topic Re: Ultimate Constraints in Fusion Support Forum

Ultimate Constraints

E_SADRIA — Sat, 10 Apr 2021 13:45:11 GMT

Hey Guys,

i have watched Lars Christensen's tutorial on constraints.

https://www.youtube.com/watch?v=pqd_wlz9gpQ&ab_channel=LarsChristensen

I know how important it is to every design so i try to do it aswell.

But i can't get my drawing to get fully constrained and i can not figure out where i go wrong. Is there a tool to check?

Re: Ultimate Constraints

jeff_strater — Sat, 10 Apr 2021 14:20:56 GMT

The technique I use is sketch drag. Try dragging any of those blue curves, and you can see what is constrained together, and that can help you figure out what constraints need to be added. I'll take a look at your sketch in a bit and see if I can show the technique.

Re: Ultimate Constraints

g-andresen — Sat, 10 Apr 2021 14:23:37 GMT

Hi,

With all the chaos, it's hard to find a beginning.
First remove all dimensions and make sure that you do not have any open connections (white dots) and double lines.

günther

Re: Ultimate Constraints

HughesTooling — Sat, 10 Apr 2021 15:23:14 GMT

Fusion should really be flagging this as over constrained but I guess all the dimensions have just overwhelmed the solver. If you have a right angle triangle with 2 equal lengths you should only need 2 dimensions to fully constrain it.

Not only have you dimensioned 3 sides and a 45° angle but on all three side you have a second set of dimensions (in affect dimensioning the line length twice). I guess you started with the triangle, if that's constrained with just the two 6.124" dimensions, if at any point it changes to unconstrained you have a problem.

You can see starting with a triangle and 2 dimensions you're fully constrained.

You are also adding to the complexity using 2 collinear lines when you could use a single line. Just add a point at the intersection if you need to dimension the intersection. If I was you I'd start again from just the triangle, add lines and fully constrain at each step and if you run into a problem like the main triangle changing to unconstrained come back here with the new design.

Mark

Re: Ultimate Constraints

HughesTooling — Sat, 10 Apr 2021 15:28:56 GMT

Forgot to add, if you try fixing this design rather than start again you have something odd going on at the bottom corner. If I window select the corner with delete active it selects 16 points, not sure how you ended up with this!

Re: Ultimate Constraints

jeff_strater — Sat, 10 Apr 2021 15:30:42 GMT

the suggestions by @HughesTooling and @g-andresen are all good. The first problem seems to be those "point stacks" where you have 2 or more points on top of each other. Fix those first. Focus on getting that construction triangle fully constrained, then work top/down on the rest of the sketch. You will have lots of angle dimensions, but will need more than that.

Re: Ultimate Constraints

HughesTooling — Sat, 10 Apr 2021 16:03:03 GMT

After cleaning up your sketch, removing duplicate geometry and adding a few construction line to help with symmetry I get this.

Fully constrained, file's attached for reference.

Mark

Re: Ultimate Constraints

TheCADWhisperer — Sat, 10 Apr 2021 20:37:36 GMT

Here is a slightly different schemata...

Re: Ultimate Constraints

E_SADRIA — Sun, 11 Apr 2021 13:38:56 GMT

This is how i ended up. Thanks a lot guys!

@g-andresen
"In the midst of chaos, there is also opportunity. - Sun Tzu

Re: Ultimate Constraints

g-andresen — Sun, 11 Apr 2021 14:14:34 GMT

Hi,

Indeed.
A wisdom that gives hope.

günther

Re: Ultimate Constraints

E_SADRIA — Sun, 11 Apr 2021 14:59:22 GMT

I get another little side effect when i mirror the construction

Re: Ultimate Constraints

davebYYPCU — Sun, 11 Apr 2021 18:15:33 GMT

Has anyone recommended you Pattern or Mirror in the modelling environment, and doing so in sketch is not recommended?

delete 3/4 of the sketch, and proceed to the modelling area.

I have not reviewed the file.

Re: Ultimate Constraints

TheCADWhisperer — Sun, 11 Apr 2021 19:28:41 GMT

What is your end goal?

It is almost always preferable to pattern (mirror is a type of pattern) at the feature or body level rather than at the sketch level.

Explain you Design Intent - show images of existing real world part(s) if possible.

Re: Ultimate Constraints

E_SADRIA — Mon, 12 Apr 2021 15:43:48 GMT

So my goal is to create the bracelet on the attached image with the pattern. Both creations are mine right now there are done from illustrator and tooled by an engraver but i would like to be able to draw it in fusion....

Re: Ultimate Constraints

TheCADWhisperer — Mon, 12 Apr 2021 16:45:18 GMT

Ahh, I recognize this work now (I don't pay any attention to names, only geometry).

As we discussed months ago - avoid patterns in sketches - keep sketches simple and pattern features, faces or bodies.