topic Fillets cause the sketch to be unconstrained. in Fusion Design, Validate & Document Forum

Fillets cause the sketch to be unconstrained.

Im1in260m — Sun, 13 Apr 2025 15:41:14 GMT

When I added fillets to an element in the Base sketch, the rectangle that it was became unconstrained. I have tried several things to connect the fillets to the vertical lines of the rectangle thinking that might fix it, but it did not. I did fix a couple of lines that were unconstrained by simply adding a dimension. But the fillets have dimensions.

Would someone mind pointing out the flaw? I have attached the file.

Re: Fillets cause the sketch to be unconstrained.

jeff_strater — Sun, 13 Apr 2025 17:21:26 GMT

I cannot say what role sketch fillet played here, but see the video to see what is still underconstrained in this sketch:

(view in My Videos)

Re: Fillets cause the sketch to be unconstrained.

Drewpan — Mon, 14 Apr 2025 04:14:48 GMT

Hi,

While not always the case, the Rule of Sketch should be to keep

things simple in the sketch and use the Tools to sculpt your model.

It is fine to use multiple sketches that each does only one or two

things to create a model. Simple sketches are the easiest to constrain

correctly and fully constrained sketches keep fusion from "guessing"

what you actually want and lead to far fewer errors later on.

I am not suggesting you are a beginner but many beginners spend much

time and effort on elaborate sketches when the tools will almost all of

what they want to do and the model is much more robust. They will then

do something simple like adding fillets to the sketch and break their

sketch and get frustrated and confused.

In fusion it is the Model that fusion bases everything upon. You don't

work out tool paths with sketches, nor do you animate them. Treat

Sketch as just another tool for sculpting models.

You should not use sketches for engineering drawings, although some

people try. The Drawings function in fusion is also based on the Model.

Cheers

Andrew

Re: Fillets cause the sketch to be unconstrained.

TheCADWhisperer — Mon, 14 Apr 2025 11:53:08 GMT

@Im1in260m wrote:

Would someone mind pointing out the flaw? I have attached the file.

@Im1in260m

The sketches are poorly done - not using best techniques.

What are you attempting to model? A sheet metal bracket?

We can get this all fixed up in a logical manner.

In addition to other issues - you are creating your Slots in a computationally expensive manner... ...there is a tool for this.

Re: Fillets cause the sketch to be unconstrained.

Im1in260m — Fri, 18 Apr 2025 11:25:54 GMT

Hi CADWhisperer, thanks for replying. That is not supposed to be a slot. That is the outline of a pedestal that will extrude into life once the sketch is completed. This is supposed to be a simple plastic bracket that I will hang my Oculus from and the holes are for the controllers. I have no idea how many itterations I will go through before I get what I want, but this is the start. As such, the beginning must be perfect. I read Drewpan's comment also. I am not offended be called a beginner. I am! He said; " Simple sketches are the easiest to constrain correctly and fully constrained sketches keep fusion from 'guessing' what you actually want and lead to far fewer errors later on." Here I thought this was a simple sketch! I did fix the part of the sketch that I originally posted about by adding a dimension that set the distance of the 'non-slot' from the edge. But there is still some unconstrained thing that I cannot identify. I read that I could enter a command in the Text Command window that would highlight the unconstrained items, but I can't find a way to open a text command window.

If I am doing this all wrong, then I will have to learn to do it right. My approach is to sketch the body I want and extrude it into a model. If, instead, I should sketch a rectangle, extrude it to a desired thickness, then start adding sketches to cut holes or slots or extrude pedestals then I can try that. Maybe I could speed up the process of design to print. But I have not seen how to do what I need to do, so I have to go with what I understand. My understanding is to outline, or sketch, the basic shape, then pull it into existence. So, this sketch is the one that defines the base of the shape that will be pulled into a model. To avoid problems with the model later, I need this to be perfect. The question then is, do I extrude the base, draw the outline of the pedestal, then extrude that? If so, then a new problem exists. That part of the model has a slightly curved surface. The arc that that curve will follow is on the other sketch. Why? Because it is on another plane perpendicular to this plane.

I appreciate the guidance of anyone with experience and a better understanding of the Fusion workflow. I find that the hardest part of Fusion is knowing how to solve, what appears to be, simple problems.

Thank you.

Re: Fillets cause the sketch to be unconstrained.

TheCADWhisperer — Fri, 18 Apr 2025 12:23:23 GMT

@Im1in260m

I'm going bird watching this morning so don't have time to go into detail - but I want to make far more changes to this when I get time.

Instead of duplicating dimensions use geometry constraints like equal, colinear, or whatever makes logical sense to replace the duplicated dimensions.

Then if you need to change a dimension there is just one instance to change.

Where you do still have duplicate dimensions make one a function of the other to make editing easier.

Back in a while with more tips...

Re: Fillets cause the sketch to be unconstrained.

TheCADWhisperer — Fri, 18 Apr 2025 22:03:04 GMT

@Im1in260m

Observe that there is symmetry from left to right, so we only need to sketch one side.

Usually better to do Fillets as Placed Features rather than in the sketch.

Re: Fillets cause the sketch to be unconstrained.

TheCADWhisperer — Sat, 19 Apr 2025 19:40:39 GMT

@Im1in260m

Keep your sketches simple.

See Attached...