How to add polygon or pattern constraint ?

[Anonymous]

Dear forum members,

In a sketch I want to lengthen the line of 51 mm shown below.

When I tell fusion 360 to that, it doesn't, but tells me in stead :

“Error: Failed to solve.

Please delete or modify one of the following constraints/dimensions”

As far as I know, the way to reslove such issues, is to delete stuff, until Fusion 360 finally consents to allow the change one wants, and then add readd all the stuff one deleted.

However, that line is part of a 48-sided polygon and I don't know how to readd the polygon constraint, other than with undo or deleting the entire polygon and readding it.

So, how could I add the polygon constraint after having made the change required to be able to change the dimension ?

[TheCADWhisperer]

Can you File>Export your *.f3d file to your local drive and then Attach it here to a Reply?

[Anonymous]

Here it is attached. It is a project you have seen a few times already.

[TheCADWhisperer]

Before I take the time to download and then upload to my data panel, have you started over from scratch?

[Anonymous]

No, although I am not sure what you are referring to. I suspect you already have a version where that line cannot be changed.

[chrisplyler]

That Midpoint constraint...is it on that 51mm line?

If so - and if the center point of the polygon ALSO is constrained to something (or in fact any other point of it is constrained to something) then perhaps the polygon is unable to grow/shrink in size. After all, if you change the length of ONE polygon segment, ALL segments of it must also change, and if you have somehow otherwise constrained the "diameter" of it, the segment change will conflict with that.

Hope that made sense.

[Anonymous]

These seem to be two midpoint constraints on top of one another. I don't know what they are constraining. When I hover the mouse button over the symbol, the purple projection highlights. If I deleted it, the constraint symbol remains and the polygon sides become blue. Mousing over the constraint symbol highlights the polygon side.

I can then change the lenght of the side, but it moves up. I imagine the midpoints of these two sides were constrained on each other. What probably happened is that I set the vertical construction line to go through the middle of both the middle of the projected line and of the polygon side, which is indeed a requirement.

So apparently the polygon center is fixed. Why I don't know.

So I slowly (because the sketch is slow) deleted stuff and the vertical construction line was the culprit. Removing it allows to move the polygon's center (but the polygon doesn't turn blue). Annoyingly all these construction lines, which ought to go through that center, don't follow and Fusion 360 refuses to move them. Etcetera, etcetera

An intermediate state as illustration :

That was not going anywhere, so I finally decided to delete everything except the inner polygon, hoping not to encounter too many problems in the 3D world. Also, I did not add the fillets in the sketch. I'll deal with the errors in the 3D world. That worked.

I like how easy it is with Fusion 360 to make a small change afterwards.

In 2015 Autodesk was already made aware of the problem that it is unclear whether something is fixed or not : http://help.autodesk.com/view/fusion360/ENU

It takes a very long time to fix things over there.

[chrisplyler]

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@Anonymous wrote:

It takes a very long time to fix things over there.

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Boy, truer words were never spoken!

Anyway... Good sketching practice will have you thoughtfully constraining things as you go, with forethought and consideration for the desired behavior. Keep in mind that sometimes Fusion will AUTO-constrain stuff. For example, if you start a circle or polygon or whatever with your cursor very near an existing point, Fusion will ASSUME you meant to make it Coincident to that point, and apply a Coincident constraint for you. If you start something near the middle of a line, Fusion will assume you want a Midpoint constraint there, and apply it for you. As you sketch, be aware of these auto-constraints...sometimes they are what you want, and sometimes they are NOT what you want. Holding the Ctrl key while you mouseclick disables auto-constraint for that click.

[Anonymous]

So, the answer is that adding a polygon or pattern constraint is impossible. To mitigate problems one should try to keep sketches simple and try to understand what Fusion 360 is doing while sketching.

I think one cause for the problems was that the sides of the outer square were not perfectly vertical and horizontal, as the parallel constraints suggest.

Does “it is impossible” qualify as a solution (to mark a post that way) ?

[laughingcreek]

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@Anonymous wrote:

So, the answer is that adding a polygon or pattern constraint is impossible.

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can you qualify that statement.   on the face of it I would say it is incorrect.

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To mitigate problems one should try to keep sketches simple and try to understand what Fusion 360 is doing while sketching.

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Yes.

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I think one cause for the problems was that the sides of the outer square were not perfectly vertical and horizontal, as the parallel constraints suggest.

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Doubtful.  I didn't open the file because its and assembly, and a pita  on this end to have to download and upload.  but using the words of that statement  "vertical and horizontal"  and "parallel constraint" makes we want to ask which you where using?  if it has a vertical/horizontal constraint on it, then it is. The constrain is not a suggestion.  If it has a parallel constraint on it, then it IS parallel to SOMETHING.  ref your second statement above. 

[Angayo]

Edit : Angayo and Thoralin are the same person.

laughingcreek : “can you qualify that statement.   on the face of it I would say it is incorrect.“

There is apparently no way to convince Fusion 360 to add a polygon or pattern constraint to a set of lines, even if they already form a

polygon or pattern.

laughingcreek : “Doubtful.  I didn't open the file because its and assembly, and a pita  on this end to have to download and upload.  but using the words of that statement  "vertical and horizontal"  and "parallel constraint" makes we want to ask which you where using?  if it has a vertical/horizontal constraint on it, then it is. The constrain is not a suggestion.  If it has a parallel constraint on it, then it IS parallel to SOMETHING.  ref your second statement above.”

One can see the parallel constraints in the second image in post 7. I suspect I used parallel constraints for that square for the following reason :

The original model was a step file, presumably made with another program. Of that model some vertical and horizontal planes are not perfectly so. I wanted the outer square sides to bo parallel / perpendicular to those planes.

[Anonymous]

Can one change the number of sides of a polygon ? Say, I want my polygon to have 52 sides in stead of 48. If so, how ?

[davebYYPCU]

Left click the polygon icon to select it,

right click, select Edit polygon.  

In the input box change 48 to 52.

Might help...

[TheCADWhisperer]

If you have any idea up-front that the number of sides might vary - you should model only one side and pattern feature rather than sketch (which is basically what a sketch polygon is - a sketch pattern).

[TheCADWhisperer]

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@davebYYPCU wrote:

Left click the polygon icon to select it,

right click, select Edit polygon.  

In the input box change 48 to 52.

Might help...

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Screen capture might help...

[davebYYPCU]

Desktop computer is 8 or 9 hours away.

[TheCADWhisperer]

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@davebYYPCU wrote:

Desktop computer is 8 or 9 hours away.

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Well, the reason I ask is I would have given exactly the same answer, but I checked - and couldn't get it to work in latest release.  Left me wondering if something got broken or if I forgot how it's done.

[davebYYPCU]

Was from muscle memory, been a while since I have done it, and 

you can change the count in the parameters window too,

there is an update floating out there, I am always a day or too behind with those, even though I am 17 hours ahead of your clock.

[TheCADWhisperer]

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@davebYYPCU wrote:

...and you can change the count in the parameters window too,

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There was an Update this morning.

Strange thing is - no Parameter for number of sides on my machine.

I'm wondering if it is just my machine or if it is a general issue with latest update.

Now I am really questioning my memory.

I can't get it to work in Autodesk Inventor either???

[laughingcreek]

@davebYYPCU , @TheCADWhisperer   -  I know this use to work, but I can't do it either.  also doesn't show up in edit parameters dialog