free Modeling software that simulates movable parts.

[MrSmiley666]

Is there a modeling software where you can simulate a part moving?

i remember when i was using solidworks back in college, it had a system where you can set up multiple components. set the parameters. then you can see everything move as they should.

simple example
align outside of the screw with the inside of a nut. now the movement is restricted.

now with complex things with multiple pieces everything is essentially tied together.
you can check to see if everything fits in place.

my current build is currently 5 pieces. 3 springs and wire/string of some sort. only 2 need to be actually glued together. so seperate pieces seems like a more viable option then going for 1 piece with supports that break away. also the spring and string seem like the best option currently. but dont think they are any prints for those.

Edit 6 pieces. 5 springs/ 0 strings.

///////sidenote//////
first print/dont own a printer. this 1 will probably go be printed out at a makerbot shop. which will also serve as a benchmark for how much i want to invest. spend $500 on a reprap kit? 2000 on a makerbot. wait for the $5k autodesk printer?

essentially a trial run to see how effectively i can print out 1 of my ideas into a functioning piece. the models of stuff look nice but i want to make something i can use =P