I honestly don't know about those other knobs hah. I was just simply given this oven. But as far as how vacuum form machines work, is you heat a sheet of plastic in a sandwich style frame and when it starts to sag (you learn the right amount by trial and error) you drop it onto the platen that holds the form, while simultaneously opening up the valve to the vacuum. The heating phase takes maybe a minute at full blast so no temperature control is needed. It's pretty simple. So that is why I do not necessarily need it to adjust the temperature or control it in any way.