How to Ensure a 2D Sketch is Fully Defined and Managing Weak Constraints in Creo?

You goal should be to not have weak dimensions in your sketches. The dimensions in your sketches and features should capture design intent which is the best way to leverage the functionality of a parametric CAD system.

Select your sketch plane and your sketch references in the context of design intent. By setting the references you can leverage the intent manager to some extent to minimize creating new dimensions when sketching. Exploit constraints and construction geometry within sketcher to minimize the number of explicit dimensions required to fully constrain a sketch.

This video should address your question.

- **Is it possible to delete weak dimensions that Creo automatically sets?**  Creo maintains a fully constrained sketch at all times.  The weak dimension created will be removed when you add your own dimension that eliminates the need for that weak dimension. 

- **How can I change this weak dimension to a strong one and set it to 5?**  If you double click on the weak dimension and enter a new number, it will change to a strong dimension.  You can also select the dimension and make it strong by selecting the icon in the mini tool bar.  You can also select the lock to lock the dimensions.  I prefer to lock most dimensions because this prevents dragging of the dimension or entity in that direction.  I also use config "sketcher_lock_modified_dims yes" to automatically lock modified dimensions.

- **Is there a reference starting point for these weak dimensions that I should be aware of?**  As @tbraxton indicated, the references set in the sketch will be used to contstain the sketch.  Preselecting the desired references will help Creo create appropriate dimensions that can then be modified.  Teh order in which you draw entities will also have some effect on what Creo creates.

I think practice makes for mastering sketches to capture design intent. I’ve been practicing with how my sketches work by using the modify button and I can see how my sketch will behave in the future. Sometimes I’ll use sketcher relations. Sometimes I give better assumptions like vertical/horizontal, and I work hard to have only few dimensions that capture design intent.