Apparatus and method for producing an article by additive manufacturing

An apparatus for producing an article by additive manufacturing comprising:

• a) a first container and a second container from which metal powder may be selectively dispensed in powder form to produce an article, wherein the first container contains a quantity of a non-recycled metal powder or a quantity of a first recycled metal powder and the second container contains a quantity of a second recycled metal powder that has been recycled to a different extent to the first recycled metal powder, and wherein each of the non-recycled metal powder or the first recycled metal powder and the second recycled metal powder are the same type of metal powder, and
• b) a control unit configured to control the quantity of the non-recycled metal powder or the quantity of the first recycled metal powder dispensed from the first container and the quantity of the second recycled metal powder dispensed from the second container, wherein the control unit is configured to dispense a greater proportion of the quantity of the non-recycled metal powder or the quantity of the first recycled metal powder when predicted stress in a certain region of the article is higher, and the control unit is configured to dispense a greater proportion of the quantity of the second recycled metal powder when the predicted stress in a certain region of the article is lower.