Best Practice for Top Down Assembly Design and Component Origins

[steven.orosz]

I would like to get recommendations for best practices for top-down design in Fusion 360 and any changes I need to make to my work flow.

In a top-down assembly design flow as new components are added, the origin the the new components default to the top-most origin in the browser.  As the assembly grows, the origin for for an individual component may not be anywhere near the component.  If I intend to reuse a component in the same project or another project, the component origins are all over the place.  Trying to correct this after a component is modeled is difficult, if not impossible.

I correct this by performing the following after I add and activate a new component:

1. Show the origin of the newly added component
2. Perform a Move and use the point-to-point option, then reorient at needed
3. Hide the origin of the newly added component
4. Continue modeling

I don't always remember to perform the above steps.  My intent is to always have the origin of a component within the 'envelope' of the component.  I feel it promotes reuse better and makes the components self contained.  It's something I've been taught and automatically happens in other CAD programs such as Creo Parametric.  However in those cases I'm following a bottom-up design flow.  Maybe there are some old habits that need to be changed on my part while working in Fusion 360 and top-down design flow.

If this needs to be part of the work flow, then I suggest it be added to the tutorials because I cannot find any references in the videos or text.  

[chrisplyler · Accepted solution]

I turn off all origins except the one for the component I am about to work on. I make sure to only use that component's origin planes, or constructed planes or geometry faces that I've developed FROM that component's origin planes, to sketch on.

Doesn't matter if you perform any pre-modeling move or not. But DO model right on the origin as desired. Later use a Joint to move the component into the desired position relative to other components if required for an assembly. Well, I guess it matters if you're concerned about avoiding any unnecessary Capture Position items in your timeline, which you should be if you start accumulating very many.

In this way, each component is developed from its own origin and is centered on it (or has a corner on it, or whatever, depending upon your intent). DON'T move a BODY within the component, as that's how you get things separated from their origins. Make sure if/when you use the move tool, you have Components selected as the Move Object type, which will keep the whole thing together, including its origin and sketches.

I don't KNOW that this is the proper way, but it seemed logical to me, so I started doing it, and haven't had any issues. The only weird thing is that, although moving or using a joint to move a component into place does take its origin and sketches with it, if you Edit Sketch the view will take you back in your timeline to when that sketch was made of course, so it will appear where it was before you moved the component. So that's kind of confusing sometimes, but you get used to it.

[HughesTooling]

Sometime it's easier to model a component if it's aligned to a feature on another component so I use a similar technique to the one you describe but I use a joint instead of move as it give you more options and will update to changes to the base component.

Simple example in screencast below.

Mark

[TrippyLighting]

@chrisplyler if you model each component starting at the top level origin and then move it into place afterward, that is more or less a bottom up, not a top down design workflow.

Components that are designed in-place in an assembly will assume the main origin as their component origin, there is no way around it in Fusion 360. 

Top down design  is a very nice way to develop a component that later on  is going to be re-used.

Historically the concept of externally linked components and the idea of re-using components was not a concept implemented in Fusion 360. This was only added after a lot of users asking for it.

Then Linked components were introduced but are still lacking much functionality.

In this specific case it would tremendously help if we would be able to define an origin when exporting a part to the data panel. It would totally eliminate the issue. I can only say that if the Fusion 360 team would peel their eyes 

away from this unhealthy and silly Solid Works competition mode they're in and look at real alternatives for benchmarking  they might actually find that ZW3D uses a lot of the same concepts that we see in Fusion 360 but takes them to full maturity. This is one thing I can easily accomplish in ZW3D.

[chrisplyler]

---

@TrippyLightingwrote:
@.if you model each component starting at the top level origin and then move it into place afterward, that is more or less a bottom up, not a top down design workflow.

---

I don't model each component starting at the top level origin.

I model each component on its own origin. Moving it the whole component into place after the fact, or moving its origin into place first and then modeling right on it, doesn't make any difference, EXCEPT if you need to reference (project) existing geometry into a sketch. Aside from that little difference, the end result seems to be the same re. reusability.

[steven.orosz]

@HughesTooling, thanks for taking the time to create the screen cast.  It clearly demonstrates the concepts you and the others were describing.

[steven.orosz]

@chrisplyler, @TrippyLighting, @HughesTooling - Thanks for the feedback.  It seems this is a common issue but the solutions are very similar to my method.  I didn't consider using a Joint to perform the 'move'.  I learned something new and have to try it out in my work flows.