Method for producing three-dimensional shaped product

1. 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.

2. The method for producing a three-dimensional shaped product according to claim 1 , wherein the step of controlling further includes:

(4) decreasing the rotational speed of the fan of the blower when the measured value has increased above the upper limit value, and

(5) 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.

3. The method for producing a three-dimensional shaped product according to claim 1 , wherein the difference between the measured value in step 6(2) and the lower limit value, and the degree of increase in the rotational speed of the fan, are in a proportional relationship.

4. 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. continuously measuring the amount of circulation per unit time with the anemometer to provide a measured value, and

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, and

(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.

5. The method for producing a three-dimensional shaped product according to claim 4 , wherein the step of controlling further includes:

(4) decreasing the rotational speed of the fan of the blower when the measured value has increased above the upper limit value, and

(5) 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.

6. The method for producing a three-dimensional shaped product according to claim 4 , wherein the degree of increase in the rotational speed of the fan of the blower in step 6(2) is set to be higher when the amount of circulation per unit time measured based on the prescribed time interval falls below the lower limit value at a greater frequency.

7. The method for producing a three-dimensional shaped product according to claim 1 , wherein the adjusting value in step 6(3) is greater than one of:

the arithmetic mean value or

the geometrical mean value of the upper limit value and lower limit value.

8. The method for producing a three-dimensional shaped product according to claim 1 , wherein, for the control in step 6(2), further comprising the step of gradually lowering the degree of increase in the rotational speed of the fan of the blower with the passage of time.

9. The method for producing a three-dimensional shaped product according to claim 4 , wherein the adjusting value in step 6(3) is greater than one of:

the arithmetic mean value or

the geometrical mean value of the upper limit value and lower limit value.

10. The method for producing a three-dimensional shaped product according to claim 4 , wherein, for the control in step 6(2), further comprising the step of gradually lowering the degree of increase in the rotational speed of the fan of the blower with the passage of time.