Machined parts are great for the inventions I make. The tiny gears and things are made using CNC machines. I have the custom cases and sheets of metal fabricated using metal laser cutting services. I do not have a building full of tools like this to make the things I come up with in my mind. I learned CAD in school, and I put together the things on a computer. Then I have a prototype printed in plastic. After that, the first parts are machined by CNC machines, or they are cut using lasers.
I assemble the products at my garage that has not held our family car since we moved here. Don’t get me wrong, I have a lot of tools. I just cannot afford the super high priced machining and laser tools to make the metal parts I need. That is why I outsource their manufacturing to professionals.