ADDITIVE MANUFACTURING COMPONENTS AND METHODS

Abstract

A method of 3D printing comprises: providing a layer of a powder bed; jetting a functional binder onto selected parts of said layer, wherein said binder infiltrates into pores in the powder bed and locally fuses particles of the powder bed in situ; sequentially repeating said steps of applying a layer of powder on top and selectively jetting functional binder, multiple times, to provide a powder bed bonded at selected locations by printed functional binder; and taking the resultant bound 3D structure out of the powder bed.

Claims

1. A method of 3D printing comprising: providing a layer of a powder bed; jetting a functional binder onto selected parts of said layer, wherein said binder infiltrates into pores in the powder bed and locally fuses particles of the powder bed in situ; sequentially repeating said steps of applying a layer of powder on top and selectively jetting functional binder, multiple times, to provide a powder bed bonded at selected locations by printed functional binder; and taking the resultant bound 3D structure out of the powder bed.

2. A method as claimed in claim 1 further comprising a subsequent step of heat treatment either inter-layer or post-build to further fuse the 3D structure.

3. A method as claimed in claim 1 wherein the functional binder comprises a metallic binder.

4. A method as claimed in claim 3 wherein the metallic binder comprises an organometallic material.

5. A method as claimed in claim 4 wherein the organometallic material is a copper metal precursor, for example comprising cyclopentadienyl and/or isocyanide ligands.

6. A method as claimed in claim 4 wherein the organometallic material is a nickel metal precursor, for example nickel acetylacetonate.

7. A method as claimed in claim 4 wherein the organometallic material is a titanium metal precursor, for example a titanium amide.

8. A method as claimed in claim 1 wherein the functional binder comprises a ceramic binder.

9. A method as claimed in claim 1 wherein the binder further comprises metallic or ceramic nanoparticles with sizes within the range of 1 to 100 nm.

10. A method as claimed in claim 1 wherein the binder further comprises metallic or ceramic microparticles with sizes within the range of 0.1 to 10 microns.

11. A method as claimed in claim 1 wherein the powder of the powder bed comprises metallic or ceramic particles.

12. A method as claimed in claim 1 wherein the functional binder is jetted onto the powder bed at a temperature within the range of 50 to 350 C.

13. A functional binder composition for binding particles of a powder bed, wherein the binder comprises: (i) an organometallic material; (ii) metallic or ceramic nanoparticles with sizes within the range of 1 to 100 nm; and (iii) metallic or ceramic microparticles with sizes within the range of 0.1 to 10 microns.

14. A 3D printed product obtainable by the method of claim 1.

15. A 3D printed product comprising fused particles of metal and/or ceramic infiltrated with binder-jetted fused metal and/or ceramic.

16. A product as claimed in claim 14 which is a part or component of a vehicle or of a medical device, implant or prosthesis.

17. Apparatus for carrying out the method of claim 1.

Description

[0079] The present invention will now be described in further non-limiting detail and with reference to the drawings in which:

[0080] FIG. 1 shows schematic representations of material produced during stages of a conventional binder jet printing process; and

[0081] FIG. 2 shows schematic representations of material produced during stages of a process in accordance with the present invention;

[0082] The left hand panel (1) of each of FIGS. 1 and 2 shows a representation of a cross-section of part of a powder bed before binder jetting has taken place. It can be seen that there are significant voids between the particles.

[0083] Subsequent stages of a conventional binder jet printing process are shown in panels 2, 3 and 4 of FIG. 1. 2 shows the product after the printing of sacrificial binder; 3 shows the product after sintering and removal of binder; 4 shows the product after a post-processing infiltration step.

[0084] In contrast, 2 in FIG. 2 shows the product after printing of metallic functional binder and simultaneous infiltration, in accordance with the present invention; and 3 shows the sintered densified end product in which no significant pores are visible.

[0085] In order to produce parts, it is necessary to deposit, layer by layer, the powder bed and to deliver ink formulations onto that bed in a controlled manner. This requires a powder bed mechanism similar to commercially available systems but with bespoke hardware and firmware to give full control over the process. The print-head jetting system is designed to give full access to control the ink jet print head system. In some embodiments the print-heads use TTPs Vista technology which uses a mechanical ejection process cable of delivering large sedimenting particle loaded inks and which can print inks that cannot currently be printed by commercially available industrial inkjet heads.

[0086] The powder bed may include a heating system that can heat the bed, with the maximum bed temperature likely to be <350 C., for example 50-350, e.g. 100-300, e.g. 150-250 C. Elevated bed temperature may be achieved by the use of a heater system under the bed or by radiant heaters above the bed, the objective in both cases being to activate the reactive binder (e.g., in the case of ROMs, to drive off the ligands from the ROM active part of the ink) and optionally to sinter the nanoparticles in the nano-component of the ink. This produces a fully-dense-high-strength green part, which can then be heat treated to create the correct final microstructure for functional use. Thus the moderate temperature at this stage fuses the nanoparticles and enables the reactive binder to release elemental metallic coating, whereas the post-processing heating fuses the larger microparticles.

[0087] Optionally the method lays metal powders with 25 m precision, using a hopper-feed and wiper blade mechanism, which are designed to operate up to the maximum powder bed temperature. The print head and powder bed may be housed in a controlled environmental chamber (N.sub.2 or Ar) to minimise atmospheric contamination and vent unwanted, noxious by-products. The system may be automated and run under computer control with a suitable build volume (e.g. 250250250 mm).