Follow me errors around a hollow circular ring


#1

I’m having problems with a simple example of the follow me tool.
I draw an ring flat on the base then I draw a profile in the Z direction.
I highlight the circular edge and evoke the follow me tool.
It seems to work until I look inside the result. It is not a solid extrusion.
If I save as an STL file and import it to Flashprint it shows a solid ring on the inside.
I upload two files, one showing the ring and then one after the follow me tool has drawn the profile around the ring.
follow1.skp (1.1 MB)
follow2.skp (2.2 MB)


#2

Yep. It won’t make a solid for two reasons that I can see easily. First, the edge segments in that region on the inside of the profile are too short to create faces with the number of segments you used on the circular path.

Even if that worked, there’s an extra edge on the profile near the top that creates some bad geometry.


You can scale the model up by, say, a factor of 10 and probably get those faces on the inside but you’ll need to decide which edges to delete at the top.


#3

Thanks for the prompt reply.
Yes, that did it and now FlashPrint is happy.
Can you tell me why the Follow Me Tool produces that small error on the side?
Cheers, Bruce


#4

At the outside top? Did you erase the edge edge that divides the profile into two faces? I showed that edge highlighted in the third screen shot. It’s not Follow Me that is creating the problem. It’s a problem with the way the profile is created.

111 segments is overkill for the path. It’s also a strange number. I prefer to stick with numbers that are divisible by 12 (because they are also divisible by 2, 3, and 4) and in this case, I think 96 sides would be plenty.


#5

OK, point taken about the number of segments.
Yes, to produce the Z profile I made a rectangle in the Z direction.
I then drew the outer and inner shapes then deleted the unwanted lines.
What should I have done?


#6

[quote=“BrucePiggott, post:5, topic:37268”]
I made a rectangle in the Z direction.I then drew the outer and inner shapes then deleted the unwanted lines.[/quote]

That would explain the vertical line. That’s the remains of the vertical edge of the rectangle.

Avoid allowing the curve to extend outside the rectangle. Either control the curve better or make the rectangular face larger.


#7

Got it! Thanks.
It’s past midnight here so, good night to you.
Cheers, Bruce


#8

Good night.


#9

One last question if I may.
The above statement that profile was too short and scaling up solved the problem, but I don’t want an eggcup big enough to hold a baseball so I scaled the result down again and all OK. Surely if I’m back to the same scale as I started with how come now the segments are drawn correctly?
I know you know. Cheers.


#10

It was the edges in the profile that were too short. Well, also the edges in the path. They work together to component the problem. Those short edges and the tiny faces can exist but SketchUp won’t create them. So you sort of trick them into existence by running Follow Me at a larger size.


#11

Thanks again, had an egg for breakfast. It tasted better because I made the eggcup (with your help).
Cheers, Bruce


#12

I guess you don’t eat your eggs lightly cooked. The yokes would run out the bottom. :smiley:

Was there a reason why you drew the bottom rim separate from the profile we’ve been talking about?

FWIW, if you are working on more models the size of an eggcup, you might consider what has been called the “Dave Method.” I’ve been using it for drawing small stuff for years.

Cheers,

Dave


#13

Ha, Ha.
The reason I started with a circular pedestal was because every time I tried starting with a flat circle the hole in the bottom kept disappearing! First I had a hole, I did some follow me and the hole was gone.


#14

Here’s a strange thing - I did as I was told and made my Z profile very carefully within a larger rectangle.
Then I did the Follow Me and everything worked out fine. No missing internals! Everything else the same?
I guess I just need to curb my enthusiasm and slow down.


#15

Ah! So you don’t like the yoke and you do want it to run out onto the table. :smiley:

The Follow Me operation can be subtractive as well as additive. If there is geometry in the way of the profile as it gets extrude, the geometry will be erased. If there isn’t any, geometry will be created. So you leverage that you get what you want at the end. In this screen shot I’ve removed the rim and extended the profile down. Follow Me would create the egg cup with no bottom.

I also moved the path down below the profile. The path doesn’t need to be in contact with the profile but for a turned or lathed object such as this, you just need to keep them on the same center.

If you did want a bottom in your egg cup, you would need to extend the profile to the center line.


#16

Thanks again, I try not to spill the yoke. Cheers


#17

The right way to look at it is that SketchUp is trying to keep your model correct as you create it, not that SketchUp “doesn’t like” or “can’t support” small edges.

SketchUp’s handling of close-together geometry (“cleanup”) is only triggered when new edges are added to a model, and involves only those edges and the ones near to them in the model. The cleanup is SketchUp’s effort to maintain model correctness when faced with situations in which it is ambiguous whether the new entities were meant to intersect or coincide with pre-existing ones. Ambiguity is unavoidable whenever SketchUp has to calculate a position because finite precision computer arithmetic introduces small errors. Two vertices that were meant to be the same may actually differ by a small amount because of the way their positions were calculated.

Scaling does not add any new content to a model, so it does not trigger the cleanup. Said another way, if the model was deemed ok at the larger size, SketchUp trusts that it is also ok when shrunk to a smaller size.


#18

Thanks for the advice on this topic.
So, as a general rule- if you wish to design something fairly small, say less than 2 inches across for the purpose of finally printing on a 3D printer, would it be good practice to increase all dimension by 10, and then finally reducing the design back by dividing by 10, before exporting as a STL file?
Cheers, Bruce


#19

Alas, there is no consistent answer for how much scaling may be necessary. It depends on the details of the shapes you are working with and the operations you apply to them. Follow-me, intersect, and the solid tools are the most common sources of small-edges issues, but other drawing operations can also encounter them, such as connecting edges tangent to a small circle. It is safest to err on the side of caution and use a greater scale factor than might seem intuitively necessary. Plus be ready to undo, scale even bigger, and try again when a problem appears.


#20

Thanks, will do.
Some people reading this may think it’s a negative statement about Sketchup that there are issues on fine detail.
Let me say that as a retired Electronic Engineer with over 50 years experience and for the last 30 years of that a software engineer I have only praise for Sketchup. I find it mostly intuitive, ingenious and the training videos and support are excellent.

Can I have a free version of Sketchup Pro?

Joking, Bruce