Problem with Constraint Orientation Assumptions

[bmancini]

Hello,
I have a problem with Creo 8.0's "Allow Assumptions" feature.
In creo 2.0 when I assembled a component by defining two constraints and the "Allow Assumptions" checked, the component was fully constrained and automatically oriented itself trying to orient the default planes of the component with those of the assembly.
The component was always "squared" with respect to the assembly.
Now in Creo 8.0 it is still completely constrained but is not oriented "squarely" with the assembly, it remains oriented in the "dynamic" position defined during the assembly phase.
In my opinion this is risky, because I could inadvertently get an unwanted orientation.

Is there any way to get back the behavior that was in Creo 2.0?

From your experience, do you find this modification appreciable? Like?

Thanks.

[StephenW]

I like assumed constraints for those times I really don't care about the orientation at all.

If there is any chance orientation is important in any way, i explicitly add a constraint defining it.

The problem is when the assumed orientation is equivalent to the required orientation and there is no reminder to set the 3rd constraint.

[kdirth]

My experience has been that the assumed constraint is almost always at least slightly rotated from needed orientation. This close, assumed, orientation can cause problems.

Items such as bolts, nuts, rollers, pulleys, etc., that do not need an orientation, can be left with an assumed orientation.

[bmancini]

Thanks kdirth for your input.
This is exactly the problem that I encounter, the pieces with the assumption instead of being perfectly positioned "squared", are slightly rotated, creating risky errors.

In Creo 2.0 this phenomenon did not occur.

[StephenW]

Option:

comp_placement_assumptions NO

will turn off the allow assumptions