I need to design a mechanism which rotates 90 degrees each time pressure is applied and removed. It will consist of an inside pipe which will rotate and an outside pipe which is stationary. The prototype is to be printed on my 3D printer in ABS plastic. I can do some of the design myself but need help in using SolidWorks 2010 to design the parts which involve carving slots into a curved surface. Picture a ball-point pen in which the mechanism rotates 90 degrees each time you press the button. One time the pen point is retracted and 90 degrees later it is extended.