Out of scale

When I print parts they are coming out to be slightly smaller than what the design of the model is supposed to be. I made sure that the model from the cad get’s exported 1:1.

What else is there to check?

Example, 13mm intended hole print’s out to be about 12.65mm.

The plastic tends to shrink when cooling which can cause smaller holes. To ensure your printer is printing well print out a couple of calibrate cubes 20x20mm and other similar parts. If you are getting 20mm or something close you are good to go. Now print out a hole calibration test (such as this one: http://www.thingiverse.com/thing:10861 ) This will allow you to figure out how much smaller a hole is from the actual designed size. Now when designing your object make the hole slightly bigger to take in account this offset. For instance if you print a 10mm circle and it ends up being 9.6mm you can enlarge this circle to 10.4mm to get the 10mm size hole you are looking for.