Method for producing three-dimensional shaped product

A method for producing a three-dimensional shaped product which employs a forming step in a shaping region, based on dispersion of powder by a squeegee on a shaping table disposed within a chamber and irradiation onto powder layers formed by the dispersion with a laser beam or electron beam, wherein a filter that removes fumes generated from the powder layers due to the irradiation in a fume collector that traps the fumes, a blower that circulates inert gas-containing gas inside and outside the chamber, and an anemometer that communicates with the blower are installed,

• wherein two said filters that trap fumes are installed in parallel,
• and the method including the step of controlling the amount of circulation of gas per unit time being circulated inside and outside the chamber by the following steps:
• 1. setting an upper limit value and a lower limit value for the amount of circulation of gas per unit time passing through the anemometer, and
• 2. setting an adjusting value within the range between the upper limit value and the lower limit value not by a specific standard value to accomplish stable and infrequent control,
• 3. selecting, at the start of gas circulation, a numerical value for the rotational speed of a fan of a blower not by a specific standard value so that an amount of circulation in the range between the upper limit value and the lower limit value is attained,
• 4. measuring the amount of circulation per unit time at prescribed time intervals with the anemometer to provide a measured value,
• 5. setting a maximum value for the rotational speed of the fan of the blower, with the rotational speed of the fan being measured at or after step 4,
• 6. controlling the amount of circulation as follows:
• (1) maintaining the rotational speed of the fan of the blower when the measured value is within the range between the upper limit value and the lower limit value,
• (2) increasing the rotational speed of the fan of the blower when the measured value has fallen below the lower limit value due to clogging of the filter,
• (3) selecting the rotational speed at the stage where the measured value has reached the adjusting value, and maintaining the rotational speed at this adjusting value,
• 7. switching the filter that is currently operating to the other filter by activation of a switching valve, when the rotational speed of the fan that produces the amount of circulation per unit time measured in step 4 has reached a rotational speed that is equal to or greater than the maximum value, and
• 8. repeating the control of the above steps 6 and 7 until circulation of the gas is complete.