Stumped on this.
Margaret had in another post said
The surfaces have a better chance of merging if you use the surface edge as the cross-section curve for a sweep.
So I did.
Upper surface (purple) had its lower edge given DuplicateEdge
I then swept2 that edge to a point using two rails that started at the lower edge and met at the bottom to get the lower surface.
As such both surfaces have an edge that has to be 0mm apart ! and meet with Margarets advice,
MergeSrf says edges too far apart.
JoinEdge declares Joining Tolerance of 6.46887
now that can’t mean 6.46 units (my doc is units mm)
I zoom right in and they appear to perfectly abutt. They use the same edge so surely they must ?
No 6mm gap !
CrvDeviation shows one red square but zooming in on that to electron microscope level !!! still shows no gap.