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To mate something like that correctly, you'll have to use a sketch entity or an axis along the centerline of the spring. Select either from the feature tree and make a concentric mate to the bolt and you should be good. (You'll probably have to remove the existing mate, which I'd guess is a tangent mate.)
In your spring part file, select the Front and Right planes and select Axis from Reference Geometry:
Or start Axis and pick these planes:
Hide the axis and save the spring part file.
Open your assembly and delete the spring's tangent mate (it's holding you back and isn't needed):
Then select the spring's new axis from the feature tree and a temp axis on "baut per" and mate them coincident.
Or select the spring's axis and baut per's cylindrical face and select the concentric mate.
anybody know why the spring can't be flexible ?
You can make the spring "flexible", but for most things that's unnecessary.
Here's a video by goengineer: SOLIDWORKS - Dynamic Spring - YouTube
I haven't watched it and I usually don't recommend people get instruction from youtube, but goengineer is pretty good. So, it should be fine.
SW2020 has enabled flexible components, springs in different positions was one of the examples when they first announced it at SWW2019.
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