how to override dimension value INTELLIGENTLY using code?

[godpaul]

when we build model, we certainly want to build it as accurately as possible.

however, sometimes, due to complexity and massive geometry calculation involved, it's hard to get the EXACT dimension as specified by ourself

in the pic, let's suppose i want to have a slot depth equal to 2 and SUPPOSE i tried by my best to make it as accurately as possible. BUT, still a little bit off target when i do direct dimensioning on the drawing.....

in that case, dimension override comes in to my view. this is what i did in inventor.

there are two ways suggested by Autodesk,
1), draw a vertical sketch line IN THE MODEL, show this sketch line in drawing, dimension it and you get exactly 2 on the print. finally, hide this sketch line to let people feel you dimensioned the slot directly.....
2). the second method is a littlt complex but has great value. First, simply dimension the slot directly(dont worry about dimension accuracy at this point). GIVE IT A NAME! in this case, SLOT DEPTH, this is very important.
open Inventor VBA code editor, find that dimension based on the name we give, wirte code to override the dimension to whatever we want. this method is powerful because i can override tolerance, change its properties like symmetric tolerance, deviant tolerance. Or, change colro, precison and so on.



back in NX, I am preety sure NX can do something like this but i need some direction and simple example from you smart people.
any suggestions are welcomed.
question will be:
is there a way to locate each object on drawing by looking through NX internally ( through API ??)


pic

http://files.engineering.com/getfile.aspx?folder=36c5a6c4-ffce-4069-9d8c-1a1678dcc96c&file=1.PNG

prt

http://files.engineering.com/getfil...5-94f8-77f46ac6e5db&file=dimension_puzzle.prt

dwg

http://files.engineering.com/getfil...5-6017ba5efaf4&file=dimension_puzzle_dwg1.prt

 

[godpaul]

HERE IS the inventor API
the "angle" name on the drawing can ba found in the API so that i can write code to find a dimension called "angle" and override its value...

http://files.engineering.com/getfil...-51e9-4bca-b30c-b378926b2cc0&file=Capture.PNG

 

[cowski]

Overriding dimension values is a bad idea in any CAD package, unless you are making a chart drawing and entering a value such as "A".

Yes, it can be done in NX as well, but I advise against it.

www.nxjournaling.com

 

[godpaul]

so in my situation, you suggest to make a chart/table list info such as parameter name, dimension, unit, tolerance on the chart/table? And all data in chart/table can be dumped from external sournce such as excel, or other database?

what's the approach to do it?

thanks

 

[ewh]

Have you tried using sketcher to define this geometry?

“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV

 

[cowski]

so in my situation, you suggest to make a chart/table list info such as parameter name, dimension, unit, tolerance on the chart/table? And all data in chart/table can be dumped from external sournce such as excel, or other database?

No.
I'm saying you should NEVER override a dimension value UNLESS you are making a chart drawing (which does not appear to be your intent).

I suggest tweaking the geometry until you get the desired dimension.

www.nxjournaling.com

 

[cowski]

These days, most parts get manufactured based on the solid geometry rather than what the drawing says. If you give a shop a model and drawing that you know don't agree; things will get interesting.

www.nxjournaling.com

 

[godpaul]

Hi cowski,

thanks for suggestion

NO, my role is just to make drawing for representation purpose which acts as messenger, so i DO NOT build a model which eventually will be sent to manufacturer.

that's the reason why i ask for help for how to dump external data into drawing, makng the drawing informative and of course, i will try to build th model as accurate as possible. If i cannot, i need to override the dimension OR better way you suggested, use a table

 

[godpaul]

I searched the forum got how to input data into table uisng internal spreadsheet written by Mr. John,

he mentioned KF programming... but i dont if this can be done using VB.

http://www.eng-tips.com/viewthread.cfm?qid=252038

manual update is tedious because one model can serve 10 or 100 different drawing BECAUSE they shared the same geometries, what make them diffeent is just dimensions. so automated the drawing process is the ultimate goal

 

[JohnRBaker]

Someone has to take responsibility for the integrity of the models being created which are subsequently going to be used to manufacture your products. If the models are not accurate enough or simply incorrect due to poor modeling technique or just plain incompetence, then your management expecting a 'draftsman' to fix the problem is simply a sign of further incompetence just at a higher level. Besides, if it's true that ONLY the Drawing is going to used to manufacture the final parts then why is your company even wasting time creating worthless 3D geometry and then spending extra time and money dicking around with the Drawings so as to make them look right with the proper dimensions? Why not just do it all in 2D AutoCAD in the first place and be done with it?

BTW, I'm not going to waste any more of MY time even looking at your models or pictures (and I recommend that others follow suit) with the idea that I MIGHT be able to offer some suggestions as to how to accomplish what you've been asking since to do so would be tantamount to 'aiding and abeting' a indefensible and unacceptable situation (after all, the P.E. after my name is more then just window decorations).

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

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

 

[godpaul]

You are a truly Professional Engineer, Mr. John. you kind of touch the morality issue.

but since this is a public forum i cannot talk too much, what i can say is this:

1) we buy tool from many manufacturers, their drawings are incomplete, missing this dimesnions and that info.
2) we finally realized we cannot let his happen, in the mean time, while we are trying to study their tool, we want to struggle them to put critical dimension on the drawing and at the same time, we are creating drawings JUST FOR OURSELF, we REALLY DO NOT send this drawing out and make real products based on our drawing, NO!! we just want to have drawiing with enough info we think it important and use those drawing as illustration purpose whihc is enough for machine setup. that's it


of course i can build a scratch model and cheat everyhhing on drawing. however, i just want to make a better model.
i can never make it accurate because i dont know how those tool are manufactuer and what kind of parameters needed to build model.

i struggle to make automated drawing generation is because those tools geometries are so identical, it will be good to have some external data which be dumped into NX and the model and drawing can be updated...the generated drawing is just for illustration purpose, NEVER for further serious purpose.

since i am the only person working this thing plus i am not into programming too much, i feel lost..

that's why i come to professional internet forum for help. of course i dont take anything granted...just need a proper direction and sample.


i am not good at expressing myself most time and lots of time people get misled and get angry with me, but i really dont mean that way


i hope this explanation is better and Mr. john, pleae dont ignore my future threads.

 

[cowski]

...i will try to build th model as accurate as possible. If i cannot, i need to override the dimension OR better way you suggested, use a table

NO, I only mentioned a table drawing to concede the point that there is a proper time to override a dimension value. Over-riding a dimension value just to get a "nice round" number on your print is, at best, a misuse of the software.

www.nxjournaling.com

 

[aluminum2]

darn, that is standard practice at every company I worked for.

 

[cowski]

Let's not confuse "standard practice" with "best practice". While they should be the same, they often are not.

www.nxjournaling.com