Patent ID: 6930278

Claim:
A method for forming a three dimensional article by laser sintering comprising the steps of: (a) delivering a quantity of powder adjacent a target area in a process chamber; (b) spreading the quantity of powder with a spreading mechanism to form a layer of powder; (c) heating the powder while adjacent to the target area, while it is spread and as it lies as a layer; (d) directing an energy beam over the target area causing the layer of powder to form an integral layer; and (e) repeating steps (a) to (d) to form additional layers that are integrally bonded to adjacent layers so as to form a three dimensional article, wherein during at least one layer forming step a radiation emitter positioned adjacent a sensor means within the process chamber emits radiation to the sensor means and a calibration means receives readings from the sensor means to compare temperature sensings received from the sensor means with set emission signals from the radiation emitter converted to temperatures from the radiation emitter to adjust the temperature sensings to thereby calibrate the sensor means during the forming of the three dimensional article.