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COG symbol in advanced weight management + 3DPMI & MBD

Creator
Creator

Hello,

I have been trying to find information about how to use advanced weight management (the point it creates) to place a symbol of sorts to Center of Gravity. Advanced weight management does give you the point in the model. This can be used in drafting no problem. Nx does not have a symbol defined for COG that could be used in drafting. This no problem to define either and most are silently accempting the fact that there is no ootb symbol.

BUT, when you think of 3D and COG the fact is that no 2D symbol can be used efficiently when you place it to COG. Sure you can put three of them, one in all planes to see it in all model views. How do you do this? do you have a 3D object that you put in to COG so it is possible to attach dimensions to COG?

 

NH

6 REPLIES

Re: COG symbol in advanced weight management + 3DPMI & MBD

Siemens Phenom Siemens Phenom
Siemens Phenom

With the 'Measure Body' command, select the associative option in the measure body dialog which will enable the 'Create Principle Axes' option. Check this option so that it will create axes along with the point of body measurement. This point can be used to create PMI dimensions,notes.

Re: COG symbol in advanced weight management + 3DPMI

Creator
Creator
Right, thats clear already. The real question is how you represent the COG. What kind of graphical symbol / 3D object should be used?
If COG is inside of a part, the point really does not help. 2D has symbol that can be used. What would be the way in 3D?

NH

Re: COG symbol in advanced weight management + 3DPMI

Siemens Phenom Siemens Phenom
Siemens Phenom

@MMCADS:

 

This should be an interesting discussion, because as far as I know, there is not a single answer.

 

Partly because I don't think there are any 3D standards for this, and even further, because I don't think there are even 2D standards. I know most engineers and scientists assume the symbol of a circle with 2 solid quadrants and 2 open ones, is a "standard symbol" for this, but I don't think applies in Drafting, let along PMI (I read somewhere that the ASME Standard, at least, does not even include this as a standard 2D symbol).

 

I've discussed this one a few times with people and they seems to fall in to 2 camps: one that wants to take the concept they know in 2D (which, as I said above, is not even a 2D standard) and try to apply it 3D. I've even heard suggestions of 3D equivalent, a sphere with alternate quadrants shaded (see attachemtent "Option #1").

 

First, it is a "clumsy" solution, since it really only looks like its 2D counterpart if you look along the XYZ orthoginal axis. In a 2D drawing, you can control that, but in 3D space, it's probably not gonig to be exaxt and will look "funny".

 

Another problem I have heard with the approach of inventing your own method, is that if it's accepted and understood in your own company, if it's not really a "standard" (global, industry, etc...), how can you be sure people outside your compamy will understand what it means.

 

The other camp, which is the one I am in, is that it does not make sense to try force a 2D concept in to 3D if it does not fit easily (trying to move 2D concepts to 3D PMI, is all-too-common approach many take, and I beleive not the best one for many cases).

 

I propose what I've heard others suggest to me as well: that you use the COG point and Principle Axes instead. (see attachemt Option #2). This actually give's a lot more info, since you get don't get the Axes withe "COG approach" in either 2D or 3D.

 

In 2D I can undersatnd the defacto symbol was an easy way to make it visually standout, but usually in 3D PMI, you are not just carrying about the Visual. You want to convey real info that automated systems can use. You probably don't need a "symbol" like you describe. In fact, to me, such a symbol just adds visual clutter and gets in the way of the real geometry.

 

There's a 3rd opinion, I've heard from a minority, which is to combine both methods, and place the "colored" ball at the COG Axes location. The thoght is that might be a way to slowly win over people who cannot easy give up their 2D method. 

 

But I've heard that logic applied to other methods that "borrow 2D concepts to 3D", and end up with clumsy solutions, and I don't really think that's a good approach. I think 3D PMI should be 3D PMI.

 

I'm sure others will have their opinions as well.

Re: COG symbol in advanced weight management + 3DPMI

Gears Esteemed Contributor Gears Esteemed Contributor
Gears Esteemed Contributor

Pat -

I don't see attachments?

Ken Akerboom Sr CAx Systems Engr, Moog, Inc.
Production: NX10.0.3.5 MP16/TC11.2
I'd rather be e-steamed than e-diseaseled


Re: COG symbol in advanced weight management + 3DPMI

Creator
Creator

@PatMcManus

 

So now the discussion has reached exactly the point where I got Smiley Happy with all statements being true. Also solutions that are point solutions to a company way a way of working specific fields. Although ISO 700 has a COG cymbol it most pbobably is not used anywhere except packing industry (google it and find a crosshair symbol).

 

Then taking this further, addin planes or objecst to a point that is a resultant from a tool that is not model view specific is an issue. What if you dimension to that and then change your arrangement. Information gotten from previous arrangement will be false and might pe persistent. Arrangements are not model view specific as. So is weight in general. PMI concept will need to have something for arrangments also. Arrangement are kind of global and independent of model views, as is weight in general.  Our use case comes from +30k part assemblies that might not be interesting for all, but certainly for us.

Re: COG symbol in advanced weight management + 3DPMI

Siemens Phenom Siemens Phenom
Siemens Phenom

Thanks for the confirmation @Ken_A!

 

When I first posted the attachments did not show either.

 

So I Editted my own post and in the Edit mode they were showing again.

 

At least I know it's not me.

 

I'll try them in-line here.

 

Option 1 first:

COG-3D-Option1.JPG

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Here's Option 2:

COG-3D-Option2.JPG

 

 

 

Pat

Highlighted

COG symbol in advanced weight management + 3DPMI & MBD

Creator
Creator

Hello,

I have been trying to find information about how to use advanced weight management (the point it creates) to place a symbol of sorts to Center of Gravity. Advanced weight management does give you the point in the model. This can be used in drafting no problem. Nx does not have a symbol defined for COG that could be used in drafting. This no problem to define either and most are silently accempting the fact that there is no ootb symbol.

BUT, when you think of 3D and COG the fact is that no 2D symbol can be used efficiently when you place it to COG. Sure you can put three of them, one in all planes to see it in all model views. How do you do this? do you have a 3D object that you put in to COG so it is possible to attach dimensions to COG?

 

NH

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