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Closed helical spring using helical sweep

Yes, make your trajectory in 3 segments. Change the pitch at each vertex to end up with a closed coil on the ends, the middle with the normal rate pitch. I do this all the time. Then make a cut on the ends to make a closed and ground spring.
 
You can add points to your trajectory sketch for places you want the pitch to change. I usually have 6 pitch values defining 5 segments:
The closed section at each end (constant pitch)
A short transition section between the closed section and the working coils (variable pitch)
The working coils (constant pitch)

Then if you need ground ends make a cut.
Capture.JPG
 
Okk Thank you.
I made it this way
1)made a trajectory sketch.
2)added 4 points symmetrically from both the ends.
3)now selected pitch points as follows
pitch.JPG
pitch points.JPG
is this the right way?
 

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You need to create the trajectory with 5 segments
1. First and the last segments: corresponds to the closed coils at the end
2. Second and the last but segments: corresponds to transition of pitch varying from wire diameter to the desired constant pitch
3. Mid segment: corresponds to constant pitch length

Finding the lengths of first and last segments are very much straight forward; they are equal to the wire diameter.
lengths of second and last but segment: There is no formula to calculate. One needs to assume or restrict to some sensible length
Length of the mid segment: Whatever is left from the total free length of the spring.

I am attaching some pictures related to this process
spring.JPGtrajectory.JPGrelations.JPG
 

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