ADDITIVE MANUFACTURING

Abstract

A method is for removing a support structure from an additive manufactured metallic component. The method includes exposing the component and support structure to at least one thermal pulse so as to weaken, or break, the interface(s) between the support structure and component prior to removal of the support.

Claims

1. A method of removing a support structure from an additive manufactured metallic component, the method comprising exposing the component and support structure to at least one thermal pulse so as to weaken, or break, the interface(s) between the support structure and component prior to removal of the support.

2. The method of claim 1, wherein the support comprises a bulk support and the interface comprises a plurality of interface support members connecting between the bulk support and the component and wherein the interface support members are weakened by the thermal pulse prior to the removal of the bulk support by any other method.

3. The method of claim 1, wherein the thermal pulse is at a temperature exceeding the melting point of the metallic material.

4. The method of claim 1, wherein the step of exposing the component and support structure to a thermal pulse comprises placing the component and support structure in a chamber, filling the chamber with a combustible gas mixture, allowing the gas mixture to surround the component and support structure and igniting the gas mixture.

5. The method of claim 4, wherein the thermal pulse is an explosive or pseudo-explosive combustion.

6. A method of additive manufacturing metallic components, the method comprising the steps of: forming a component in a layer-by-layer process, the component being formed integrally with at least one support structure to be separated from the component after the layer-by-layer process; and wherein after completion of the layer-by-layer process, the method comprises removal of the support structure from the additive manufactured metal component in accordance with claim 1.

7. The method of claim 6, wherein the metallic component and support structure is formed on a baseplate and prior to the removal of the support structure from the additive manufactured metallic component the method further comprises the steps of: heat treating the metallic component and the support structure to remove or reduce residual stresses induced the layer-by-layer process; and subsequently removing the component and support structure from the base plate.

8. The method of claim 1, wherein after mechanical removal of the support structure from the metallic component, at least one further thermal pulse is applied to the separated metallic component.

9. The method of claim 8, wherein a plurality of thermal pulses are applied to the separated metallic component.

10. The method of claim 8, wherein the surface of the metallic component is abrasively cleaned after the application of at least one thermal pulse to the separated metallic component.

11. The method of claim 1, wherein the additive manufacturing process comprises powder bed selective laser manufacturing.

12. The method of claim 6, wherein after mechanical removal of the support structure from the metallic component, at least one further thermal pulse is applied to the separated metallic component.

13. The method of claim 12, wherein a plurality of thermal pulses are applied to the separated metallic component.

14. The method of claim 13, wherein the surface of the metallic component is abrasively cleaned after the application of at least one thermal pulse to the separated metallic component.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Specific embodiments of the invention will now be described in detail, by way of example only, and with reference to the accompanying drawings in which:

[0033] FIG. 1 is a schematic representation of a part manufactured by a conventional additive manufacturing method;

[0034] FIG. 2 shows examples metal parts formed by additive manufacturing with support structures both present and removed; and

[0035] FIG. 3 shows a flow chart for the forming an additive manufactured component in accordance with embodiments of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0036] A schematic representation of a metal part 1 manufactured in an additive manufacturing method is shown in FIG. 1. The metal part is for example a casing and includes a cavity la within its body. The part 1 is formed by being built up on a layer-by-layer manner on a baseplate 4 in a manner which will be well known to those skilled in the art.

[0037] A bulk support structure 2 is provided within the cavity la of the part 1. The bulk support is arranged to be built relatively quickly during the additive layer manufacture but to have sufficient strength to resist the loads from the part 1 and, for example to resists geometric distortion of the part 1. The skilled person will appreciate that the support 2 may have any convenient (optimised) form and could be a solid or for example a lattice or honeycomb structure.

[0038] To ensure that the support 2 can be removed from the component 1 after manufacture it is provided with an interface 3 which forms a distinct break line between the support 2 and component 1. The interface may comprise a number of distinct, tooth like, interface members 3a, 3b, 3c which join the component 1 and support 2. It will be appreciated that the component 1, support 2 and interface 3 are all integrally formed on a layer-by-layer basis during the additive manufacturing process.

