Problems with Follow Me on a Piston! (noob inside)

Hi guys! :smiley:

Let me introduce myself, new to the forum actually!
My name is Lorenzo, and i’m from italy. I’ve already worked on many Sketch-Up (simple) designs but i’m encountering some serious problems with that project in particular.

It’s a quite simple structure actually. It’s a piston, where i have to draw a curved part with a 3.5 mm radius instead of the linear one.

Looking simple, but i’m having tons of problem in using the Follow Me function to get the job done. I drew a semi-circle with 3.5 mm radius outside the structure, moved it into position and used the follow me function to create the ring.

Missing faces, weird results, just can’t get that curved part right at all. I’m getting mad. :dizzy_face:

Down below there’s the file with the old piston and the work in progress new.

Can some of you guys help me? :confounded:

pistone con scasso curvo (WORK IN PROGRESS).skp (1.7 MB)

Without looking at your model I would say you are running into the tiny faces problem.
SU has problems forming faces when the segment length is down around 1mm, scale everything up by 10 or 100 etc, do your follow me and scale back down. Tiny faces can exist, but it’s hard to create them.

I agree with @Box - Scale up temporarily to avoid tiny edges and faces.
In passing you current form cannot be ‘solid’ without further work.
There is a single face in the center - it needs thickening to be like the real-world, then any internal partition-faces removed…
Also some of your faces are current ‘backwards’ - you should never see any ‘blue’ back-faces in the completed object.

Your picture is no longer showing on the site, at least for me. But looking at the model you posted, @Box and @TIG are absolutely correct: you need to scale the model up before manipulating the geometry, it is too close to SketchUp’s cleanup threshold that causes small edges to get lost. I’m also not sure which of your objects is old vs new piston. The one at left has all its surfaces triangulated, whereas the one at right has rectangular faces - suggesting they were created by different methods?

Thank you guys. I tried to scale the object at 10x, doing the job, than scaling it to normal again and…it worked! :smiley:

But still can’t create a solid group at all for the print. I have tried to print it but it failed halfway through the curved section. Yep, noticed the blue, backwards faces too. How to solve it? :frowning:

edit: slbaumgartner, It is the right that i’m working with. The left one was done in Solid Edge, but doesn’t have the curved section so i had to do it again on Sketchup.

Get TT’s Solid Inspector 2 and/or TIG’s Solid Solver. They will tell you what is keeping your model from being a SketchUp solid and can repair many kinds of flaws.

One quick way to fix reversed faces is to select one that is correct, right-click, and select “Orient Faces”. I use a style with a glaring green color for the default back face so that it is harder to miss situations where I got something reversed.

Can you post the model that won’t print?

Sure! Here it is.

WORK IN PROGRESS 2.5.skp (2.4 MB)

I tried to load in on Cura and here it is the result

In case you can’t see it
http: //

3D print failed exactly at that point. He “skipped” that empty part and continued, but it was all ruined obviously.
There has to be some major problems there, let alone the blue faces. :frowning:

I also don’t know how to close the top section correctly actually.

A shame that the website isn’t working at all at the moment, want to download Solid Inspector 2.

There are numerous issues with the model - so many that you might be best off to start over. Here are some screenshots of problems:

From the look of these, the “second stage” of your piston is badly modeled (at least in SketchUp). Some of its sides are rectangles, and others are triangulated, meaning they are not planar. Some of the vertices seem slightly out of place. There are places where your new follow-me’d curve does not cleanly meet the boundary of the second stage. There are loose edges hanging over the place where they should meet. And on and on. In addition, there are disks joining inner and outer parts that are single faces with no thickness. These can’t be printed!

My recommendation would be to try drawing this a different way: draw a planar half cross-section of the whole part and then use follow-me to “lathe” it around a circle (as before, do this at a large size and then scale down). While drawing the cross-section, make sure it is a closed shape that encloses area, without any single edges, infinitely thin areas, or disconnected parts.

Here’s an animation of what I mean (be patient - the follow me takes a bit):


Great help mate. That could solve the problem. :smile:

Just another one (very noob) question. How to have the exact section of the piece like you did? Doing it manually by taking measures or some particular function?

I started with your model, drew a large vertical rectangle through the center, and did right-click->Intersect Faces with model. The shape that produced had a bunch of flaws, but it was not too hard to repair them and to thicken some walls.

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Yeah, done it and it’s a solid group finally! :smile:

http :// (in case you can’t see it)

My last question would be: how to close the model in the upper part without causing troubles, missing faces, ecc?

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I don’t understand the question. Exactly what do you mean by “the upper part” and “close”? If another rotationally symmetric surface, it’s possible you could have added it to the cross-section before running followme. But you can also cause SketchUp to close a “hole” that has a continuous boundary by drawing atop one of the edges. Just remember that the face created will have no thickness until you pushpull it.

I meant closed like the design on the left (in the original file).

I’ve added the section directly before running followme like you said, and it looks perfect! :smiley:

Will try to print it today or tomorrow and tell you the results! :smiley:

One additional factor to consider is whether or not you have a manifold volume. Most 3D printers require that the faces share only one edge with an adjacent face:

No doubt it is an extremely simple situation.