Thingiverse nickel test and print size

[inventiprint 0]

My prints are coming out in the correct shapes but they seem to off dimensionally. I figured this out when I printed the nickel test print from Thingiverse, http://www.thingiverse.com/thing:11261. My nickel would not fit into the test piece. The x and y slot were both too narrow for the nickel and the round hole was too small for nickle to sit in. I'm a little stumped as too the reason for this. The slots are both undersized by the same amount. For the settings I just used the default Cura settings with skin enabled. I tightened the belts, leveled the bed, printed at 220C but I need to know what "knob" to turn in order to get the size right. Is this an extruder problem or a belt problem or software problem. I was reading some forums online about possible adjust the extrusion rate or x y steps but wanted some feedback before trying these things.

[billdempsey 0]

One of the drawbacks of printing in plastic is that plastic shrinks as it cools. It is normal for holes to be slightly smaller than the dimensions in your CAD program. You just learn to adjust dimensions in the CAD program so that you get the desired size in the final print. For example, if I need a precise 3mm hole, I make it 3.2mm in the CAD program. As you use your printer more, you get used to putting in adjusted values for things you use a lot.