I don't know of anyone that makes pellets themselves -- only those who purchase them from bird supply distributors.
There are various brands such as Harrisons, Roudybush, LaFarbers, and Zupreem.
If you do a "Google-Search" you may be able to find information on the process used to make them.
My budgies came to me already weaned on pellet's, roudybush to be specific. Over the last couple year's, I have done some reading on the subject. Pellet's can be made in different process's so it really depend's on who you get it from. My personal opinion is that my breeder made a wise choice in what pellet to use, and I feel no desire to switch from roudybush. You can check out their website, and the other's to learn more about the process, and why one may result in a higher quality pellet than the other's...