CAD drawing methods.

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Mathieu
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CAD drawing methods.

Wed Nov 23, 2011 10:18 pm

I was wondering what method people are using to go from a 2D to 3D design. I am sure it depends somewhat on what software you are using but nonetheless I am interested in the approach used.
Personally I am using AutoCAD which I am finally getting confident with. Once I understood the workflow it isn't all that hard.
So far I have only been drafting 2D and I was wondering how to go from here.
Chris, did you, for example with the design of the mazerolle sawhorse, start from a 2D draft as described in the text and then ' extruded' a 3D model from that. Or did you just created the 3D solids directly without a 2D draft? If you did what was your approach?

If anyone else has any suggestions or is willing to share his views, that would be appreciated.
Ok back to the drawing table now. Oh yes, one more thing... does anyone has experience with drawing tablets and CAD software?
Looking forward to your answers.
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Jack_Ervin.
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Re: CAD drawing methods.

Thu Nov 24, 2011 9:56 am

Mathieu,

I used Pro-Engineer CAD, in a tool room environment, which is an integrated package. Accomplishing 2D or detailed drawings starts with 3D primitives which are building blocks ie. squares, rectangles, cylinders, cones etc. They are merged to form a single solid model. Models are assembled and placed on a Cartesian coordinate system then brought into the detail part of the program to use various views, top, front, left, right, bottom, back. The model is displayed using wireframe, hidden line, no hidden line, etc. with the underlying solid model displaying the line work, dimension lines, center lines, notes, etc. are added. So to sum up, 2D in this software starts as a real world size solid depiction and then is used as an underlying model to project its shape onto a plane.

Sketchup works in a similar fashion.

I studied Autocad 2D and know the in's and out's of that but don't know how Autodesk addressed the 3D discipline.

Hope this helps you to sort this out.

Regards,

Jack
Mathieu
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Re: CAD drawing methods.

Fri Nov 25, 2011 12:30 am

Thanks, Jack that was helpful. I am sure I will figure it out once I start playing around with it.
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Chris Hall
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Re: CAD drawing methods.

Fri Nov 25, 2011 11:15 am

Chris, did you, for example with the design of the Mazerolle sawhorse, start from a 2D draft as described in the text and then ' extruded' a 3D model from that. Or did you just created the 3D solids directly without a 2D draft? If you did what was your approach?
It was a mix of both approaches. When I started using the 3D approach, I had completed most of the drawing in 2D, but was unsure if certain aspects were correct or not. Once I had gotten a handle on using SketchUp, I thereby re-drew all my 2D in SketchUp and constructed the 3D parts by drawing plumb lines up from the floor to particular heights. Connecting points together until planes and then solids were formed allowed me to confirm whether my 2D understanding was correct or not. In other places where I found the 2D puzzling or incomplete detail-wise, I would construct a 3D piece, place it at the required slope and location atop the 2D plan and then 'reverse engineer' to better understand how the 2D was supposed to work.

It was through this combination of 2D and 3D problem solving that I was able to complete the Mazerolle drawing of the 'crazy' sawhorse, and to confirm the errors in the original that I suspected, and in fact to discover even more errors in the original. All said, some 1100 hours of work just on the sawhorse drawing. I must have re-drawn it from scratch a dozen times. The 3D was a godsend in solving various issues in the drawing, however it would be next to impossible to set the drawing up in 3D without a grasp of the underlying 2D establishment and methods of positioning the parts. Also, the goal of the drawing work really is the completion and understanding of the 2D. The 3D helps to confirm that the 2D works, and helps fill in those areas where it may be very hard to visualize what the 2D is supposed to produce. In Mazerolle's class, there would have been scale models of the various pieces under study, and students could examine them as they needed to help understand the drawing work. I had no such option, and the 3D was there, as I said, to fill in those gaps and make those confirmations. I think it would be very hard to draw that sawhorse only in 3D.
Mathieu
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Re: CAD drawing methods.

Sat Nov 26, 2011 8:28 am

Thanx Chris, your explanation is very useful and it makes it obvious for me how to proceed. It appears to be a combination of different methods.
If I understand correctly the 2D drafting is the core where to start from and the 3D comes in very helpful in confirming what you are doing and gaining better understanding regarding certain aspects.
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Chris Hall
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Re: CAD drawing methods.

Sat Nov 26, 2011 10:55 am

Exactly!

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