Method of forming an article

#This invention relates to a method of forming an article.

#The laser or electron beam sintering/melting of powdered materials to form solid parts is now well known—though not so well known as for there to be an established nomenclature. In particular there are commercial powder bed ‘Selective Laser Sintering’/‘Selective Laser Melting’ (SLS/SLM) machines such as the M270 produced by Electron Optical Systems (EOS) M270 and the Realizer II marketed by MCP. These take metal powders under an inert atmosphere and direct a CO2 or fibre laser onto a layer of powder.

#There are also other similar powder bed machines sometimes using an electron beam and somewhat related processes where there is no bed of powder, but the powder is ejected from a nozzle proximate the laser such as in the Trumpf DMD 505. These processes are called such things as ‘Direct Laser Fabrication’ or ‘Direct Metal Deposition’.

#The invention may be performed in various ways and specific embodiments will now be described, by way of example, with reference to the accompanying drawings, in which:

#FIG. 1 is a side view of part of selective sinter or melt powder forming apparatus with a formed article shown;

#FIG. 2 is a corresponding article with a different support structure;

#FIG. 1 is a diagrammatic view at the completion of the build of a solid object 1 formed by the solidification of powder 2 by the application of a point source of heat (not shown) in a layer wise process. The building commences at a platen 3 bolted by bolt 4 to an elevator platform 5 within a powder bed machine. To enable the solid object to be built and allow a cutting gap between the object and the platen a support structure is needed. The support structure of the invention is shown at 6 being a solid support with grooves or channels 6a that contain loose powder 2. The grooves or channels are orientated such that they line along the line of traverse of the powder recoater blade 7. The grooves or channels are open at least one end so that powder can be removed from them, e.g. by vacuum, prior to heat treatment of the article or object 1.

#FIG. 2 again shows a support structure of an embodiment of the invention at 6 as a discrete layer below a support structure 8 of the prior art. A plan view of this prior art support 8 is shown at FIG. 3 (prior art). Here is shown an “EOSTYLE” support generated by a module within the “Magics” software produced by Materialise, Leuven, Belgium. The software generates a ‘Manhattan’ style of support consisting of thin walls 12 and contained voids 10. Around blocks of walls there can be selectable gaps 11 and the whole is enclosed by a selectable outer wall 9. The distance between the walls 12 is also selectable and is typically 1 mm. The purpose of the gaps 11 is to enable the ‘Manhattan’ blocks made of thin walls 12 to be easily snapped off the built part 1 by hand or using hand tools.

#The trapping of powder is a known problem and the intended solution within the EOSTYLE support is shown at FIG. 4 (prior art). This is a view of a wall 9/12 of the EOSTYLE support 8 of the prior art with the platen 3 and the built part 1. holes 13 of a diamond or square shape can be added for the intended purpose of releasing powder. Unfortunately it is impractical to get the powder from an enclosed solid support 8 through these holes and if the hole size is enlarged the support structure does not build reliably.