Dimensions in additive manufacturing

A method comprising:

• receiving, by a processor, object model data for an object,
• wherein the object is to be additively manufactured by an additive-manufacturing apparatus depositing layers of build material, selectively applying fusing agent to the layers on a layer-by-layer basis in accordance with the object model data, and selectively fusing the build material via energy application,
• wherein the fusing agent promotes fusing of the build material during the energy application by absorbing the energy,
• wherein the object model data specifies a nominal value of each first dimension of a plurality of first dimensions of the object, each first dimension being defined between a first external surface point of the object and a first non-surface point of the object,
• and wherein either or both of:
• when the fusing agent is applied to the build material in regions that are to be fused, but the build material in neighboring regions that are not to be fused become sufficiently heated during the energy application to also fuse, each first dimension of one or more of the first dimensions is greater than the nominal value, as first dimensional deformation when the object is additively manufactured, and
• after the fusing agent is selectively applied to the build material and the build material is selectively fused via the energy application, and some of the build material shrinks during subsequent cooling, each first dimension of one or more other of the first dimensions is smaller than the nominal value, as second dimensional deformation when the object is additively manufactured;
• generating, by the additive manufacturing apparatus, the object using the object model data, such that either or both of the first and second dimensional deformations occur;
• determining, by the processor, a deviation between the nominal value and an actual value of each first dimension of the object as generated from the object model data, wherein the actual value for each of at least one of the first dimensions is greater or smaller than the nominal value per the first or second dimensional deformation, respectively;
• based on the determined deviation for each first dimension, determining, by the processor, a scaling factor and a positive offset factor that minimizes a sum of first squared quantities corresponding to the first dimensions,
• wherein each first squared quantity comprises a product of the actual value of a corresponding first dimension and the scaling factor, plus half of the offset factor, minus the nominal value of the corresponding first dimension;
• modifying, by the processor, the object model data, using the scaling factor and the positive offset factor to compensate for either or both of the first and second dimensional deformation when the additive manufacturing apparatus generates the object again;
• and
• generating, by the additive manufacturing apparatus, the object using the modified object model data, such that modification of the object model data and usage of the modified object model data to generate the object again at least ameliorates either or both of the first and second dimensional deformations, improving dimensional accuracy of the generated object.