Use Driven Dimension as a Parameter?

[Anonymous]

Hello all,

I am wondering if there is some way to do this, to use a driven dimension as a parameter. As it is, driven dimensions do not appear in the parameters menu.

if you hover over a driven dimension, it gives you the dimension number (i.e. d22, d46, etc) but you can't use it in the parameters menu.

Here is what I am trying to do:

We make custom cases/shipping crates. I want to put in the L, W, H of a part, say 3 x 4 x 5, define thickness packing material, define part spacing, and use the resultant size to make the case.

Usually, I'd just say (in the parameters menu)something like the folowing:

CaseW = (PartL+(Packing*2)) to define the case width if there is only one part.

But in most of our cases there are several parts (most the same size, and some very different). So the math looks more like:

((Part1L+Part2L+Part3L)+((NumOfParts-1)*Spacing)+(Packing*2)) for individual parts

(((PartL*PartQty)+((NumofParts-1)*SpacingBetween)+(Packing*2)) for patterned parts

which is driving me crazy.

What I did was this: I made a sketch with L+W, using rectangular pattern. Then, I used a rectangle around and defined the rectangle as always being 2" larger than the pattern (I will attach a simple representation of what I am talking about). This way I can change the pattern quantity and the parts sizing and it should be able to quickly define the length and width of the case.

BUT - when trying to use the driven dimensions (like to define (CaseW=d22) when d22 is a driven dimension), the parameter window simply won't accept it.

I think I understand why this is - because if I were to try and change this driven dimenison in the parameter window, I wouldn't (and shouldn't) be able to. But that also means I can't use it - ever? That seems a little strange.

In the attached file, try to use d22 and d23 (the driven dimensions) to create a parameter - you'll find you can't. it gives an error - "Invalid string" - as if d22 and d23 aren't defined.

Does anyone have any ideas? Or do I keep using my (long) equations to define my cases?

Thanks!

[Anonymous]

...

In my rush to get a sample made I definitely kept some values as numbers when they should have been parameters....

The file attached should reflect what I described much better, sorry....

I don't have it together today

[TrippyLighting]

I believe this has been asked before and AFAIK at the moment this is not possible.

However, you can search through the idea station and if you don't find a similar idea this would make a good one!

[jeff_strater · Accepted solution]

@TrippyLighting is correct.  This is not yet part of Fusion.  It is in our plans, but it is actually much harder than it seems on the surface, so it may be a while before we get around to it, in all honesty.

Here is the Idea station item for this:  ability-to-reference-driven-dimensions.  Please add your vote.

Jeff

[Anonymous]

I guess the "difficulty" lies in the difficulty to get into a situation where you actually solve a system of equations iteratively, i.e. when the parameter that is composed of driven dimensions modifies the driven dimensions in turn?

But that could be circumvented rather straightforwardly, I'd think, by detecting if the change of the parameter led to the driven dimension being different (sensitivity?) and if so, the system will flag the relationship as currently not solveable and forbid the relationship? 

My problem doesn't create such loops but doing the maths for two driven dimensions is horror compared to the simplicity of just comparing two in a Min/Max function and using that in a parameter. My model is highly complex, parameterized and constrained so I can scale different dimensions and angles at will and still get something meaningful out as total design (i love Fusion 360 for this but am surprised to see this one feature doesn't exist).

I would think only if you try to solve the iterative solving of equations at the same time does this get difficult at all.

Thoughts?

Cheers - Marc 

[jeff_strater]

Thanks for the very thoughtful post @Anonymous.  You understand the complexity here very well.  I'm interested in what others think about this approach.  Would a limitation like Marc suggests be useful enough to be worth implementing, as a stepping-stone to a more complete implementation?

I took the liberty of copy/pasting your comments into the IdeaStation post:  ability-to-reference-driven-dimensions, to also gauge other customers' reaction.

Jeff

[Anonymous]

Thanks Jeff - so much is clear, I'd looooove the feature with that limitation already. I'd even venture the guess that the class of problems that can be solved even with that limitation is huge. I can solve my problem by doing all the pretty complex trigonometry myself but it's just not desirable if it could be so much easier and intuitive. Thanks for copying over to the other thread - sorry I had discovered it too late. Have a great Sunday (stormy here). - Best, Marc

PS: For the hard part of the problem, here a quick shot - maybe useful: https://www2.math.ethz.ch/education/bachelor/lectures/fs2013/other/nm_pc/NPch1.pdf 

[paul.sisneros]

I could use this feature and I see this was posted 2 years ago. Soo, hows that feature coming along?

[frankstardelux]

I'm a CAD engineer and have been using Autodesk Inventor for years now. This whole topic of using Driven Dimensions was solved a very long time ago with Inventor and so I really don't see the problem here.

I've only moved to using Fusion 360 at home since my use of the trial of Inventor has run out. Every aspect of Fusion 360 seems deliberately ****, and the worse bit is those people who only know Fusion 360 will then get pissed off if they went to try Inventor because everything is different. Referencing a driven dimension is bread and butter for CAD software... stop messing about and fix this!

