a) comprises amorphous polymeric material.

8. A 3D printed 3D item (10) obtainable by the method according to any one of claims 1-7, wherein the 3D printed 3D item (10) comprises (i) an edge part (11) and (ii) a body part (12) in contact with the edge part (11), wherein the edge part (11) comprises the adhesion layer of the 3D item (10), and wherein the body part comprises the one or more subsequent layers of the 3D item (10).

9. The 3D printed 3D item (10) according to claim 8, wherein a difference between the first glass transition temperature (T_gl) and the one or more of the second glass transition temperature (T_g2) and the second melting temperature (T^) is at least 10 °C, and wherein the first 3D printed material (202a) comprises amorphous polymeric material.

10. The 3D printed 3D item (10) according to any one of the preceding claims 8-9, wherein the adhesion layer has a layer height (h2) selected from the range of 100-1000 μιη.

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

10, wherein the first 3D printed material (202a) comprises PET and wherein the second 3D printed material (202b) comprises PC, or wherein the first 3D printed material (202a) comprises ABS and wherein the second 3D printed material (202b) comprises PC.

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

11, wherein the edge part (11) is planar.