How the scale is worked out
The scale factor is the designed size divided by the measured size. Shrinkage is the difference between them as a share of the designed size. A part drawn at 100 mm that measures 99.3 mm has shrunk 0.7%, and the model needs scaling to about 100.7%.
Measure something long, since a 0.1 mm caliper error on a 20 mm cube is 0.5% while on a 100 mm bar it is 0.1%. Materials that shrink more, such as ABS, ASA and nylon, are the ones where this matters most, and the engineering filaments guide covers why.
For the reasoning behind the figures, see the engineering filaments guide.
Questions
How do I compensate for shrinkage in a 3D print?
Print a long test part, measure it once it has cooled, and scale the model by the designed size divided by the measured size. A 100 mm part that measures 99.3 mm needs about 100.7%.
Should I scale every axis the same?
Only if they shrink the same. Measure X, Y and Z separately and enter each in the calculator if the numbers differ.
