topic Re: Trouble Fully Defining Sketches in Fusion Design, Validate & Document Forum

Trouble Fully Defining Sketches

Anonymous — Wed, 11 Mar 2020 13:00:43 GMT

Hello,

I am quite new to Fusion360. I am having a problem getting my sketches fully defined. I cannot discover why the sketches are not fully defined. For example, I have attached the following sketch:

https://a360.co/2W3DsDi

Everything looks defined. For example, lines are tangent to arcs.

What should I be doing to create fully defined sketches?

Is there a function on Fusion360 that automatically fully defines under-defined sketches?

Thank you,

Marty

Re: Trouble Fully Defining Sketches

TheCADWhisperer — Wed, 11 Mar 2020 13:20:10 GMT

File>Export and then Attach your *.f3d file here.

The sketcher has been hopelessly broken since the beginning and doesn't always show as fully defined - even on the most simple of geometry.

(See Attached)

Re: Trouble Fully Defining Sketches

jeff_strater — Wed, 11 Mar 2020 14:30:03 GMT

much to @TheCADWhisperer 's dismay, I was able to quite easily get this sketch to be fully constrained. You are missing quite a few dimensions and constraints. One issue is on the left side, there is some extra geometry that I assume is unwanted:

zooming in:

deleted those, and re-attached the vertical arcs to the horizontal line. Then added these dimensions and constraints:

on the right-hand side:

and on the left-hand side:

repaired model is attached.

Re: Trouble Fully Defining Sketches

TheCADWhisperer — Wed, 11 Mar 2020 14:49:07 GMT

@jeff_strater wrote:
much to @TheCADWhisperer 's dismay, I was able to quite easily..

@jeff_strater

Did you check the file that I attached (created from scratch)?

I was not able do download the OP's file.

Re: Trouble Fully Defining Sketches

TheCADWhisperer — Wed, 11 Mar 2020 15:02:10 GMT

@jeff_strater

The file that you attached is not fully constrained.

(I don't think it matches the pdf either, but that is a different issue. Are those two long lines supposed to be Horizontally constrained?)

I interpret this to be tapered.

Re: Trouble Fully Defining Sketches

jeff_strater — Wed, 11 Mar 2020 15:43:55 GMT

ah, yes, missed that other small line. Deleted that and connected things back up. I think it's fully constrained now. Whether it matches the PDF or not is a different thing. The question was whether this sketch could be constrained. I think it can.

Re: Trouble Fully Defining Sketches

TheCADWhisperer — Wed, 11 Mar 2020 15:49:32 GMT

@jeff_strater wrote:
The question was whether this sketch could be constrained. I think it can.

What about the file that I attached?

Re: Trouble Fully Defining Sketches

jeff_strater — Wed, 11 Mar 2020 17:24:57 GMT

yes, that does look like an issue with the fully constrained logic. Here is another way to do that.

Re: Trouble Fully Defining Sketches

Anonymous — Wed, 11 Mar 2020 17:42:29 GMT

Thank you both for helping. I see the "Eccentric Rod" (steam locomotive part) is fully constrained in the previous post. However, the vertical extension on the left side of the rod is missing. The drawing I provided does not indicate fillet radii. Is it possible to add fillets that automatically constrain when applied? I thought I was doing this, but then I noticed those two vertical extensions Jeff found.

Also, the two long lines are NOT parallel. There is a slight taper from left to right.

I'm sorry I haven't been able to respond sooner. Gotta work!

Marty

Re: Trouble Fully Defining Sketches

TheCADWhisperer — Wed, 11 Mar 2020 18:40:47 GMT

@jeff_strater wrote:
Here is another way to do that.

About a week ago I realized that I was having to do this every day, find another way to do something that should just work. I have gotten so used to this that I didn't even think about it anymore. Doesn't work as expected, just delete and do it another way.

I wonder if the desker QC people have fallen into the same routine. Surely I can't be the only one experiencing these issues.

Re: Trouble Fully Defining Sketches

TheCADWhisperer — Wed, 11 Mar 2020 19:41:40 GMT

@Anonymous

File>Export and then Attach your *.f3d attempt directly here (for some reason your link doesn't work for me) and I will show how I would model the geometry.

Re: Trouble Fully Defining Sketches

Anonymous — Wed, 11 Mar 2020 20:06:28 GMT

Does this attachment work?

Again, new at this. Not sure if I am attaching files correctly.

Marty

Re: Trouble Fully Defining Sketches

TheCADWhisperer — Wed, 11 Mar 2020 20:11:52 GMT

I was under the impression that you had gotten further along with this after Jeff's input.

Attached is my "solution".

Hopefully you know how to interrogate the sketches and features to see how I built the geometry.

Re: Trouble Fully Defining Sketches

michroz — Wed, 11 Mar 2020 20:42:29 GMT

You have attached the file correctly.

And your sketch is not fully defined indeed.
You have to add quite a few more constraints. The choice of constraints is up to you - the designer. I can only give you a few ideas:
1. The central long handle - probably both lines should be horizontal (=), symmetrical to each other relative to the X-axis and also mark the dimension - the width of the handle.

2. The left 'eye' - make the center of the circles coincident with the X-axis.

3. The upper 'tooth' on the left 'eye' - it is not defined well enough. Make the edge horizontaland define the length of the tooth relative to the eye center.
IN GENERAL - when you sketch a sketch and you see it is not defined (thou you think like it should be and you don't know what to do) - try to click and drag one undefined object (don't worry - you can always undo the drag). You will see the 'degrees of freedom' for this object (how it moves - why it is undefined) and you will figure out what constraints would help.

Good luck.
Addition: See attached your file with the sketch defined. But check everything, because you are the responsible designer!

Re: Trouble Fully Defining Sketches

TheCADWhisperer — Wed, 11 Mar 2020 21:15:00 GMT

@michroz wrote:
1. The central long handle - probably both lines should be horizontal

1. Nope. This has already been discussed.

And

The sketch in the file that you attached is not fully defined.

And

The circle on the right side is incorrect diameter.

Re: Trouble Fully Defining Sketches

billbedford — Wed, 11 Mar 2020 21:38:39 GMT

Try drawing the bosses as arc segments, then overlay the boss faces when the outline is finished and defined.

Re: Trouble Fully Defining Sketches

TheCADWhisperer — Wed, 11 Mar 2020 21:53:02 GMT

The solution is attached in Post #13.

Re: Trouble Fully Defining Sketches

Anonymous — Sun, 12 Apr 2020 19:26:37 GMT

I wanted to thank everyone for helping me. I realize this post is a month old, but it was right before the virus hit and life got all turned upside down. Things are beginning to get back to (the new) normal. How funny does that sound?

I hope all are well.

Marty