Three dimensional printer

A powder sintering lamination molding method, comprising the steps of:

• forming a material powder layer corresponding to a sliced layer obtained by slicing a model of a molded product having a desired three-dimensional profile, the model being sliced by a horizontal plane at a unit height;
• and
• irradiating an irradiation region of the sliced layer of the molded product surrounded by an outline profile with a laser to selectively sinter the material powder of the material powder layer within the irradiation region;
• wherein the steps of the forming of the material powder layer and the irradiating of the irradiation region are repeated to produce the molded product;
• the laser is scanned along a scanning passage comprising a plurality of lines, thereby irradiating the material powder layer, the scanning passage provided to allow irradiation of the laser throughout the entire irradiation region;
• the plurality of lines are classified into a plurality of line groups;
• each line group of the plurality of line groups contains a plurality of lines arranged in a first direction of a width of line and a plurality of lines arranged in a second direction orthogonal to the first direction;
• condition (a):
• wherein a first line is a line irradiated with the laser among a plurality of lines, and a second line is a line affected by heat of the first line such that each of the plurality of lines is discontinuous from any other line within the entire irradiation region;
• condition (b):
• a cooling period is provided after the laser is irradiated along the first line and before the laser is irradiated along the second line;
• condition (c):
• irradiation of the laser is controlled to irradiate the laser, along a line besides the second line and belonging to a line group other than a line group in which the first line and the second line belongs, during the cooling period;
• and
• condition (d):
• the plurality of line groups are selected in order and the laser is irradiated along one line belonging to the selected line group, when the laser is irradiated;
• wherein no matter which line among the plurality of lines is selected as the first line, all of the conditions (a) to (d) are satisfied.