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MBD in seconds: MBD with 3D PMI makes interpretation easier than 2D

Question asked by Alessandro Tornincasa on Jan 1, 2017
Latest reply on Jan 2, 2017 by Oboe Wu

Hi,

following Oboe's idea on MBD in seconds YouTube playlist, I'm proposing to put short post here to spread MBD culture and benefits.

Let's call these posts MBD in seconds to keep consistent with the YouTube playlist.

Practical examples should be used in order to show use cases familiar to everybody that will stimulate discussion.

I encourage other users to contribute with more cases.

My first case is this part shown on the 2D drawing:

2D.PNG

 

And this is the MBD version:

3D MBD.PNG

For what concerns the 2D drawing, there are these disadvantages:

  1. You need to decode it
  2. You need to have perfect knowledge of GD&T semantics
  3. You're never 100 % sure the part has all dimesions and tolerances to completely define manufacturing features

 

With the MBD model you can consume a 3d model (either native model or 3D PDF) and:

1) You don't need to decode it because you read a 3D model which is a very natural process

2) The MBD model is more "forgiving" if you don't have perfect knowledge of GD&T semantics

For example in this case the profile tolerance symbol has an all over symbol. This one:

All over.jpg

If you don't know the meaning of that double circle symbol you can have serious problems on intepreting geometric tolerances on the 2D drawing. The 3D model instead gives you visual feedback: just click on the profile tolerance and all model surfaces to which tolerance refers to are highlighted.

PDf 3D.PNG

No way to interpretation.

 

3) MBD will give you feedback on whether all required manufacturing dimensions have been created or not

 

Actually, I wouldn't even need that symbol when working MBD (I've put it only because the ASME norm requires me to do so).

In MBD I can put my design intent into my 3D model in an inteligent way: I define a collection by selecting all the surfaces that will be referenced by the surface profile tolerance.

Collection.PNG

This way when I will create my tolerance I will exactly know that it will reference all those surfaces because all involved surfaces will be highlighted when clicking on tolerance symbol.

 

Finally, show tolerance status tells me that all manufacturing features are completely defined!

Tolerance status.PNG

Alex

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