# rotational feature

#### rullan

##### New member
I'm trying to create a part that acts like a rotating control dial. I have created a round protrusion with a triangular tip that serves as a pointer. When I change the angle of the pointer, there seems to be a point where the angle I specify isn't recognized. The feature flips over some imaginary180 degree mirror.

Does anyone know what's going on?

#### xandu

##### New member
I'm assuming you modeled the tip as centered around a construction line which has an angle dimension to one of your datums, correct? The problem here, I think, is that the construction lines don't have any orientation associated with them, so when you rotate through 180 degrees the sketch might as well be back where you started - i.e. multiple solutions are possible. Try, instead, to set the horizontal reference of the sketch to a created datum, which is at an angle to a fixed datum. Since the datums inherently have an orientation, this way is a little more robust than the construction line method, it shouldn't result in the flipping you're getting, and you'll still get your angle for control.

#### FDdesign

##### New member
I assume that the pointer is an extra feature ? If yes,... be sure that the second feature has no references to the circle of the first feature. Normally, when I create something like that, my second feature has an internal datum 'on the fly' that I use as left or right, and (this is very important).... the second feature may only have references to the central axis and that 'datum on the fly'. If you do that, you will normally have no problem anymore.

The 'datum on the fly' must be created through the central axis and 'angle' to another datum plane. (The best thing is one datum plane of the base features)

The reason of this behavior is that ProE divide a full circle allways in 2 half circles. In your case: that's the reason why ProE 'flips' each time when he passes the 180

#### kvision

##### Moderator
Don't use centerlines as angular dimension references in Pro/E. Use datums as the reference plane to solve this. The RED/Yellow sides have normals associated with them that allow them to rotate through full circles.