Patent ID: 8303886

Claim:
A method of manufacturing a three-dimensional object, in which the object is solidified layer by layer by solidifying a building material by means of a beam of a gas laser at locations in the layer corresponding to the cross section of the object, wherein the solidifying of the building material comprises the selective solidification of a powder material, the method comprising: splitting an output of the laser into a first component to be impinged on the powder material and a second component to be measured by a sensor, thereby facilitating simultaneous measurement of output power and solidification of the powder; solidifying a first track of the three-dimensional object by switching the laser on at the beginning of the first track and switching the laser off at the end of the first track; measuring the power of the laser in a time window in which solidification of the first track occurs, the time window including: i) the switch-on operation, ii) the switch-off operation, iii) an abrupt change of power between two power values, or some combination of at least two of i)-iii); using the measurement of power during solidification of the first track to generate an input control signal for the laser for solidification of a subsequent track, the input control signal including a switch-on ramp having a start impulse followed by a temporary attenuation of the input control signal; and solidifying the subsequent track of the three dimensional object by actuating the laser according to the input control signal generated from the measurement of the first track, wherein the solidification of the subsequent track follows the solidification of the first track.