Adaptive path for additive manufacturing using a laser source

1 . A method of determining a trajectory followed by a laser beam for selective additive manufacture of a three-dimensional object, the method comprising:

(I) an emitting step including emitting, via a laser source, a laser beam toward a layer of powder for manufacturing the three-dimensional object;

(II) a determining step comprising:

(a) a first determining step including determining, on a predetermined reference path, a plurality of reference points,

(b) a second determining step including determining a plurality of adjacent points located on a same side of the predetermined reference path, each adjacent point being associated with a reference point and being such that a simulated adjacent melt zone that surrounds the adjacent point and a simulated reference melt zone that surrounds the reference point have an overlap corresponding to a fraction of a transverse width of the simulated reference melt zone that is comprised between a predetermined minimum fraction and a predetermined maximum fraction, the second determining step comprising successively, for each adjacent point in one direction of travel of a trajectory of the laser beam, the following steps:

(1) estimating, for a reference point associated with an adjacent point, a transverse width of a reference simulated melt zone;

(2) determining an initial position of the adjacent point, a distance separating the initial position of the adjacent point from a position of the reference point being equal to a product of the transverse width of the reference simulated melt zone and of a predetermined target degree of overlap, the adjacent point being placed with respect to the reference point in a direction that is orthogonal to the predetermined reference path at the reference point, comprised in a plane of the layer of powder and directed from the predetermined reference path toward an adjacent path; and

(3) carrying out secondary steps, which are as follows:

(i) estimating an initial transverse width of a simulated adjacent melt zone;

(ii) estimating an overlap between the reference simulated melt zone and the adjacent simulated melt zone; and

(iii) repeating the secondary steps while modifying the initial position of the adjacent point if the estimated overlap corresponds to a fraction of the simulated reference melt zone less than a predetermined minimum fraction or greater than a predetermined maximum fraction;

(c) a third determining step including determining an adjacent path linking the plurality of adjacent points; and

(d) repeating the first determining step, the second determining step, and the third determining step in a loop using the adjacent path determined as a new reference path, so as to determine, on each iteration, a new adjacent path among the plurality of adjacent paths, until all adjacent paths to be travelled by the laser beam in the layer of powder have been determined, the plurality of adjacent paths that have been determined defining a determined trajectory, which is followed by the laser beam;

(III) a storing or transmitting step including storing or transmitting the determined trajectory to the control unit of a selective additive manufacturing apparatus;

(IV) an estimating step including estimating the transverse width of a zone being a total width in a direction transverse to a direction of scanning of the laser beam; and

(V) a moving step, occurring after the determining step (II), including moving the laser beam along the determined trajectory made up of the plurality of adjacent paths to cause the layer of powder to melt according to the determined trajectory to optimize overlapping of melt zones for melting the layer of powder such that non-melted portions of the layer of powder are avoided to prevent defects in the three-dimensional object, the determined trajectory being directed by a computer simulation that provides a desired path of the laser beam, wherein the moving step includes controlling the laser source, via a control unit, to emit the laser beam onto the layer of powder according to the determined trajectory.

2 . The method according to claim 1 , further comprising:

determining a numerical dissimilarity between the estimated overlap and a target overlap equal to a product of the transverse width of the reference simulated melt zone and of the predetermined target degree of overlap.

3 . The method according to claim 2 , wherein the predetermined target degree of overlap is equal to 15%, the predetermined minimum fraction is equal to 12%, and the predetermined maximum fraction is equal to 18%.

4 . The method according to claim 2 , wherein, to estimate the overlap between the reference simulated melt zone and the simulated adjacent melt zone, a half-sum of a transverse width of the reference simulated melt zone and of an initial transverse width of the simulated adjacent melt zone subtracted from a distance separating the initial position of the adjacent point and the position of the reference point is determined.

5 . The method according to claim 2 , wherein, when repeating the secondary steps, the initial position of the adjacent point is modified so that the distance separating the initial position of the adjacent point and the position of the reference point is replaced by a difference between the distance and the dissimilarity between the estimated overlap and a product of the transverse width of the reference simulated melt zone and of the predetermined target degree of overlap.

6 . The method according to claim 1 , wherein the step of estimating a transverse width of the simulated melt zone that surrounds a study point located on the layer of powder, the study point being a reference point of the reference path or a point at an initial position of an adjacent point, comprises the following steps:

determining a plurality of computation points, the computation points being points of the layer of powder that are located in a neighborhood of the study point;

estimating a maximum temperature reached at each of the computation points, the estimate being made on the basis of variations in temperature due to the emitting step so as to consolidate zones of the layer of powder surrounding upstream points located on a plurality of paths upstream of a passage of the laser beam to the study point, and the estimate being made on the basis of a variation in temperature of the powder at the computation point due to the emitting step so as to consolidate a zone of the layer of powder surrounding the study point;

comparing the maximum temperature reached estimated with a melting point of the powder;

identifying, among the computation points, melted points for which the estimate of the maximum temperature reached is greater than or equal to the melting point of the powder; and

estimating a transverse width of a zone occupied by the melted points.

7 . The method according to claim 6 , wherein the step of estimating the maximum temperature at the computation point comprises the following steps:

computing, for each upstream point located on the plurality of paths upstream of a passage of the laser beam to the study point, an estimate of a variation in temperature of the powder at the computation point due to emission of a laser beam so as to consolidate a zone of the layer of powder surrounding the upstream point;

computing an estimate of a variation in temperature of the powder at the computation point due to emission of a laser beam so as to consolidate a zone of the layer of powder surrounding the study point;

computing the estimate of a temperature of the powder at the computation point depending on the estimates of the variations in temperature due to emission of a laser beam so as to consolidate zones of the layer of powder surrounding the study point or upstream points; and

computing the estimate of a maximum temperature at the computation point by extracting a maximum value retained as the maximum temperature reached at the computation point from a series of dated values forming the estimate of the temperature of the powder at the computation point.

8 . The method according to claim 6 , wherein the step of estimating, for each upstream point, an estimate of a variation in temperature of the powder at the computation point due to emission of a laser beam so as to consolidate a zone of the layer of powder surrounding the upstream point comprises the following steps:

computing, for each upstream point, a distance separating the study point and the upstream point;

comparing the distance to a predetermined spatial-neighborhood distance; and

estimating as zero, for each upstream point separated from the study point by a distance greater than the spatial-neighborhood distance, a variation in temperature of the powder at the computation point due to the emitting step so as to consolidate a zone of the layer of powder surrounding the upstream point.

9 . The method according to claim 6 , wherein the step of estimating, for each upstream point, an estimate of a variation in temperature of the powder at the computation point due to the emitting step so as to consolidate a zone of the layer of powder surrounding the upstream point comprises the following steps:

computing, for each upstream point, a duration separating emission of a laser beam so as to consolidate a zone of the layer of powder surrounding the upstream point and the passage of the laser beam to the study point;

comparing the duration to a predetermined temporal-neighborhood duration; and

estimating as zero, for each upstream point the computed duration of which is greater than the temporal-neighborhood duration, a variation in temperature of the powder at the computation point due to the emitting step so as to consolidate a zone of the layer of powder surrounding the upstream point.

10 . A process for selective additive manufacture of a three-dimensional object from a layer of powder, the process comprising, in a selective additive manufacturing apparatus:

determining a trajectory by implementing the method according to claim 1 ;

applying a layer of additive manufacturing powder to a carrier or to a previously consolidated layer; and

emitting a laser beam onto the layer of powder following the trajectory.

11 . A computer program stored in a computer readable medium comprising instructions suitable for implementing the steps of the method according to claim 1 when the computer program is executed on a computer.