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Descriptive Geometry

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WHITMIREGT

WHITMIREGT

Aerospace
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Does the CAD systems do descriptive geometry as we had to do manually years ago?
 
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Which CAD system?

By "descriptive geometry" I assume you mean the construction or witness lines used to create alternative views of an object?

If so, then I don't know of any CAD system that does that automatically. Why would they need to? Are you looking for the artistic effect? Any CAD system would be able to easily create the construction lines manually.

[cheers]
 
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With 3D modeling, there is no reason for a CAD system to do descriptive geometry. It is my understanding that the purpose of descriptive geometry is to manually develop various projected views. If you need to show examples of how views are developed using descriptve geometry, you will have to place your desired views and manually add the witness or construction lines.

"The ambassador and the general were briefing me on the - the vast majority of Iraqis want to live in a peaceful, free world. And we will find these people and we will bring them to justice." - [small]George Bush, Washington DC, 27 October, 2003[/small]
 
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I used descriptive geometry back in 1955 to determine if the tubing around a rocket motor would run into other tubing. I'm just wondering if there is a need for drafters and designer to take a class on this subject these days.
 
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Maybe a fairly brief explanation but any CAD which incorporates 3D modelling to generate the drawing views probably removes the need for a detailed class.

On the other hand, if they're stuck doing 2D then maybe it's of use.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:
 
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While it is an essential skill to have for manual or 2D drafting, drafting boards seem to be going the way of the buggy whip. Personally, think it is a worthwhile subject of study, but I don't think that there is much demand for it in today's design environment. Though if we wake up one day and everyones computers don't work, it will be a valuable skill to have.

"The ambassador and the general were briefing me on the - the vast majority of Iraqis want to live in a peaceful, free world. And we will find these people and we will bring them to justice." - [small]George Bush, Washington DC, 27 October, 2003[/small]
 
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ewh,
That has happened to me a lot. I wake up and the stupid computer doesn't work!
IMG


...then it's back to the drawing board!
IMG


Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 08; CATIA V5
ctopher's home (updated Aug 5, 2008)
ctopher's blog
SolidWorks Legion
 
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WHITMIREGT,

Most CAD systems offer an option to use a grid when sketching in the 3D model and the 2D drawing. The grid lines could effectively be used to do what you are asking.

[cheers]
 
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Descriptive Geometry was the graphical method of developing a "true shape" view--i.e. a view perpendicular to the surface--that is not an orthogonal view. With solid modeling it is about as useful as using trigonometry to find an angle or a length. The computer does it faster.
 
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ctopher,
You mean you still have a drawing board? Most of us dumped ours. But since I don't yet have the portability of a laptop, I still occasionally use a quad pad, triangles and scale. So the descriptive geometry I learned still gets used.

 
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I've used CADAM which is a very interesting 2D cad program (Dassault systems It uses a function that builds projected views off the first main view. It also has the capability of projecting geometry on a user defined surface.
 
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I took descriptive geometry in school and it was a PITA. That being said, I would not be able to tell you how the computer finds the auxiliary views that it does and why, or how to create a similar view in 2d without it. I have used the things I learned on multiple occasions and have found it to be an invaluable addition to my knowledge.

Someone that only ever uses 3d CAD and doesn't want to know how or why the program did what it did (I would venture to say that there is not a single designer, engineer, or draftsman worth anything that could say that with a straight face.) doesn't need it. Anyone that wants to understand what they do and not just trust the program to do things right, should know it.

Perhaps not on the drawing board, (although I found that to be invaluable experience as well.) but in AutoCAD at least it should be taught.

Besides if no one learns how to do this stuff, who is going to tell the software programmers what to make the software do?

David
 
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Descriptive Geometry is still, but rarely, taught. I have an associates in drafting and design engineering technology and a basic course in DG was required.

Most of the problems were architectural and piping with a few planes to figure out.
 
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I think today's engineers/designers/cad jockies could use a short course in DG. Even when making CAD drawings, where I have 3D models, I like to flip my views out, the same way I would, if I was doing it on the board. Many of today's CAD jockies create the primary views, and then the true view, with no visible connection between the two. I think it helps the guys on the shop floor, if they can see where the view came from. Plus, depending on the CAD system, it keeps the views more parametric, so they update better. ymmv.

-Dave
Everything should be designed as simple as possible, but not simpler.
 
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Gunman, while it might help, that's not so much a descriptive Geometry issue as a general unfamiliarity/lack of adherance to good drafting standards.

I see the same issue all the time.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:
 
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In my drawing board days it was considered a skill to create DG which was near invisible. Only to be used for drawing view layout and construction, not for the machine shop to "follow the lines". If they couldn't read the drawings using the features shown, they were gone. Besides, we used First Angle Projection, which made 'heavy line' DG very undesirable.
 
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Kenat: True, but I think some descriptive geometry would get them thinking along the proper lines. I'd bet they couldn't develop a view if their lives depended on it...heck, 50% of our engineering staff never heard of an RPN calculator until last week, when one of them asked to borrow mine.

*end rant*

-Dave
Everything should be designed as simple as possible, but not simpler.
 
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