topic Re: Draft Bug in Fusion Design, Validate & Document Forum

Draft Bug

OrhunUnal — Wed, 15 Jan 2025 14:04:07 GMT

I have sketched rectangle and extruded that then arrayed that body on the first one I have sketched the chamfer manually for the second one I have used chamfer command. But when I try to draft they act differently.

(view in My Videos)

Re: Draft Bug

jhackney1972 — Wed, 15 Jan 2025 14:18:25 GMT

Please attach the model in question to a reply post. Open the model in Fusion, select the File menu, then Export and save to your hard drive. Attach it to a reply post.

Betreff: Draft Bug

g-andresen — Wed, 15 Jan 2025 14:21:56 GMT

Hi,

You use a reference surface of the left body for both
What do you finally want to achieve? > Which surface should be angled in which direction?

Please share the file for reply.

File > export > save as f3d on local drive > attach to post.

günther

Re: Draft Bug

OrhunUnal — Wed, 15 Jan 2025 14:23:42 GMT

I have uploaded the model.

Re: Draft Bug

jhackney1972 — Wed, 15 Jan 2025 14:29:40 GMT

You used an Extrude to create the angled corners in the original model and a chamfer to create them in the second. They will react differently to the Draft command with the chamfer adjusting to the Draft where the Extrude will not.

Re: Draft Bug

OrhunUnal — Wed, 15 Jan 2025 14:41:46 GMT

I know I already mentioned this at the beginning of the post, I purposely showed it in the rectangular prism to make it very simple. Basically, does it match the logic of the draft command and why the adjacent surfaces are affected. What I am trying to learn is that why they are act differently. My expected result on the left one because other surfaces shouldn’t be affected.

Re: Draft Bug

jhackney1972 — Wed, 15 Jan 2025 15:35:22 GMT

As I said, the Extruded features will not be affected by the Draft operation because it is a sketched base feature where the Chamfer will be affected because it is a placed feature and will be influenced by the Draft.

Re: Draft Bug

laughingcreek — Wed, 15 Jan 2025 15:37:22 GMT

this looks like a bug to me also. if draft is going to modify previous features instead of working an the obvious way visually, it should have a type setting like offset faces does-

@Phil.E ?

Re: Draft Bug

OrhunUnal — Wed, 15 Jan 2025 15:40:24 GMT

Thanks for your reply you are saying that it is not a bug it’s feature.

Re: Draft Bug

OrhunUnal — Wed, 15 Jan 2025 15:43:57 GMT

I also thinks it is a bug because when we basically export these models and import them and try to draft they will draft similar to left one I know that when we export and import we lose the parametric features but we see the normal behavior of the geometric modeling kernel. Because algorithms behind the draft command shouldn’t affect from the features I believe I am not an engineer or programmer but after the extrusion and chamfer command we have b-rep body.

Re: Draft Bug

g-andresen — Wed, 15 Jan 2025 16:45:23 GMT

Hi,

1. When I get into a design like this, I can't see how a chamfer was created which leads to irritation and the subsequent (time-consuming) search for causes.

It should also be noted that it is repeatedly pointed out that fillets, chamfers ... should not be created in sketches, but as features.
2. I have never seen a draft pull adjacent surfaces along with it.
3. The same phenomenon also occurs with Move > Face > Rotate

@Phil.E

can you give an explanation of this

günther

Re: Draft Bug

jeff_strater — Wed, 15 Jan 2025 17:24:38 GMT

I can explain what is happening here. Whether it is a bug or a feature is probably a matter of opinion. It is intentional, I will say that. I apologize up front - this might get long.

what is at play here: Chamfer and Fillet operations are handled differently during "local operations", which include Face Draft, or Move Faces. The main reason for this is: if you want to move this face to the right:

The fillet is the problem. You cannot move that face with the fillet in place. So, what Fusion does is:

find and remove all relevant fillets (and keep that info)
move the face
reapply the fillets

The same is done for Chamfer, being a similar operation to Fillet (select an edge, Fillet/Chamfer it, which removes the edge, and replaces it with a new surface).

Most of the time, it works without any surprises. But, there are cases where it does, and you have found one of those.

Anticipating the next question, I've created a similar case with Fillet instead of Chamfer (the body on the left has a sketch fillet, while the one on the right has a fillet feature).

(view in My Videos)

As you can see, both behave the same. Why is that? Well, it turns out that Fillets are easy to identify: tangent faces, probably cylindrical/conical/toroidal. Chamfers, however, are not. So, in your case, the one on the right is correctly being identified as a Chamfer (because it is), so is treated as one. On the left, it is ambiguous. I'm not even sure it should be considered a Chamfer. It might just be an angled face. In this case, maybe it should, but that might be only because the one next to it is the same, and that is a Chamfer.

Anyway, you asked why. That is why.

Re: Draft Bug

OrhunUnal — Wed, 15 Jan 2025 17:44:02 GMT

Thank you for your answer, what I wanted to learn here was actually about why the modeling program behaves differently in two operations. I normally encountered this problem with a more complex model and it took me a long time to realize it. That's why I reduced it to the simplest way to show this problem. Thank you for an adequate and informative answer for me.

Apart from that, do you plan to update the Fusion api page.

Re: Draft Bug

TrippyLighting — Wed, 15 Jan 2025 19:26:10 GMT

@jeff_strater wrote:

... It is intentional, I will say that. ...

...meaning the team has made a decision on behalf of the user. That decision addresses 90% of the use cases.

For the other 10% it is undesirable behavior. In essence we'd like to have a choice and sensible defaults.

Disclaimer: percentages were chosen arbitrarily. Actual situation might be worse 😉

Re: Draft Bug

OrhunUnal — Thu, 16 Jan 2025 15:45:25 GMT

Does the process of removing the previous commands you mentioned for move face also apply to the shell command?