Nothing shown there is going to be causing this issue. I suspect that you have something loose in the machine - The shapes you show have a nice sharp corner here: But the resulting output appears to be rounded: Any looseness in the belts or mechanical parts of the motion system could be...
How do you do it? With a 3d printer, it is very easy to create complex 3d shapes. The problem is that you are limited to various kinds of plastic. If you want your object to be made from wood, for example, you’re out of luck. If you own a laser-cutter, however, it is quite...