Spot preheating
AssigneeFreemelt AB
InventorUlric Ljungblad
Life of this patent
Estimating the term…
Abstract
The present invention relates to a heating method for preparing a powder bed for subsequent processing by irradiating the powder bed with an electron beam from an electron source. The electron source may be designed for fast moving of the electron beam to different heating positions at the powder bed comprising the step, local heating of at least two powder bed heating positions by successive resting of said electron beam at the at least two powder bed heating positions. By jumping between local preheating positions at the powder bed before the powder is fused, charged powder can be prevented from levitation and scattering from the powder bed.
Claims27
A heating method for heating a powder bed to fuse the powder by melting by irradiating said powder bed with an electron beam from an electron source, said electron source being designed for fast moving of said electron beam to different heating positions at said powder bed, comprising local heating of at least two fixed powder bed heating positions to fuse the powder by successive holding of said electron beam spot at said at least two fixed powder bed heating positions according to a heating pattern, comprising the following steps:
- holding the electron beam spot at one of said at least two fixed powder bed heating positions for a first predetermined time to heat the powder to fuse the powder in that position;
- moving the electron beam spot rapidly with a jumping speed to another of said at least two fixed powder bed heating positions, wherein said electron beam spot is moved in a powder bed plane from one powder bed heating position where it is held to another powder bed heating position where it is held again at a location having a different x- and y-coordinate within the powder bed plane from the one powder bed heating position;
- and
- holding the electron beam spot at the another of said at least two fixed powder bed heating positions for a second predetermined time to heat the powder to fuse the powder in that position, wherein the heating pattern of subsequent fixed powder bed heating positions at the powder layer bed achieves a minimum time span during which the powder bed is heated,
- wherein time between repeated heating of two subsequent and adjacent fixed powder bed heating positions according to the heating pattern is not less than a minimum time required for electrical charge to dissipate so as to avoid levitation and scattering of charged powder from the powder bed.
A heating method for heating a powder bed to fuse the powder by melting by irradiating said powder bed with an electron beam from an electron source, said electron source being designed for moving of said electron beam between different heating positions at said powder bed, comprising the steps:
- local heating of at least two fixed powder bed heating positions in a powder bed plane to fuse the powder, wherein the electron beam spot is repeatedly moved to new powder bed heating positions until a predetermined heating pattern of a selected region of the powder bed has been achieved, said heating pattern including successive holding of said electron beam at each fixed powder bed heating position wherein when the electron beam spot arrives to a new heating position, a fixed position is held and the electron beam heats the powder in that position for a predetermined time to fuse the powder, and wherein the electron beam spot subsequently moves rapidly with a jumping speed to the next heating position, where again a fixed position is held and the electron beam heats the powder in that position for a predetermined time to fuse the powder, wherein each next heating position has a different x- and y-coordinate within the powder bed plane from the previous heating position, and wherein time between repeated heating of adjacent heating positions is not less than a minimum time required for electrical charge to dissipate so as to avoid levitation and scattering of charged powder from the powder bed.
A heating method for preheating a powder bed before a region of a top powder layer of the powder bed is fused or melted, by irradiating said powder bed with an electron beam from an electron source, said electron source being designed for moving of said electron beam to different heating positions at said powder bed, comprising the step:
- local preheating of at least two fixed powder bed heating positions by successive holding of said electron beam spot at said at least two fixed powder bed heating positions according to a heating pattern determined based on electrical charge distribution at the powder bed,
- wherein the heating pattern reduces the risk for levitation and scattering of charged powder particles during the preheating comprising the following steps:
- holding the electron beam spot at one of said at least two fixed powder bed heating positions for a first predetermined time to preheat the powder in that position;
- moving the electron beam spot rapidly with a jumping speed to another of said at least two fixed powder bed heating positions in a powder bed plane;
- holding the electron beam spot at the another of said at least two fixed powder bed heating positions for a second predetermined time to preheat the powder in that position, repeating the holding of the electron beam spot at fixed powder bed heating positions until the heating pattern is achieved, wherein each subsequent one of said at least two fixed powder bed heating positions is in a different x- and y-coordinate within the powder bed plane from each previous one of said at least two fixed powder bed heating positions, and
- wherein the heating pattern of powder bed heating positions is provided at the powder layer bed for achieving a minimum time span during which the powder bed is heated to a predetermined temperature wherein said jumping speed is high enough to give negligible heat transfer and charging potential to the powder bed.
Dependencies are inferred from the claim text.