Creating a domed pin


#1

I am working on drawing a tool that has some pressed pins with a dome on the top and for some reason when I am trying to draw the dome, the follow me tool isn’t working right and its not finishing. Please see the attached picture. The way I did it was created the pin, and then drew an arc from one point of the circle on the top of the pin to the other side. I then drew a line on the blue axis from the center point of the top up to the arc and then from the center of the top to the side where the arc connects to the outside of the circle. I select the outer circle of the cylinder and click follow me and then click the face of the half arc and it does this. I opened a new window and was able to do it there but for some reason it wont work on this one. What am I doing wrong?


#2

Probably working at too small a size. Could you share the SKP?


#3

Dave’s Tool.skp (172.0 KB)


#4

As I suspected. It’s too small. Is the pin part of the rest of that thing or does it get pressed into a hole?

The method I would use is to get the geometry 3D at the real size, make it a component and scale up a copy of the component. Run Follow Me on the big one, close it to get out of Edit mode and delete it. Return to the original with zoom Extents.




#5

If you look at @DaveR’s large figure, you can see how the edges of the dome converge at the “north pole” of the shape. That was the issue with your original attempt. At real size, those edges are too small for SketchUp to create, and deleting them loses the entire center part of the dome.


#6

An 8mm circle is too small to create a dome? How do you scale the item back down once its created?


#7

That is the classic question about how SketchUp works. The model can have tiny geometry, but when creating new geometry, SketchUp performs a cleanup operation that looks for vertices that are so close together that it can’t tell whether the difference is deliberate or the result of finite computer arithmetic. So, as a precaution, it merges them into a single vertex. Doing so can cause related edges to be lost, and losing the edges can cause faces to be lost.

But if you do the modeling at a large size so that all vertices are well-separated, scaling back down to real size does not trigger the cleanup and so preserves the tiny edges and faces.

There are two ways you can scale back down. One is to just use the scale tool. That can be a nuisance when the scale factor is not a nice number. Another (which many of us prefer) is to create a component from the geometry, make a copy of the component and scale that copy up. When you have completed the operation to add new geometry, you can just delete the oversize copy and the real size one will have the correct geometry.


#8

If you read Steve’s post you’ll see he describes what I described immediately before my screenshots.


#9

Im sorry to be a bother but the second way you described went way over my head. I understood the making it a component part and I know how to make copies but maybe im just reading it wrong. So far I took the dome I had made from a bigger cylinder and made it a component. When you say add new geometry, im not sure what tha tmeans or where to find that or why you would have to make a copy instead of just using the original dome since you are making it oversized. Thank you for the help so far!