Extrude cut bug

[stingray_01]

Hi

When I extrude cut beyond a point, the cut leaves behind a thin wall.

Anyone seen this weird behaviour before?

[g-andresen]

Hi,

without seeing the design you cannot give any hints.

Please share your design to take a look.

günther

[stingray_01]

Sorry I added a screencast but I didn't click insert.

[stingray_01]

Problem has gone away after I made some changes. Not sure how I fixed it.

[mickey.wakefield]

Hi stingray_01 -

Without having the model, its really tough to say what's going on. It certainly looks strange. I wouldn't expect the extrude to remove that sliver volume when the cut only goes a ways, but then to leave it when you extrude further. 

That being said, the modelling looks a bit wonky overall. You've got some cuts in there, and, by the looks of it, nothing is truly straight, and you're putting additional cuts in to remove (relatively speaking) small amounts of material.

My guess is that somewhere in this model, you have so-called sliver surfaces which are causing the underlying geometry kernel to try and figure out how to put the whole volume together to form a water-tight solid. (All this is fancy speak for "trying to calculate your shape.) 

Sliver surfaces are generally unintended tiny tiny tiny faces that most often happen when one models something just a tiny bit off. They are often so small - you cannot see them unless you zoom in really close to them. If your cut here removes one of them, or perhaps adds one, then the calculation of the geometry overall might change, causing the addition of that weird face. (which is, itself, a sliver face)

You can try to fix this by doctoring up the resulting shape. By this, I mean, you could put the cut in, then perhaps select that sliver face, and press the delete key, or any number of different strategies to clean up the geometry. Who knows which one will work - or if it is even possible. You'll need to try them out. It can be frustrating.

On the other hand - the fact that this is happening at all is an indication to me that the modelling up until this point is not right. (This happens to everyone sometimes.) My recommendation to you would be to remodel the geometry before this cut. Something is not right there. I know this might not be the greatest thing to hear - but its definitely the best course. I am sure there is something in this model that is causing this, which is something you did not intend, and that cannot be manufactured.

Your timeline is very short. I didn't look in detail, but could it be that this is an imported model? Grabcad and other imported models are notorious for their sometimes poor quality. This is also very much the sort of thing I might expect from a mesh file that has been converted to a solid CAD format without much care. (That is a whole other area of expertise - and not an easy one.)