Reversing dimensions problem

[amirrezapakroo]

Hi All

I have a rare and random problem for controlling my sketch via dimensions by inputting parameters.

In a complicate sketch I have a form to control some important dimensions 

I have a dimension wich some times I need to set it to zero but for another design when some times I try to add 10mm (for example) the sketch will move in reverse direction! And sometimes it will move the sketch in right direction as it was at first time.

I attached a simple image to explain it for you

Imagine you design two circle both above the horizontal line when you add 0 to left it will move to point zero but when you add 10 it must move above of the horizontal line but some time i can see without any reason the circle will move below the horizontal line by this 10mm input!

In other hand how i can move it above horizontal line or below it by just entering parameters or via a form?

I mean if I can control the way of moving my sketch in second issue I will solve my first problem inside a complicate sketch as well...

(as you can see - or + inputs are same for inventor to control direction of moving )

Thanks for any suggestion or help...

[salariua]

This is not rare and very common to me. Unfortunatelly dimensions in sketches can not have negative value but work features (planes in your case) can have negative values.

Create planes for your references and dimension the distance to each plane as Right and Left as you've done with your circles. Go inside sketch, project the planes and constrain the circles to that. 

Now you can control the position of the planes that will drive the position of your circles.

[salariua · Accepted solution]

Try the attached part.

[amirrezapakroo]

Thank you for your solution

is there any way to control forms of each part directly from sub assembly without opening the part?

[salariua]

You can have it as prompted when placing componet in assembly.

Or you can add another form in the subassembly that will modify the parameters of the part.