A method of determining a life defining quantity of a production component (100, 200) manufactured by an additive manufacturing process, the method comprising the steps of: defining a plurality of components (100, 200, 300) to be manufactured by an additive manufacturing process defined by a parameter set; wherein the plurality of components (100, 200, 300) comprises a first test piece and a first production component; manufacturing the components in the same manufacturing batch using an additive manufacturing process and with nominally the same material composition, determining a characteristic mechanical property of the first test piece; and determining a value of a life defining quantity of the first production component as a function of the first test piece characteristic mechanical property, providing the first production component with a first indicator and providing the first test piece with a second indicator, wherein the first indicator and the second indicator associate the first production component and first test piece respectively with the determined life defining quantity, the first test piece mechanical property and the additive manufacturing parameter set, wherein for a further manufacturing batch of the plurality of components, build parameters of a machine operable to execute the additive manufacturing process are determined in dependence of the determined mechanical property of the first test piece and determined value of the life defining quantity, wherein the manufacturing batch is formed on a common build plate, wherein the characteristic mechanical property is one of: elasticity modulus, density, ultimate tensile strength, proof strength, low cycle fatigue strength, high fatigue strength, creep strength and/or ductility, oxidation resistance or corrosion resistance, and wherein the life defining quantity is indicative of the expected operational life and/or number of operational cycles of the first production component, wherein the plurality of components (100, 200, 300) are manufactured in a three dimensional space defined by orthogonal axes x, y and z, wherein the first test piece has a first longitudinal axis and the first test piece is formed such that its longitudinal axis is parallel to one of the x, y or z axes, characterized in that the plurality of components comprises a second test piece; and the second test piece has a second longitudinal axis and the second test piece is formed such that its second longitudinal axis is parallel to a different one of the axes x, y or z than the first longitudinal axis of the first test piece, and the method further comprises the steps of determining a characteristic mechanical property of the second test piece; and determining the value of a life defining quantity of the first production component as a function of the second test piece characteristic mechanical property. defining a plurality of components (100, 200, 300) to be manufactured by an additive manufacturing process defined by a parameter set; wherein the plurality of components (100, 200, 300) comprises a first test piece and a first production component; manufacturing the components in the same manufacturing batch using an additive manufacturing process and with nominally the same material composition, determining a characteristic mechanical property of the first test piece; and determining a value of a life defining quantity of the first production component as a function of the first test piece characteristic mechanical property, providing the first production component with a first indicator and providing the first test piece with a second indicator, wherein the first indicator and the second indicator associate the first production component and first test piece respectively with the determined life defining quantity, the first test piece mechanical property and the additive manufacturing parameter set, wherein for a further manufacturing batch of the plurality of components, build parameters of a machine operable to execute the additive manufacturing process are determined in dependence of the determined mechanical property of the first test piece and determined value of the life defining quantity, wherein the manufacturing batch is formed on a common build plate, wherein the characteristic mechanical property is one of: elasticity modulus, density, ultimate tensile strength, proof strength, low cycle fatigue strength, high fatigue strength, creep strength and/or ductility, oxidation resistance or corrosion resistance, and wherein the life defining quantity is indicative of the expected operational life and/or number of operational cycles of the first production component, wherein the plurality of components (100, 200, 300) are manufactured in a three dimensional space defined by orthogonal axes x, y and z, wherein the first test piece has a first longitudinal axis and the first test piece is formed such that its longitudinal axis is parallel to one of the x, y or z axes, characterized in that the plurality of components comprises a second test piece; and the second test piece has a second longitudinal axis and the second test piece is formed such that its second longitudinal axis is parallel to a different one of the axes x, y or z than the first longitudinal axis of the first test piece, and the method further comprises the steps of determining a characteristic mechanical property of the second test piece; and determining the value of a life defining quantity of the first production component as a function of the second test piece characteristic mechanical property.