funny Arc Length dimension

[Crocostimpy]

I have a question about the Arc Length dimension in NX6 (6.0.2.8.). I'm attaching a pic that will show what I'm talking about. You'll see that the 10.420 dimension looks like one would expect when it's on the inside of the section, but when it's moved to the outside the witness lines change to a vertical position. It looks pretty silly and I'm wondering if that's the way it was designed to work. It doesn't make sense to me that it would change between the inside and outside of the geometry. It's not good drafting practice to put dimensions on the inside of geometry, but I'm going to have to do it in this case so the customer doesn't wonder what the heck I was doing.

Mike

 

[JohnRBaker]

It would appear that this is the behavior as defined by the various drafting standards. And note that people who use are CAD systems seem to be asking similar questions and getting similar answers. I found several treads for products like AutoCAD, SolidWorks, PRO-E, etc. and people keep asking for what you have and generally the response is that it's just the way Arc Length Dimensions are supposed to work.

Now I did see a couple of AutoCAD responses where they suggested writing AutoLISP programs to do what the user wanted, but I've also seen a Pro-E example (see below) virtually identical to what yours was showing, with what is called 'orthogonal' extensions for Arc Length dimensions placed outside the arc and 'radial' extensions for those placed inside the arc.

Either the entire CAD industry got it wrong, or we're all working from the same Drafting Standards (what a concept ;-) ).

John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

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To an Engineer, the glass is twice as big as it needs to be.

 

[Crocostimpy]

Well, ok, it was my guess that this couldn't be a standard because it looks so ridiculous. Obviously I was not correct. That still doesn't answer the question of why it looks "normal" when it's on the inside.

Now that I think about it, when I was using Pro-E we used to use an angle dimension and text edit it to the correct numbers because we didn't like the way the Arc Dimension looked and customers always questioned it. The only problem with that is it didn't update when you made changes to the model. I guess I'll have to do the same thing here.

Mike

 

[cowski]

Or, you could leave it as is and tell your customer that you are following standard X or are using standard drafting best practices. When (more likely IF) they check the standard and see that you are right you may gain some credibility in their eyes. And you won't have to worry about unassociative dimensions (a bigger problem than telling the customer 'just because it looks odd to you doesn't mean it is wrong' in my opinion).

 

[Crocostimpy]

Well, I think what our customers are expecting is that they receive the same drawings as they have been. One could argue that as times change and evolve so should our methodology, but the fact remains that in Ideas the Arc Dimension looks "normal", and now it does not in NX. Does that mean that Ideas wasn't following the proper Drafting Standards? Or following antiquated standards?

I'm not trying to be argumentative here. I got the answer to my question. I still fail to see why the transition from Ideas to NX involves compromise in my end product though. I may be able to get around the non-updating dimension by using a measurement of the arc length, then assigning it to a parameter or expression, then referencing that in the dimension.

Mike

 

[hudson888]

As a matter of opinion I tend to agree with Mike the extension lines ought always to be normal to the Arc, anything else just looks wrong to me. Various drafting standards clearly support different things but the attached example does seem hard to accept.

However the statement that was made .... "the transition from Ideas to NX involves compromise in my end product"..., holds no promise that the product was not compromised in the first place by being in I-deas. Which is simply to say that there is a difference between wanting things to be done in an acceptable way and just wanting them to be made to look the same as whatever some other system happens to support. The former is reasonable the latter leads some people to attempt work around methods that are just plain counter productive. In my opinion you're better to just bite the bullet and use any CAD system as it was intended to be used to the best of your ability.

Best Regards

Hudson

www.jamb.com.au

Nil Desperandum illegitimi non carborundum

 

[Crocostimpy]

Hudson, I see what you're saying. I think what I should have said was that my customers should not see any difference in the drawings they receive. The transition from Ideas to NX should be seamless as far as they're comcerned. They don't even need to know that we have switched CAD systems.

Like I said before, I don't want to belabor the point. I got an answer to my question. I'll come up with a way of making it look like I want.

Mike