Hi, you can't change one type to another. To get a driven dimension, you need to fully constrain your sketch using constraints and dimensioning. Then try to dimension the lines you want to be shown as driven. Inventor will display a message dialog box telling you the dimension is not required but you can show it as driven. Accept it and place it. To make that driven dimension normal you would have to remove enough normal dimensions to make the sketch un-constrained, delete the driven one then re-dimension those lines again. Finally, you might still need to add some more dimensions to fully constrain the sketch once again. Play around with it to get your desired values.
I understand what you have stated and have been doing things exactly this way. However, on some intricate sketches, there may be many dimensions required to make the sketch fully constrained before a driven dimension becomes an option. If I know some segment requires a driven dimension before I start, can I not create this driven dimension until after the sketch is fully defined?
The help file (driven dimensions) states:
"Only normal dimensions may be edited. To convert driven dimensions to normal dimensions, select the Style box, then click Normal. To avoid overconstraining the sketch, you might need to convert other dimensions to driven."
What is the Style box? Is this the same as the style editor?
Can you explain why you would want "driven" dimensions? What are you trying to accomplish? I may be off base here, but:
If you want one dimension to be a function of another dimension (or other dimensions) there are a couple of easy ways to do that.
When placing a dimension (in a sketch) you can place that dimension, and when the edit window comes up you can click a different dimension to bring that value into this dimension (and add any mathmatic function).
OR you can go into the parameters window and in the equation field, add a function (like "2*d0+.45")...you can use most functions common to excel line SIN, and PI.
OR for even more complex problems I would link the parameters to an excel spreadsheet and do all kinds of crazy calculations to control the dimensions of a part.
I would guess that the "style box" is refering the the dimension properties that you can change when you right-click on a dimension (which is a good place to change the name of a dimension) It is a lot easier to keep track of "thickness" instead of "D22". I have found that the help files are not very up to date with the new styles information sometimes.
Sorry if I am off-base on what your goals are, I almost NEVER use the driven dimensions you are refering to.
I noticed, today, that there is a driven dimension button that allows you to make a driven dimension before everything is constrained. It's in the 2-D Sketch category under the command tab of the customize menu window. I do know that in version 8 there was a drop-down list on the standard sketch tool bar that let you select what type of line to draw. It has been replaced by buttons in version 9 (perhaps 10 also). I agree, the Help may be faulty here. It also states you can change geometry to normal but I can't find that button or pull down item either. I avoid the use of construction lines, as well as driven dimensions, too.
DesignerMike,
Simple example: flip dimension from + to -. Make any dimension driven, pull it to the other direction, make it normal back and edit the value. This way is several steps shorter than any other solution.
I am using driven dimensions and construction geometry quite a lot recently instead of making lengthy calculations. It is so much easier and saves a lot of time.
In fact some problems would be impossible to solve without using driven dimensions. For example: building adaptive springs, which change their length just as in real life is done by means of adaptive dimensions.
There are even more applications for driven dimensions by using phantom adaptive parts and exporting driven dimensions values to other parts. One can simulate very complicated movements and dependences by using these techniques.
I don't particularly feel there is any need to use driven dimensioning. The only feasible reason I can think of is the one alphram mentioned whereby you would define other dimensions from the driven one. Driven dimensions generally mean you have over constrained a sketch and should press f9 to see where you have gone wrong, typically one of the lines you have placed has snapped when you didn't want it to. The constraints can be removed by right clicking on them and selecting delete. I personnally never use driven dimensions and feel much happier controlling my sketches with normal dimensions
You SHOULD use driven dimensions when you can. You use them to relate one dimension to another. For example let's say you have a rectangle and you offset it by some amount. Now you try to dimension the larger rectangle. It wants to give you a driven dimension. Allow it to do so. Now you can refer to the size of the larger rectangle directly. Keeping the design intent is the #1 priority in 3D modeling.
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