Next semester, I am going to teach a small section of advanced high school students a class of Multivariable Calculus (it's about 3-4 students that have completed AP Calculus BC). Multivariable Calculus is usually a 1 semester college course, but I have the advantage of being able to teach the material over the entire school yea, which is two semesters. So I am looking for project ideas to help fill some of the time but also give the students some practical applications of calculus. I also have the great advantage that the school I work at has access to 3D printers.
I feel lucky to be in the position to work with a small and dedicated group of students and have plenty of time to get through the material and great resources to take advantage of, but on the other hand, I am relatively inexperienced with Multivariable Calculus (I know the content, but I don't know any good ideas for a projects) and I have no experience even using a 3D printer. So, what are some good project ideas for Multivariable Calculus that hopefully don't require too much of a learning curve if using the 3D printer?