Finding the Source of a Driven Dimension?
@aesilky wrote:... How can I tell what in the current design is causing this dimension to be 'driven'?...
There is no definitive answer for the general case, it really depends on the constraints you have. For example in following picture both blue lines have driven dimensions but each for a different reason (and one can construct infinite number of these):
If you share a particular case someone may help you figure out.
... Fusion 360 has to know what's driving the dimension...
No, that's not true, a driven dimension is not like a projected entity that is explicitly referenced to another; in sketching mode a set of unknows + equations is solved and generally driven dimensions are determined implicitly.
Edit: I decided to include following to help you understand what I said above. In a set of linear equations like the following picture (from Wikipedia), you can't say x = 1 because of what reason. In general the state of the whole set including every single symbol is the reason for x being equal to 1.
Now you can think of cases with more explicit relationships: e.g. if we add two more equations: v = 5 and w = 3 * v. Obviously w = 15 only because of the new equations [being explicit], but this is not the general case.
If the driven dimension is from another feature, you may be able to move the Timeline back one feature at a time or suppress one feature at a time to find the references.
If it is coming from something in the same sketch, then use the Undo command until you find the references. Once found, use the Redo command until you're back to the end. Whether or not you can remove the references depends on the structure of the sketch.
ETFrench
@davebYYPCU wrote:... Fusion 360 has to know what's driving the dimension...
No, that's not true,
@hamid.sh. Of course it's true... The file contains the recipe to drive the outcome. Fusion does know why a sketch is over constrained, (you are offered driven dimensions if you wish, because it DOES know why a driving dimension is disallowed, just doesn't tell the user.)..
In Sketch there is no "recipe". Recipe is a step by step procedure in which each step depends on previous ones, like in Design mode with timeline. In sketch there are a set of unknowns (points' coordinates) and a set of equations (dimensions and constraints). Once you add a dimension that leads to an impossible set, you are prompted that the dimension is driven. What Fusion knows is that it can't get a solution now.
In following sketch nothing on its own is DRIDVING the Φ67.70 circle, but the interplay of all of the dimensions and constraints that I have added lead to this solution. I can delete any one of them and toggle the dimension driving. In essence ALL OF THEM are driving this dimension, together. Also the order of applying them is not important, because again it's not a recipe, but a set of equations being solved simultaneously.
Deleting the driven dimension in the 'Axle Centerlines Construction' sketch and re-dimensioning the centerline results in a normal dimension of 1200mm. How it originally was a driven dimension probably depends on how the line was drawn or what points were selected for the dimension.
ETFrench
Well, it would be nice to have Fusion 360 highlight the geometry and dimensions which affect the driven dimension, but it's probably not easy to do and many more users would need to ask for it.
Only one end of the line was anchored to projected geometry. The other was not, so that dimension should not be driven. It's not possible to tell what that end was initially referencing. If you can recall what actions you took in that sketch, Autodesk will be able to determine if a bug exists.
ETFrench
Your problem is easy diagnosed.
Doesn't matter what comes first the chicken or the egg,
Boils down to Fusion is not a mind reader, the user has to document all things entered into the file.
The problem sketch, has a few sketch lines, but no correlation to anything.
No reference to the origin.
2 small Projected lines, (purple) from the axle unit.
A vertical black line that is connected to both purple lines at the midpoint. (but nothing else - deleted for clarity in pic)
there is an orange construction H set of lines the horizontal is 1200 and this dimension is not being driven by anything, other than the toggle switch to do that, toggle it back to driving - (user error here). The construction line is not colinear with but is close to the black line, so the dimension is not being taken from the black line.
A Parameter named Wheelbase that is not used anywhere. If you reset the 1200 dimension with Wheelbase, when you change wheelbase it will change the length of this line.
So as I see it, if you later move the wheels that the purple lines come from, nothing is tied to them, so they won't follow..
Might help.....
