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Whats saved in 2D/3D DWG or DXF file format
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* March 23, 2016, 03:16:30 PM
Hi All

If I save a 3D TC file to a Dwg file format, what should I expect when its reopened in another
CAD program. For example if I have a 3D box only saved then reopened will I get the same info?

More, if I have the same 3D opened in 2D will I see the dimensions when only viewed as 2D?

If the same 3D box had 1 or more simple bends, then saved as a dwg, reopened as 2D only can
I view the bend data in the 2D format.

FWIW, I trying to establish if a dwg or dxf viewed as a 2D from 2 distinct
CAD programs will permit the user to see all the data, or would the user
need a separate 3D file to establish the 3D object and relevant bend sngles and
data.

This came about due to cutting errors at the eng shop, where I was told by one
person that the eng shop should be able to see the bend data from the 2D dwg file
alone.

Finally, do different CAD programs save data (bend data etc) in diffetent methods?

Thanks

Aussiebloke

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.


* March 23, 2016, 06:22:16 PM
#1
Sheet metal bends are quite specialized, very few general CAD apps do it, a few have add-ons, historically they've been dedicated.  TC does bends using neutral depth of the material, the depth at which the material doesn't stretch or compress, others use a so-called "K" factor, which gives the neutral depth as a ratio of material thickness, it differs with material. 
For the most part, dwgs created in TC will be similar to dwgs created in AutoCAD.  Other CAD programs interpret the data the same way, but appearance and details will vary.   
Dimensions will be visible if the 2D viewpoint is looking at their workplane from above or they'll be reversed if viewed from below, and they might be oblique if the viewpoint isn't normal/orthogonal, and they might not be on the same apparent plane as the figure they're dimensioning, so there might be parallax effect.
There's no innate bend data in a drawing or model.  If you look at a bend in sheet material end-on, a sheet thickness will be displayed as two arcs, which is enough to evaluate the bend if you know what you're doing, but there's not so much a guarantee that a bend is 90 degrees, the view must be along the bend axis.  It's not clear if that's what your technician is referring to, or talking about the bend tangent lines and centerline, features that TC automates in unbending in recent versions.  Neutral depth/K-factor affects those features, and there are reliable references, but people (usually hands-on sheet metal people) still declare that it's inexact science, and they also deal with spring back, which is material having to have a bend applied that's greater than the end wanted, so that the material's spring takes it back to that intended. 
2D drawings were done on paper with plan and elevation views, drawn to "1st angle projection"  or "3rd angle projection" (there are explanations of them everywhere).  2D drawings produced from 3D models need that information, they don't incorporate them simply because you're only using one viewpoint.   You have to present drawing angles that convey the information needed, so you need to know what information's needed.
« Last Edit: March 23, 2016, 06:24:41 PM by murray dickinson »

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* March 24, 2016, 12:46:34 PM
#2
Thanks Murray.

So if I read that right then, the eng shop really needs to see a 3D view as well if they
don't have the same CAD system or the bend data is supplied another way. That explains
why we got errors in one cut and bend on a file that was not seen with an associated explanation
or alternate view. What I do know is that the supplied data was in 2D and read by Autocad at the shop end in an older bend machine.

Thanks

Aussiebloke

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Daz
TCW V21, 2016-2018 PP, Animation Lab V5, TurboPDF V2-V3 & LightWorks Rendering Engine mostly.