[Anonymous]

Why is this hard? I can think of an exceptionally easy way to implement this...

1. Go into the Edit Parameters dialog

2. Create a placeholder for the parameter. This would be just like adding any other parameter (Name, Type, etc.) but leaving the Expression part blank (or adding some superficial token such as "PLACEHOLDER" or "DRIVEN" or something). The "Value" column would show the actual computed / driven value from the drawing or "NaN" if not yet computed.

3. On the drawing set the dimension to the name of the parameter.

4. When the drawing is computed, update the value in the parameters table with the computed driven value. If the value is unable to be computed, raise an error-- just like you do for anything else which is suddenly not there or out of bounds.

I don't see why you believe this is difficult. It is no different from any other thing you do with values and references.

John Whitten

[TrippyLighting]

@Anonymous He probably has vast experience and insight into Fusion 360 architecture because he is a Senior Software Architect for Autodesk and one of the brains behind Fusion 360. Before being part of the Fusion 360 team he worked on Autodesk Inventor.

I can say from my own coding (limited) and engineering (vast) experience over the last 3 decades that things are often much, much harder to implement than to verbalize and common sense invariably fails to address complex problems.

[TheCADWhisperer]

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@TrippyLighting wrote:Before being part of the Fusion 360 team he worked on Autodesk Inventor...

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This has been doable in Autodesk Inventor for as long as I can remember (I think at least 10 years ago).

[TrippyLighting]

I am sure this is doable in other CAD systems as well, e.g Solid Works 😉

[jeff_strater]

This was NOT part of Inventor for the first 5 years of its existence, just FYI.  Inventor has had LOTS of stuff in it for 10 years or more (alternate representations, position representations, design views, weldments, tube/pipe, etc, etc, etc) that Fusion does not have.

Specific to the topic at hand, Inventor uses a different sketch solver, and a different parametric compute engine, so the argument that "Inventor has it, so it should be easy for Fusion" does not, unfortunately, help us very much towards implementing this in Fusion.  I just want to try to clear up the idea that this is just cut/paste of code from Inventor.  It is not.

We completely understand the desire for this and the workflows that are prevented without it.  No one is arguing that this is not important.  It will get implemented eventually.  At the risk of repeating myself, this is a big project, so it will take some time to carve out space to get it done.

[chrisplyler]

You can't use them in parameter expressions.

But you CAN use them directly in other dimension values/formulae. If you have a lot to do, this would be slightly annoying, but it works. If you only have a few, it isn't a big deal.

[MichaelT_123]

Hi Mr John Whitten,

I do understand your frustration (and in secret tell only you that you have got my sympathy)... but I also try to understand F360 side although I totally fail on occasions.

Regarding your problem which can be described (if I am correct) as:

d1 = g(x)

d2 = f(g(x))

This happens quite often in the real world and even more so in minds of crazy mathematicians.

Sometime however there is a solution for it by parameterizing equations:

t   = T(x)

d1 = G(t)

d2 = F(t)

Check if you are LUCKY!

Regards

MichaelT

[Anonymous]

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@chrisplyler wrote:

You can't use them in parameter expressions.

But you CAN use them directly in other dimension values/formulae. If you have a lot to do, this would be slightly annoying, but it works. If you only have a few, it isn't a big deal.

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If you don't mind my asking... How would you do that? I can't get it to give me a dimension link (aka 'd:nn') when I hover over it. So how could I use it anywhere?

[Anonymous]

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@TrippyLighting wrote:

@Anonymous He probably has vast experience and insight into Fusion 360 architecture because he is a Senior Software Architect for Autodesk and one of the brains behind Fusion 360. Before being part of the Fusion 360 team he worked on Autodesk Inventor.

I can say from my own coding (limited) and engineering (vast) experience over the last 3 decades that things are often much, much harder to implement than to verbalize and common sense invariably fails to address complex problems.

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There's no reason to be INSULTING.

If it can't be done, as you say, then how is it *already* being done? The parameter *IS* being resolved already by the solver. The answer is arriving there to show in the display as a driven parameter. The only thing we're talking about is taking THAT NUMBER and plugging it into an equation in the parameters dialog. The issue is not that it cannot be done-- because it is already being done. It is simply not getting updated in the equations area.

[chrisplyler]

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@Anonymous wrote:

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If you don't mind my asking... How would you do that? I can't get it to give me a dimension link (aka 'd:nn') when I hover over it. So how could I use it anywhere?

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Never mind. I mean, you CAN click on a driven dimension while entering another dimension, but it only evaluates to the hard value and doesn't update as expected. My bad.

[Anonymous]

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@chrisplyler wrote:

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@Anonymous wrote:

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If you don't mind my asking... How would you do that? I can't get it to give me a dimension link (aka 'd:nn') when I hover over it. So how could I use it anywhere?

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Never mind. I mean, you CAN click on a driven dimension while entering another dimension, but it only evaluates to the hard value and doesn't update as expected. My bad.

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No worries! 😉