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How do I know my sketch is definitive ?

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Re: How do I know my sketch is definitive ?

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?

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Re: How do I know my sketch is definitive ?

For me, that's kind of missing the point, for two reasons:

  1. I want to have all the right dimensions in my sketch, and the auto-constrained (weak) ones are usually inappropriate - Sketcher seems to have a real knack for finding the wrong thing to dimension.
  2. I want all my dimension values to be correct, which they won't be on a shape that's just sketched by eye (although sometimes it's unnerving how close I can get!).
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Re: How do I know my sketch is definitive ?

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.

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Re: How do I know my sketch is definitive ?

I want fully constrained sketches.

The tip is to look for gray things on your screen.

Poor implementation.

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.

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Re: How do I know my sketch is definitive ?

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.

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Re: How do I know my sketch is definitive ?

Have you tried using Lock Scale in Modify Dimensions?

Regards

David.

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Re: How do I know my sketch is definitive ?

Don,

       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.

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Re: How do I know my sketch is definitive ?

I've never utilized the lock scale.  I'll give it a try next time.  Thanks for the advice.

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Re: How do I know my sketch is definitive ?

The method I use for sketches is:

  1. I don't worry about defining references first. I can do so on the fly later.
  2. Sketch the number and type of entities that you need.  I generally exaggerate the sketch here, make it oversized or out of proportion to prevent Creo from creating constraints that might be hard to have it automatically remove later.
  3. Add the dims and constraints that I want.  I can directly select geometry at this point to create the references I want as well.
  4. Modify dims to the values I want.

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.

--
Doug Schaefer | Experienced Mechanical Design Engineer
LinkedIn

Re: How do I know my sketch is definitive ?

I think that was version 19 of Pro|E, Doug

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