I see what you are asking.
In extrude 1, I am controlling the OD of the spring at .9" and a wire diameter of .048" (1:30)
This leaves a mean diameter of .804" (ref dim).
The height of the surface quilt is .595"; the height I want the final part to be. I extruded equal in both directions as a personal preference (1:40)
DTM4 is to help make sure the wrap is made where I want it. You can make it on the center plane, but you cannot control the direction of the wrap from there. (2:00)
The sketch for the wrap is internal to the feature (optional) and you see me place the coordinate feature 1st (2:25). This is often forgotten but controls exactly where the wrap begins. Otherwise, it can offset if the sketch is not symmetrical in any way. Always use the coordinate system!
Then I align the ends to the quilt at 2:35. This sets the height I originally defined with the quilt.
In order to make a spring closed and ground, the pitch changes. This is controlled by the horizontal ends and the radius. This may require tweaking later, but for a quick feature, you can place it and adjust later. (4:00)
I can control exactly how many wraps of the wire I get around the quilt using the circumference formula pi*D. Recall the .804 diameter reference dimension. Therefore, pi * .804 * 6 equals 6 full wraps. You can use any formula here. Wrap is very accurate about transferring properly. I know the ends will be right on top of each other and they will be aligned with on of the vertical planes. (4:50)
You can see how this operation can make some very specific pitch variation for springs.
Next is a simple sweep using the wire diameter determined in Extrude 1. (5:45) Here I make sure the wire does not intersect itself. I then tweak the wrap sketch to get a good closed end. (6:00-7:00)
Next, I trim the spring using the original quilt to determine the centers of the top and bottom wire ends. This is the "ground" requirement of the part. Notice how the part is now too thin at the ends. (@ 8:30 was an error in defining the extrude cut) The wrap section is again tweaked to make the ends a little more substantial. 10:30)
Much of this can be automated by using relations. You can even make this more universal with control of the straight and round in the wrap sketch. In general, this is an -on the fly- version of a spring. If you work with these a lot, and others also need to create them, it might be good to invest the time to make a universal version that can be set in the relation or added to family tables. It takes a bit of extra effort to ensure success as a universal model.
