Problem with arc - please help


Hi All.

I’d appreciate help on 2 questions:

  1. I have 2 arcs connected at bottom, I drew them with “draw arc through 3 points” there’s an angle between them. To my eye they look like a closed loop, so I though a face would be created over that loop BUT the arcs’ lines are ebossed, and the face is not created. I have no idea why or where/how to look for the problem.

  2. I have half circle with thickness1mm. I would like to move the top of one arc, so the thickness of that semi circle would be, for example 10mm on top but the bottom will stay the same (so the semicircle varies in thikness).
    I tried rotation tool, using the base of the semicircle face and axis of rotation, but the edge the top face (side of the half-circle) in no longer parallel to he base i.e. the face is curving toward the ground (which is sort of reasonable, as it rotates around the axis which is base). I also tried the move tool, to move the arc itself, but then the whole face moves and thus the semicircle is 10mm thick both on top and bottom (which is also sort of reasonable as I move the whole arc).
    How do I move only the top of the ark in parallel to the base of the arc that needs to stay put?

Thanks a lot!


I would like to help, but without an image or the model I’m not able to understand your question…


arcZ.skp (1.1 MB)

  1. I am attaching an example model. 2 arcs have the faces, but the space between them is not filled with face

  2. Now I want to move the top of the arc A so that the space between the arcs on top would be say 7 mm, while the bottom stays at the same place.

I hope it helps to understand the Qs


Did you want something like this? (see attached file too)arcZ.skp (1.1 MB)


In the version I made I just rotated by eye, and it seemed to want to be 25 degrees. I checked with a calculator, and it should be 25.3769335 degrees to get exactly 7mm between the top edges.


Pretty much yes.
So, what did you do to? How did you fix it?


Please, do tell me how and what did you do? This component, by itself, is an example of what I need to do, I was hoping to gain understanding/knowledge, rather than ready problem solution.


The gap at the bottom is 1mm, and you said the gap at the top should be 7mm, and the height is already 7mm. That means the top needs to move outwards 3mm on each side. Effectively you’ve created a triangle where the shortest edge is 3mm and the longest edge is 7mm. The angle needed to do that is asin(3/7) radians, or 25.3769335 degrees.

If you select one of the faces by clicking on it, then look at it end on, you can use the rotate tool in a locked plane to rotate in a controlled way. Pressing the right arrow key will lock it into the red axis. Then click at the near side base endpoint of the face, mouse straight upwards any amount and click again, then mouse sideways to start the rotation.

Release the mouse button and type 25.3769335 followed by the enter key. The face will jump to be rotated by exactly that amount.

Click on the other side’s face, and repeat the steps, only mousing the other way when doing the rotation.

By now you have something that looks like a taco. To fill in the gap just draw lines from each endpoint in one arc to the matching endpoint in the other arc.


Please correct me if I am wrong, but won’t that make the total height of the body less than original 7mm?
Technically I needed it to stay the same heights (and move only one face’s top outward). So tat the side view would become something like this: L/ where the the plane connecting tops of the arcs is still parallel to the base face.


Is this what you want?

This will keep the height of the arc you drew.

Draw the arc and the bottom edge to get the face. Extrude it with Push/Pull.
Set up a rectangle to use as a cutting plane (shown in blue) at the proper angle to give the top and bottom dimensions you’re after.
Select all of it and use Intersect Faces>With Selection.
Erase the perimeter of the cutting plane.
arcZ.skp (68.5 KB)


Perfect explanation, I can repeat that. Thank you very much!