The following image will certainly explain better what I want to achieve, The goal being to symmetrize the surface with respect to the vertical and merge it with the existing volume, but I don't understand how to do it in solidworks 2018.
So in fact, make a volume delimited by these profiles:
Although I could only look at this tomorrow morning under SW, and not being a specialist in surface at all, I would still say that you need 2 profiles and 2 guide curves.
For the profiles you use the small one that is vertical that you already have and I think you need another one that is vertical too but at the other end of your shape.
For the Guides uses the existing and the horizontal ones.
To be tested from Monday ;) (what do you mean we like challenges)
I also have a dedicated book on the surface under SW, see if there isn't something close to it.
@Ac Cobra, I don't think that in his case the revolution works because the horizontal and vertical shapes are different.
By you should also try the opposite of what I said, that is to say use your arc as a guide and use 3 shape sketches, the horizontal one on the left then the vertical then the horizontal one on the right, pay attention to the position of your click on the sketches, aim for the end on the arc side of the circle. otherwise the faces will cross.
Well I tested the shell in my model and it's frankly strange.
Already, I couldn't realize this semblance of a shell when the side profiles were splines. I had to convert this to 3 arcs of circles like you did.
Then, I can't select the sketches but the open loops. I then arrive at this:
Another problem, maybe due to the "open loops", I don't have the constraint "Tangent to the face" but "Normal to the profile". I don't know if it changes much but in the end, when I try to constrain to the background arc with "Guide curves", the function fails with the message "Guide curve n°1 is invalid, it does not intersect section N°2"; Which I find rather unexplanatory.
Finally, I have the impression that I don't need the complementary surfaces and the sewing function because by omitting the fact that I don't stick to the arc of the circle, I get a volume it seems to me?
I'm attaching my model, it may be easier to identify what's wrong.
OK I'll look at it tomorrow morning. (annoying not to have the double home/work license anymore)
As for knowing if you have a volume or a surface, just look at the top of your creation tree, or simply make a cut that goes through your shape and you see if it's hollow or not.
So, I looked at your piece and it's normal that you don't have the same thing because you did it directly in volume and not in surface and therefore more appropriate if the goal is to make a volume. So obviously it's normal that you don't have the same words as the surface function.
As for the guide curve, you have to keep only the arc part and change the horizontal line to construction geometry or simply delete it.
Attached is the corrected part with the guide curve.
NB: It's a bit my fault to have made you the demo in surface, and I think it comes from the fact that you used the term Surface and merge in your 1st post, obviously I wasn't the only one, while yes (and can be seen on your photo) that we can do it directly in volume which will automatically merge (unless we unchecked) with the master volume.
So sorry to have misled by going through the surface. (even if the final result is the same but longer)