Face Based Void Can't be Hosted on Extrusion Base Face - Why ?

[jnoordzij]

Hi,

I am experiencing some Revit behaviour that I do not understand.

I have a face based void family that I often use.

I just found out that I can not host this face based void family to the 'base' face of an extrusion.

By 'base' face of extrusion I mean the face being the work plane of the extrusion, in which the profile of the extrusion was sketched.
I can host the void family on every other face of the extrusion just fine. Just not the base face.

Attached I have an example family. In it you find a simple cube extrusion, modeled from work plane Ref Level.

The family has a nested family in it called Gat Rond, which is the face based void family.

In the screenshot you can see the face based void family placed on some sides of the cube.

But I can not place it on the bottom face.

Do any of you understand why this happens and what is the logic behind it?

Many thanks in advance.

[Alfredo_Medina]

I think the void volume is just too small, 5 millimeters in diameter, and it is too short in relation to the phase it is cutting. I don't know why the problem happens only in the bottom face, though. However, you can fix it by making the void pass through the face volume (in the void family), as shown here:

By the way, you have too many constraints for a circle. The fewer constraints the better. A circle needs just one constrain, either the diameter or the radius, instead of equal-equal constraints on both vertical and horizontal dimensions.

[jnoordzij]

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I think the void volume is just too small, 5 millimeters in diameter, and it is too short in relation to the phase it is cutting.

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Thanks for your reply. But if so, then why is it cutting the other faces just fine? I doubt if this is it. Think it's something else. But what?

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I don't know why the problem happens only in the bottom face, though.

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That's exactly the point. Anybody?

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However, you can fix it by making the void pass through the face volume (in the void family), as shown here:

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Thanks for your suggestion. But that is not a desirable solution for me. I need parametric depth of the void. Sometimes it should not go all the way through.

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By the way, you have too many constraints for a circle. The fewer constraints the better. A circle needs just one constrain, either the diameter or the radius, instead of equal-equal constraints on both vertical and horizontal dimensions.

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I understand that in order to make a circle i could do with less constraints. However, once in a while I need to align to a side of the circle. Which is why there are references there.

So, question not completely solved yet. Does anybody have another idea?

[Anonymous]

Yeah, this has bugged me for quite some time.   I am currently revising all my countertops to sweeps, which allow sinks with voids to work just fine.

[Alfredo_Medina]

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@jnoordzij wrote:

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Still not solved. Who has the magic vision?

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Still not solved? When I make the void cylinder pass through the face of the family then I can host it well to bottom of the cube.

[jnoordzij]

@Alfredo_Medina I'm sorry.  I just edited my reply to you, in order to explain better.

Again: I need the parametric depth of the void. Sometimes it should not go all the way through, only a couple of mm. That is why I can not extend it all the way through the face (in the void family).

I hope I made this a bit more clear.

Anyway, thanks a lot for your help and suggestions! I am very grateful. But still, not completely solved.

[jnoordzij]

Could it be that the normal of the base face / bottom face is pointing outwards, while the other faces are pointing inwards?

So that when the void is hosted, it is being placed outwards instead of inwards? And it doesnt cut anything?

See screenshot:

[ToanDN]

I created a face based void family to test and I can host it on any surfaces of an extrusion (top, sides, bottom).

[barthbradley]

@jnoordzij: Just curious to know what the purpose of modeling 0.50mm holes is.  Are you designing drill hole templates -- perhaps for 3D printing?  

[jnoordzij]

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@ToanDN wrote:

I created a face based void family to test and I can host it on any surfaces of an extrusion (top, sides, bottom).

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@ToanDN That's great!

From which work plane dit you model this extrusion?

Can you maybe share the family so I can test / study it?

[Anonymous]

ha ha...I figured out why my countertops were not working the way they should...which is probably what your problem is @jnoordzij

If you are trying to host a face based item on a family and it isn't found?  Guess what? That is because it is turned off in the view.  Open up the family and click on the object that it should be hosting to and click on visibility, more than likely it is turned off in plan. Turn it on...then go to the floor plan view and get rid of the masking regions.  Reload back into the project.  Bet it works after that.  <smiley headbutting a brick wall>

[jnoordzij]

@barthbradley Yes, sometimes drill hole patterns. But sometimes just holes in construction parts, anchors for example. They are not 0.50 mm.

[jnoordzij]

@Anonymous Great I'll give that a try.

[ToanDN]

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@jnoordzij wrote:

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From which work plane dit you model this extrusion?

Can you maybe share the family so I can test / study it?

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I created the extrusion as an in place model, draw the floor plan.  2019 file attached.

[barthbradley]

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@jnoordzij wrote:

@barthbradley Yes, sometimes drill hole patterns. But sometimes just holes in construction parts, anchors for example. They are not 0.50 mm.

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Thanks. Yes, I just looked at your file. Not 0.50mm, but still mighty small at the 25/128".  Probably just a blob of ink on your CDs -- and when Thin Lines are turned off.  

Anyways, thanks again for responding to my inquiry.  Always learning.  

[Alfredo_Medina]

@jnoordzij

I think you are right in your assumption about the direction of the normal plane at bottom face of the cube. It is reversed in relation to the other faces. Considering this, the solution for making this face-based family with a cylinder void with a parametric length would be like this:

1) Make the void family have a top offset, as show below. This avoids that error of "Can't cut instance(s) of [family name]... out of its host.

2) After placing this void family on the bottom face of the cube, immediately use the "Flip Work Plane" symbol, to force the void family to reverse direction. 

[ToanDN]

I see the issue if placing the face based void on an extrusion in a family, but no issue if placing the same one on an extrusion in a project.

[Anonymous]

Doh...okay your issue is way different than mine....and I didn't realize you uploaded a family.

The top of your Gat Rond wasn't locked to a reference plane.  I created one about 1mm away from the generic face and locked it...then dragged the void shape handle to lock with the reference plane I created and reloaded....places into the bottom of the cube just fine now.

[AaronEllsworth]

Apologies for the necropost, but eight years later (using Revit 2026) I'm running into this same issue, and solved it with the ideas I found here. Thank you Alfredo.

Just to recap: The bottom face of an extrusion in a family and not a project has a reversed normal direction from the other faces. Extrusions in projects behave as expected. This problem does not occur on a sweep.

The work around:

1. The void family needs to extend both above and below the hosting face.  This allows the void to be placed on the bottom face by cutting it, even with the Work Plane flipped.

2. Once placed, the void can be reversed with the little "Flip Work Plane" icon that appears when the void is selected, and then it cuts the bottom face as one would expect.

Incidentally, the bottom of walls in a project have this same behavior. I've never needed to put a reveal on the bottom of a wall, but I just had to test it.