John, Thanks for the reply, the assembly helps but not quite answer my question. I'm trying to use the same spring in different application with different installed height. I created a spring using tube feature with a join curves formed by 3 helical curves. 1st & last helix with a pitch same as the wire diameter & one turn only. The middle helix has a pitch equals to ((spring_length-2*wire_dia)/no of turn). Then I trim the top & bottom ends with datum planes. My problem is on the last helix, I don't know how to get the location of helix associate with the 2nd helix. When I change the spring length in the assembly, the join curve operation fails because the last helix eill stay where it was & not touching the 2nd helix. I hope I explain it better this time.