Any idea what would cause this and how to correct it?

Hello,

I've started cutting out my first test parts with RhinoCAM 2.0.4.0 and Mach3. All my parts are cutting out on average .02" to .03" small in all axis. Any idea what would cause this and how to correct it?

I'm using a self-built blueChick 36" CNC. When I use manual input in Mach3 to test the travel distance of the axis the controlled point actually moves long on each axis by 1/16" or so, so I would have thought my parts would be slightly larger.

Please help.

I didn't find the right solution from the internet.

References:
https://mecsoft.com/phpbb/viewtopic.php?t=2124
Wealth Management System Video

Thank you.