Rounding a 3D model evenly

[WillAdams (William Adams (Carbide 3D))]

as requested on support…

I am working on a project where I need to round over the edge of a trapezoid. I am trying to put a 1" roundover along the outside edge of a piece of high-density packing foam for a seat pad. I have watched several tutorials and looked on the community site, but I can’t find a way to eliminate the bubbles at the corners; file attached. Is there a way to accomplish a smooth 1" roundover on a shape like this?

where the provided file is:

and the provided geometry is:

It will be necessary to draw rounded forms which describe the four edges, as well as a central element which describes the perimeter of the top edge.

Probably the easiest part to work from will be the current central dividing geometry:

Delete everything else which is not needed:

then duplicate this geometry and line up the copies so as to square up the four corners:

For the top/bottom straight lines, simply draw a line:

Done

and increase its length by more than double:

Done

Select all the geometry which one wishes to work with:

and use Region Builder:

Yes

to define the desired geometry:

If a given corner won’t fill in, then it may be addressed after.

[WillAdams (William Adams (Carbide 3D))]

Simply duplicate the geometry in place:

Then Mirror Horizontal:

Drag into registration with the other:

Select both:

and Boolean Union:

OK

Draw a circle of the desired radius:

at each corner

For the top and bottom it is possible to draw a rectangle:

Get the width based on the dimensions of the two circles:

Then apply that horizontal dimension:

(or just remember than one could just add the radius)

Then apply the radius as the corner rounding:

For the sides it will be necessary to measure the angles of the sides:

to get the angle of rotation which will need to be undone.

Select two circles:

and rotate

Done

as before draw a rectangle:

(taking advantage of the fact that circles do not rotate when rotated)

As before increase the appropriate dimension:

and round:

Then re-apply the rotation, including the circles so that they may be used for alignment if need be:

Done

copy-paste

and Mirror Horizontal

and drag into alignment:

Select each opposing pair:

and model to the desired height:

Note that when the second is modeled:

Max must be used for the modeling

Naturally, the rounding may be adjusted as desired to arrive at the desired result.

Then the central geometry may be selected:

and modeled to the desired height:

Probably the rounded elements should be adjusted to: