Bug Report Feature History Update Error

[eike.scholz]

I am trying to find a parametric CAD system for an upcoming project for ABB-Hitachi doing geometry optimization with inhouse FEM algorithms.  Sadly my combination of component movement and user parameters does not work. If there is no work around, for the trial version I can not order Fusion 360 for that project. 

EDIT: Trying to append a screencast of the error explaining everything! However, the form software rejects its own generated html to my public screencast as invalid html: So here is the link:

https://knowledge.autodesk.com/community/screencast/217b31dd-31f1-40df-89bb-9494d73def35

[eike.scholz]

Please see the added screencast. I had problems with posting it, but now it should work!

[jhackney1972]

You do not want to use the Move command to position components as it does not relate the component to the rest of the assembly.  Use Joints.  If you attach your model, the Forum users can show you how.  If you do not know how to attach your Fusion 360 model follow these easy steps. Open the model in Fusion 360, select the File menu, then Export and save as a F3D or F3Z file to your hard drive. Then use the Attachments section of a forum post to attach it.

[eike.scholz]

Well, I actually do want to use the move command! The problem is that it forgets the user parameter it uses. This should not happen. Further I thought joints are for kinematics not for computing placements with user parameters. 

But they should work I will try it Monday! 

With respect to uploading the complete the model, its unclear to me if this could be a confidentially requirements violation. So I will not do that at the moment. What can be seen from the screencast can be measured directly from the product as well or from a photo. Further, its a simplification for FEM simulations so that is not a problem. But my customer might not want having that complete file shared!

[g-andresen]

Hi,

just share a sample file to illustrate the process

günther

[jeff_strater · Accepted solution]

This is not a bug, this is intended functionality.  Component movement is never parametric in Fusion.  There will never be a Move Component in the timeline.  Component positions are captured using Capture Position features.  You can tell that a component is in a moved position when the "Capture Pending" UI appears in the toolbar:

When this UI appears, you can either choose to Capture it, in which case a Capture feature will be added to the timeline, or Revert, in which case components go back to their "home" positions.

However, even if you choose to Capture the position, there will not be a parametric relationship added.  If you want to parametrically drive a Component's position, add a Joint with a degree of freedom in the direction you want to move it.  Then, you can use Drive Joint, with that parameter to create a parametric relationship.  See the screencast below.

[eike.scholz]

I do accept your answer, but a proper GUI should not just *discard* user entered data without warning. I still entered "L1+L2" for the computation of the movement, and then recalculating user parameters dos not update it. The movement does apparently exist in display but not on the datastrucute representing the assembly. If this is intended behavior, disallow user parameters to be entered in component movements, they are invalid once changed and never have the expectable behavior.  The GUI is well too carefully constructed on other aspects for this to be not a bug, but ok, its a feature not a bug - I see you learned from the best! 😉  

In all seriousness, this is very likely not intended functionality, but a consequence of the way components are implemented, which is not bad or anything if there are alternatives. However this does not serve a function! What function could it have? Deceive users about the fact that entered formulas are quietly dropped and not used again? So after a time and adding components, changing the user parameters breaks everything without a single hit from the GUI and for Fusion 360 beginners can waste hours of productive work?  

[eike.scholz · Accepted solution]

With joints I have different non-intuitive problems! I would need two joints, "edges as common axis" to fix the construction i.e. remove all degrees of freedom for proper re-computation when changing user parameters. But I can not apply two joints between two components without breaking the link of the first one, so this does not work!

Screencast of the problem: https://knowledge.autodesk.com/community/screencast/e1f53b0b-2fb3-4b65-ae18-593eac01090c

I would consider this a Bug too, but its probably indented functionality as well, because of internal complexities. Well Freecad is no longer looking that bad in comparison, I must admit. Freecad wastes my worktime with similar but equally annoying behavior. Sadly I can not afford a complete Solidworks for the occasional CAD related projects I have.

PS: I can still not use my screencasts form the inserted with the forum GUI, it is also "buggy" or my system is hacked to slow my productivity 🙂 . The error is "link to members" but the screencast was included using the predefined forum interface. 

[eike.scholz]

Ok,ok, ... my system is not hacked - well unless the hacker just choose wired defaults for the joint types. I removed the joints video, since I found where to enter the correct joint types. Everything works as expected for now, aside from the two times Fusion 360 crashed on me.

However, using joints is still overkill for what I was trying to figure out! I was just grumpy because I lost a lot of work time due to unexpected behavior. Fusion 360 is very impressive for the price but I still think some workflow aspects can be improved!

I just do not understand why degrees of freedom of joints do behave in the way they do. They do once I ground a component. Further I would not add movement or distances into the joint data. For me joints just reduce degrees of freedom in a specific way. For me, the degrees of freedom data of joints seems to be what is position data in the system. For kinematics I would add constraints with a tool similar to the inspection tool, to generate an explicit set of degrees of freedom for kinematic simulation. The remaining degrees of freedom are just stuff where it was forgotten to "bolt/weld/glue/etc" things together. So animation can be used to identify parts where a design is unfinished, as well as using the dedicated kinematic parameters to test function before it is decide how components are "bolted" together.  

With respect to that an, adding a fastener option that simultaneously creates holes and puts a fastener though multiple components would help a lot. In case of screws there could be a option for tabbing the last component. Options for adding washers and nuts may be usefully as well. Sadly I do not have time to write macros at the moment. 

Further, position data should not be hidden and then captured or reverted. If you grab a component with the mouse just create the corresponding position data in the history and update it until the next feature is added, reverting is removing that feature from history. Further implementing movements of components that remember the entered user parameters should create a "free movement" feature, which actually is a position feature. Grabbing a component with the mouse afterwards adds a new position feature. 

[jeff_strater]

I don't disagree with most of what you say here.  Some of your suggestions are things we do plan to do in the future.  I do have a couple of comments:

"I just do not understand why degrees of freedom of joints do behave in the way they do. They do once I ground a component."

Yes, this is true.  Without a grounded component, there are just too many degrees of freedom for the system to know what to do.  Further, there may be subtle differences in behavior from the different methods of exercising the model, where there is no grounded component:  component drag vs drive joints vs animate model.  Those differences are mainly caused by assumptions that Fusion must make to try to get the best behavior, and usually results in the system temporarily grounding some component for you.  Once all components are fully connected with joints, everything works better, in my experience

"Further, position data should not be hidden and then captured or reverted. If you grab a component with the mouse just create the corresponding position data in the history and update it until the next feature is added"

We did consider that, and actually at one point had it implemented that way.  However... this is a case of be careful what you ask for.  The result of doing this could be a very long timeline that has a lot of these position features in it.  Each position feature takes time to compute, and the larger your assembly is, the longer each one will take.  So, while I understand your view here, I suspect that the cure would be worse than the disease.