Method for manufacturing a 3D item

1. A method for manufacturing a 3D item by means of 3D printing, wherein the method comprises the step of:

depositing, during a printing stage, a 3D printable material to provide 3D printed material, wherein the 3D printable material comprises a core-shell filament, the core-shell filament comprising a core and a shell, the core comprising a core material having one or more of a core glass temperature Tg1 and a core melting temperature Tm1, and the shell comprising a shell material having one or more of a shell glass temperature Tg2 and a shell melting temperature Tm2, wherein one or more of the shell glass temperature Tg2 and the shell melting temperature Tm2 is lower than one or more of the core glass temperature Tg1 and the core melting temperature Tm1, and

wherein the method further comprises the step of:

heating, during a finishing stage, the 3D printed material to a temperature equal to or higher than one or more of the shell glass temperature Tg2 and the shell melting temperature Tm2, and lower than one or more of the core glass temperature Tg1 and the core melting temperature Tm1.

2. The method according to claim 1 , wherein one or more of (a) the core glass temperature Tg1 and shell glass temperature Tg2, (b) the core melting temperature Tm1 and the shell melting temperature Tm2, (c) the core melting temperature Tm1 and the shell glass temperature Tg2, and (d) the core glass temperature Tg1 and the shell melting temperature Tm2, differ with at least 40° C.

3. The method according to claim 1 , wherein the core material comprises one or more materials selected from the group consisting of polycarbonate, polysulfone, polyphenyleen sulfide, high Tg polycarbonate, polybutylene terephthalate, crystalline polyethylene terephthalate, polyethylene naphthalate, polyether ether ketone, and wherein the shell material comprises one or more materials selected from the group consisting of amorphous polyethylene terephthalate, acrylonitrile butadiene styrene, poly(methyl methacrylate), polystyrene, styrene methylmethacrylate, methylmethacrylate acrylonitrile butadiene styrene, styrenic block copolymer, and thermoplastic polyurethane.

4. The method according to claim 1 wherein the core-shell filament has a core diameter selected from the range of 100-3000 μm, wherein the shell thickness is selected from the range of 100-2000 μm, and wherein the core diameter is larger than the shell thickness.

5. The method according to claim 1 , wherein the heating step comprises one or more of (i) providing a hot gas to the 3D printed material, (ii) providing IR radiation to the 3D printed material, and (iii) heating the 3D printed material in a heating chamber.

6. The method according to claim 1 , wherein the 3D printed material forms a surface of the 3D item ( 1 ), and wherein during the finishing stage the 3D printed material is heated until at least a part of the surface has a predetermined average surface roughness (Ra) equal to or lower than 5 μm for an area of at least 25 mm 2 .

7. The method according to claim 1 , wherein during the printing stage pressure is applied to the core-shell filament to provide a deposited core-shell filament having a deformed core with a first dimension and a second dimension perpendicular to each other and perpendicular to a longitudinal axis (A) of the core-shell filament that have a ratio of less than 1.