If you haven't already it would behoove you to learn a 3d modeling program, I will be using blender
for this creation.
> First you need to make sure that the programs coordinates are using the metric system to allow an easier flow from idea to physical object. This can be done by selecting the option in blender from the picture shown. If you do not see whats in the picture make sure that a properties panel is open and make sure that you have selected the Scenes tab. Making sure you do this at the beginning of the project will save you a lot of unnecessary hassle later on.