Surgical Tech Working Hours?

Can a Surgical Tech ask to work a set 40 hours or more a week, like a set amount of hours they want to work? Like for example if they ask for 12 hours a day for monday to friday and ask for weekends off. Do you think the hospital will let them set their own hours they want? Or they have no choice but to be on call when ever they need Surgical Techs? Please give me truthful answers, i will give 10 points! thanks =)