What determines what face to select when placing a Form iFeature

[fsdolphin]

Hi,

From the attached .ipt I can extract a Form iFeature where that behaves as follow...

1. I create a point.

2. Then I place the Form Feature by selecting the 'opposite surface' from where the point is located, then the Form Feature forms up, which is what I want.

Everything is working fine but there is one thing in the placement process that I would like to have a better understanding and possibly change. What I would like to be able to do is select the same surface where the point is located and have the form feature still form up, in other words, instead of selecting the opposite side/surface I would like to just select the same surface where the point is located.

What dictates what surface needs to be selected when placing Form Features?

Is it possible to create the Form Feature in a way that I don't have to select the opposite side when placing it?

Thanks

[johnsonshiue]

Hi! I think it may have something to do with the source features generating the iFeature/Punchtool. It has dependency on the back side of the face. Please share the source feature part also. I would like to see how the iFeature/Punchtool was extracted.

Many thanks!

[fsdolphin]

The iFeature/Punchtool was extracted from the .ipt file I attached and no matter how I extract it, it always requires the user to select the opposite side/surface from where the center point is located, that's the part I'm not sure if it can be changed to either select the surface where the center point is or no selection it all. I'm just trying to understand what's driving that selection. Thanks.

[johnsonshiue]

Hi! I suspect the features (extracted) have dependency on the back face. Without seeing the actual ipt file, it is impossible to tell. Please share it here or send it to me directly (johnson.shiue@autodesk.com).

Many thanks!

[fsdolphin]

Do you want to see the actual, generated Form Feature? As I mentioned it in my previous comment, the actual .ipt file is attached in this thread (Punch Tool Example.ipt).

[johnsonshiue]

Hi! I am sorry I did not notice the part you attached. I took a look. There are two places depending on the back face. 1) Sketch4 has a horizontal line projected from the back face. 2) The Fillet requires an edge on that face.

Many thanks!

[fsdolphin]

I deleted the horizontal line, the Fillet and any other reference to that face and re-extracted the feature but I get the same result.

Is there some documentation that explains how iFeatures and From iFeatures work? If this is not possible it's fine, I just want to have a better understanding of how this works.

[Tom_Sturtevant · Accepted solution]

Hello – the inputs are based on the dependencies in the internal data model.  I don’t know if there is any documentation on this but in general it comes down to understanding the dependencies you create in your model (projections into your sketch, work feature inputs, sketch planes, termination faces, etc, etc…).   Turning off Tools > Application Options > Sketch > “Autoproject edges for sketch creation and edit” will make it easier to control what dependencies creep into your model.

One trick to understanding the dependencies is to change the set of features and sketches that are selected in the iFeature extraction process and see how that effects the Inputs for the iFeature.

I was able to edit your revolution sketch and remove ALL projected geometry – the tricky one was the point projection on the back face, I needed to first delete the attached lines and arc then recreate them using a Thickness dimension rather than constraining to anything on the back face.  It will now extract an iFeature with only the single face as an input (see attached).

Hope this helps!

T.0.M.

[fsdolphin]

Thanks a lot for demonstrating how it could be done.  I cannot think of any instances where someone would want to select other faces when placing an iFeature, why the extra steps, my point is, wouldn't be nice if Inventor would ignore any extra geometry and make it the default. I'm probably not seeing the whole picture here, I will keep practicing to have a better understanding. Thank you all for your help.

[johnsonshiue]

Hi! Please take a look at attached part and the extracted punch tool. I modified your file and made it work. This is quite similar to another thread I just looked at. Please also take a look at reply#10 in the following thread. There is a bit explanation of how I made it work and some rules to follow to get a good iFeature/Punchtool.

https://forums.autodesk.com/t5/inventor-forum/ifeatures-interfering-with-each-other/td-p/9494764

Many thanks!