I have created a bolt, a nut and a spring, In the part stage the spring compresses and un compresses correctly, I then create an assembly with the bolt as the fixed feature. I have tried mating the spring to the bolt in various fashions and can do that ok....but that's where I get stuck. Because when I try to compress the spring it doesn't move. I entend to have the nut do a screw on type motion with a screw mate and I can do that ok as well but I don't know how to animate the spring into a compression uncompression stage....can you help?