Setting Dimensions: The Wrong Thing Moves

[apostM2K9B]

I've come across t his issue many times and have yet to find a solution.  Probably because I'm not sure what keywords to use in the search.  

So...I'm trying to move the circle closer to the center of the sketch.  I'll add a dimension between the center of the circle and the center of the rectangle and the entire sketch moves.  it looks like I've chosen the center point of the plane rather than that of the rectangle, so I understand what it's doing.  

I tried adding a  construction line through that center point, and added the dimension and it must moved the construction line closer to the circle.  Also not what I wanted.  I see that happen a LOT.  I thought construction lines were supposed to be a reference point, but I seem to be making movable goal posts.  

So, when making dimensions, how do I tell it what to leave where it is, and which feature to move?

[apostM2K9B]

Ah...in this case I see I'd already dimensioned the distance from the center point to the right side of the rectangle, so that was locked.  I'd still like to know how to lock down a construction line.  

[wersy]

It looks like the rectangles aren't really fixed to the center.
The right circle is also dimensioned to the right of the large rectangle. This dependency shifts everything when dimension 16.25 is changed.

Construction lines are to constrain the same way as normal lines.

Michael

[mavigogun]

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@apostM2K9B wrote:

*snip* I seem to be making movable goal posts.  

So, when making dimensions, how do I tell it what to leave where it is, and which feature to move?

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Construction Lines are subject to change, just like other lines; aside from appearing different from other Sketch elements, they don't contribute to Profiles, so are able to transit a Profile without interfering with selection of the Profile- say, for Extrusion.

The Fix Constraint will immobilize a Sketch element- particularly useful when trying to control how elements respond to the application of other Constraints.   Transform Construction Lines (or other Sketch elements) into fixed reference locations by applying the Fix Constraint.

All that said, you might need a cluster of Sketch elements to be relocatable within the Sketch while maintaining relation to one another- in which case, you will need to define the relationships using Constraints other than Fix- often achieved using Dimensioned and Constrained Construction lines.    However, the Fix Constraint may be useful for locating elements before other Constraints lock in their relationships- after which, the Fix may be dispensed with (in that way, working within a Sketch is akin to modelling without a Design History).

[TheCADWhisperer]

I see numerous issues clearly indicated in your Timeline - right back to the beginning.

You should ask questions much earlier on and 

File>Export and then Attach your *.f3d file here with the issue for resolution.

I recommend research on the keywords BORN Technique - absolutely rock solid and predictable modeling technique.

Attach your file here and I will demonstrate 30 things you have done incorrectly.

[apostM2K9B]

Mr. Whisperer,

I have no doubt at all that I've done things wrong right from the start, as I'm bran spanking new to Fusion and using the basic tutorials to build this thing.  I'm certain I'm miles away from working the way the app is designed rather than the way I think.  File is attached.  Please be as gentle as you were in your first post.....

[GRSnyder]

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@TheCADWhisperer wrote: I recommend research on the keywords BORN Technique - absolutely rock solid and predictable modeling technique.

Interesting reference - thanks for this. The best description I found is this document.

It seems pretty well summarized by: 1) Everything should have a defined relationship to the one true global coordinate system. 2) Indirectly-expressed relationships to the global coordinate system are OK, but try to link everything through a single designated base part or feature that is itself anchored to global coordinates.

Is that a fair summary?

[TheCADWhisperer]

@mflayler is one of the best in the business.