Method and apparatus for producing three-dimensional objects

1. Method for producing three-dimensional objects ( 6 ) layer by layer using a powdery material ( 7 ) which can be solidified by irradiating it with a high-energy beam ( 4 ), said method comprising the steps of;

applying a first layer of powdery material onto a working area ( 5 );

solidifying a part of said first layer by irradiating it with a high-energy beam;

applying a second layer ( 8 ) of powdery material onto the first, partly solidified layer;

determining a rate at which the temperature of the second layer ( 8 ) increases after application onto the first layer; and

determining a layer thickness of the second layer based upon the determined rate at which the temperature of the second layer ( 8 ) increases after application onto the first layer,

wherein:

the step of determining the layer thickness of the second layer involves performing a plurality of sequential temperature measurements before the second layer ( 8 ) reaches a maximum temperature (T 1 ); and

the maximum temperature (T 1 ) represents a point in time at which a rate that heat is conducted from the first layer equals a rate that heat is radiated away from an upper surface of the second layer ( 8 ), such that upon reaching the maximum temperature (T 1 ), the temperature of the second layer ( 8 ) is no longer increasing.

2. Method according to claim 1 , further comprising the step of measuring a temperature in at least one position of said second layer ( 8 ) using a temperature sensing device ( 14 ).

3. Method according to claim 2 , wherein the step of performing the plurality of sequential temperature measurements occurs in the same at least one position of said second layer ( 8 ).

4. Method according to claim 2 , further comprising the step of fitting a mathematical function to data obtained from said plurality of sequential temperature measurements.

5. Method according to claim 2 , wherein the step of measuring a temperature in at least one position of said second layer ( 8 ) comprises measuring the temperature in a plurality of positions of said second layer ( 8 ), wherein said plurality of positions are distributed over the second layer ( 8 ).

6. Method according to claim 2 , wherein the temperature sensing device is a thermographic camera ( 14 ).

7. Method according to claim 6 , wherein the thermographic camera ( 14 ) is directed towards an upper surface of the second layer ( 8 ).

8. Method according to claim 1 , further comprising the step of comparing the determined temperature increase rate with at least one reference value.