Dimension Constraints, controlling the direction

[TKey_Luttrell]

I have a minor issue that i am trying to figure here.  I have two closed objects in a sketch, which i want a specific distance appart depending on variables set, and controlled by iLogic.  The variables and iLogic work fine to change the dimension constraint i have between the two objects, but if the dimension hits zero, when it goes back up above zero, the dimension is going the wrong direction.  So my two seperate closed objects are now overlaping...and there seems to be no way to get the dimension going back in the other direction, except deleting it and moving the whole shooting match back on the other side of the line.  is there a way to control the direction of a dimension constraint?

[Mark_Wigan]

hi TKey,

 this is a pain sometimes & i am not aware of a fix.

  for now, i would say to try not take the dim all the way to zero, with the hope to keep it moving in the correct direction when it increases in size afterwards...

 (if it does jump around though i wouldn't delete the dimension, just make it a reference dim, drag your sketch element back to the appropriate position, and then restore the dimension again).

ps- i recall discussing this topic quite some time ago. The random inability for sketches to update with respect to maintaining the relative positions of elements can go on to create further issues. ie, in an example i had to deal with, i had to change the value of an overall dimension gradually, sneaking up on my destination value in relatively small incremental changes, to ensure that the other relative elements did not suddenly find themself sitting on the wrong side of the fence.

i will see if i can follow up on it.

[SBix26]

I don't know of any way to directly address this.  One workaround that I recall someone else proposing is to establish a datum element of some kind (a line, for instance) from which the dimension will always be greater than zero, and use this instead of the direct dimension of interest.

In your example, make a construction line 1" (or 1mm) back from the edge of one of your closed objects, and use this to dimension to the edge of the other closed object.  Then your dimension to be controlled by iLogic will never be less than 1.

Sam B

Inventor Professional 2015 SP1 Update 3
Windows 7 Enterprise 64-bit, SP1
HP EliteBook 8770w; 8 GB RAM; Core™ i7-3720QM 2.60 GHz; Quadro K4000M

[TKey_Luttrell]

Thanks guys, my workaround was just to lock down one of the elements, and control the SIZE of the other through ilogic instead of controling the distance between the two.  Since this assembly does have an overall size i can apply math to.