[0039] Some example photographs are shown in FIG. 2 to illustrate the removal of a support structure 2 from a component 1 using the method in accordance with embodiments of the invention. It may be noted that the photographs show the support 2 both in situ, partially removed and after removal (with remnants of the interface showing).

[0040] The method in accordance with an embodiment of the invention is shown by the flow chart of FIG. 3. In the initial step 10 a component is built along with support structures by a known metallic additive manufacture process. A subsequent heat treatment 20 is applied to the part after removal from the additive layer manufacturing machine (but with the part remaining attached to the baseplate to resist deformation. This heat treatment is in a non-oxidising atmosphere (inert or vacuum) and is intended to reduce or minimise residual stresses.

[0041] With the residual stresses reduced by the heat treatment process 20, the component may processed 30 to remove it from the baseplate (but will still have associated support structure attached or embedded within it).

[0042] After this removal the part and support structure are subjected to a thermal pulse process 40 to weaken the interfaces between the support and component. This thermal pulse is carried out in a sealed chamber at increased pressure. The chamber is filled with methane and air which is allowed to fully surround the component prior to ignition to provide extremely rapid and high temperature combustion (an explosive or pseudo explosive process). The thermal pulse may for example last approximately 20 milliseconds and result in an increase in temperature within the chamber of between 2500 C. and 3500 C. and a pressure spike of up to 2000 bar. The heat will strike the surfaces of the component and support structure but is of insufficient duration to cause bulk heating thereof. The thermal pulse step may for example be carried out using a conventional thermal deburring apparatus.

[0043] The thermal pulse step 40 has been found to weaken the interface parts 3 of the support 2 but since it does not cause any bulk heating of the component 1 it does not cause any change in its material properties. In contrast the interface parts are assumed to have a greater thermal conductivity so experience more significant surface oxidation and/or vaporisation and/or melting during the thermal pulse. This has been found to have provide a significant weakening of the interface and aid removal of the support (in step 50 below)

[0044] After the thermal pulse step 40, the support 50 using any convenient mechanical processing step 50 (and the skilled person will appreciate that the particular mechanical process selected may depend upon several factors such as the material and geometry of the component and support).

[0045] Once the support has been fully removed it is normal to apply a final abrasive cleaning step 70 such as abrasive blasting to remove any remaining remnants of the interface members 3 from the separated component 1. In accordance with an embodiment prior to such abrasive blasting the component may optionally be subjected to a further thermal pulse step 60. The thermal pulse step 60 may include the application of a plurality of thermal pulses.

[0046] It has surprisingly been found that the application of this additional step 70 produces a greater reduction in final surface reduction. This appears to go directly against the teaching in the art since an advantage of utilising thermal pulses in known processes such as thermal deburring is that component surfaces should not be affected. When the method of an embodiment was applied to test pieces by the applicant it was found to demonstrate a reduce surface roughness (Ra measurement), measured using a surface profilometer following the subsequent abrasive blasting process 70, of at least 30% and typically 50% to 60%.

[0047] Without being bound to any particular theory, the applicants believe that the reduction in surface roughness is a result of the residual high points of the interface (and for example high points of roughness on downward faces) being vaporised, oxidised or melted by the thermal pulse creating a selectivity to the process and thereby enabling a smoothing to take place. The surface oxide than results from the thermal process is then removed by abrasive blasting.

[0048] Although the invention has been described above with reference to a preferred embodiment, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims. For example, there may be more than one thermal pulse to process step 40 and some (or all) interface members 3a, 3b, 3c may be completely broken by the thermal pulse process step 40. Indeed the complete breaking of all interface members would be idealthereby allowing the simplest possible removal of the support (including by gravity). A limiting factor to interface breaking by additional thermal pulses may be an undesirable bulk heating of the part or simply cost and timeat some point it may be more desirable to mechanically cut the support away (including by unconventional methods such as electro discharge machining). In all regards though the support is mechanically removed; a thermal pulse does not of itself remove the support.