Method of selective laser solidification

A method of selectively melting a plurality of powder layers deposited on a powder bed to form a three-dimensional object, the method comprising:

• passing a flow of gas over the powder bed along at least one gas flow direction;
• and
• scanning a laser beam along a scan path on each of the plurality of powder layers to selectively melt at least part of each of the powder layers to form a required pattern,
• wherein, for each of the plurality of powder layers, a direction along which the laser beam is moved is orientated relative to the at least one gas flow direction so that particles ejected during the selective melting are carried by the flow of gas in a direction that substantially prevents the ejected particles from reducing laser power that reaches the powder layer when melting regions of the scan path that have yet to be scanned.

A method of selectively melting a plurality of powder layers deposited on a powder bed to form a three-dimensional object, the method comprising:

• passing a flow of gas over the powder bed along a predefined gas flow direction;
• and
• scanning a laser beam over each of the plurality of powder layers to selectively melt at least part of each powder layer to form a required pattern, the required pattern of each powder layer being formed from a series of hatch lines that are advanced over each powder layer along a hatch line movement direction,
• wherein the hatch line movement direction subtends an angle of at least 10° to a normal to the gas flow direction for each of the plurality of powder layers.

A method of selectively melting a plurality of powder layers deposited on a powder bed to form a three-dimensional object, the method comprising:

• passing a flow of gas over the powder bed along a predefined gas flow direction;
• and
• scanning a laser beam over each of the plurality of powder layers to selectively melt at least part of each powder layer to form a required pattern, the required pattern of each powder layer being formed from one or more stripes or stripe segments, each stripe or stripe segment being formed by advancing the laser beam along the stripe or stripe segment along a stripe formation direction,
• wherein the stripe formation direction subtends an angle of at least 10° to a normal to the gas flow direction for each of the plurality of powder layers.