Modeling for 3D-Printing - How to avoid creating internal faces with Push-Pull

Hi everyone,

I’m trying to figure out why internal faces are created when using Push-Pull and if there are ways to avoid it, which seems like an impossible task without extensions.

Why is it that an internal face is created when engaging in the create new face mode? (Ignoring the name) I can’t come up with any situation where this would be the desired outcome. Maybe someone has an example of where this particular behavior would be useful?

Just leaving the lines behind would be enough, wouldn’t it?

Note that I might be blinded because throughout the 13-years I have been 3d modeling I have always made sure everything was watertight and had some thickness.

The normal push pull mode don’t create internal faces and you have to use a modifier key to force the creation? Can you create an example file?

I would be interested to see one of your models where this sort of thing is a problem. As @Cotty says, Push/Pull doesn’t normally leave internal faces. You have to make it do that. What I see often is the approach to constructing the model is not as efficient as it could be and the user does things to create those internal faces that a minor workflow change would avoid.

Hi Cotty,

should have been more clear. I have included a .gif of an example scenario.

I know there are other methods for achieving the exact same shape as this example. I’m just trying to understand why Push-Pull was made to work this way technically.

You appear to be hitting the modifier key (Ctrl on Windows) for the additional Push/Pull steps. Notice the + added to the cursor. Also notice the message says “Ctrl + toggle new starting face.”

Without the modifier:

With the modifier:

If you want to add the rings so you can modify the shape, either pull the cylinder to full height and copy the edge to the positions on the cylinder or modify the diameter at each step and then Push/Pull for the next one.

Hi Dave,

I’m aware that I was using what I dubbed the"create new face mode" in my original post.

The method you posted would be the go-to method to use to avoid this.

I would still like to know why the tool leaves an internal face behind. The new surface that get created hides it after all.

It is designed to create the face. This is a feature that has been in SketchUp long before there was ever any such thing as 3D printing and there are a number of applications for it. I expect its original use was intended for sketching things like multi-story buildings since SketchUp was originally designed for architecture.

If you need this often, I would suggest Vertextools from Thomthom for this task.

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