Sketch does not enforce contraints after referenced lines change dimension

[Anonymous]

I am creating complicated profiles for stamped sheet parts.  Aside from the numerous issues with Fusion 360 complaining about overconstraints when they don't exist (I can still move lines in the axis of freedom I attempt to constrain), I'm having a serious issue with referenced lines.

I can build and constrain the sketch to referenced intersections, lines, and arcs without issue while sketching.  However, when a parameter value change causes the lines to move or change dimension, the sketch is broken into pieces.  The reference attached portions of the sketch don't move with the referenced lines, but oddly the lines and arcs that had been constrained to the 'frozen' sketch lines do move appropriately.

A common thing that happens is where arcs are tangent to another arc or line, and the ends are coincident.  The tangent and coincident constraints remain and highlight the appropriate sketch elements, but the elements are NOT actually in the correct places.  The profiles and contours read the shown (broken) sketch and not the sketch that should build from the constraints.

Additionally even tiny movements of the referenced line cause the current dimension satisfied position of a line to jump to another dimension satisfied position, calling for substantial additional lines and dimensions to prevent this.

I don't have issues like this in an Inventor 30 day trial or in Solidworks.  This is a major problem and makes referencing other parts in sketches totally useless in Fusion 360.

Thank you all for the help!

EDIT: 11/25/2015 1:37PM -8GMT [ADDED SCREENSHOT]

[HughesTooling]

I've seen some problems like yours, I found I needed to add coincident constrains to keep things together. The only why i found end points stay together was to draw the arcs with a gap and add the constrain rather than picking an end point while drawing an arc.

Mark

[Anonymous]

Looking back at my sketch I can see that where I did exactly as you suggest it did hold together.  I'll try that, but that's very annoying.  Coincident constraints should be automatically generated when selecting points as an arc end point.

I'm still hoping for this to be resolved on the software side for future users.

[HughesTooling]

Where the problem really shows up is if the end of an existing arc is on a construction line or arc and you start a new curve picking what you think is the end point but the coincident constraint end up between the construction line and the new curve. What's needed is for normal entities to have a higher priority than construction entities.

Mark

[Anonymous]

This works perfectly as a solution, however it is a bandaid fix to the priority issue. I even went back and did it making sure to select the primary lines and not construction lines, but it only works if you build the primary lines totally apart from the construction and later constrain the already constrained lines to the construction lines.

[jeff_strater]

I agree - if there are cases where concident constraints to endpoints should be created but are not, that's a bad bug, and one that should be fixed.

If anyone has a case that shows how to create this bug in the arc commands, please post a screencast.  I believe that this can occur, but I haven't yet been able to reproduce it.  I admit that I haven't tried all that hard.  So any assistance would be much appreciated.

thanks!

Jeff Strater (Fusion development)

[HughesTooling]

Hi @jeff_strater

Here's a screencast that demonstrates the problem.

Mark

[daniel_lyall]

when you do a slot like that with a arc or straight lines they both go like that, it is a big bug when doing it with straight lines you have to have all 4 point where they meet the circle constrained using a tangent constraint before you can do anything to it most times. other time you have to do it again or it goes like what is in your screen cast, or it work's sometimes more often it don't work at all.

i just played it goes all over the show when you add the tangent constraint's but once you add the last one it can come good, I did it with the arc's connected to the back of the circule's way off center and cutting through the circle's, once all 4 tangent constraint are there it's fine.

[HughesTooling]

If you look at this point when I draw the small arcs there's a square where I've picked the end point of the larger arc but when I add the tangents it pulls the 2 arcs apart. So what is the square in the image supposed to be telling me!

Mark

[daniel_lyall]

don't know never seen that before see, if you can delete it can you post that file mark I wont to have a play

[HughesTooling]

Here's a file, it's not the same one but it is in the same state, as soon as you add tangent constrains it comes apart.

Mark

[daniel_lyall]

got it not knowing the best work flow (how would anyone know), plus over constrant BS I will do a screen cast.

[daniel_lyall]

[daniel_lyall]

hope this help's http://autode.sk/21iSG2f

[HughesTooling]

Hi Daniel

Thanks for the screencast. Really my post was to demonstrate the problem for @jeff_strater. The best work flow for now is to draw without joining the parts then add coincident constrains to pull it all together. See this screencast.

Mark

[daniel_lyall]

they will all help other's in the long run.

I think you could call that the best practise for doing slots that shape for now it will change. its one of the way to do straight lined slots aswell where they don't fail, there is a faster way to do straight slots but it does not work for the slot shape like you did.

[jeff_strater]

thanks, @HughesTooling, that's exactly what I needed.  The problem is that the Center Point Arc is not picking up the coincident constraint on creation.  I'll file that bug.  Yes, the workaround is to create the coincident constraint.

Here's a small hint for the future.  When you see the while dot at the endpoint of a curve:

That means that the curve (in this case the purple arc) is not connected to anything else.  So, if you see this, it's a reminder that you probably want to create a coincident constraint to make sure things stick together.

Jeff

[jeff_strater]

the bug has been filed as FUS-21272

[Anonymous]

Thank you all for the screenshots and screencasts.  I'm going to make a screencast if I can figure out how and show you, since the problem Hughes showed is not what I'm referring to.

When I mean referenced elements, I mean from an existing body or component.  Projected elements might be a more informative term to use.

[Anonymous]

The screencast of the problem is here:

https://knowledge.autodesk.com/community/screencast/51140563-0b9b-4a5d-9473-0412088438b9