Sketch elements flipping while draggging - OK?

[kristianY3VSG]

In the screencast you see a rectangle, whose right upper corner is set coincident with the upper arc. While dragging the rectangle the vertical sides suddenly flip, the horizontal dimension and the constraint flip to the left side. Is this normal? How can I prevent this?

I work with parameters very much, little changes of their values may cause larger movements of sketch elements. The idea that this can make the constraints confusing is quite scary!!!

Thanks for explanation and suggestions...

Kristian

[g-andresen]

Hi Kristian,

I have tested it several times. The elements  behave as expected and the dimensions don´t move.
The only thing I could discover is that the coincidence is top left and not right.

günther

[kristianY3VSG]

Hallo Günther,

thanks for your response. You are right - I accidently exported the design with the constraint at the left upper corner and the dimension on the left side.  But if you grab the vertical center line and drag it horizontal, you´ll need only 2-3 seconds, and the dimension flips to the other side (and the constraint too, I´ve just tested it from the f3d).

Meanwhile I figured out, that this doesn´t happen, when the horizontal dimension reaches from left to right, no matter, whether horizontal line lenght or distance of the vertical lines. 

OK, I´ll rememer this, but I see, that even after 1,5 years working with F360 I still can´t be sure to know, how F360 "thinks" and what it doesn´t like, and have to be afraid of unexpected behavior. I stopped to count, how many designs I had to re-create from scratch again, as something weird occured, that I wasn´t able to fix. The actual example was the start of such a re-design. When I worked with the original file last time (some 2 months ago, attached), everything worked fine, any change of any parameter was realized immediately, the driven dimensions showing the wears I need to know.  Now I can´t do anything in this file, any parameter change results in a warning! Is the updated SW really better then the old one???

Kristian

[g-andresen]

Hi Kristian,

in your first example, the rectangle is not fully defined. Moving the rectangle causes conflicts in the conditions. Unfortunately, I can't see where the problem is at the moment*. Therefore I created the radius of the arc as a construction line and dimensioned it. Effect > fully defined. As you can see, the rectangle can be moved along the arc without losing its reference.

constraint behavior
I would like to recommend you not to put everything into one sketch ind the 2. file (Bogen...).

regards

günther

* @jeff_strater ; @TrippyLighting >  maybe you can help in this case.

[chrisplyler]

Think about this:

Your rectangle does not have any constraint that requires the right side to remain on the right side and the left side to remain on the left side. So for any position you drag it to, there are TWO possible solutions that the solver must decide between. It's just stumbling on to the undesired, flipped solution once in a while.

[kristianY3VSG]

Hi Günther,

thanks for your suggestions, but I can´t fix the position of the rectangle, as it will be defined in a later stadium by other elements - see "Bogenlauf..." And I can´t divide that design into partial designs, as the positions of the particular elements depend on each other. The goal of this sketch is to find optimal dimensions and wears, as the model has to pass smaller track radiuses (considering the scale) than the original locomotive: the back frame must be slimmer, the cylinders more outside...

Meanwhile I re-created the Bogenlauf (though a bit simplified, see attached), everything works well now. I can change the track radius, dimensions or various constraints... At this moment the vertical center line of the center rectangle is concident with the origin, but I can delete this constraint and set any corner coincident to track arcs (or define some distance), no problems, all the parts move to the left or rigth as expected, and the driven dimensions show the values I need to find out.

But as I said before: I´m still waisting more and more time re-creating designs, that became not usable due to some weird mysteries inside F360 - that´s anoying :-((

Thanks and regards...

Kristian

[kristianY3VSG · Accepted solution]

Hi @chrisplyler 

thanks for your response. Though I try to design quite complicated things, I´ve not learned all about F360, that´s why I asked, how I can prevent this effect. Well, one solution I did find - dimensioning the overall length.  Could you maybe suggest some other? But I don´t want to add some distiguishing geometry not needed for my design.

Thanks and regards...

Kristian

[chrisplyler]

It is not possible to have sketch elements fully defined such that this phenomenon is prevented, while still being able to click-n-drag the sketch elements. You can partially constrain stuff in various ways, but you just have to use logic to predict what behavior any constraint or combination of constraints will create.

You might not want to create unnecessary sketch elements, but sometimes a construction line is your friend.

[kristianY3VSG]

I understand all this, of course 🙂 

I tried to add a diagonal construction line or a vertical construction line colinear with the dimensioned vertical line, nothing helped, the geometry still toggles.  But one solution I´ve found, so it´s not necessary to talk about this anymore.

Thanks

Kristian

[TrippyLighting]

This flipping behavior is not always easy to avoid and I would agree with @g-andresen that I would already break this down into simpler sketches. In general I avoid mirroring and parenting ins sketches. If I do use mirroring I might use I on 2-3 items but I don't usually mirror a complete profile.

Can you mates share more of what you want to design, so we might suggest alternative methods of designing it ?

I personally try to use as few sketches as practical.

[kristianY3VSG]

Hi Peter,

as I explained above, the Bogenlauf design I created for finding an optimal constelation of these parts and their dimensions, so breaking it down makes no sense. Well, I´ll try to use less mirroring 🙂

What I want to design - a model of this wonderful engine:

You can imagine, how complicated such a design is - dozens of parts, which are to be adapted to model scale, available materials and changes due to park railway standards.

I try to use as few sketches as possible too, but e.g. for the rear frame module (maybe 5% of the whole engine, still not complete) I created 25 sketches, as I don´t like to extrude from confusing overlapping profiles :-). You can imagine, that re-creating this design from scratch (though in an earlier stage with only some 10 sketches) due to F360 crashing because of still unkonwn reasons has really upset me.

To coordinate all designs needed in future I wanted to use Insert Derive for sharing some sketches defining basic dimensions and positions. At that moment all my problems began, at the very first designs. I´ve published several posts about this in the Support forum (this thread got here maybe by missclick, didn´t notice this, sorry). I lost several weeks waiting for explanations, how to avoid all these problems, or for SW updates fixing the bugs, if the problems are caused by bugs, but can´t see any evident improvement so far.... 😞

Thanks and regards...

Kristian

[chrisplyler]

---

@kristianY3VSG wrote:
I created 25 sketches, as I don´t like to extrude from confusing overlapping profiles

---

Weird. I love to do exactly that instead of have so many sketches! Different strokes and all that.