Selective solidification apparatus and methods

Abstract

A selective solidification apparatus includes a build chamber, a build platform lowerable in the build chamber, a wiper for spreading powder material across the build platform to form successive powder layers of a powder bed, an energy beam unit for generating an energy beam for consolidating the powder material, a scanner for directing and focussing the energy beam onto each powder layer and a processor for controlling the scanner. The processor is arranged to control the scanner to scan the energy beam across the powder bed to consolidate powder material either side of the wiper when the wiper is moving across the powder bed and to scan the energy beam across at least one of the powder layers during two or more strokes of the wiper across the powder bed.

1 . (canceled) 
     
     
         2 . A powder bed selective solidification apparatus comprising a build chamber, a build platform lowerable in the build chamber; a wiper unit for spreading powder material across the build platform, the wiper unit is arranged to form successive powder layers of a powder bed in a common plane; an energy beam unit for generating an energy beam; a scanner for directing the energy beam onto each powder layer; and a processor for controlling the scanner; wherein, the processor is arranged to control the scanner to scan the energy beam across the powder bed to heat powder material on either side of the wiper unit when the wiper unit is moving across the powder bed. 
     
     
         3 . A powder bed selective solidification apparatus according to  claim 2 , wherein the processor is further arranged to control movement of the wiper unit to vary a speed of the wiper unit based upon at least one of: i) an area of a layer to be heated with the energy beam, and ii) scan paths for the energy beam to take in heating the powder material. 
     
     
         4 . A powder bed selective solidification apparatus according to  claim 2 , wherein the processor is further arranged to control movement of the wiper unit to vary a time the wiper unit is stationary between strokes of the wiper unit based upon at least one of: i) an area of a layer to be heated with the energy beam, and ii) scan paths for the energy beam to take in heating the powder material. 
     
     
         5 . A powder bed selective solidification apparatus according to  claim 2 , wherein the wiper unit comprises a single wiper. 
     
     
         6 . A powder bed selective solidification apparatus according to  claim 2 , wherein the wiper unit comprises two spaced apart wipers, each wiper arranged to spread powder in the common plane, and a dispenser arranged to dispense powder into a gap between the two spaced apart wipers. 
     
     
         7 . A powder bed selective solidification apparatus according to  claim 2 , wherein the scanner comprises titling optics for scanning a laser beam across the powder bed, wherein the processor is arranged to control the tilting optics to automatically compensate for the fact that a single position of the titling optics will scan different spots on the surface of the powder bed dependent on the level of the surface being scanned. 
     
     
         8 . A powder bed selective solidification apparatus according to  claim 2 , wherein the scanner comprises titling optics for scanning a laser beam across the powder bed, wherein the processor comprises a first map for mapping a position of the tilting optics to a position of the laser beam in an upper plane and a different, second map for mapping a position of the tilting optics to a position of the laser beam in a lower plane. 
     
     
         9 . A powder bed selective solidification apparatus according to  claim 8 , wherein the upper plane is the common plane in which the successive powder layers are formed. 
     
     
         10 . A powder bed selective solidification apparatus according to  claim 2 , wherein the processor is arranged to control the scanner to scan the energy beam across the powder bed to heat powder material during lowering of the build platform. 
     
     
         11 . A powder bed selective solidification apparatus according to  claim 2 , wherein the processor is arranged to control the scanner to scan the energy beam across the powder bed to consolidate powder material on either side of the wiper unit when the wiper unit is moving across the powder bed. 
     
     
         12 . A powder bed selective solidification apparatus according to  claim 10 , wherein the processor is arranged to control the scanner to scan the energy beam across the powder bed to consolidate powder material during lowering of the build platform. 
     
     
         13 . A powder bed selective solidification apparatus according to  claim 2 , wherein the energy beam is a laser beam. 
     
     
         14 . A method for forming an object by powder bed selective solidification, in which powder layers are solidified using an energy beam in a layer-by-layer manner to form an object, the method comprising, repeatedly, spreading powder material across a build platform with a wiper unit to form successive powder layers of a powder bed in a common plane, and, during movement of the wiper unit across the powder bed, scanning the energy beam across the powder bed to heat powder material on either side of the wiper unit. 
     
     
         15 . A method according to  claim 14 , comprising controlling movement of the wiper unit to vary a speed of the wiper unit based upon at least one of: i) an area of a layer to be heated with the energy beam, and ii) scan paths for the energy beam to take in heating the powder material. 
     
     
         16 . A method according to  claim 14 , comprising controlling movement of the wiper unit to vary a time the wiper unit is stationary between strokes of the wiper unit based upon at least one of: i) an area of a layer to be heated with the energy beam, and ii) scan paths for the energy beam to take in heating the powder material. 
     
     
         17 . A method according to  claim 14 , comprising controlling titling optics for scanning a laser beam across the powder bed, wherein the tilting optics are controlled to automatically compensate for the fact that a single position of the titling optics will scan different spots on the surface of the powder bed dependent on the level of the surface being scanned. 
     
     
         18 . A method according to  claim 14 , comprising controlling titling optics for scanning a laser beam across the powder bed, wherein the tilting optics are controlled using a first map for mapping a position of the tilting optics to a position of the laser beam in an upper plane and a different, second map is used for mapping a position of the tilting optics to a position of the laser beam in a lower plane. 
     
     
         19 . A method according to  claim 18 , wherein the upper plane is the common plane in which the successive powder layers are formed. 
     
     
         20 . A method according to  claim 14 , comprising controlling the scanner to scan the energy beam across the powder bed to heat powder material during lowering of the build platform. 
     
     
         21 . A method according to  claim 14 , comprising consolidating powder material on either side of the wiper unit when the wiper unit is moving across the powder bed. 
     
     
         22 . A method according to  claim 20 , comprising consolidating powder material during lowering of the build platform. 
     
     
         23 . A method according to  claim 14 , wherein the energy beam is a laser beam. 
     
     
         24 . A data carrier having instructions stored thereon, the instructions for execution by a processor for controlling a powder bed selective solidification apparatus a build chamber, a build platform lowerable in the build chamber, a wiper unit for spreading powder material across the build platform, an energy beam unit for generating an energy beam, a scanner for directing the energy beam onto each powder layer and a processor for controlling the scanner; wherein the wiper unit is arranged to form successive powder layers of a powder bed in a common plane, wherein, the instructions, when executed by the processor, cause the processor to carry out the method according to  claim 14 . 
     
     
         25 . A powder bed selective solidification apparatus comprising a build chamber, a build platform lowerable in the build chamber; a wiper unit for spreading powder material across the build platform, the wiper unit arranged to form powder layers of a powder bed; an energy beam unit for generating an energy beam; a scanner for directing the energy beam onto each powder layer; and a processor for controlling the scanner to scan the energy beam across the powder bed to heat powder material during lowering of the build platform. 
     
     
         26 . A powder bed selective solidification apparatus according to  claim 25 , wherein the processor is arranged to control the scanner to scan the energy beam across the powder bed to consolidate powder material during lowering of the build platform.