6dof spring damper
 

In the 6dof method, I have given mass and gravity as the input for force, and given spring constant. my piston is also moving.

but the problem is it goes down(-3cm in y direction) and come back to its intial position (0,0). after it is not going upwards instead it goes again downwards(in real case, it should go upwards that is +3 cm in y direction)
can u help me?
thanks in advance,
SUNIL