Thank you for your answer
Question 1 : is it Always necessary to have strong dimensions ( I mean based on principals not requirements)
2 : how do I use and/or apply these mapkeys and how do they work, shall you explain please?
For me, that's kind of missing the point, for two reasons:
Just a note from another beginner trying to learn. I find that frequently I'll have a sketch started and change one dimension thereby making it strong. Often this completely throws my sketch unrecognizable so bad I'll start over. If I make the first line and then lock the dimension to the correct value then I can sketch the rest or at least part of the rest so it looks about correct. After it looks about right then go back and either insert dimensions where I need them or modify the existing weak ones making them strong. Maybe not the correct way but it seems effective for me.
I want fully constrained sketches.
The tip is to look for gray things on your screen.
The way Creo does sketches by default makes them unreliable in my view.
If you accidently move a node, you never know what other nodes moved with it.
I want locked values. If I leave on movable, it is on purpose.
I deal with this in config.pro. This makes it simple to implement.
Know that sneaking up on sketches is not a crime. A lot of times I have to go through several iterations on a dimension to get to the scale I want. Over time, you will develop techniques to make this easier. one tip I use is to draw a 1/2" circle... or 10mm, whatever. Let it zoom to that scale and then start the sketch. That way I am already sketching to a relevant scale.
Have you tried lock scale? Once you create your sketch if you grab all the dimensions and right mouse select modify, in the modify dimensions dialogue box there is a select button for lock scale, select that then change one of the dimensions that you know the number you want to change to. The other dimensions will scale accordingly and the sketch should not fail. Then you can deselect the lock scale and modify the other dimensions.
The method I use for sketches is:
This works pretty well and puts me in charge. Typically Creo will remove the dims and constraints that are not needed as I go, but not infrequently it tries to delete things I'd rather keep and I have to manually delete them. I also sometimes have to sneak up on the final dims as Antonius said because the geometry becomes invalid if I scale a dim in one step.
Frankly, an option to have Creo do nothing and let me define what I want would be great as long as it wouldn't let me exit sketcher unless the sketch was fully defined.