When Replace Face doesn't work

[ic198]

This post is related to this product enhancement idea

I would like a Thicken To option because Replace Face does not work in the situation in the attached ipt. Yes I know there are any number of other ways I could draw this part and not need Replace Face- this is a simplified version of a more complex problem.

As a side note, I have in the past wanted to be able to Draft one of the tangent faces using the Fixed Plane option (see screenshot), but you can't do that- anyone know why not?

[johnsonshiue]

Hi! The reason why the Replace Face fails in this case is because the desirable result requires new topology to be created. The selected face shares an edge with the adjacent face on the same plane. When you try to replace it with the workplane, the shared edge will have to turn into a vertical face. This is not what Replace Face is capable of. RF simply extends the lateral faces to the new face and re-intersect. In this case, there is no lateral face on the shared edge, as a result, the face cannot be replaced.

To prove my point, simply create a Thicken feature on the selected face (with Auto-Blend off). Then replace the thickened face with the workplane. It will work. This is because Thicken creates the lateral face allowing the RF to work.

Regarding the Face Draft, I think you want to use Fixed-Edge type in your case. Why do you want to use Fixed Plane but an edge has to be fixed?

Many thanks!

[DRoam]

@johnsonshiue, what are your thoughts on a Thicken "To" capability? Right now Thicken must be given a distance; we can't thicken "to" a selection.

Do you think that a "Thicken To" functionality could replace the "Replace Face" command? Basically, could we move Replace Face's functionality to the Thicken command, but also take advantage of Thicken's ability to add perpendicular faces like in the instance you described above? It seems to me that "Thicken To" could work in all instances that Replace Face does, AND in situations where it doesn't, like the one discussed above.

In my opinion, "Replace Face" doesn't belong in the Surface commands anyway, because it isn't a surface modeling tool. Yes, you select a surface as one input for the command; but the command operates on a solid. It seems very misplaced in the Surface tools, in my opinion. "Thicken To" might make a lot more sense.

What are your thoughts?

[johnsonshiue]

Hi! Interesting discussion. Replace Face and Thicken are totally two different commands using different algorithm. Like I mentioned before, Replace Face is more about replacing an existing face and then let the lateral faces re-intersect with the new face. When it fails, it is either the lateral face does not exist or re-intersection fails. Thicken on the other hand is like offsetting. It offsets the current face in its normal direction to certain distance. The lateral faces will be created not extended. So the definition of the two commands is different. They are for different purposes.

Many thanks!

[ic198]

Hi @johnsonshiue,

Thanks for your reply. What are your thoughts on a Thicken To option?

For the draft, the reason I don't use Fixed Edge is because the results appear to be completely inconsistent- see attached screenshots. Capture.jpg shows what happens if I use the inputs I want to use i.e. I pick an edge I want to fix (as it's called Fixed Edge this makes sense), and a face I want to draft, but I don't get the result I want.

Captures 2 & 3 shows that with a minor tweak of the underlying geometry you can get the same command with the same inputs to achieve totally different results.

[johnsonshiue]

Hi! Thicken To is an interesting idea. Please feel free to report it on Inventor Ideas if there is no existing entry. What concerns me is that what we really thicken to. Like I mentioned earlier, Thicken is an offset operation based on the face normal. So after thickening the face to another face (plane), should the face be replaced or the face simply offsets up to the terminating face (plane)? They will yield completely two different results.

To be more technically accurate, the request is more like protruding a face to a distance or up to a face (plane). It is actually closer to Replace Face than Thicken.

Many thanks!