3-sided rectangle; missing faces in extrusions

Technical Problems SketchUp
1

I created a flat cylinder and added a depressed center and further depressions in the top face (via the push/pull tool). I then used the extrusion tool to create fillets around the bottom of each depression. I encountered two problems, which you can see in the linked 1-minute video.

  1. In creating the fillet, I first made a rectangle with the rotated-rectangle tool. But when I attempted to extrude it, SU said that the surface was curved. I switched to wireframe display and saw that the rectangle had only three sides. I added the fourth side, and could then do the extrusion. Can anyone explain this problem to me?

  2. When I did the extrusion, several faces were left unfilled at corners. I thought that this might have something to do with drawing scale, but the problem persisted when I redid the drawing in feet rather than inches. Would this be caused by too small a corner radius? (I had corners rounded to 1/2" radius, and used a 3/8" quarter-arc for the fillet. Or 6" and 4.5", in the up-scaled model.)

2

First, the edge of the rectangle you drew was shared with a softened or hidden edge on the existing surface. The edge of the rectangle was there but because it was softened or hidden, the neighboring faces are considered as part of the surface. You’d get exactly the same result if you tried to use Push/Pull or Follow Me on any curved surfaces which would be made of multiple faces.

Second, the scale at when you’re working means that there would be line segments that are too short for SU’s tolerances. So, yes, it’s too small. Try scaling the model up by a factor of 100 or even 1000 before running Follow Me.

If I were drawing that, I would draw most of it at normal size but I would make it a component and scale a copy up before running operations like Follow Me to avoid the tiny face issue. After I got finished with that stuff, I would close the large copy and simply delete it. Then return to the original which will be where you left it.

I would also suggest that you leave materials turned off while you are working so you can identify and correct reversed faces if and when they occur.

3

Wow! Thanks for the immediate reply and the suggestions. I’ll give them a try.

4

The pleasure is mine.