A three-dimensional additive manufacturing device, comprising:
- a base plate configured to move along a vertical direction;
- a powder feeding unit configured to laminate a powder layer including a powder sample on an upper surface of the base plate;
- a beam generating unit configured to generate a beam in a designated quantity of heat;
- and
- a control unit configured to control modeling by causing the beam generating unit to irradiate a designated position of the powder layer prepared on the base plate with the beam in a scan order programed based on three-dimensional model data,
- wherein the control unit controls modeling by repeating steps including:
- spreading the powder sample thinly on a top surface of the base plate and laminating the powder layer;
- presintering to mildly sinter the powder sample of the powder layer after the spreading;
- primarily preheating the powder layer to return the temperature of the designated position at a desired temperature by scanning through the powder layer with the beam after the presintering;
- modeling by irradiating the designated position of the powder layer with the beam in the scan order programed based on the three-dimensional model data;
- and
- secondarily preheating the powder layer to set the temperature of the designated position at a target temperature by irradiating the powder layer with the beam after the modeling and before moving on to the spreading,
- wherein the control unit calculates heat capacity of the designated position of the powder layer by following formula (4):
- C=Vacc×Σj(Ij×τj)/Ttarget−Tnow+α·Δt (4)
- where
- C represents heat capacity of the designated position of the powder layer;
- Ttarget represents temperature right before the spreading;
- Tnow represents temperature right before the primary preheating;
- Vacc represents acceleration voltage of the beam generating unit;
- Ij represents an emission current of electron beam;
- τj represents irradiation time of the emission current;
- Δt represents time difference between the temperature right before the primary preheating and the temperature right before the powder spreading;
- and
- α represents cooling rate calculated using the maximum temperature during the presintering, the temperature right before the primary preheating, and the time interval between those two temperatures,
- wherein the control unit determines a required quantity of heat to be input to the designated position, based on the calculated heat capacity, to set a temperature of the designated position at a desired temperature at a future designated time, and the control unit controls the beam generated by the beam generating unit to enable input of the required quantity of heat to the designated position.