Object production using an additive manufacturing process and quality assessment of the object

1. A method of producing and assessing at least part of an object ( 2 ), the method comprising:

providing an initial object; and

performing, using common Additive Manufacturing apparatus ( 8 ), an Additive Manufacturing process to:

add additional material to the initial object; and

produce a test specimen ( 30 , 34 , 38 ), the test specimen ( 30 , 34 , 38 ) being produced from the same material as the additional material that is added to the initial object, the test specimen ( 30 , 34 , 38 ) being produced on a surface of the initial object at a location that is at or proximate to the location, on the initial object, of the additional material that is added by the Additive Manufacturing apparatus ( 8 ) performing the Additive Manufacturing process;

performing, using computed-tomography apparatus ( 40 ), on the produced test specimen ( 30 , 34 , 38 ), a computed-tomography process to create a model ( 50 ), the model ( 50 ) being a digital model of the internal structure of the test specimen ( 30 , 34 , 38 );

determining whether or not the model ( 50 ) satisfies one or more criteria; and

if the model ( 50 ) satisfies the one or more criteria, determining that the additional material added to the initial object is acceptable; or

if the model ( 50 ) does not satisfy the one or more criteria, determining that the additional material added to the initial object is not acceptable.

2. The method according to claim 1 , wherein a portion of the test specimen ( 30 ) is produced, by the Additive Manufacturing apparatus ( 8 ) performing the Additive Manufacturing process, before the Additive Manufacturing apparatus ( 8 ) has begun to add the additional material to the initial object.

3. The method according to claim 1 , wherein a portion of the test specimen ( 30 ) is produced, by the Additive Manufacturing apparatus ( 8 ) performing the Additive Manufacturing process, after the Additive Manufacturing apparatus ( 8 ) has begun to add the additional material to the initial object and before the Additive Manufacturing apparatus has finished adding the additional material to the initial object.

4. The method according to claim 1 , wherein a portion of the test specimen ( 38 ) is produced, by the Additive Manufacturing apparatus ( 8 ) performing the Additive Manufacturing process, after the Additive Manufacturing apparatus ( 8 ) has finished adding the additional material to the initial object.

5. The method according to claim 1 , wherein

the test specimen ( 30 , 34 , 38 ) comprises two or more portions selected from the group consisting of:

a portion ( 30 ) that is produced, by the Additive Manufacturing apparatus ( 8 ) performing the Additive Manufacturing process, before the Additive Manufacturing apparatus ( 8 ) has begun to add the additional material to the initial object;

a portion ( 34 ) that is produced, by the Additive Manufacturing apparatus ( 8 ) performing the Additive Manufacturing process, after the Additive Manufacturing apparatus ( 8 ) has begun to add the additional material to the initial object and before the Additive Manufacturing apparatus has finished adding the additional material to the initial object; and

a portion ( 38 ) that is produced, by the Additive Manufacturing apparatus ( 8 ) performing the Additive Manufacturing process, after the Additive Manufacturing apparatus ( 8 ) has finished adding the additional material to the initial object; and

the portions of the test specimen ( 30 , 34 , 38 ) are created as a stack of contiguous portions.

6. The method according to claim 5 , wherein each portion has a differently shaped cross-sectional area to the one or more other portions with which that portion is contiguous.

7. The method according to claim 1 , wherein the step of determining whether or not the model ( 50 ) satisfies one or more criteria comprises:

analysing the model ( 50 ) to detect features ( 52 ) in the model ( 50 ) that correspond to defects with the test specimen ( 30 , 34 , 38 ); and

determining whether or not the detected model features ( 52 ) satisfy the one or more criteria.

8. The method according to claim 7 , wherein the features ( 52 ) are voids within the test specimen ( 30 , 34 , 38 ).

9. The method according to claim 7 , wherein each of the one or more criteria is a criterion selected from the group of criteria consisting of:

a criterion that the total volume of the detected model features ( 52 ) is below a first pre-determined threshold value;

a criterion that the total surface area of the detected model features ( 52 ) is below a second pre-determined threshold value;

a criterion that the maximum volume of a detected model features ( 52 ) is below a third pre-determined threshold value;

a criterion that the maximum length of a detected model features ( 52 ) is below a fourth pre-determined threshold value;

a criterion that the total number of detected model features ( 52 ) is below a fifth pre-determined threshold value; and

a criterion that the detected model features ( 52 ) are not arranged in a predetermined pattern.

10. The method according to claim 1 , the method further comprising:

after the production of the test specimen ( 30 , 34 , 38 ), performing, using the Additive Manufacturing apparatus ( 8 ), an Additive Manufacturing process to produce a further test specimen, the further test specimen being produced from the same material as the additional material that is added to the initial object;

performing, using the computed-tomography apparatus, a computed-tomography process to create a further model, the further model being a digital model of the internal structure of the further test specimen;

determining whether or not the further model satisfies the one or more criteria; wherein

the at least part of the object ( 2 ) produced by performing the Additive Manufacturing process is only acceptable if the both the model ( 50 ) and the further model satisfy the one or more criteria; and

at least some of the at least part ( 2 ) of the object is produced, by the Additive Manufacturing apparatus performing the Additive Manufacturing process, between the production of the test specimen ( 30 , 34 , 38 ) and the production of the further test specimen.

11. The method according to claim 1 , wherein the Additive Manufacturing process is a process selected from the group of Additive Manufacturing processes consisting of: a blown powder Additive Manufacturing process, a powder bed fusion Additive Manufacturing process, a sheet lamination Additive Manufacturing process, a vat photopolymerisation Additive Manufacturing process, a laser blown powder Additive Manufacturing process, a laser powder bed Additive Manufacturing process, and an Additive Manufacturing process that implemented wire and arc technology.